diff options
Diffstat (limited to 'tools/objtool/check.c')
| -rw-r--r-- | tools/objtool/check.c | 4371 |
1 files changed, 4371 insertions, 0 deletions
diff --git a/tools/objtool/check.c b/tools/objtool/check.c new file mode 100644 index 000000000..cb363b507 --- /dev/null +++ b/tools/objtool/check.c @@ -0,0 +1,4371 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Copyright (C) 2015-2017 Josh Poimboeuf <jpoimboe@redhat.com> + */ + +#include <string.h> +#include <stdlib.h> +#include <inttypes.h> +#include <sys/mman.h> + +#include <arch/elf.h> +#include <objtool/builtin.h> +#include <objtool/cfi.h> +#include <objtool/arch.h> +#include <objtool/check.h> +#include <objtool/special.h> +#include <objtool/warn.h> +#include <objtool/endianness.h> + +#include <linux/objtool.h> +#include <linux/hashtable.h> +#include <linux/kernel.h> +#include <linux/static_call_types.h> + +struct alternative { + struct list_head list; + struct instruction *insn; + bool skip_orig; +}; + +static unsigned long nr_cfi, nr_cfi_reused, nr_cfi_cache; + +static struct cfi_init_state initial_func_cfi; +static struct cfi_state init_cfi; +static struct cfi_state func_cfi; + +struct instruction *find_insn(struct objtool_file *file, + struct section *sec, unsigned long offset) +{ + struct instruction *insn; + + hash_for_each_possible(file->insn_hash, insn, hash, sec_offset_hash(sec, offset)) { + if (insn->sec == sec && insn->offset == offset) + return insn; + } + + return NULL; +} + +static struct instruction *next_insn_same_sec(struct objtool_file *file, + struct instruction *insn) +{ + struct instruction *next = list_next_entry(insn, list); + + if (!next || &next->list == &file->insn_list || next->sec != insn->sec) + return NULL; + + return next; +} + +static struct instruction *next_insn_same_func(struct objtool_file *file, + struct instruction *insn) +{ + struct instruction *next = list_next_entry(insn, list); + struct symbol *func = insn->func; + + if (!func) + return NULL; + + if (&next->list != &file->insn_list && next->func == func) + return next; + + /* Check if we're already in the subfunction: */ + if (func == func->cfunc) + return NULL; + + /* Move to the subfunction: */ + return find_insn(file, func->cfunc->sec, func->cfunc->offset); +} + +static struct instruction *prev_insn_same_sym(struct objtool_file *file, + struct instruction *insn) +{ + struct instruction *prev = list_prev_entry(insn, list); + + if (&prev->list != &file->insn_list && prev->func == insn->func) + return prev; + + return NULL; +} + +#define func_for_each_insn(file, func, insn) \ + for (insn = find_insn(file, func->sec, func->offset); \ + insn; \ + insn = next_insn_same_func(file, insn)) + +#define sym_for_each_insn(file, sym, insn) \ + for (insn = find_insn(file, sym->sec, sym->offset); \ + insn && &insn->list != &file->insn_list && \ + insn->sec == sym->sec && \ + insn->offset < sym->offset + sym->len; \ + insn = list_next_entry(insn, list)) + +#define sym_for_each_insn_continue_reverse(file, sym, insn) \ + for (insn = list_prev_entry(insn, list); \ + &insn->list != &file->insn_list && \ + insn->sec == sym->sec && insn->offset >= sym->offset; \ + insn = list_prev_entry(insn, list)) + +#define sec_for_each_insn_from(file, insn) \ + for (; insn; insn = next_insn_same_sec(file, insn)) + +#define sec_for_each_insn_continue(file, insn) \ + for (insn = next_insn_same_sec(file, insn); insn; \ + insn = next_insn_same_sec(file, insn)) + +static bool is_jump_table_jump(struct instruction *insn) +{ + struct alt_group *alt_group = insn->alt_group; + + if (insn->jump_table) + return true; + + /* Retpoline alternative for a jump table? */ + return alt_group && alt_group->orig_group && + alt_group->orig_group->first_insn->jump_table; +} + +static bool is_sibling_call(struct instruction *insn) +{ + /* + * Assume only ELF functions can make sibling calls. This ensures + * sibling call detection consistency between vmlinux.o and individual + * objects. + */ + if (!insn->func) + return false; + + /* An indirect jump is either a sibling call or a jump to a table. */ + if (insn->type == INSN_JUMP_DYNAMIC) + return !is_jump_table_jump(insn); + + /* add_jump_destinations() sets insn->call_dest for sibling calls. */ + return (is_static_jump(insn) && insn->call_dest); +} + +/* + * This checks to see if the given function is a "noreturn" function. + * + * For global functions which are outside the scope of this object file, we + * have to keep a manual list of them. + * + * For local functions, we have to detect them manually by simply looking for + * the lack of a return instruction. + */ +static bool __dead_end_function(struct objtool_file *file, struct symbol *func, + int recursion) +{ + int i; + struct instruction *insn; + bool empty = true; + + /* + * Unfortunately these have to be hard coded because the noreturn + * attribute isn't provided in ELF data. Keep 'em sorted. + */ + static const char * const global_noreturns[] = { + "__invalid_creds", + "__module_put_and_kthread_exit", + "__reiserfs_panic", + "__stack_chk_fail", + "__ubsan_handle_builtin_unreachable", + "cpu_bringup_and_idle", + "cpu_startup_entry", + "do_exit", + "do_group_exit", + "do_task_dead", + "ex_handler_msr_mce", + "fortify_panic", + "kthread_complete_and_exit", + "kthread_exit", + "kunit_try_catch_throw", + "lbug_with_loc", + "machine_real_restart", + "make_task_dead", + "panic", + "rewind_stack_and_make_dead", + "sev_es_terminate", + "snp_abort", + "stop_this_cpu", + "usercopy_abort", + "xen_start_kernel", + }; + + if (!func) + return false; + + if (func->bind == STB_WEAK) + return false; + + if (func->bind == STB_GLOBAL) + for (i = 0; i < ARRAY_SIZE(global_noreturns); i++) + if (!strcmp(func->name, global_noreturns[i])) + return true; + + if (!func->len) + return false; + + insn = find_insn(file, func->sec, func->offset); + if (!insn || !insn->func) + return false; + + func_for_each_insn(file, func, insn) { + empty = false; + + if (insn->type == INSN_RETURN) + return false; + } + + if (empty) + return false; + + /* + * A function can have a sibling call instead of a return. In that + * case, the function's dead-end status depends on whether the target + * of the sibling call returns. + */ + func_for_each_insn(file, func, insn) { + if (is_sibling_call(insn)) { + struct instruction *dest = insn->jump_dest; + + if (!dest) + /* sibling call to another file */ + return false; + + /* local sibling call */ + if (recursion == 5) { + /* + * Infinite recursion: two functions have + * sibling calls to each other. This is a very + * rare case. It means they aren't dead ends. + */ + return false; + } + + return __dead_end_function(file, dest->func, recursion+1); + } + } + + return true; +} + +static bool dead_end_function(struct objtool_file *file, struct symbol *func) +{ + return __dead_end_function(file, func, 0); +} + +static void init_cfi_state(struct cfi_state *cfi) +{ + int i; + + for (i = 0; i < CFI_NUM_REGS; i++) { + cfi->regs[i].base = CFI_UNDEFINED; + cfi->vals[i].base = CFI_UNDEFINED; + } + cfi->cfa.base = CFI_UNDEFINED; + cfi->drap_reg = CFI_UNDEFINED; + cfi->drap_offset = -1; +} + +static void init_insn_state(struct objtool_file *file, struct insn_state *state, + struct section *sec) +{ + memset(state, 0, sizeof(*state)); + init_cfi_state(&state->cfi); + + /* + * We need the full vmlinux for noinstr validation, otherwise we can + * not correctly determine insn->call_dest->sec (external symbols do + * not have a section). + */ + if (opts.link && opts.noinstr && sec) + state->noinstr = sec->noinstr; +} + +static struct cfi_state *cfi_alloc(void) +{ + struct cfi_state *cfi = calloc(sizeof(struct cfi_state), 1); + if (!cfi) { + WARN("calloc failed"); + exit(1); + } + nr_cfi++; + return cfi; +} + +static int cfi_bits; +static struct hlist_head *cfi_hash; + +static inline bool cficmp(struct cfi_state *cfi1, struct cfi_state *cfi2) +{ + return memcmp((void *)cfi1 + sizeof(cfi1->hash), + (void *)cfi2 + sizeof(cfi2->hash), + sizeof(struct cfi_state) - sizeof(struct hlist_node)); +} + +static inline u32 cfi_key(struct cfi_state *cfi) +{ + return jhash((void *)cfi + sizeof(cfi->hash), + sizeof(*cfi) - sizeof(cfi->hash), 0); +} + +static struct cfi_state *cfi_hash_find_or_add(struct cfi_state *cfi) +{ + struct hlist_head *head = &cfi_hash[hash_min(cfi_key(cfi), cfi_bits)]; + struct cfi_state *obj; + + hlist_for_each_entry(obj, head, hash) { + if (!cficmp(cfi, obj)) { + nr_cfi_cache++; + return obj; + } + } + + obj = cfi_alloc(); + *obj = *cfi; + hlist_add_head(&obj->hash, head); + + return obj; +} + +static void cfi_hash_add(struct cfi_state *cfi) +{ + struct hlist_head *head = &cfi_hash[hash_min(cfi_key(cfi), cfi_bits)]; + + hlist_add_head(&cfi->hash, head); +} + +static void *cfi_hash_alloc(unsigned long size) +{ + cfi_bits = max(10, ilog2(size)); + cfi_hash = mmap(NULL, sizeof(struct hlist_head) << cfi_bits, + PROT_READ|PROT_WRITE, + MAP_PRIVATE|MAP_ANON, -1, 0); + if (cfi_hash == (void *)-1L) { + WARN("mmap fail cfi_hash"); + cfi_hash = NULL; + } else if (opts.stats) { + printf("cfi_bits: %d\n", cfi_bits); + } + + return cfi_hash; +} + +static unsigned long nr_insns; +static unsigned long nr_insns_visited; + +/* + * Call the arch-specific instruction decoder for all the instructions and add + * them to the global instruction list. + */ +static int decode_instructions(struct objtool_file *file) +{ + struct section *sec; + struct symbol *func; + unsigned long offset; + struct instruction *insn; + int ret; + + for_each_sec(file, sec) { + + if (!(sec->sh.sh_flags & SHF_EXECINSTR)) + continue; + + if (strcmp(sec->name, ".altinstr_replacement") && + strcmp(sec->name, ".altinstr_aux") && + strncmp(sec->name, ".discard.", 9)) + sec->text = true; + + if (!strcmp(sec->name, ".noinstr.text") || + !strcmp(sec->name, ".entry.text") || + !strncmp(sec->name, ".text..__x86.", 13)) + sec->noinstr = true; + + for (offset = 0; offset < sec->sh.sh_size; offset += insn->len) { + insn = malloc(sizeof(*insn)); + if (!insn) { + WARN("malloc failed"); + return -1; + } + memset(insn, 0, sizeof(*insn)); + INIT_LIST_HEAD(&insn->alts); + INIT_LIST_HEAD(&insn->stack_ops); + INIT_LIST_HEAD(&insn->call_node); + + insn->sec = sec; + insn->offset = offset; + + ret = arch_decode_instruction(file, sec, offset, + sec->sh.sh_size - offset, + &insn->len, &insn->type, + &insn->immediate, + &insn->stack_ops); + if (ret) + goto err; + + /* + * By default, "ud2" is a dead end unless otherwise + * annotated, because GCC 7 inserts it for certain + * divide-by-zero cases. + */ + if (insn->type == INSN_BUG) + insn->dead_end = true; + + hash_add(file->insn_hash, &insn->hash, sec_offset_hash(sec, insn->offset)); + list_add_tail(&insn->list, &file->insn_list); + nr_insns++; + } + + list_for_each_entry(func, &sec->symbol_list, list) { + if (func->type != STT_FUNC || func->alias != func) + continue; + + if (!find_insn(file, sec, func->offset)) { + WARN("%s(): can't find starting instruction", + func->name); + return -1; + } + + sym_for_each_insn(file, func, insn) { + insn->func = func; + if (insn->type == INSN_ENDBR && list_empty(&insn->call_node)) { + if (insn->offset == insn->func->offset) { + list_add_tail(&insn->call_node, &file->endbr_list); + file->nr_endbr++; + } else { + file->nr_endbr_int++; + } + } + } + } + } + + if (opts.stats) + printf("nr_insns: %lu\n", nr_insns); + + return 0; + +err: + free(insn); + return ret; +} + +/* + * Read the pv_ops[] .data table to find the static initialized values. + */ +static int add_pv_ops(struct objtool_file *file, const char *symname) +{ + struct symbol *sym, *func; + unsigned long off, end; + struct reloc *rel; + int idx; + + sym = find_symbol_by_name(file->elf, symname); + if (!sym) + return 0; + + off = sym->offset; + end = off + sym->len; + for (;;) { + rel = find_reloc_by_dest_range(file->elf, sym->sec, off, end - off); + if (!rel) + break; + + func = rel->sym; + if (func->type == STT_SECTION) + func = find_symbol_by_offset(rel->sym->sec, rel->addend); + + idx = (rel->offset - sym->offset) / sizeof(unsigned long); + + objtool_pv_add(file, idx, func); + + off = rel->offset + 1; + if (off > end) + break; + } + + return 0; +} + +/* + * Allocate and initialize file->pv_ops[]. + */ +static int init_pv_ops(struct objtool_file *file) +{ + static const char *pv_ops_tables[] = { + "pv_ops", + "xen_cpu_ops", + "xen_irq_ops", + "xen_mmu_ops", + NULL, + }; + const char *pv_ops; + struct symbol *sym; + int idx, nr; + + if (!opts.noinstr) + return 0; + + file->pv_ops = NULL; + + sym = find_symbol_by_name(file->elf, "pv_ops"); + if (!sym) + return 0; + + nr = sym->len / sizeof(unsigned long); + file->pv_ops = calloc(sizeof(struct pv_state), nr); + if (!file->pv_ops) + return -1; + + for (idx = 0; idx < nr; idx++) + INIT_LIST_HEAD(&file->pv_ops[idx].targets); + + for (idx = 0; (pv_ops = pv_ops_tables[idx]); idx++) + add_pv_ops(file, pv_ops); + + return 0; +} + +static struct instruction *find_last_insn(struct objtool_file *file, + struct section *sec) +{ + struct instruction *insn = NULL; + unsigned int offset; + unsigned int end = (sec->sh.sh_size > 10) ? sec->sh.sh_size - 10 : 0; + + for (offset = sec->sh.sh_size - 1; offset >= end && !insn; offset--) + insn = find_insn(file, sec, offset); + + return insn; +} + +/* + * Mark "ud2" instructions and manually annotated dead ends. + */ +static int add_dead_ends(struct objtool_file *file) +{ + struct section *sec; + struct reloc *reloc; + struct instruction *insn; + + /* + * Check for manually annotated dead ends. + */ + sec = find_section_by_name(file->elf, ".rela.discard.unreachable"); + if (!sec) + goto reachable; + + list_for_each_entry(reloc, &sec->reloc_list, list) { + if (reloc->sym->type != STT_SECTION) { + WARN("unexpected relocation symbol type in %s", sec->name); + return -1; + } + insn = find_insn(file, reloc->sym->sec, reloc->addend); + if (insn) + insn = list_prev_entry(insn, list); + else if (reloc->addend == reloc->sym->sec->sh.sh_size) { + insn = find_last_insn(file, reloc->sym->sec); + if (!insn) { + WARN("can't find unreachable insn at %s+0x%" PRIx64, + reloc->sym->sec->name, reloc->addend); + return -1; + } + } else { + WARN("can't find unreachable insn at %s+0x%" PRIx64, + reloc->sym->sec->name, reloc->addend); + return -1; + } + + insn->dead_end = true; + } + +reachable: + /* + * These manually annotated reachable checks are needed for GCC 4.4, + * where the Linux unreachable() macro isn't supported. In that case + * GCC doesn't know the "ud2" is fatal, so it generates code as if it's + * not a dead end. + */ + sec = find_section_by_name(file->elf, ".rela.discard.reachable"); + if (!sec) + return 0; + + list_for_each_entry(reloc, &sec->reloc_list, list) { + if (reloc->sym->type != STT_SECTION) { + WARN("unexpected relocation symbol type in %s", sec->name); + return -1; + } + insn = find_insn(file, reloc->sym->sec, reloc->addend); + if (insn) + insn = list_prev_entry(insn, list); + else if (reloc->addend == reloc->sym->sec->sh.sh_size) { + insn = find_last_insn(file, reloc->sym->sec); + if (!insn) { + WARN("can't find reachable insn at %s+0x%" PRIx64, + reloc->sym->sec->name, reloc->addend); + return -1; + } + } else { + WARN("can't find reachable insn at %s+0x%" PRIx64, + reloc->sym->sec->name, reloc->addend); + return -1; + } + + insn->dead_end = false; + } + + return 0; +} + +static int create_static_call_sections(struct objtool_file *file) +{ + struct section *sec; + struct static_call_site *site; + struct instruction *insn; + struct symbol *key_sym; + char *key_name, *tmp; + int idx; + + sec = find_section_by_name(file->elf, ".static_call_sites"); + if (sec) { + INIT_LIST_HEAD(&file->static_call_list); + WARN("file already has .static_call_sites section, skipping"); + return 0; + } + + if (list_empty(&file->static_call_list)) + return 0; + + idx = 0; + list_for_each_entry(insn, &file->static_call_list, call_node) + idx++; + + sec = elf_create_section(file->elf, ".static_call_sites", SHF_WRITE, + sizeof(struct static_call_site), idx); + if (!sec) + return -1; + + idx = 0; + list_for_each_entry(insn, &file->static_call_list, call_node) { + + site = (struct static_call_site *)sec->data->d_buf + idx; + memset(site, 0, sizeof(struct static_call_site)); + + /* populate reloc for 'addr' */ + if (elf_add_reloc_to_insn(file->elf, sec, + idx * sizeof(struct static_call_site), + R_X86_64_PC32, + insn->sec, insn->offset)) + return -1; + + /* find key symbol */ + key_name = strdup(insn->call_dest->name); + if (!key_name) { + perror("strdup"); + return -1; + } + if (strncmp(key_name, STATIC_CALL_TRAMP_PREFIX_STR, + STATIC_CALL_TRAMP_PREFIX_LEN)) { + WARN("static_call: trampoline name malformed: %s", key_name); + free(key_name); + return -1; + } + tmp = key_name + STATIC_CALL_TRAMP_PREFIX_LEN - STATIC_CALL_KEY_PREFIX_LEN; + memcpy(tmp, STATIC_CALL_KEY_PREFIX_STR, STATIC_CALL_KEY_PREFIX_LEN); + + key_sym = find_symbol_by_name(file->elf, tmp); + if (!key_sym) { + if (!opts.module) { + WARN("static_call: can't find static_call_key symbol: %s", tmp); + free(key_name); + return -1; + } + + /* + * For modules(), the key might not be exported, which + * means the module can make static calls but isn't + * allowed to change them. + * + * In that case we temporarily set the key to be the + * trampoline address. This is fixed up in + * static_call_add_module(). + */ + key_sym = insn->call_dest; + } + free(key_name); + + /* populate reloc for 'key' */ + if (elf_add_reloc(file->elf, sec, + idx * sizeof(struct static_call_site) + 4, + R_X86_64_PC32, key_sym, + is_sibling_call(insn) * STATIC_CALL_SITE_TAIL)) + return -1; + + idx++; + } + + return 0; +} + +static int create_retpoline_sites_sections(struct objtool_file *file) +{ + struct instruction *insn; + struct section *sec; + int idx; + + sec = find_section_by_name(file->elf, ".retpoline_sites"); + if (sec) { + WARN("file already has .retpoline_sites, skipping"); + return 0; + } + + idx = 0; + list_for_each_entry(insn, &file->retpoline_call_list, call_node) + idx++; + + if (!idx) + return 0; + + sec = elf_create_section(file->elf, ".retpoline_sites", 0, + sizeof(int), idx); + if (!sec) { + WARN("elf_create_section: .retpoline_sites"); + return -1; + } + + idx = 0; + list_for_each_entry(insn, &file->retpoline_call_list, call_node) { + + int *site = (int *)sec->data->d_buf + idx; + *site = 0; + + if (elf_add_reloc_to_insn(file->elf, sec, + idx * sizeof(int), + R_X86_64_PC32, + insn->sec, insn->offset)) { + WARN("elf_add_reloc_to_insn: .retpoline_sites"); + return -1; + } + + idx++; + } + + return 0; +} + +static int create_return_sites_sections(struct objtool_file *file) +{ + struct instruction *insn; + struct section *sec; + int idx; + + sec = find_section_by_name(file->elf, ".return_sites"); + if (sec) { + WARN("file already has .return_sites, skipping"); + return 0; + } + + idx = 0; + list_for_each_entry(insn, &file->return_thunk_list, call_node) + idx++; + + if (!idx) + return 0; + + sec = elf_create_section(file->elf, ".return_sites", 0, + sizeof(int), idx); + if (!sec) { + WARN("elf_create_section: .return_sites"); + return -1; + } + + idx = 0; + list_for_each_entry(insn, &file->return_thunk_list, call_node) { + + int *site = (int *)sec->data->d_buf + idx; + *site = 0; + + if (elf_add_reloc_to_insn(file->elf, sec, + idx * sizeof(int), + R_X86_64_PC32, + insn->sec, insn->offset)) { + WARN("elf_add_reloc_to_insn: .return_sites"); + return -1; + } + + idx++; + } + + return 0; +} + +static int create_ibt_endbr_seal_sections(struct objtool_file *file) +{ + struct instruction *insn; + struct section *sec; + int idx; + + sec = find_section_by_name(file->elf, ".ibt_endbr_seal"); + if (sec) { + WARN("file already has .ibt_endbr_seal, skipping"); + return 0; + } + + idx = 0; + list_for_each_entry(insn, &file->endbr_list, call_node) + idx++; + + if (opts.stats) { + printf("ibt: ENDBR at function start: %d\n", file->nr_endbr); + printf("ibt: ENDBR inside functions: %d\n", file->nr_endbr_int); + printf("ibt: superfluous ENDBR: %d\n", idx); + } + + if (!idx) + return 0; + + sec = elf_create_section(file->elf, ".ibt_endbr_seal", 0, + sizeof(int), idx); + if (!sec) { + WARN("elf_create_section: .ibt_endbr_seal"); + return -1; + } + + idx = 0; + list_for_each_entry(insn, &file->endbr_list, call_node) { + + int *site = (int *)sec->data->d_buf + idx; + *site = 0; + + if (elf_add_reloc_to_insn(file->elf, sec, + idx * sizeof(int), + R_X86_64_PC32, + insn->sec, insn->offset)) { + WARN("elf_add_reloc_to_insn: .ibt_endbr_seal"); + return -1; + } + + idx++; + } + + return 0; +} + +static int create_mcount_loc_sections(struct objtool_file *file) +{ + struct section *sec; + unsigned long *loc; + struct instruction *insn; + int idx; + + sec = find_section_by_name(file->elf, "__mcount_loc"); + if (sec) { + INIT_LIST_HEAD(&file->mcount_loc_list); + WARN("file already has __mcount_loc section, skipping"); + return 0; + } + + if (list_empty(&file->mcount_loc_list)) + return 0; + + idx = 0; + list_for_each_entry(insn, &file->mcount_loc_list, call_node) + idx++; + + sec = elf_create_section(file->elf, "__mcount_loc", 0, sizeof(unsigned long), idx); + if (!sec) + return -1; + + idx = 0; + list_for_each_entry(insn, &file->mcount_loc_list, call_node) { + + loc = (unsigned long *)sec->data->d_buf + idx; + memset(loc, 0, sizeof(unsigned long)); + + if (elf_add_reloc_to_insn(file->elf, sec, + idx * sizeof(unsigned long), + R_X86_64_64, + insn->sec, insn->offset)) + return -1; + + idx++; + } + + return 0; +} + +/* + * Warnings shouldn't be reported for ignored functions. + */ +static void add_ignores(struct objtool_file *file) +{ + struct instruction *insn; + struct section *sec; + struct symbol *func; + struct reloc *reloc; + + sec = find_section_by_name(file->elf, ".rela.discard.func_stack_frame_non_standard"); + if (!sec) + return; + + list_for_each_entry(reloc, &sec->reloc_list, list) { + switch (reloc->sym->type) { + case STT_FUNC: + func = reloc->sym; + break; + + case STT_SECTION: + func = find_func_by_offset(reloc->sym->sec, reloc->addend); + if (!func) + continue; + break; + + default: + WARN("unexpected relocation symbol type in %s: %d", sec->name, reloc->sym->type); + continue; + } + + func_for_each_insn(file, func, insn) + insn->ignore = true; + } +} + +/* + * This is a whitelist of functions that is allowed to be called with AC set. + * The list is meant to be minimal and only contains compiler instrumentation + * ABI and a few functions used to implement *_{to,from}_user() functions. + * + * These functions must not directly change AC, but may PUSHF/POPF. + */ +static const char *uaccess_safe_builtin[] = { + /* KASAN */ + "kasan_report", + "kasan_check_range", + /* KASAN out-of-line */ + "__asan_loadN_noabort", + "__asan_load1_noabort", + "__asan_load2_noabort", + "__asan_load4_noabort", + "__asan_load8_noabort", + "__asan_load16_noabort", + "__asan_storeN_noabort", + "__asan_store1_noabort", + "__asan_store2_noabort", + "__asan_store4_noabort", + "__asan_store8_noabort", + "__asan_store16_noabort", + "__kasan_check_read", + "__kasan_check_write", + /* KASAN in-line */ + "__asan_report_load_n_noabort", + "__asan_report_load1_noabort", + "__asan_report_load2_noabort", + "__asan_report_load4_noabort", + "__asan_report_load8_noabort", + "__asan_report_load16_noabort", + "__asan_report_store_n_noabort", + "__asan_report_store1_noabort", + "__asan_report_store2_noabort", + "__asan_report_store4_noabort", + "__asan_report_store8_noabort", + "__asan_report_store16_noabort", + /* KCSAN */ + "__kcsan_check_access", + "__kcsan_mb", + "__kcsan_wmb", + "__kcsan_rmb", + "__kcsan_release", + "kcsan_found_watchpoint", + "kcsan_setup_watchpoint", + "kcsan_check_scoped_accesses", + "kcsan_disable_current", + "kcsan_enable_current_nowarn", + /* KCSAN/TSAN */ + "__tsan_func_entry", + "__tsan_func_exit", + "__tsan_read_range", + "__tsan_write_range", + "__tsan_read1", + "__tsan_read2", + "__tsan_read4", + "__tsan_read8", + "__tsan_read16", + "__tsan_write1", + "__tsan_write2", + "__tsan_write4", + "__tsan_write8", + "__tsan_write16", + "__tsan_read_write1", + "__tsan_read_write2", + "__tsan_read_write4", + "__tsan_read_write8", + "__tsan_read_write16", + "__tsan_volatile_read1", + "__tsan_volatile_read2", + "__tsan_volatile_read4", + "__tsan_volatile_read8", + "__tsan_volatile_read16", + "__tsan_volatile_write1", + "__tsan_volatile_write2", + "__tsan_volatile_write4", + "__tsan_volatile_write8", + "__tsan_volatile_write16", + "__tsan_atomic8_load", + "__tsan_atomic16_load", + "__tsan_atomic32_load", + "__tsan_atomic64_load", + "__tsan_atomic8_store", + "__tsan_atomic16_store", + "__tsan_atomic32_store", + "__tsan_atomic64_store", + "__tsan_atomic8_exchange", + "__tsan_atomic16_exchange", + "__tsan_atomic32_exchange", + "__tsan_atomic64_exchange", + "__tsan_atomic8_fetch_add", + "__tsan_atomic16_fetch_add", + "__tsan_atomic32_fetch_add", + "__tsan_atomic64_fetch_add", + "__tsan_atomic8_fetch_sub", + "__tsan_atomic16_fetch_sub", + "__tsan_atomic32_fetch_sub", + "__tsan_atomic64_fetch_sub", + "__tsan_atomic8_fetch_and", + "__tsan_atomic16_fetch_and", + "__tsan_atomic32_fetch_and", + "__tsan_atomic64_fetch_and", + "__tsan_atomic8_fetch_or", + "__tsan_atomic16_fetch_or", + "__tsan_atomic32_fetch_or", + "__tsan_atomic64_fetch_or", + "__tsan_atomic8_fetch_xor", + "__tsan_atomic16_fetch_xor", + "__tsan_atomic32_fetch_xor", + "__tsan_atomic64_fetch_xor", + "__tsan_atomic8_fetch_nand", + "__tsan_atomic16_fetch_nand", + "__tsan_atomic32_fetch_nand", + "__tsan_atomic64_fetch_nand", + "__tsan_atomic8_compare_exchange_strong", + "__tsan_atomic16_compare_exchange_strong", + "__tsan_atomic32_compare_exchange_strong", + "__tsan_atomic64_compare_exchange_strong", + "__tsan_atomic8_compare_exchange_weak", + "__tsan_atomic16_compare_exchange_weak", + "__tsan_atomic32_compare_exchange_weak", + "__tsan_atomic64_compare_exchange_weak", + "__tsan_atomic8_compare_exchange_val", + "__tsan_atomic16_compare_exchange_val", + "__tsan_atomic32_compare_exchange_val", + "__tsan_atomic64_compare_exchange_val", + "__tsan_atomic_thread_fence", + "__tsan_atomic_signal_fence", + "__tsan_unaligned_read16", + "__tsan_unaligned_write16", + /* KCOV */ + "write_comp_data", + "check_kcov_mode", + "__sanitizer_cov_trace_pc", + "__sanitizer_cov_trace_const_cmp1", + "__sanitizer_cov_trace_const_cmp2", + "__sanitizer_cov_trace_const_cmp4", + "__sanitizer_cov_trace_const_cmp8", + "__sanitizer_cov_trace_cmp1", + "__sanitizer_cov_trace_cmp2", + "__sanitizer_cov_trace_cmp4", + "__sanitizer_cov_trace_cmp8", + "__sanitizer_cov_trace_switch", + /* KMSAN */ + "kmsan_copy_to_user", + "kmsan_report", + "kmsan_unpoison_entry_regs", + "kmsan_unpoison_memory", + "__msan_chain_origin", + "__msan_get_context_state", + "__msan_instrument_asm_store", + "__msan_metadata_ptr_for_load_1", + "__msan_metadata_ptr_for_load_2", + "__msan_metadata_ptr_for_load_4", + "__msan_metadata_ptr_for_load_8", + "__msan_metadata_ptr_for_load_n", + "__msan_metadata_ptr_for_store_1", + "__msan_metadata_ptr_for_store_2", + "__msan_metadata_ptr_for_store_4", + "__msan_metadata_ptr_for_store_8", + "__msan_metadata_ptr_for_store_n", + "__msan_poison_alloca", + "__msan_warning", + /* UBSAN */ + "ubsan_type_mismatch_common", + "__ubsan_handle_type_mismatch", + "__ubsan_handle_type_mismatch_v1", + "__ubsan_handle_shift_out_of_bounds", + /* misc */ + "csum_partial_copy_generic", + "copy_mc_fragile", + "copy_mc_fragile_handle_tail", + "copy_mc_enhanced_fast_string", + "ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */ + "clear_user_erms", + "clear_user_rep_good", + "clear_user_original", + NULL +}; + +static void add_uaccess_safe(struct objtool_file *file) +{ + struct symbol *func; + const char **name; + + if (!opts.uaccess) + return; + + for (name = uaccess_safe_builtin; *name; name++) { + func = find_symbol_by_name(file->elf, *name); + if (!func) + continue; + + func->uaccess_safe = true; + } +} + +/* + * FIXME: For now, just ignore any alternatives which add retpolines. This is + * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline. + * But it at least allows objtool to understand the control flow *around* the + * retpoline. + */ +static int add_ignore_alternatives(struct objtool_file *file) +{ + struct section *sec; + struct reloc *reloc; + struct instruction *insn; + + sec = find_section_by_name(file->elf, ".rela.discard.ignore_alts"); + if (!sec) + return 0; + + list_for_each_entry(reloc, &sec->reloc_list, list) { + if (reloc->sym->type != STT_SECTION) { + WARN("unexpected relocation symbol type in %s", sec->name); + return -1; + } + + insn = find_insn(file, reloc->sym->sec, reloc->addend); + if (!insn) { + WARN("bad .discard.ignore_alts entry"); + return -1; + } + + insn->ignore_alts = true; + } + + return 0; +} + +/* + * Symbols that replace INSN_CALL_DYNAMIC, every (tail) call to such a symbol + * will be added to the .retpoline_sites section. + */ +__weak bool arch_is_retpoline(struct symbol *sym) +{ + return false; +} + +/* + * Symbols that replace INSN_RETURN, every (tail) call to such a symbol + * will be added to the .return_sites section. + */ +__weak bool arch_is_rethunk(struct symbol *sym) +{ + return false; +} + +/* + * Symbols that are embedded inside other instructions, because sometimes crazy + * code exists. These are mostly ignored for validation purposes. + */ +__weak bool arch_is_embedded_insn(struct symbol *sym) +{ + return false; +} + +#define NEGATIVE_RELOC ((void *)-1L) + +static struct reloc *insn_reloc(struct objtool_file *file, struct instruction *insn) +{ + if (insn->reloc == NEGATIVE_RELOC) + return NULL; + + if (!insn->reloc) { + if (!file) + return NULL; + + insn->reloc = find_reloc_by_dest_range(file->elf, insn->sec, + insn->offset, insn->len); + if (!insn->reloc) { + insn->reloc = NEGATIVE_RELOC; + return NULL; + } + } + + return insn->reloc; +} + +static void remove_insn_ops(struct instruction *insn) +{ + struct stack_op *op, *tmp; + + list_for_each_entry_safe(op, tmp, &insn->stack_ops, list) { + list_del(&op->list); + free(op); + } +} + +static void annotate_call_site(struct objtool_file *file, + struct instruction *insn, bool sibling) +{ + struct reloc *reloc = insn_reloc(file, insn); + struct symbol *sym = insn->call_dest; + + if (!sym) + sym = reloc->sym; + + /* + * Alternative replacement code is just template code which is + * sometimes copied to the original instruction. For now, don't + * annotate it. (In the future we might consider annotating the + * original instruction if/when it ever makes sense to do so.) + */ + if (!strcmp(insn->sec->name, ".altinstr_replacement")) + return; + + if (sym->static_call_tramp) { + list_add_tail(&insn->call_node, &file->static_call_list); + return; + } + + if (sym->retpoline_thunk) { + list_add_tail(&insn->call_node, &file->retpoline_call_list); + return; + } + + /* + * Many compilers cannot disable KCOV or sanitizer calls with a function + * attribute so they need a little help, NOP out any such calls from + * noinstr text. + */ + if (opts.hack_noinstr && insn->sec->noinstr && sym->profiling_func) { + if (reloc) { + reloc->type = R_NONE; + elf_write_reloc(file->elf, reloc); + } + + elf_write_insn(file->elf, insn->sec, + insn->offset, insn->len, + sibling ? arch_ret_insn(insn->len) + : arch_nop_insn(insn->len)); + + insn->type = sibling ? INSN_RETURN : INSN_NOP; + + if (sibling) { + /* + * We've replaced the tail-call JMP insn by two new + * insn: RET; INT3, except we only have a single struct + * insn here. Mark it retpoline_safe to avoid the SLS + * warning, instead of adding another insn. + */ + insn->retpoline_safe = true; + } + + return; + } + + if (opts.mcount && sym->fentry) { + if (sibling) + WARN_FUNC("Tail call to __fentry__ !?!?", insn->sec, insn->offset); + + if (reloc) { + reloc->type = R_NONE; + elf_write_reloc(file->elf, reloc); + } + + elf_write_insn(file->elf, insn->sec, + insn->offset, insn->len, + arch_nop_insn(insn->len)); + + insn->type = INSN_NOP; + + list_add_tail(&insn->call_node, &file->mcount_loc_list); + return; + } + + if (!sibling && dead_end_function(file, sym)) + insn->dead_end = true; +} + +static void add_call_dest(struct objtool_file *file, struct instruction *insn, + struct symbol *dest, bool sibling) +{ + insn->call_dest = dest; + if (!dest) + return; + + /* + * Whatever stack impact regular CALLs have, should be undone + * by the RETURN of the called function. + * + * Annotated intra-function calls retain the stack_ops but + * are converted to JUMP, see read_intra_function_calls(). + */ + remove_insn_ops(insn); + + annotate_call_site(file, insn, sibling); +} + +static void add_retpoline_call(struct objtool_file *file, struct instruction *insn) +{ + /* + * Retpoline calls/jumps are really dynamic calls/jumps in disguise, + * so convert them accordingly. + */ + switch (insn->type) { + case INSN_CALL: + insn->type = INSN_CALL_DYNAMIC; + break; + case INSN_JUMP_UNCONDITIONAL: + insn->type = INSN_JUMP_DYNAMIC; + break; + case INSN_JUMP_CONDITIONAL: + insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL; + break; + default: + return; + } + + insn->retpoline_safe = true; + + /* + * Whatever stack impact regular CALLs have, should be undone + * by the RETURN of the called function. + * + * Annotated intra-function calls retain the stack_ops but + * are converted to JUMP, see read_intra_function_calls(). + */ + remove_insn_ops(insn); + + annotate_call_site(file, insn, false); +} + +static void add_return_call(struct objtool_file *file, struct instruction *insn, bool add) +{ + /* + * Return thunk tail calls are really just returns in disguise, + * so convert them accordingly. + */ + insn->type = INSN_RETURN; + insn->retpoline_safe = true; + + if (add) + list_add_tail(&insn->call_node, &file->return_thunk_list); +} + +static bool same_function(struct instruction *insn1, struct instruction *insn2) +{ + return insn1->func->pfunc == insn2->func->pfunc; +} + +static bool is_first_func_insn(struct objtool_file *file, struct instruction *insn) +{ + if (insn->offset == insn->func->offset) + return true; + + if (opts.ibt) { + struct instruction *prev = prev_insn_same_sym(file, insn); + + if (prev && prev->type == INSN_ENDBR && + insn->offset == insn->func->offset + prev->len) + return true; + } + + return false; +} + +/* + * Find the destination instructions for all jumps. + */ +static int add_jump_destinations(struct objtool_file *file) +{ + struct instruction *insn, *jump_dest; + struct reloc *reloc; + struct section *dest_sec; + unsigned long dest_off; + + for_each_insn(file, insn) { + if (insn->jump_dest) { + /* + * handle_group_alt() may have previously set + * 'jump_dest' for some alternatives. + */ + continue; + } + if (!is_static_jump(insn)) + continue; + + reloc = insn_reloc(file, insn); + if (!reloc) { + dest_sec = insn->sec; + dest_off = arch_jump_destination(insn); + } else if (reloc->sym->type == STT_SECTION) { + dest_sec = reloc->sym->sec; + dest_off = arch_dest_reloc_offset(reloc->addend); + } else if (reloc->sym->retpoline_thunk) { + add_retpoline_call(file, insn); + continue; + } else if (reloc->sym->return_thunk) { + add_return_call(file, insn, true); + continue; + } else if (insn->func) { + /* + * External sibling call or internal sibling call with + * STT_FUNC reloc. + */ + add_call_dest(file, insn, reloc->sym, true); + continue; + } else if (reloc->sym->sec->idx) { + dest_sec = reloc->sym->sec; + dest_off = reloc->sym->sym.st_value + + arch_dest_reloc_offset(reloc->addend); + } else { + /* non-func asm code jumping to another file */ + continue; + } + + jump_dest = find_insn(file, dest_sec, dest_off); + if (!jump_dest) { + struct symbol *sym = find_symbol_by_offset(dest_sec, dest_off); + + /* + * This is a special case for retbleed_untrain_ret(). + * It jumps to __x86_return_thunk(), but objtool + * can't find the thunk's starting RET + * instruction, because the RET is also in the + * middle of another instruction. Objtool only + * knows about the outer instruction. + */ + if (sym && sym->embedded_insn) { + add_return_call(file, insn, false); + continue; + } + + WARN_FUNC("can't find jump dest instruction at %s+0x%lx", + insn->sec, insn->offset, dest_sec->name, + dest_off); + return -1; + } + + /* + * Cross-function jump. + */ + if (insn->func && jump_dest->func && + insn->func != jump_dest->func) { + + /* + * For GCC 8+, create parent/child links for any cold + * subfunctions. This is _mostly_ redundant with a + * similar initialization in read_symbols(). + * + * If a function has aliases, we want the *first* such + * function in the symbol table to be the subfunction's + * parent. In that case we overwrite the + * initialization done in read_symbols(). + * + * However this code can't completely replace the + * read_symbols() code because this doesn't detect the + * case where the parent function's only reference to a + * subfunction is through a jump table. + */ + if (!strstr(insn->func->name, ".cold") && + strstr(jump_dest->func->name, ".cold")) { + insn->func->cfunc = jump_dest->func; + jump_dest->func->pfunc = insn->func; + + } else if (!same_function(insn, jump_dest) && + is_first_func_insn(file, jump_dest)) { + /* + * Internal sibling call without reloc or with + * STT_SECTION reloc. + */ + add_call_dest(file, insn, jump_dest->func, true); + continue; + } + } + + insn->jump_dest = jump_dest; + } + + return 0; +} + +static struct symbol *find_call_destination(struct section *sec, unsigned long offset) +{ + struct symbol *call_dest; + + call_dest = find_func_by_offset(sec, offset); + if (!call_dest) + call_dest = find_symbol_by_offset(sec, offset); + + return call_dest; +} + +/* + * Find the destination instructions for all calls. + */ +static int add_call_destinations(struct objtool_file *file) +{ + struct instruction *insn; + unsigned long dest_off; + struct symbol *dest; + struct reloc *reloc; + + for_each_insn(file, insn) { + if (insn->type != INSN_CALL) + continue; + + reloc = insn_reloc(file, insn); + if (!reloc) { + dest_off = arch_jump_destination(insn); + dest = find_call_destination(insn->sec, dest_off); + + add_call_dest(file, insn, dest, false); + + if (insn->ignore) + continue; + + if (!insn->call_dest) { + WARN_FUNC("unannotated intra-function call", insn->sec, insn->offset); + return -1; + } + + if (insn->func && insn->call_dest->type != STT_FUNC) { + WARN_FUNC("unsupported call to non-function", + insn->sec, insn->offset); + return -1; + } + + } else if (reloc->sym->type == STT_SECTION) { + dest_off = arch_dest_reloc_offset(reloc->addend); + dest = find_call_destination(reloc->sym->sec, dest_off); + if (!dest) { + WARN_FUNC("can't find call dest symbol at %s+0x%lx", + insn->sec, insn->offset, + reloc->sym->sec->name, + dest_off); + return -1; + } + + add_call_dest(file, insn, dest, false); + + } else if (reloc->sym->retpoline_thunk) { + add_retpoline_call(file, insn); + + } else + add_call_dest(file, insn, reloc->sym, false); + } + + return 0; +} + +/* + * The .alternatives section requires some extra special care over and above + * other special sections because alternatives are patched in place. + */ +static int handle_group_alt(struct objtool_file *file, + struct special_alt *special_alt, + struct instruction *orig_insn, + struct instruction **new_insn) +{ + struct instruction *last_orig_insn, *last_new_insn = NULL, *insn, *nop = NULL; + struct alt_group *orig_alt_group, *new_alt_group; + unsigned long dest_off; + + + orig_alt_group = malloc(sizeof(*orig_alt_group)); + if (!orig_alt_group) { + WARN("malloc failed"); + return -1; + } + orig_alt_group->cfi = calloc(special_alt->orig_len, + sizeof(struct cfi_state *)); + if (!orig_alt_group->cfi) { + WARN("calloc failed"); + return -1; + } + + last_orig_insn = NULL; + insn = orig_insn; + sec_for_each_insn_from(file, insn) { + if (insn->offset >= special_alt->orig_off + special_alt->orig_len) + break; + + insn->alt_group = orig_alt_group; + last_orig_insn = insn; + } + orig_alt_group->orig_group = NULL; + orig_alt_group->first_insn = orig_insn; + orig_alt_group->last_insn = last_orig_insn; + + + new_alt_group = malloc(sizeof(*new_alt_group)); + if (!new_alt_group) { + WARN("malloc failed"); + return -1; + } + + if (special_alt->new_len < special_alt->orig_len) { + /* + * Insert a fake nop at the end to make the replacement + * alt_group the same size as the original. This is needed to + * allow propagate_alt_cfi() to do its magic. When the last + * instruction affects the stack, the instruction after it (the + * nop) will propagate the new state to the shared CFI array. + */ + nop = malloc(sizeof(*nop)); + if (!nop) { + WARN("malloc failed"); + return -1; + } + memset(nop, 0, sizeof(*nop)); + INIT_LIST_HEAD(&nop->alts); + INIT_LIST_HEAD(&nop->stack_ops); + + nop->sec = special_alt->new_sec; + nop->offset = special_alt->new_off + special_alt->new_len; + nop->len = special_alt->orig_len - special_alt->new_len; + nop->type = INSN_NOP; + nop->func = orig_insn->func; + nop->alt_group = new_alt_group; + nop->ignore = orig_insn->ignore_alts; + } + + if (!special_alt->new_len) { + *new_insn = nop; + goto end; + } + + insn = *new_insn; + sec_for_each_insn_from(file, insn) { + struct reloc *alt_reloc; + + if (insn->offset >= special_alt->new_off + special_alt->new_len) + break; + + last_new_insn = insn; + + insn->ignore = orig_insn->ignore_alts; + insn->func = orig_insn->func; + insn->alt_group = new_alt_group; + + /* + * Since alternative replacement code is copy/pasted by the + * kernel after applying relocations, generally such code can't + * have relative-address relocation references to outside the + * .altinstr_replacement section, unless the arch's + * alternatives code can adjust the relative offsets + * accordingly. + */ + alt_reloc = insn_reloc(file, insn); + if (alt_reloc && + !arch_support_alt_relocation(special_alt, insn, alt_reloc)) { + + WARN_FUNC("unsupported relocation in alternatives section", + insn->sec, insn->offset); + return -1; + } + + if (!is_static_jump(insn)) + continue; + + if (!insn->immediate) + continue; + + dest_off = arch_jump_destination(insn); + if (dest_off == special_alt->new_off + special_alt->new_len) { + insn->jump_dest = next_insn_same_sec(file, last_orig_insn); + if (!insn->jump_dest) { + WARN_FUNC("can't find alternative jump destination", + insn->sec, insn->offset); + return -1; + } + } + } + + if (!last_new_insn) { + WARN_FUNC("can't find last new alternative instruction", + special_alt->new_sec, special_alt->new_off); + return -1; + } + + if (nop) + list_add(&nop->list, &last_new_insn->list); +end: + new_alt_group->orig_group = orig_alt_group; + new_alt_group->first_insn = *new_insn; + new_alt_group->last_insn = nop ? : last_new_insn; + new_alt_group->cfi = orig_alt_group->cfi; + return 0; +} + +/* + * A jump table entry can either convert a nop to a jump or a jump to a nop. + * If the original instruction is a jump, make the alt entry an effective nop + * by just skipping the original instruction. + */ +static int handle_jump_alt(struct objtool_file *file, + struct special_alt *special_alt, + struct instruction *orig_insn, + struct instruction **new_insn) +{ + if (orig_insn->type != INSN_JUMP_UNCONDITIONAL && + orig_insn->type != INSN_NOP) { + + WARN_FUNC("unsupported instruction at jump label", + orig_insn->sec, orig_insn->offset); + return -1; + } + + if (opts.hack_jump_label && special_alt->key_addend & 2) { + struct reloc *reloc = insn_reloc(file, orig_insn); + + if (reloc) { + reloc->type = R_NONE; + elf_write_reloc(file->elf, reloc); + } + elf_write_insn(file->elf, orig_insn->sec, + orig_insn->offset, orig_insn->len, + arch_nop_insn(orig_insn->len)); + orig_insn->type = INSN_NOP; + } + + if (orig_insn->type == INSN_NOP) { + if (orig_insn->len == 2) + file->jl_nop_short++; + else + file->jl_nop_long++; + + return 0; + } + + if (orig_insn->len == 2) + file->jl_short++; + else + file->jl_long++; + + *new_insn = list_next_entry(orig_insn, list); + return 0; +} + +/* + * Read all the special sections which have alternate instructions which can be + * patched in or redirected to at runtime. Each instruction having alternate + * instruction(s) has them added to its insn->alts list, which will be + * traversed in validate_branch(). + */ +static int add_special_section_alts(struct objtool_file *file) +{ + struct list_head special_alts; + struct instruction *orig_insn, *new_insn; + struct special_alt *special_alt, *tmp; + struct alternative *alt; + int ret; + + ret = special_get_alts(file->elf, &special_alts); + if (ret) + return ret; + + list_for_each_entry_safe(special_alt, tmp, &special_alts, list) { + + orig_insn = find_insn(file, special_alt->orig_sec, + special_alt->orig_off); + if (!orig_insn) { + WARN_FUNC("special: can't find orig instruction", + special_alt->orig_sec, special_alt->orig_off); + ret = -1; + goto out; + } + + new_insn = NULL; + if (!special_alt->group || special_alt->new_len) { + new_insn = find_insn(file, special_alt->new_sec, + special_alt->new_off); + if (!new_insn) { + WARN_FUNC("special: can't find new instruction", + special_alt->new_sec, + special_alt->new_off); + ret = -1; + goto out; + } + } + + if (special_alt->group) { + if (!special_alt->orig_len) { + WARN_FUNC("empty alternative entry", + orig_insn->sec, orig_insn->offset); + continue; + } + + ret = handle_group_alt(file, special_alt, orig_insn, + &new_insn); + if (ret) + goto out; + } else if (special_alt->jump_or_nop) { + ret = handle_jump_alt(file, special_alt, orig_insn, + &new_insn); + if (ret) + goto out; + } + + alt = malloc(sizeof(*alt)); + if (!alt) { + WARN("malloc failed"); + ret = -1; + goto out; + } + + alt->insn = new_insn; + alt->skip_orig = special_alt->skip_orig; + orig_insn->ignore_alts |= special_alt->skip_alt; + list_add_tail(&alt->list, &orig_insn->alts); + + list_del(&special_alt->list); + free(special_alt); + } + + if (opts.stats) { + printf("jl\\\tNOP\tJMP\n"); + printf("short:\t%ld\t%ld\n", file->jl_nop_short, file->jl_short); + printf("long:\t%ld\t%ld\n", file->jl_nop_long, file->jl_long); + } + +out: + return ret; +} + +static int add_jump_table(struct objtool_file *file, struct instruction *insn, + struct reloc *table) +{ + struct reloc *reloc = table; + struct instruction *dest_insn; + struct alternative *alt; + struct symbol *pfunc = insn->func->pfunc; + unsigned int prev_offset = 0; + + /* + * Each @reloc is a switch table relocation which points to the target + * instruction. + */ + list_for_each_entry_from(reloc, &table->sec->reloc_list, list) { + + /* Check for the end of the table: */ + if (reloc != table && reloc->jump_table_start) + break; + + /* Make sure the table entries are consecutive: */ + if (prev_offset && reloc->offset != prev_offset + 8) + break; + + /* Detect function pointers from contiguous objects: */ + if (reloc->sym->sec == pfunc->sec && + reloc->addend == pfunc->offset) + break; + + dest_insn = find_insn(file, reloc->sym->sec, reloc->addend); + if (!dest_insn) + break; + + /* Make sure the destination is in the same function: */ + if (!dest_insn->func || dest_insn->func->pfunc != pfunc) + break; + + alt = malloc(sizeof(*alt)); + if (!alt) { + WARN("malloc failed"); + return -1; + } + + alt->insn = dest_insn; + list_add_tail(&alt->list, &insn->alts); + prev_offset = reloc->offset; + } + + if (!prev_offset) { + WARN_FUNC("can't find switch jump table", + insn->sec, insn->offset); + return -1; + } + + return 0; +} + +/* + * find_jump_table() - Given a dynamic jump, find the switch jump table + * associated with it. + */ +static struct reloc *find_jump_table(struct objtool_file *file, + struct symbol *func, + struct instruction *insn) +{ + struct reloc *table_reloc; + struct instruction *dest_insn, *orig_insn = insn; + + /* + * Backward search using the @first_jump_src links, these help avoid + * much of the 'in between' code. Which avoids us getting confused by + * it. + */ + for (; + insn && insn->func && insn->func->pfunc == func; + insn = insn->first_jump_src ?: prev_insn_same_sym(file, insn)) { + + if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC) + break; + + /* allow small jumps within the range */ + if (insn->type == INSN_JUMP_UNCONDITIONAL && + insn->jump_dest && + (insn->jump_dest->offset <= insn->offset || + insn->jump_dest->offset > orig_insn->offset)) + break; + + table_reloc = arch_find_switch_table(file, insn); + if (!table_reloc) + continue; + dest_insn = find_insn(file, table_reloc->sym->sec, table_reloc->addend); + if (!dest_insn || !dest_insn->func || dest_insn->func->pfunc != func) + continue; + + return table_reloc; + } + + return NULL; +} + +/* + * First pass: Mark the head of each jump table so that in the next pass, + * we know when a given jump table ends and the next one starts. + */ +static void mark_func_jump_tables(struct objtool_file *file, + struct symbol *func) +{ + struct instruction *insn, *last = NULL; + struct reloc *reloc; + + func_for_each_insn(file, func, insn) { + if (!last) + last = insn; + + /* + * Store back-pointers for unconditional forward jumps such + * that find_jump_table() can back-track using those and + * avoid some potentially confusing code. + */ + if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest && + insn->offset > last->offset && + insn->jump_dest->offset > insn->offset && + !insn->jump_dest->first_jump_src) { + + insn->jump_dest->first_jump_src = insn; + last = insn->jump_dest; + } + + if (insn->type != INSN_JUMP_DYNAMIC) + continue; + + reloc = find_jump_table(file, func, insn); + if (reloc) { + reloc->jump_table_start = true; + insn->jump_table = reloc; + } + } +} + +static int add_func_jump_tables(struct objtool_file *file, + struct symbol *func) +{ + struct instruction *insn; + int ret; + + func_for_each_insn(file, func, insn) { + if (!insn->jump_table) + continue; + + ret = add_jump_table(file, insn, insn->jump_table); + if (ret) + return ret; + } + + return 0; +} + +/* + * For some switch statements, gcc generates a jump table in the .rodata + * section which contains a list of addresses within the function to jump to. + * This finds these jump tables and adds them to the insn->alts lists. + */ +static int add_jump_table_alts(struct objtool_file *file) +{ + struct section *sec; + struct symbol *func; + int ret; + + if (!file->rodata) + return 0; + + for_each_sec(file, sec) { + list_for_each_entry(func, &sec->symbol_list, list) { + if (func->type != STT_FUNC) + continue; + + mark_func_jump_tables(file, func); + ret = add_func_jump_tables(file, func); + if (ret) + return ret; + } + } + + return 0; +} + +static void set_func_state(struct cfi_state *state) +{ + state->cfa = initial_func_cfi.cfa; + memcpy(&state->regs, &initial_func_cfi.regs, + CFI_NUM_REGS * sizeof(struct cfi_reg)); + state->stack_size = initial_func_cfi.cfa.offset; +} + +static int read_unwind_hints(struct objtool_file *file) +{ + struct cfi_state cfi = init_cfi; + struct section *sec, *relocsec; + struct unwind_hint *hint; + struct instruction *insn; + struct reloc *reloc; + int i; + + sec = find_section_by_name(file->elf, ".discard.unwind_hints"); + if (!sec) + return 0; + + relocsec = sec->reloc; + if (!relocsec) { + WARN("missing .rela.discard.unwind_hints section"); + return -1; + } + + if (sec->sh.sh_size % sizeof(struct unwind_hint)) { + WARN("struct unwind_hint size mismatch"); + return -1; + } + + file->hints = true; + + for (i = 0; i < sec->sh.sh_size / sizeof(struct unwind_hint); i++) { + hint = (struct unwind_hint *)sec->data->d_buf + i; + + reloc = find_reloc_by_dest(file->elf, sec, i * sizeof(*hint)); + if (!reloc) { + WARN("can't find reloc for unwind_hints[%d]", i); + return -1; + } + + insn = find_insn(file, reloc->sym->sec, reloc->addend); + if (!insn) { + WARN("can't find insn for unwind_hints[%d]", i); + return -1; + } + + insn->hint = true; + + if (hint->type == UNWIND_HINT_TYPE_SAVE) { + insn->hint = false; + insn->save = true; + continue; + } + + if (hint->type == UNWIND_HINT_TYPE_RESTORE) { + insn->restore = true; + continue; + } + + if (hint->type == UNWIND_HINT_TYPE_REGS_PARTIAL) { + struct symbol *sym = find_symbol_by_offset(insn->sec, insn->offset); + + if (sym && sym->bind == STB_GLOBAL) { + if (opts.ibt && insn->type != INSN_ENDBR && !insn->noendbr) { + WARN_FUNC("UNWIND_HINT_IRET_REGS without ENDBR", + insn->sec, insn->offset); + } + + insn->entry = 1; + } + } + + if (hint->type == UNWIND_HINT_TYPE_ENTRY) { + hint->type = UNWIND_HINT_TYPE_CALL; + insn->entry = 1; + } + + if (hint->type == UNWIND_HINT_TYPE_FUNC) { + insn->cfi = &func_cfi; + continue; + } + + if (insn->cfi) + cfi = *(insn->cfi); + + if (arch_decode_hint_reg(hint->sp_reg, &cfi.cfa.base)) { + WARN_FUNC("unsupported unwind_hint sp base reg %d", + insn->sec, insn->offset, hint->sp_reg); + return -1; + } + + cfi.cfa.offset = bswap_if_needed(hint->sp_offset); + cfi.type = hint->type; + cfi.end = hint->end; + + insn->cfi = cfi_hash_find_or_add(&cfi); + } + + return 0; +} + +static int read_noendbr_hints(struct objtool_file *file) +{ + struct section *sec; + struct instruction *insn; + struct reloc *reloc; + + sec = find_section_by_name(file->elf, ".rela.discard.noendbr"); + if (!sec) + return 0; + + list_for_each_entry(reloc, &sec->reloc_list, list) { + insn = find_insn(file, reloc->sym->sec, reloc->sym->offset + reloc->addend); + if (!insn) { + WARN("bad .discard.noendbr entry"); + return -1; + } + + insn->noendbr = 1; + } + + return 0; +} + +static int read_retpoline_hints(struct objtool_file *file) +{ + struct section *sec; + struct instruction *insn; + struct reloc *reloc; + + sec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe"); + if (!sec) + return 0; + + list_for_each_entry(reloc, &sec->reloc_list, list) { + if (reloc->sym->type != STT_SECTION) { + WARN("unexpected relocation symbol type in %s", sec->name); + return -1; + } + + insn = find_insn(file, reloc->sym->sec, reloc->addend); + if (!insn) { + WARN("bad .discard.retpoline_safe entry"); + return -1; + } + + if (insn->type != INSN_JUMP_DYNAMIC && + insn->type != INSN_CALL_DYNAMIC && + insn->type != INSN_RETURN && + insn->type != INSN_NOP) { + WARN_FUNC("retpoline_safe hint not an indirect jump/call/ret/nop", + insn->sec, insn->offset); + return -1; + } + + insn->retpoline_safe = true; + } + + return 0; +} + +static int read_instr_hints(struct objtool_file *file) +{ + struct section *sec; + struct instruction *insn; + struct reloc *reloc; + + sec = find_section_by_name(file->elf, ".rela.discard.instr_end"); + if (!sec) + return 0; + + list_for_each_entry(reloc, &sec->reloc_list, list) { + if (reloc->sym->type != STT_SECTION) { + WARN("unexpected relocation symbol type in %s", sec->name); + return -1; + } + + insn = find_insn(file, reloc->sym->sec, reloc->addend); + if (!insn) { + WARN("bad .discard.instr_end entry"); + return -1; + } + + insn->instr--; + } + + sec = find_section_by_name(file->elf, ".rela.discard.instr_begin"); + if (!sec) + return 0; + + list_for_each_entry(reloc, &sec->reloc_list, list) { + if (reloc->sym->type != STT_SECTION) { + WARN("unexpected relocation symbol type in %s", sec->name); + return -1; + } + + insn = find_insn(file, reloc->sym->sec, reloc->addend); + if (!insn) { + WARN("bad .discard.instr_begin entry"); + return -1; + } + + insn->instr++; + } + + return 0; +} + +static int read_intra_function_calls(struct objtool_file *file) +{ + struct instruction *insn; + struct section *sec; + struct reloc *reloc; + + sec = find_section_by_name(file->elf, ".rela.discard.intra_function_calls"); + if (!sec) + return 0; + + list_for_each_entry(reloc, &sec->reloc_list, list) { + unsigned long dest_off; + + if (reloc->sym->type != STT_SECTION) { + WARN("unexpected relocation symbol type in %s", + sec->name); + return -1; + } + + insn = find_insn(file, reloc->sym->sec, reloc->addend); + if (!insn) { + WARN("bad .discard.intra_function_call entry"); + return -1; + } + + if (insn->type != INSN_CALL) { + WARN_FUNC("intra_function_call not a direct call", + insn->sec, insn->offset); + return -1; + } + + /* + * Treat intra-function CALLs as JMPs, but with a stack_op. + * See add_call_destinations(), which strips stack_ops from + * normal CALLs. + */ + insn->type = INSN_JUMP_UNCONDITIONAL; + + dest_off = arch_jump_destination(insn); + insn->jump_dest = find_insn(file, insn->sec, dest_off); + if (!insn->jump_dest) { + WARN_FUNC("can't find call dest at %s+0x%lx", + insn->sec, insn->offset, + insn->sec->name, dest_off); + return -1; + } + } + + return 0; +} + +/* + * Return true if name matches an instrumentation function, where calls to that + * function from noinstr code can safely be removed, but compilers won't do so. + */ +static bool is_profiling_func(const char *name) +{ + /* + * Many compilers cannot disable KCOV with a function attribute. + */ + if (!strncmp(name, "__sanitizer_cov_", 16)) + return true; + + /* + * Some compilers currently do not remove __tsan_func_entry/exit nor + * __tsan_atomic_signal_fence (used for barrier instrumentation) with + * the __no_sanitize_thread attribute, remove them. Once the kernel's + * minimum Clang version is 14.0, this can be removed. + */ + if (!strncmp(name, "__tsan_func_", 12) || + !strcmp(name, "__tsan_atomic_signal_fence")) + return true; + + return false; +} + +static int classify_symbols(struct objtool_file *file) +{ + struct section *sec; + struct symbol *func; + + for_each_sec(file, sec) { + list_for_each_entry(func, &sec->symbol_list, list) { + if (func->bind != STB_GLOBAL) + continue; + + if (!strncmp(func->name, STATIC_CALL_TRAMP_PREFIX_STR, + strlen(STATIC_CALL_TRAMP_PREFIX_STR))) + func->static_call_tramp = true; + + if (arch_is_retpoline(func)) + func->retpoline_thunk = true; + + if (arch_is_rethunk(func)) + func->return_thunk = true; + + if (arch_is_embedded_insn(func)) + func->embedded_insn = true; + + if (!strcmp(func->name, "__fentry__")) + func->fentry = true; + + if (is_profiling_func(func->name)) + func->profiling_func = true; + } + } + + return 0; +} + +static void mark_rodata(struct objtool_file *file) +{ + struct section *sec; + bool found = false; + + /* + * Search for the following rodata sections, each of which can + * potentially contain jump tables: + * + * - .rodata: can contain GCC switch tables + * - .rodata.<func>: same, if -fdata-sections is being used + * - .rodata..c_jump_table: contains C annotated jump tables + * + * .rodata.str1.* sections are ignored; they don't contain jump tables. + */ + for_each_sec(file, sec) { + if (!strncmp(sec->name, ".rodata", 7) && + !strstr(sec->name, ".str1.")) { + sec->rodata = true; + found = true; + } + } + + file->rodata = found; +} + +static int decode_sections(struct objtool_file *file) +{ + int ret; + + mark_rodata(file); + + ret = init_pv_ops(file); + if (ret) + return ret; + + ret = decode_instructions(file); + if (ret) + return ret; + + add_ignores(file); + add_uaccess_safe(file); + + ret = add_ignore_alternatives(file); + if (ret) + return ret; + + /* + * Must be before read_unwind_hints() since that needs insn->noendbr. + */ + ret = read_noendbr_hints(file); + if (ret) + return ret; + + /* + * Must be before add_{jump_call}_destination. + */ + ret = classify_symbols(file); + if (ret) + return ret; + + /* + * Must be before add_jump_destinations(), which depends on 'func' + * being set for alternatives, to enable proper sibling call detection. + */ + ret = add_special_section_alts(file); + if (ret) + return ret; + + ret = add_jump_destinations(file); + if (ret) + return ret; + + /* + * Must be before add_call_destination(); it changes INSN_CALL to + * INSN_JUMP. + */ + ret = read_intra_function_calls(file); + if (ret) + return ret; + + ret = add_call_destinations(file); + if (ret) + return ret; + + /* + * Must be after add_call_destinations() such that it can override + * dead_end_function() marks. + */ + ret = add_dead_ends(file); + if (ret) + return ret; + + ret = add_jump_table_alts(file); + if (ret) + return ret; + + ret = read_unwind_hints(file); + if (ret) + return ret; + + ret = read_retpoline_hints(file); + if (ret) + return ret; + + ret = read_instr_hints(file); + if (ret) + return ret; + + return 0; +} + +static bool is_special_call(struct instruction *insn) +{ + if (insn->type == INSN_CALL) { + struct symbol *dest = insn->call_dest; + + if (!dest) + return false; + + if (dest->fentry || dest->embedded_insn) + return true; + } + + return false; +} + +static bool has_modified_stack_frame(struct instruction *insn, struct insn_state *state) +{ + struct cfi_state *cfi = &state->cfi; + int i; + + if (cfi->cfa.base != initial_func_cfi.cfa.base || cfi->drap) + return true; + + if (cfi->cfa.offset != initial_func_cfi.cfa.offset) + return true; + + if (cfi->stack_size != initial_func_cfi.cfa.offset) + return true; + + for (i = 0; i < CFI_NUM_REGS; i++) { + if (cfi->regs[i].base != initial_func_cfi.regs[i].base || + cfi->regs[i].offset != initial_func_cfi.regs[i].offset) + return true; + } + + return false; +} + +static bool check_reg_frame_pos(const struct cfi_reg *reg, + int expected_offset) +{ + return reg->base == CFI_CFA && + reg->offset == expected_offset; +} + +static bool has_valid_stack_frame(struct insn_state *state) +{ + struct cfi_state *cfi = &state->cfi; + + if (cfi->cfa.base == CFI_BP && + check_reg_frame_pos(&cfi->regs[CFI_BP], -cfi->cfa.offset) && + check_reg_frame_pos(&cfi->regs[CFI_RA], -cfi->cfa.offset + 8)) + return true; + + if (cfi->drap && cfi->regs[CFI_BP].base == CFI_BP) + return true; + + return false; +} + +static int update_cfi_state_regs(struct instruction *insn, + struct cfi_state *cfi, + struct stack_op *op) +{ + struct cfi_reg *cfa = &cfi->cfa; + + if (cfa->base != CFI_SP && cfa->base != CFI_SP_INDIRECT) + return 0; + + /* push */ + if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF) + cfa->offset += 8; + + /* pop */ + if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF) + cfa->offset -= 8; + + /* add immediate to sp */ + if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD && + op->dest.reg == CFI_SP && op->src.reg == CFI_SP) + cfa->offset -= op->src.offset; + + return 0; +} + +static void save_reg(struct cfi_state *cfi, unsigned char reg, int base, int offset) +{ + if (arch_callee_saved_reg(reg) && + cfi->regs[reg].base == CFI_UNDEFINED) { + cfi->regs[reg].base = base; + cfi->regs[reg].offset = offset; + } +} + +static void restore_reg(struct cfi_state *cfi, unsigned char reg) +{ + cfi->regs[reg].base = initial_func_cfi.regs[reg].base; + cfi->regs[reg].offset = initial_func_cfi.regs[reg].offset; +} + +/* + * A note about DRAP stack alignment: + * + * GCC has the concept of a DRAP register, which is used to help keep track of + * the stack pointer when aligning the stack. r10 or r13 is used as the DRAP + * register. The typical DRAP pattern is: + * + * 4c 8d 54 24 08 lea 0x8(%rsp),%r10 + * 48 83 e4 c0 and $0xffffffffffffffc0,%rsp + * 41 ff 72 f8 pushq -0x8(%r10) + * 55 push %rbp + * 48 89 e5 mov %rsp,%rbp + * (more pushes) + * 41 52 push %r10 + * ... + * 41 5a pop %r10 + * (more pops) + * 5d pop %rbp + * 49 8d 62 f8 lea -0x8(%r10),%rsp + * c3 retq + * + * There are some variations in the epilogues, like: + * + * 5b pop %rbx + * 41 5a pop %r10 + * 41 5c pop %r12 + * 41 5d pop %r13 + * 41 5e pop %r14 + * c9 leaveq + * 49 8d 62 f8 lea -0x8(%r10),%rsp + * c3 retq + * + * and: + * + * 4c 8b 55 e8 mov -0x18(%rbp),%r10 + * 48 8b 5d e0 mov -0x20(%rbp),%rbx + * 4c 8b 65 f0 mov -0x10(%rbp),%r12 + * 4c 8b 6d f8 mov -0x8(%rbp),%r13 + * c9 leaveq + * 49 8d 62 f8 lea -0x8(%r10),%rsp + * c3 retq + * + * Sometimes r13 is used as the DRAP register, in which case it's saved and + * restored beforehand: + * + * 41 55 push %r13 + * 4c 8d 6c 24 10 lea 0x10(%rsp),%r13 + * 48 83 e4 f0 and $0xfffffffffffffff0,%rsp + * ... + * 49 8d 65 f0 lea -0x10(%r13),%rsp + * 41 5d pop %r13 + * c3 retq + */ +static int update_cfi_state(struct instruction *insn, + struct instruction *next_insn, + struct cfi_state *cfi, struct stack_op *op) +{ + struct cfi_reg *cfa = &cfi->cfa; + struct cfi_reg *regs = cfi->regs; + + /* stack operations don't make sense with an undefined CFA */ + if (cfa->base == CFI_UNDEFINED) { + if (insn->func) { + WARN_FUNC("undefined stack state", insn->sec, insn->offset); + return -1; + } + return 0; + } + + if (cfi->type == UNWIND_HINT_TYPE_REGS || + cfi->type == UNWIND_HINT_TYPE_REGS_PARTIAL) + return update_cfi_state_regs(insn, cfi, op); + + switch (op->dest.type) { + + case OP_DEST_REG: + switch (op->src.type) { + + case OP_SRC_REG: + if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP && + cfa->base == CFI_SP && + check_reg_frame_pos(®s[CFI_BP], -cfa->offset)) { + + /* mov %rsp, %rbp */ + cfa->base = op->dest.reg; + cfi->bp_scratch = false; + } + + else if (op->src.reg == CFI_SP && + op->dest.reg == CFI_BP && cfi->drap) { + + /* drap: mov %rsp, %rbp */ + regs[CFI_BP].base = CFI_BP; + regs[CFI_BP].offset = -cfi->stack_size; + cfi->bp_scratch = false; + } + + else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) { + + /* + * mov %rsp, %reg + * + * This is needed for the rare case where GCC + * does: + * + * mov %rsp, %rax + * ... + * mov %rax, %rsp + */ + cfi->vals[op->dest.reg].base = CFI_CFA; + cfi->vals[op->dest.reg].offset = -cfi->stack_size; + } + + else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP && + (cfa->base == CFI_BP || cfa->base == cfi->drap_reg)) { + + /* + * mov %rbp, %rsp + * + * Restore the original stack pointer (Clang). + */ + cfi->stack_size = -cfi->regs[CFI_BP].offset; + } + + else if (op->dest.reg == cfa->base) { + + /* mov %reg, %rsp */ + if (cfa->base == CFI_SP && + cfi->vals[op->src.reg].base == CFI_CFA) { + + /* + * This is needed for the rare case + * where GCC does something dumb like: + * + * lea 0x8(%rsp), %rcx + * ... + * mov %rcx, %rsp + */ + cfa->offset = -cfi->vals[op->src.reg].offset; + cfi->stack_size = cfa->offset; + + } else if (cfa->base == CFI_SP && + cfi->vals[op->src.reg].base == CFI_SP_INDIRECT && + cfi->vals[op->src.reg].offset == cfa->offset) { + + /* + * Stack swizzle: + * + * 1: mov %rsp, (%[tos]) + * 2: mov %[tos], %rsp + * ... + * 3: pop %rsp + * + * Where: + * + * 1 - places a pointer to the previous + * stack at the Top-of-Stack of the + * new stack. + * + * 2 - switches to the new stack. + * + * 3 - pops the Top-of-Stack to restore + * the original stack. + * + * Note: we set base to SP_INDIRECT + * here and preserve offset. Therefore + * when the unwinder reaches ToS it + * will dereference SP and then add the + * offset to find the next frame, IOW: + * (%rsp) + offset. + */ + cfa->base = CFI_SP_INDIRECT; + + } else { + cfa->base = CFI_UNDEFINED; + cfa->offset = 0; + } + } + + else if (op->dest.reg == CFI_SP && + cfi->vals[op->src.reg].base == CFI_SP_INDIRECT && + cfi->vals[op->src.reg].offset == cfa->offset) { + + /* + * The same stack swizzle case 2) as above. But + * because we can't change cfa->base, case 3) + * will become a regular POP. Pretend we're a + * PUSH so things don't go unbalanced. + */ + cfi->stack_size += 8; + } + + + break; + + case OP_SRC_ADD: + if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) { + + /* add imm, %rsp */ + cfi->stack_size -= op->src.offset; + if (cfa->base == CFI_SP) + cfa->offset -= op->src.offset; + break; + } + + if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) { + + /* lea disp(%rbp), %rsp */ + cfi->stack_size = -(op->src.offset + regs[CFI_BP].offset); + break; + } + + if (op->src.reg == CFI_SP && cfa->base == CFI_SP) { + + /* drap: lea disp(%rsp), %drap */ + cfi->drap_reg = op->dest.reg; + + /* + * lea disp(%rsp), %reg + * + * This is needed for the rare case where GCC + * does something dumb like: + * + * lea 0x8(%rsp), %rcx + * ... + * mov %rcx, %rsp + */ + cfi->vals[op->dest.reg].base = CFI_CFA; + cfi->vals[op->dest.reg].offset = \ + -cfi->stack_size + op->src.offset; + + break; + } + + if (cfi->drap && op->dest.reg == CFI_SP && + op->src.reg == cfi->drap_reg) { + + /* drap: lea disp(%drap), %rsp */ + cfa->base = CFI_SP; + cfa->offset = cfi->stack_size = -op->src.offset; + cfi->drap_reg = CFI_UNDEFINED; + cfi->drap = false; + break; + } + + if (op->dest.reg == cfi->cfa.base && !(next_insn && next_insn->hint)) { + WARN_FUNC("unsupported stack register modification", + insn->sec, insn->offset); + return -1; + } + + break; + + case OP_SRC_AND: + if (op->dest.reg != CFI_SP || + (cfi->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) || + (cfi->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) { + WARN_FUNC("unsupported stack pointer realignment", + insn->sec, insn->offset); + return -1; + } + + if (cfi->drap_reg != CFI_UNDEFINED) { + /* drap: and imm, %rsp */ + cfa->base = cfi->drap_reg; + cfa->offset = cfi->stack_size = 0; + cfi->drap = true; + } + + /* + * Older versions of GCC (4.8ish) realign the stack + * without DRAP, with a frame pointer. + */ + + break; + + case OP_SRC_POP: + case OP_SRC_POPF: + if (op->dest.reg == CFI_SP && cfa->base == CFI_SP_INDIRECT) { + + /* pop %rsp; # restore from a stack swizzle */ + cfa->base = CFI_SP; + break; + } + + if (!cfi->drap && op->dest.reg == cfa->base) { + + /* pop %rbp */ + cfa->base = CFI_SP; + } + + if (cfi->drap && cfa->base == CFI_BP_INDIRECT && + op->dest.reg == cfi->drap_reg && + cfi->drap_offset == -cfi->stack_size) { + + /* drap: pop %drap */ + cfa->base = cfi->drap_reg; + cfa->offset = 0; + cfi->drap_offset = -1; + + } else if (cfi->stack_size == -regs[op->dest.reg].offset) { + + /* pop %reg */ + restore_reg(cfi, op->dest.reg); + } + + cfi->stack_size -= 8; + if (cfa->base == CFI_SP) + cfa->offset -= 8; + + break; + + case OP_SRC_REG_INDIRECT: + if (!cfi->drap && op->dest.reg == cfa->base && + op->dest.reg == CFI_BP) { + + /* mov disp(%rsp), %rbp */ + cfa->base = CFI_SP; + cfa->offset = cfi->stack_size; + } + + if (cfi->drap && op->src.reg == CFI_BP && + op->src.offset == cfi->drap_offset) { + + /* drap: mov disp(%rbp), %drap */ + cfa->base = cfi->drap_reg; + cfa->offset = 0; + cfi->drap_offset = -1; + } + + if (cfi->drap && op->src.reg == CFI_BP && + op->src.offset == regs[op->dest.reg].offset) { + + /* drap: mov disp(%rbp), %reg */ + restore_reg(cfi, op->dest.reg); + + } else if (op->src.reg == cfa->base && + op->src.offset == regs[op->dest.reg].offset + cfa->offset) { + + /* mov disp(%rbp), %reg */ + /* mov disp(%rsp), %reg */ + restore_reg(cfi, op->dest.reg); + + } else if (op->src.reg == CFI_SP && + op->src.offset == regs[op->dest.reg].offset + cfi->stack_size) { + + /* mov disp(%rsp), %reg */ + restore_reg(cfi, op->dest.reg); + } + + break; + + default: + WARN_FUNC("unknown stack-related instruction", + insn->sec, insn->offset); + return -1; + } + + break; + + case OP_DEST_PUSH: + case OP_DEST_PUSHF: + cfi->stack_size += 8; + if (cfa->base == CFI_SP) + cfa->offset += 8; + + if (op->src.type != OP_SRC_REG) + break; + + if (cfi->drap) { + if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) { + + /* drap: push %drap */ + cfa->base = CFI_BP_INDIRECT; + cfa->offset = -cfi->stack_size; + + /* save drap so we know when to restore it */ + cfi->drap_offset = -cfi->stack_size; + + } else if (op->src.reg == CFI_BP && cfa->base == cfi->drap_reg) { + + /* drap: push %rbp */ + cfi->stack_size = 0; + + } else { + + /* drap: push %reg */ + save_reg(cfi, op->src.reg, CFI_BP, -cfi->stack_size); + } + + } else { + + /* push %reg */ + save_reg(cfi, op->src.reg, CFI_CFA, -cfi->stack_size); + } + + /* detect when asm code uses rbp as a scratch register */ + if (opts.stackval && insn->func && op->src.reg == CFI_BP && + cfa->base != CFI_BP) + cfi->bp_scratch = true; + break; + + case OP_DEST_REG_INDIRECT: + + if (cfi->drap) { + if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) { + + /* drap: mov %drap, disp(%rbp) */ + cfa->base = CFI_BP_INDIRECT; + cfa->offset = op->dest.offset; + + /* save drap offset so we know when to restore it */ + cfi->drap_offset = op->dest.offset; + } else { + + /* drap: mov reg, disp(%rbp) */ + save_reg(cfi, op->src.reg, CFI_BP, op->dest.offset); + } + + } else if (op->dest.reg == cfa->base) { + + /* mov reg, disp(%rbp) */ + /* mov reg, disp(%rsp) */ + save_reg(cfi, op->src.reg, CFI_CFA, + op->dest.offset - cfi->cfa.offset); + + } else if (op->dest.reg == CFI_SP) { + + /* mov reg, disp(%rsp) */ + save_reg(cfi, op->src.reg, CFI_CFA, + op->dest.offset - cfi->stack_size); + + } else if (op->src.reg == CFI_SP && op->dest.offset == 0) { + + /* mov %rsp, (%reg); # setup a stack swizzle. */ + cfi->vals[op->dest.reg].base = CFI_SP_INDIRECT; + cfi->vals[op->dest.reg].offset = cfa->offset; + } + + break; + + case OP_DEST_MEM: + if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) { + WARN_FUNC("unknown stack-related memory operation", + insn->sec, insn->offset); + return -1; + } + + /* pop mem */ + cfi->stack_size -= 8; + if (cfa->base == CFI_SP) + cfa->offset -= 8; + + break; + + default: + WARN_FUNC("unknown stack-related instruction", + insn->sec, insn->offset); + return -1; + } + + return 0; +} + +/* + * The stack layouts of alternatives instructions can sometimes diverge when + * they have stack modifications. That's fine as long as the potential stack + * layouts don't conflict at any given potential instruction boundary. + * + * Flatten the CFIs of the different alternative code streams (both original + * and replacement) into a single shared CFI array which can be used to detect + * conflicts and nicely feed a linear array of ORC entries to the unwinder. + */ +static int propagate_alt_cfi(struct objtool_file *file, struct instruction *insn) +{ + struct cfi_state **alt_cfi; + int group_off; + + if (!insn->alt_group) + return 0; + + if (!insn->cfi) { + WARN("CFI missing"); + return -1; + } + + alt_cfi = insn->alt_group->cfi; + group_off = insn->offset - insn->alt_group->first_insn->offset; + + if (!alt_cfi[group_off]) { + alt_cfi[group_off] = insn->cfi; + } else { + if (cficmp(alt_cfi[group_off], insn->cfi)) { + WARN_FUNC("stack layout conflict in alternatives", + insn->sec, insn->offset); + return -1; + } + } + + return 0; +} + +static int handle_insn_ops(struct instruction *insn, + struct instruction *next_insn, + struct insn_state *state) +{ + struct stack_op *op; + + list_for_each_entry(op, &insn->stack_ops, list) { + + if (update_cfi_state(insn, next_insn, &state->cfi, op)) + return 1; + + if (!insn->alt_group) + continue; + + if (op->dest.type == OP_DEST_PUSHF) { + if (!state->uaccess_stack) { + state->uaccess_stack = 1; + } else if (state->uaccess_stack >> 31) { + WARN_FUNC("PUSHF stack exhausted", + insn->sec, insn->offset); + return 1; + } + state->uaccess_stack <<= 1; + state->uaccess_stack |= state->uaccess; + } + + if (op->src.type == OP_SRC_POPF) { + if (state->uaccess_stack) { + state->uaccess = state->uaccess_stack & 1; + state->uaccess_stack >>= 1; + if (state->uaccess_stack == 1) + state->uaccess_stack = 0; + } + } + } + + return 0; +} + +static bool insn_cfi_match(struct instruction *insn, struct cfi_state *cfi2) +{ + struct cfi_state *cfi1 = insn->cfi; + int i; + + if (!cfi1) { + WARN("CFI missing"); + return false; + } + + if (memcmp(&cfi1->cfa, &cfi2->cfa, sizeof(cfi1->cfa))) { + + WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d", + insn->sec, insn->offset, + cfi1->cfa.base, cfi1->cfa.offset, + cfi2->cfa.base, cfi2->cfa.offset); + + } else if (memcmp(&cfi1->regs, &cfi2->regs, sizeof(cfi1->regs))) { + for (i = 0; i < CFI_NUM_REGS; i++) { + if (!memcmp(&cfi1->regs[i], &cfi2->regs[i], + sizeof(struct cfi_reg))) + continue; + + WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d", + insn->sec, insn->offset, + i, cfi1->regs[i].base, cfi1->regs[i].offset, + i, cfi2->regs[i].base, cfi2->regs[i].offset); + break; + } + + } else if (cfi1->type != cfi2->type) { + + WARN_FUNC("stack state mismatch: type1=%d type2=%d", + insn->sec, insn->offset, cfi1->type, cfi2->type); + + } else if (cfi1->drap != cfi2->drap || + (cfi1->drap && cfi1->drap_reg != cfi2->drap_reg) || + (cfi1->drap && cfi1->drap_offset != cfi2->drap_offset)) { + + WARN_FUNC("stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)", + insn->sec, insn->offset, + cfi1->drap, cfi1->drap_reg, cfi1->drap_offset, + cfi2->drap, cfi2->drap_reg, cfi2->drap_offset); + + } else + return true; + + return false; +} + +static inline bool func_uaccess_safe(struct symbol *func) +{ + if (func) + return func->uaccess_safe; + + return false; +} + +static inline const char *call_dest_name(struct instruction *insn) +{ + static char pvname[19]; + struct reloc *rel; + int idx; + + if (insn->call_dest) + return insn->call_dest->name; + + rel = insn_reloc(NULL, insn); + if (rel && !strcmp(rel->sym->name, "pv_ops")) { + idx = (rel->addend / sizeof(void *)); + snprintf(pvname, sizeof(pvname), "pv_ops[%d]", idx); + return pvname; + } + + return "{dynamic}"; +} + +static bool pv_call_dest(struct objtool_file *file, struct instruction *insn) +{ + struct symbol *target; + struct reloc *rel; + int idx; + + rel = insn_reloc(file, insn); + if (!rel || strcmp(rel->sym->name, "pv_ops")) + return false; + + idx = (arch_dest_reloc_offset(rel->addend) / sizeof(void *)); + + if (file->pv_ops[idx].clean) + return true; + + file->pv_ops[idx].clean = true; + + list_for_each_entry(target, &file->pv_ops[idx].targets, pv_target) { + if (!target->sec->noinstr) { + WARN("pv_ops[%d]: %s", idx, target->name); + file->pv_ops[idx].clean = false; + } + } + + return file->pv_ops[idx].clean; +} + +static inline bool noinstr_call_dest(struct objtool_file *file, + struct instruction *insn, + struct symbol *func) +{ + /* + * We can't deal with indirect function calls at present; + * assume they're instrumented. + */ + if (!func) { + if (file->pv_ops) + return pv_call_dest(file, insn); + + return false; + } + + /* + * If the symbol is from a noinstr section; we good. + */ + if (func->sec->noinstr) + return true; + + /* + * The __ubsan_handle_*() calls are like WARN(), they only happen when + * something 'BAD' happened. At the risk of taking the machine down, + * let them proceed to get the message out. + */ + if (!strncmp(func->name, "__ubsan_handle_", 15)) + return true; + + return false; +} + +static int validate_call(struct objtool_file *file, + struct instruction *insn, + struct insn_state *state) +{ + if (state->noinstr && state->instr <= 0 && + !noinstr_call_dest(file, insn, insn->call_dest)) { + WARN_FUNC("call to %s() leaves .noinstr.text section", + insn->sec, insn->offset, call_dest_name(insn)); + return 1; + } + + if (state->uaccess && !func_uaccess_safe(insn->call_dest)) { + WARN_FUNC("call to %s() with UACCESS enabled", + insn->sec, insn->offset, call_dest_name(insn)); + return 1; + } + + if (state->df) { + WARN_FUNC("call to %s() with DF set", + insn->sec, insn->offset, call_dest_name(insn)); + return 1; + } + + return 0; +} + +static int validate_sibling_call(struct objtool_file *file, + struct instruction *insn, + struct insn_state *state) +{ + if (has_modified_stack_frame(insn, state)) { + WARN_FUNC("sibling call from callable instruction with modified stack frame", + insn->sec, insn->offset); + return 1; + } + + return validate_call(file, insn, state); +} + +static int validate_return(struct symbol *func, struct instruction *insn, struct insn_state *state) +{ + if (state->noinstr && state->instr > 0) { + WARN_FUNC("return with instrumentation enabled", + insn->sec, insn->offset); + return 1; + } + + if (state->uaccess && !func_uaccess_safe(func)) { + WARN_FUNC("return with UACCESS enabled", + insn->sec, insn->offset); + return 1; + } + + if (!state->uaccess && func_uaccess_safe(func)) { + WARN_FUNC("return with UACCESS disabled from a UACCESS-safe function", + insn->sec, insn->offset); + return 1; + } + + if (state->df) { + WARN_FUNC("return with DF set", + insn->sec, insn->offset); + return 1; + } + + if (func && has_modified_stack_frame(insn, state)) { + WARN_FUNC("return with modified stack frame", + insn->sec, insn->offset); + return 1; + } + + if (state->cfi.bp_scratch) { + WARN_FUNC("BP used as a scratch register", + insn->sec, insn->offset); + return 1; + } + + return 0; +} + +static struct instruction *next_insn_to_validate(struct objtool_file *file, + struct instruction *insn) +{ + struct alt_group *alt_group = insn->alt_group; + + /* + * Simulate the fact that alternatives are patched in-place. When the + * end of a replacement alt_group is reached, redirect objtool flow to + * the end of the original alt_group. + */ + if (alt_group && insn == alt_group->last_insn && alt_group->orig_group) + return next_insn_same_sec(file, alt_group->orig_group->last_insn); + + return next_insn_same_sec(file, insn); +} + +/* + * Follow the branch starting at the given instruction, and recursively follow + * any other branches (jumps). Meanwhile, track the frame pointer state at + * each instruction and validate all the rules described in + * tools/objtool/Documentation/objtool.txt. + */ +static int validate_branch(struct objtool_file *file, struct symbol *func, + struct instruction *insn, struct insn_state state) +{ + struct alternative *alt; + struct instruction *next_insn, *prev_insn = NULL; + struct section *sec; + u8 visited; + int ret; + + sec = insn->sec; + + while (1) { + next_insn = next_insn_to_validate(file, insn); + + if (func && insn->func && func != insn->func->pfunc) { + /* Ignore KCFI type preambles, which always fall through */ + if (!strncmp(func->name, "__cfi_", 6)) + return 0; + + WARN("%s() falls through to next function %s()", + func->name, insn->func->name); + return 1; + } + + if (func && insn->ignore) { + WARN_FUNC("BUG: why am I validating an ignored function?", + sec, insn->offset); + return 1; + } + + visited = VISITED_BRANCH << state.uaccess; + if (insn->visited & VISITED_BRANCH_MASK) { + if (!insn->hint && !insn_cfi_match(insn, &state.cfi)) + return 1; + + if (insn->visited & visited) + return 0; + } else { + nr_insns_visited++; + } + + if (state.noinstr) + state.instr += insn->instr; + + if (insn->hint) { + if (insn->restore) { + struct instruction *save_insn, *i; + + i = insn; + save_insn = NULL; + + sym_for_each_insn_continue_reverse(file, func, i) { + if (i->save) { + save_insn = i; + break; + } + } + + if (!save_insn) { + WARN_FUNC("no corresponding CFI save for CFI restore", + sec, insn->offset); + return 1; + } + + if (!save_insn->visited) { + WARN_FUNC("objtool isn't smart enough to handle this CFI save/restore combo", + sec, insn->offset); + return 1; + } + + insn->cfi = save_insn->cfi; + nr_cfi_reused++; + } + + state.cfi = *insn->cfi; + } else { + /* XXX track if we actually changed state.cfi */ + + if (prev_insn && !cficmp(prev_insn->cfi, &state.cfi)) { + insn->cfi = prev_insn->cfi; + nr_cfi_reused++; + } else { + insn->cfi = cfi_hash_find_or_add(&state.cfi); + } + } + + insn->visited |= visited; + + if (propagate_alt_cfi(file, insn)) + return 1; + + if (!insn->ignore_alts && !list_empty(&insn->alts)) { + bool skip_orig = false; + + list_for_each_entry(alt, &insn->alts, list) { + if (alt->skip_orig) + skip_orig = true; + + ret = validate_branch(file, func, alt->insn, state); + if (ret) { + if (opts.backtrace) + BT_FUNC("(alt)", insn); + return ret; + } + } + + if (skip_orig) + return 0; + } + + if (handle_insn_ops(insn, next_insn, &state)) + return 1; + + switch (insn->type) { + + case INSN_RETURN: + return validate_return(func, insn, &state); + + case INSN_CALL: + case INSN_CALL_DYNAMIC: + ret = validate_call(file, insn, &state); + if (ret) + return ret; + + if (opts.stackval && func && !is_special_call(insn) && + !has_valid_stack_frame(&state)) { + WARN_FUNC("call without frame pointer save/setup", + sec, insn->offset); + return 1; + } + + if (insn->dead_end) + return 0; + + break; + + case INSN_JUMP_CONDITIONAL: + case INSN_JUMP_UNCONDITIONAL: + if (is_sibling_call(insn)) { + ret = validate_sibling_call(file, insn, &state); + if (ret) + return ret; + + } else if (insn->jump_dest) { + ret = validate_branch(file, func, + insn->jump_dest, state); + if (ret) { + if (opts.backtrace) + BT_FUNC("(branch)", insn); + return ret; + } + } + + if (insn->type == INSN_JUMP_UNCONDITIONAL) + return 0; + + break; + + case INSN_JUMP_DYNAMIC: + case INSN_JUMP_DYNAMIC_CONDITIONAL: + if (is_sibling_call(insn)) { + ret = validate_sibling_call(file, insn, &state); + if (ret) + return ret; + } + + if (insn->type == INSN_JUMP_DYNAMIC) + return 0; + + break; + + case INSN_CONTEXT_SWITCH: + if (func && (!next_insn || !next_insn->hint)) { + WARN_FUNC("unsupported instruction in callable function", + sec, insn->offset); + return 1; + } + return 0; + + case INSN_STAC: + if (state.uaccess) { + WARN_FUNC("recursive UACCESS enable", sec, insn->offset); + return 1; + } + + state.uaccess = true; + break; + + case INSN_CLAC: + if (!state.uaccess && func) { + WARN_FUNC("redundant UACCESS disable", sec, insn->offset); + return 1; + } + + if (func_uaccess_safe(func) && !state.uaccess_stack) { + WARN_FUNC("UACCESS-safe disables UACCESS", sec, insn->offset); + return 1; + } + + state.uaccess = false; + break; + + case INSN_STD: + if (state.df) { + WARN_FUNC("recursive STD", sec, insn->offset); + return 1; + } + + state.df = true; + break; + + case INSN_CLD: + if (!state.df && func) { + WARN_FUNC("redundant CLD", sec, insn->offset); + return 1; + } + + state.df = false; + break; + + default: + break; + } + + if (insn->dead_end) + return 0; + + if (!next_insn) { + if (state.cfi.cfa.base == CFI_UNDEFINED) + return 0; + WARN("%s: unexpected end of section", sec->name); + return 1; + } + + prev_insn = insn; + insn = next_insn; + } + + return 0; +} + +static int validate_unwind_hints(struct objtool_file *file, struct section *sec) +{ + struct instruction *insn; + struct insn_state state; + int ret, warnings = 0; + + if (!file->hints) + return 0; + + init_insn_state(file, &state, sec); + + if (sec) { + insn = find_insn(file, sec, 0); + if (!insn) + return 0; + } else { + insn = list_first_entry(&file->insn_list, typeof(*insn), list); + } + + while (&insn->list != &file->insn_list && (!sec || insn->sec == sec)) { + if (insn->hint && !insn->visited && !insn->ignore) { + ret = validate_branch(file, insn->func, insn, state); + if (ret && opts.backtrace) + BT_FUNC("<=== (hint)", insn); + warnings += ret; + } + + insn = list_next_entry(insn, list); + } + + return warnings; +} + +/* + * Validate rethunk entry constraint: must untrain RET before the first RET. + * + * Follow every branch (intra-function) and ensure ANNOTATE_UNRET_END comes + * before an actual RET instruction. + */ +static int validate_entry(struct objtool_file *file, struct instruction *insn) +{ + struct instruction *next, *dest; + int ret, warnings = 0; + + for (;;) { + next = next_insn_to_validate(file, insn); + + if (insn->visited & VISITED_ENTRY) + return 0; + + insn->visited |= VISITED_ENTRY; + + if (!insn->ignore_alts && !list_empty(&insn->alts)) { + struct alternative *alt; + bool skip_orig = false; + + list_for_each_entry(alt, &insn->alts, list) { + if (alt->skip_orig) + skip_orig = true; + + ret = validate_entry(file, alt->insn); + if (ret) { + if (opts.backtrace) + BT_FUNC("(alt)", insn); + return ret; + } + } + + if (skip_orig) + return 0; + } + + switch (insn->type) { + + case INSN_CALL_DYNAMIC: + case INSN_JUMP_DYNAMIC: + case INSN_JUMP_DYNAMIC_CONDITIONAL: + WARN_FUNC("early indirect call", insn->sec, insn->offset); + return 1; + + case INSN_JUMP_UNCONDITIONAL: + case INSN_JUMP_CONDITIONAL: + if (!is_sibling_call(insn)) { + if (!insn->jump_dest) { + WARN_FUNC("unresolved jump target after linking?!?", + insn->sec, insn->offset); + return -1; + } + ret = validate_entry(file, insn->jump_dest); + if (ret) { + if (opts.backtrace) { + BT_FUNC("(branch%s)", insn, + insn->type == INSN_JUMP_CONDITIONAL ? "-cond" : ""); + } + return ret; + } + + if (insn->type == INSN_JUMP_UNCONDITIONAL) + return 0; + + break; + } + + /* fallthrough */ + case INSN_CALL: + dest = find_insn(file, insn->call_dest->sec, + insn->call_dest->offset); + if (!dest) { + WARN("Unresolved function after linking!?: %s", + insn->call_dest->name); + return -1; + } + + ret = validate_entry(file, dest); + if (ret) { + if (opts.backtrace) + BT_FUNC("(call)", insn); + return ret; + } + /* + * If a call returns without error, it must have seen UNTRAIN_RET. + * Therefore any non-error return is a success. + */ + return 0; + + case INSN_RETURN: + WARN_FUNC("RET before UNTRAIN", insn->sec, insn->offset); + return 1; + + case INSN_NOP: + if (insn->retpoline_safe) + return 0; + break; + + default: + break; + } + + if (!next) { + WARN_FUNC("teh end!", insn->sec, insn->offset); + return -1; + } + insn = next; + } + + return warnings; +} + +/* + * Validate that all branches starting at 'insn->entry' encounter UNRET_END + * before RET. + */ +static int validate_unret(struct objtool_file *file) +{ + struct instruction *insn; + int ret, warnings = 0; + + for_each_insn(file, insn) { + if (!insn->entry) + continue; + + ret = validate_entry(file, insn); + if (ret < 0) { + WARN_FUNC("Failed UNRET validation", insn->sec, insn->offset); + return ret; + } + warnings += ret; + } + + return warnings; +} + +static int validate_retpoline(struct objtool_file *file) +{ + struct instruction *insn; + int warnings = 0; + + for_each_insn(file, insn) { + if (insn->type != INSN_JUMP_DYNAMIC && + insn->type != INSN_CALL_DYNAMIC && + insn->type != INSN_RETURN) + continue; + + if (insn->retpoline_safe) + continue; + + /* + * .init.text code is ran before userspace and thus doesn't + * strictly need retpolines, except for modules which are + * loaded late, they very much do need retpoline in their + * .init.text + */ + if (!strcmp(insn->sec->name, ".init.text") && !opts.module) + continue; + + if (insn->type == INSN_RETURN) { + if (opts.rethunk) { + WARN_FUNC("'naked' return found in RETHUNK build", + insn->sec, insn->offset); + } else + continue; + } else { + WARN_FUNC("indirect %s found in RETPOLINE build", + insn->sec, insn->offset, + insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call"); + } + + warnings++; + } + + return warnings; +} + +static bool is_kasan_insn(struct instruction *insn) +{ + return (insn->type == INSN_CALL && + !strcmp(insn->call_dest->name, "__asan_handle_no_return")); +} + +static bool is_ubsan_insn(struct instruction *insn) +{ + return (insn->type == INSN_CALL && + !strcmp(insn->call_dest->name, + "__ubsan_handle_builtin_unreachable")); +} + +static bool ignore_unreachable_insn(struct objtool_file *file, struct instruction *insn) +{ + int i; + struct instruction *prev_insn; + + if (insn->ignore || insn->type == INSN_NOP || insn->type == INSN_TRAP) + return true; + + /* + * Ignore alternative replacement instructions. This can happen + * when a whitelisted function uses one of the ALTERNATIVE macros. + */ + if (!strcmp(insn->sec->name, ".altinstr_replacement") || + !strcmp(insn->sec->name, ".altinstr_aux")) + return true; + + /* + * Whole archive runs might encounter dead code from weak symbols. + * This is where the linker will have dropped the weak symbol in + * favour of a regular symbol, but leaves the code in place. + * + * In this case we'll find a piece of code (whole function) that is not + * covered by a !section symbol. Ignore them. + */ + if (opts.link && !insn->func) { + int size = find_symbol_hole_containing(insn->sec, insn->offset); + unsigned long end = insn->offset + size; + + if (!size) /* not a hole */ + return false; + + if (size < 0) /* hole until the end */ + return true; + + sec_for_each_insn_continue(file, insn) { + /* + * If we reach a visited instruction at or before the + * end of the hole, ignore the unreachable. + */ + if (insn->visited) + return true; + + if (insn->offset >= end) + break; + + /* + * If this hole jumps to a .cold function, mark it ignore too. + */ + if (insn->jump_dest && insn->jump_dest->func && + strstr(insn->jump_dest->func->name, ".cold")) { + struct instruction *dest = insn->jump_dest; + func_for_each_insn(file, dest->func, dest) + dest->ignore = true; + } + } + + return false; + } + + if (!insn->func) + return false; + + if (insn->func->static_call_tramp) + return true; + + /* + * CONFIG_UBSAN_TRAP inserts a UD2 when it sees + * __builtin_unreachable(). The BUG() macro has an unreachable() after + * the UD2, which causes GCC's undefined trap logic to emit another UD2 + * (or occasionally a JMP to UD2). + * + * It may also insert a UD2 after calling a __noreturn function. + */ + prev_insn = list_prev_entry(insn, list); + if ((prev_insn->dead_end || dead_end_function(file, prev_insn->call_dest)) && + (insn->type == INSN_BUG || + (insn->type == INSN_JUMP_UNCONDITIONAL && + insn->jump_dest && insn->jump_dest->type == INSN_BUG))) + return true; + + /* + * Check if this (or a subsequent) instruction is related to + * CONFIG_UBSAN or CONFIG_KASAN. + * + * End the search at 5 instructions to avoid going into the weeds. + */ + for (i = 0; i < 5; i++) { + + if (is_kasan_insn(insn) || is_ubsan_insn(insn)) + return true; + + if (insn->type == INSN_JUMP_UNCONDITIONAL) { + if (insn->jump_dest && + insn->jump_dest->func == insn->func) { + insn = insn->jump_dest; + continue; + } + + break; + } + + if (insn->offset + insn->len >= insn->func->offset + insn->func->len) + break; + + insn = list_next_entry(insn, list); + } + + return false; +} + +static int validate_symbol(struct objtool_file *file, struct section *sec, + struct symbol *sym, struct insn_state *state) +{ + struct instruction *insn; + int ret; + + if (!sym->len) { + WARN("%s() is missing an ELF size annotation", sym->name); + return 1; + } + + if (sym->pfunc != sym || sym->alias != sym) + return 0; + + insn = find_insn(file, sec, sym->offset); + if (!insn || insn->ignore || insn->visited) + return 0; + + state->uaccess = sym->uaccess_safe; + + ret = validate_branch(file, insn->func, insn, *state); + if (ret && opts.backtrace) + BT_FUNC("<=== (sym)", insn); + return ret; +} + +static int validate_section(struct objtool_file *file, struct section *sec) +{ + struct insn_state state; + struct symbol *func; + int warnings = 0; + + list_for_each_entry(func, &sec->symbol_list, list) { + if (func->type != STT_FUNC) + continue; + + init_insn_state(file, &state, sec); + set_func_state(&state.cfi); + + warnings += validate_symbol(file, sec, func, &state); + } + + return warnings; +} + +static int validate_noinstr_sections(struct objtool_file *file) +{ + struct section *sec; + int warnings = 0; + + sec = find_section_by_name(file->elf, ".noinstr.text"); + if (sec) { + warnings += validate_section(file, sec); + warnings += validate_unwind_hints(file, sec); + } + + sec = find_section_by_name(file->elf, ".entry.text"); + if (sec) { + warnings += validate_section(file, sec); + warnings += validate_unwind_hints(file, sec); + } + + return warnings; +} + +static int validate_functions(struct objtool_file *file) +{ + struct section *sec; + int warnings = 0; + + for_each_sec(file, sec) { + if (!(sec->sh.sh_flags & SHF_EXECINSTR)) + continue; + + warnings += validate_section(file, sec); + } + + return warnings; +} + +static void mark_endbr_used(struct instruction *insn) +{ + if (!list_empty(&insn->call_node)) + list_del_init(&insn->call_node); +} + +static int validate_ibt_insn(struct objtool_file *file, struct instruction *insn) +{ + struct instruction *dest; + struct reloc *reloc; + unsigned long off; + int warnings = 0; + + /* + * Looking for function pointer load relocations. Ignore + * direct/indirect branches: + */ + switch (insn->type) { + case INSN_CALL: + case INSN_CALL_DYNAMIC: + case INSN_JUMP_CONDITIONAL: + case INSN_JUMP_UNCONDITIONAL: + case INSN_JUMP_DYNAMIC: + case INSN_JUMP_DYNAMIC_CONDITIONAL: + case INSN_RETURN: + case INSN_NOP: + return 0; + default: + break; + } + + for (reloc = insn_reloc(file, insn); + reloc; + reloc = find_reloc_by_dest_range(file->elf, insn->sec, + reloc->offset + 1, + (insn->offset + insn->len) - (reloc->offset + 1))) { + + /* + * static_call_update() references the trampoline, which + * doesn't have (or need) ENDBR. Skip warning in that case. + */ + if (reloc->sym->static_call_tramp) + continue; + + off = reloc->sym->offset; + if (reloc->type == R_X86_64_PC32 || reloc->type == R_X86_64_PLT32) + off += arch_dest_reloc_offset(reloc->addend); + else + off += reloc->addend; + + dest = find_insn(file, reloc->sym->sec, off); + if (!dest) + continue; + + if (dest->type == INSN_ENDBR) { + mark_endbr_used(dest); + continue; + } + + if (dest->func && dest->func == insn->func) { + /* + * Anything from->to self is either _THIS_IP_ or + * IRET-to-self. + * + * There is no sane way to annotate _THIS_IP_ since the + * compiler treats the relocation as a constant and is + * happy to fold in offsets, skewing any annotation we + * do, leading to vast amounts of false-positives. + * + * There's also compiler generated _THIS_IP_ through + * KCOV and such which we have no hope of annotating. + * + * As such, blanket accept self-references without + * issue. + */ + continue; + } + + if (dest->noendbr) + continue; + + WARN_FUNC("relocation to !ENDBR: %s", + insn->sec, insn->offset, + offstr(dest->sec, dest->offset)); + + warnings++; + } + + return warnings; +} + +static int validate_ibt_data_reloc(struct objtool_file *file, + struct reloc *reloc) +{ + struct instruction *dest; + + dest = find_insn(file, reloc->sym->sec, + reloc->sym->offset + reloc->addend); + if (!dest) + return 0; + + if (dest->type == INSN_ENDBR) { + mark_endbr_used(dest); + return 0; + } + + if (dest->noendbr) + return 0; + + WARN_FUNC("data relocation to !ENDBR: %s", + reloc->sec->base, reloc->offset, + offstr(dest->sec, dest->offset)); + + return 1; +} + +/* + * Validate IBT rules and remove used ENDBR instructions from the seal list. + * Unused ENDBR instructions will be annotated for sealing (i.e., replaced with + * NOPs) later, in create_ibt_endbr_seal_sections(). + */ +static int validate_ibt(struct objtool_file *file) +{ + struct section *sec; + struct reloc *reloc; + struct instruction *insn; + int warnings = 0; + + for_each_insn(file, insn) + warnings += validate_ibt_insn(file, insn); + + for_each_sec(file, sec) { + + /* Already done by validate_ibt_insn() */ + if (sec->sh.sh_flags & SHF_EXECINSTR) + continue; + + if (!sec->reloc) + continue; + + /* + * These sections can reference text addresses, but not with + * the intent to indirect branch to them. + */ + if ((!strncmp(sec->name, ".discard", 8) && + strcmp(sec->name, ".discard.ibt_endbr_noseal")) || + !strncmp(sec->name, ".debug", 6) || + !strcmp(sec->name, ".altinstructions") || + !strcmp(sec->name, ".ibt_endbr_seal") || + !strcmp(sec->name, ".orc_unwind_ip") || + !strcmp(sec->name, ".parainstructions") || + !strcmp(sec->name, ".retpoline_sites") || + !strcmp(sec->name, ".smp_locks") || + !strcmp(sec->name, ".static_call_sites") || + !strcmp(sec->name, "_error_injection_whitelist") || + !strcmp(sec->name, "_kprobe_blacklist") || + !strcmp(sec->name, "__bug_table") || + !strcmp(sec->name, "__ex_table") || + !strcmp(sec->name, "__jump_table") || + !strcmp(sec->name, "__mcount_loc") || + !strcmp(sec->name, ".kcfi_traps") || + strstr(sec->name, "__patchable_function_entries")) + continue; + + list_for_each_entry(reloc, &sec->reloc->reloc_list, list) + warnings += validate_ibt_data_reloc(file, reloc); + } + + return warnings; +} + +static int validate_sls(struct objtool_file *file) +{ + struct instruction *insn, *next_insn; + int warnings = 0; + + for_each_insn(file, insn) { + next_insn = next_insn_same_sec(file, insn); + + if (insn->retpoline_safe) + continue; + + switch (insn->type) { + case INSN_RETURN: + if (!next_insn || next_insn->type != INSN_TRAP) { + WARN_FUNC("missing int3 after ret", + insn->sec, insn->offset); + warnings++; + } + + break; + case INSN_JUMP_DYNAMIC: + if (!next_insn || next_insn->type != INSN_TRAP) { + WARN_FUNC("missing int3 after indirect jump", + insn->sec, insn->offset); + warnings++; + } + break; + default: + break; + } + } + + return warnings; +} + +static int validate_reachable_instructions(struct objtool_file *file) +{ + struct instruction *insn; + + if (file->ignore_unreachables) + return 0; + + for_each_insn(file, insn) { + if (insn->visited || ignore_unreachable_insn(file, insn)) + continue; + + WARN_FUNC("unreachable instruction", insn->sec, insn->offset); + return 1; + } + + return 0; +} + +int check(struct objtool_file *file) +{ + int ret, warnings = 0; + + arch_initial_func_cfi_state(&initial_func_cfi); + init_cfi_state(&init_cfi); + init_cfi_state(&func_cfi); + set_func_state(&func_cfi); + + if (!cfi_hash_alloc(1UL << (file->elf->symbol_bits - 3))) + goto out; + + cfi_hash_add(&init_cfi); + cfi_hash_add(&func_cfi); + + ret = decode_sections(file); + if (ret < 0) + goto out; + + warnings += ret; + + if (list_empty(&file->insn_list)) + goto out; + + if (opts.retpoline) { + ret = validate_retpoline(file); + if (ret < 0) + return ret; + warnings += ret; + } + + if (opts.stackval || opts.orc || opts.uaccess) { + ret = validate_functions(file); + if (ret < 0) + goto out; + warnings += ret; + + ret = validate_unwind_hints(file, NULL); + if (ret < 0) + goto out; + warnings += ret; + + if (!warnings) { + ret = validate_reachable_instructions(file); + if (ret < 0) + goto out; + warnings += ret; + } + + } else if (opts.noinstr) { + ret = validate_noinstr_sections(file); + if (ret < 0) + goto out; + warnings += ret; + } + + if (opts.unret) { + /* + * Must be after validate_branch() and friends, it plays + * further games with insn->visited. + */ + ret = validate_unret(file); + if (ret < 0) + return ret; + warnings += ret; + } + + if (opts.ibt) { + ret = validate_ibt(file); + if (ret < 0) + goto out; + warnings += ret; + } + + if (opts.sls) { + ret = validate_sls(file); + if (ret < 0) + goto out; + warnings += ret; + } + + if (opts.static_call) { + ret = create_static_call_sections(file); + if (ret < 0) + goto out; + warnings += ret; + } + + if (opts.retpoline) { + ret = create_retpoline_sites_sections(file); + if (ret < 0) + goto out; + warnings += ret; + } + + if (opts.rethunk) { + ret = create_return_sites_sections(file); + if (ret < 0) + goto out; + warnings += ret; + } + + if (opts.mcount) { + ret = create_mcount_loc_sections(file); + if (ret < 0) + goto out; + warnings += ret; + } + + if (opts.ibt) { + ret = create_ibt_endbr_seal_sections(file); + if (ret < 0) + goto out; + warnings += ret; + } + + if (opts.orc && !list_empty(&file->insn_list)) { + ret = orc_create(file); + if (ret < 0) + goto out; + warnings += ret; + } + + + if (opts.stats) { + printf("nr_insns_visited: %ld\n", nr_insns_visited); + printf("nr_cfi: %ld\n", nr_cfi); + printf("nr_cfi_reused: %ld\n", nr_cfi_reused); + printf("nr_cfi_cache: %ld\n", nr_cfi_cache); + } + +out: + /* + * For now, don't fail the kernel build on fatal warnings. These + * errors are still fairly common due to the growing matrix of + * supported toolchains and their recent pace of change. + */ + return 0; +} |