diff options
Diffstat (limited to 'arch/x86/kernel/alternative.c')
| -rw-r--r-- | arch/x86/kernel/alternative.c | 1767 |
1 files changed, 1767 insertions, 0 deletions
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c new file mode 100644 index 000000000..6b8c93989 --- /dev/null +++ b/arch/x86/kernel/alternative.c @@ -0,0 +1,1767 @@ +// SPDX-License-Identifier: GPL-2.0-only +#define pr_fmt(fmt) "SMP alternatives: " fmt + +#include <linux/module.h> +#include <linux/sched.h> +#include <linux/perf_event.h> +#include <linux/mutex.h> +#include <linux/list.h> +#include <linux/stringify.h> +#include <linux/highmem.h> +#include <linux/mm.h> +#include <linux/vmalloc.h> +#include <linux/memory.h> +#include <linux/stop_machine.h> +#include <linux/slab.h> +#include <linux/kdebug.h> +#include <linux/kprobes.h> +#include <linux/mmu_context.h> +#include <linux/bsearch.h> +#include <linux/sync_core.h> +#include <asm/text-patching.h> +#include <asm/alternative.h> +#include <asm/sections.h> +#include <asm/mce.h> +#include <asm/nmi.h> +#include <asm/cacheflush.h> +#include <asm/tlbflush.h> +#include <asm/insn.h> +#include <asm/io.h> +#include <asm/fixmap.h> +#include <asm/paravirt.h> +#include <asm/asm-prototypes.h> + +int __read_mostly alternatives_patched; + +EXPORT_SYMBOL_GPL(alternatives_patched); + +#define MAX_PATCH_LEN (255-1) + +static int __initdata_or_module debug_alternative; + +static int __init debug_alt(char *str) +{ + debug_alternative = 1; + return 1; +} +__setup("debug-alternative", debug_alt); + +static int noreplace_smp; + +static int __init setup_noreplace_smp(char *str) +{ + noreplace_smp = 1; + return 1; +} +__setup("noreplace-smp", setup_noreplace_smp); + +#define DPRINTK(fmt, args...) \ +do { \ + if (debug_alternative) \ + printk(KERN_DEBUG pr_fmt(fmt) "\n", ##args); \ +} while (0) + +#define DUMP_BYTES(buf, len, fmt, args...) \ +do { \ + if (unlikely(debug_alternative)) { \ + int j; \ + \ + if (!(len)) \ + break; \ + \ + printk(KERN_DEBUG pr_fmt(fmt), ##args); \ + for (j = 0; j < (len) - 1; j++) \ + printk(KERN_CONT "%02hhx ", buf[j]); \ + printk(KERN_CONT "%02hhx\n", buf[j]); \ + } \ +} while (0) + +static const unsigned char x86nops[] = +{ + BYTES_NOP1, + BYTES_NOP2, + BYTES_NOP3, + BYTES_NOP4, + BYTES_NOP5, + BYTES_NOP6, + BYTES_NOP7, + BYTES_NOP8, +}; + +const unsigned char * const x86_nops[ASM_NOP_MAX+1] = +{ + NULL, + x86nops, + x86nops + 1, + x86nops + 1 + 2, + x86nops + 1 + 2 + 3, + x86nops + 1 + 2 + 3 + 4, + x86nops + 1 + 2 + 3 + 4 + 5, + x86nops + 1 + 2 + 3 + 4 + 5 + 6, + x86nops + 1 + 2 + 3 + 4 + 5 + 6 + 7, +}; + +/* Use this to add nops to a buffer, then text_poke the whole buffer. */ +static void __init_or_module add_nops(void *insns, unsigned int len) +{ + while (len > 0) { + unsigned int noplen = len; + if (noplen > ASM_NOP_MAX) + noplen = ASM_NOP_MAX; + memcpy(insns, x86_nops[noplen], noplen); + insns += noplen; + len -= noplen; + } +} + +extern s32 __retpoline_sites[], __retpoline_sites_end[]; +extern s32 __return_sites[], __return_sites_end[]; +extern s32 __ibt_endbr_seal[], __ibt_endbr_seal_end[]; +extern struct alt_instr __alt_instructions[], __alt_instructions_end[]; +extern s32 __smp_locks[], __smp_locks_end[]; +void text_poke_early(void *addr, const void *opcode, size_t len); + +/* + * Are we looking at a near JMP with a 1 or 4-byte displacement. + */ +static inline bool is_jmp(const u8 opcode) +{ + return opcode == 0xeb || opcode == 0xe9; +} + +static void __init_or_module +recompute_jump(struct alt_instr *a, u8 *orig_insn, u8 *repl_insn, u8 *insn_buff) +{ + u8 *next_rip, *tgt_rip; + s32 n_dspl, o_dspl; + int repl_len; + + if (a->replacementlen != 5) + return; + + o_dspl = *(s32 *)(insn_buff + 1); + + /* next_rip of the replacement JMP */ + next_rip = repl_insn + a->replacementlen; + /* target rip of the replacement JMP */ + tgt_rip = next_rip + o_dspl; + n_dspl = tgt_rip - orig_insn; + + DPRINTK("target RIP: %px, new_displ: 0x%x", tgt_rip, n_dspl); + + if (tgt_rip - orig_insn >= 0) { + if (n_dspl - 2 <= 127) + goto two_byte_jmp; + else + goto five_byte_jmp; + /* negative offset */ + } else { + if (((n_dspl - 2) & 0xff) == (n_dspl - 2)) + goto two_byte_jmp; + else + goto five_byte_jmp; + } + +two_byte_jmp: + n_dspl -= 2; + + insn_buff[0] = 0xeb; + insn_buff[1] = (s8)n_dspl; + add_nops(insn_buff + 2, 3); + + repl_len = 2; + goto done; + +five_byte_jmp: + n_dspl -= 5; + + insn_buff[0] = 0xe9; + *(s32 *)&insn_buff[1] = n_dspl; + + repl_len = 5; + +done: + + DPRINTK("final displ: 0x%08x, JMP 0x%lx", + n_dspl, (unsigned long)orig_insn + n_dspl + repl_len); +} + +/* + * optimize_nops_range() - Optimize a sequence of single byte NOPs (0x90) + * + * @instr: instruction byte stream + * @instrlen: length of the above + * @off: offset within @instr where the first NOP has been detected + * + * Return: number of NOPs found (and replaced). + */ +static __always_inline int optimize_nops_range(u8 *instr, u8 instrlen, int off) +{ + unsigned long flags; + int i = off, nnops; + + while (i < instrlen) { + if (instr[i] != 0x90) + break; + + i++; + } + + nnops = i - off; + + if (nnops <= 1) + return nnops; + + local_irq_save(flags); + add_nops(instr + off, nnops); + local_irq_restore(flags); + + DUMP_BYTES(instr, instrlen, "%px: [%d:%d) optimized NOPs: ", instr, off, i); + + return nnops; +} + +/* + * "noinline" to cause control flow change and thus invalidate I$ and + * cause refetch after modification. + */ +static void __init_or_module noinline optimize_nops(u8 *instr, size_t len) +{ + struct insn insn; + int i = 0; + + /* + * Jump over the non-NOP insns and optimize single-byte NOPs into bigger + * ones. + */ + for (;;) { + if (insn_decode_kernel(&insn, &instr[i])) + return; + + /* + * See if this and any potentially following NOPs can be + * optimized. + */ + if (insn.length == 1 && insn.opcode.bytes[0] == 0x90) + i += optimize_nops_range(instr, len, i); + else + i += insn.length; + + if (i >= len) + return; + } +} + +/* + * Replace instructions with better alternatives for this CPU type. This runs + * before SMP is initialized to avoid SMP problems with self modifying code. + * This implies that asymmetric systems where APs have less capabilities than + * the boot processor are not handled. Tough. Make sure you disable such + * features by hand. + * + * Marked "noinline" to cause control flow change and thus insn cache + * to refetch changed I$ lines. + */ +void __init_or_module noinline apply_alternatives(struct alt_instr *start, + struct alt_instr *end) +{ + struct alt_instr *a; + u8 *instr, *replacement; + u8 insn_buff[MAX_PATCH_LEN]; + + DPRINTK("alt table %px, -> %px", start, end); + + /* + * In the case CONFIG_X86_5LEVEL=y, KASAN_SHADOW_START is defined using + * cpu_feature_enabled(X86_FEATURE_LA57) and is therefore patched here. + * During the process, KASAN becomes confused seeing partial LA57 + * conversion and triggers a false-positive out-of-bound report. + * + * Disable KASAN until the patching is complete. + */ + kasan_disable_current(); + + /* + * The scan order should be from start to end. A later scanned + * alternative code can overwrite previously scanned alternative code. + * Some kernel functions (e.g. memcpy, memset, etc) use this order to + * patch code. + * + * So be careful if you want to change the scan order to any other + * order. + */ + for (a = start; a < end; a++) { + int insn_buff_sz = 0; + /* Mask away "NOT" flag bit for feature to test. */ + u16 feature = a->cpuid & ~ALTINSTR_FLAG_INV; + + instr = (u8 *)&a->instr_offset + a->instr_offset; + replacement = (u8 *)&a->repl_offset + a->repl_offset; + BUG_ON(a->instrlen > sizeof(insn_buff)); + BUG_ON(feature >= (NCAPINTS + NBUGINTS) * 32); + + /* + * Patch if either: + * - feature is present + * - feature not present but ALTINSTR_FLAG_INV is set to mean, + * patch if feature is *NOT* present. + */ + if (!boot_cpu_has(feature) == !(a->cpuid & ALTINSTR_FLAG_INV)) + goto next; + + DPRINTK("feat: %s%d*32+%d, old: (%pS (%px) len: %d), repl: (%px, len: %d)", + (a->cpuid & ALTINSTR_FLAG_INV) ? "!" : "", + feature >> 5, + feature & 0x1f, + instr, instr, a->instrlen, + replacement, a->replacementlen); + + DUMP_BYTES(instr, a->instrlen, "%px: old_insn: ", instr); + DUMP_BYTES(replacement, a->replacementlen, "%px: rpl_insn: ", replacement); + + memcpy(insn_buff, replacement, a->replacementlen); + insn_buff_sz = a->replacementlen; + + /* + * 0xe8 is a relative jump; fix the offset. + * + * Instruction length is checked before the opcode to avoid + * accessing uninitialized bytes for zero-length replacements. + */ + if (a->replacementlen == 5 && *insn_buff == 0xe8) { + *(s32 *)(insn_buff + 1) += replacement - instr; + DPRINTK("Fix CALL offset: 0x%x, CALL 0x%lx", + *(s32 *)(insn_buff + 1), + (unsigned long)instr + *(s32 *)(insn_buff + 1) + 5); + } + + if (a->replacementlen && is_jmp(replacement[0])) + recompute_jump(a, instr, replacement, insn_buff); + + for (; insn_buff_sz < a->instrlen; insn_buff_sz++) + insn_buff[insn_buff_sz] = 0x90; + + DUMP_BYTES(insn_buff, insn_buff_sz, "%px: final_insn: ", instr); + + text_poke_early(instr, insn_buff, insn_buff_sz); + +next: + optimize_nops(instr, a->instrlen); + } + + kasan_enable_current(); +} + +static inline bool is_jcc32(struct insn *insn) +{ + /* Jcc.d32 second opcode byte is in the range: 0x80-0x8f */ + return insn->opcode.bytes[0] == 0x0f && (insn->opcode.bytes[1] & 0xf0) == 0x80; +} + +#if defined(CONFIG_RETPOLINE) && defined(CONFIG_OBJTOOL) + +/* + * CALL/JMP *%\reg + */ +static int emit_indirect(int op, int reg, u8 *bytes) +{ + int i = 0; + u8 modrm; + + switch (op) { + case CALL_INSN_OPCODE: + modrm = 0x10; /* Reg = 2; CALL r/m */ + break; + + case JMP32_INSN_OPCODE: + modrm = 0x20; /* Reg = 4; JMP r/m */ + break; + + default: + WARN_ON_ONCE(1); + return -1; + } + + if (reg >= 8) { + bytes[i++] = 0x41; /* REX.B prefix */ + reg -= 8; + } + + modrm |= 0xc0; /* Mod = 3 */ + modrm += reg; + + bytes[i++] = 0xff; /* opcode */ + bytes[i++] = modrm; + + return i; +} + +/* + * Rewrite the compiler generated retpoline thunk calls. + * + * For spectre_v2=off (!X86_FEATURE_RETPOLINE), rewrite them into immediate + * indirect instructions, avoiding the extra indirection. + * + * For example, convert: + * + * CALL __x86_indirect_thunk_\reg + * + * into: + * + * CALL *%\reg + * + * It also tries to inline spectre_v2=retpoline,lfence when size permits. + */ +static int patch_retpoline(void *addr, struct insn *insn, u8 *bytes) +{ + retpoline_thunk_t *target; + int reg, ret, i = 0; + u8 op, cc; + + target = addr + insn->length + insn->immediate.value; + reg = target - __x86_indirect_thunk_array; + + if (WARN_ON_ONCE(reg & ~0xf)) + return -1; + + /* If anyone ever does: CALL/JMP *%rsp, we're in deep trouble. */ + BUG_ON(reg == 4); + + if (cpu_feature_enabled(X86_FEATURE_RETPOLINE) && + !cpu_feature_enabled(X86_FEATURE_RETPOLINE_LFENCE)) + return -1; + + op = insn->opcode.bytes[0]; + + /* + * Convert: + * + * Jcc.d32 __x86_indirect_thunk_\reg + * + * into: + * + * Jncc.d8 1f + * [ LFENCE ] + * JMP *%\reg + * [ NOP ] + * 1: + */ + if (is_jcc32(insn)) { + cc = insn->opcode.bytes[1] & 0xf; + cc ^= 1; /* invert condition */ + + bytes[i++] = 0x70 + cc; /* Jcc.d8 */ + bytes[i++] = insn->length - 2; /* sizeof(Jcc.d8) == 2 */ + + /* Continue as if: JMP.d32 __x86_indirect_thunk_\reg */ + op = JMP32_INSN_OPCODE; + } + + /* + * For RETPOLINE_LFENCE: prepend the indirect CALL/JMP with an LFENCE. + */ + if (cpu_feature_enabled(X86_FEATURE_RETPOLINE_LFENCE)) { + bytes[i++] = 0x0f; + bytes[i++] = 0xae; + bytes[i++] = 0xe8; /* LFENCE */ + } + + ret = emit_indirect(op, reg, bytes + i); + if (ret < 0) + return ret; + i += ret; + + /* + * The compiler is supposed to EMIT an INT3 after every unconditional + * JMP instruction due to AMD BTC. However, if the compiler is too old + * or SLS isn't enabled, we still need an INT3 after indirect JMPs + * even on Intel. + */ + if (op == JMP32_INSN_OPCODE && i < insn->length) + bytes[i++] = INT3_INSN_OPCODE; + + for (; i < insn->length;) + bytes[i++] = BYTES_NOP1; + + return i; +} + +/* + * Generated by 'objtool --retpoline'. + */ +void __init_or_module noinline apply_retpolines(s32 *start, s32 *end) +{ + s32 *s; + + for (s = start; s < end; s++) { + void *addr = (void *)s + *s; + struct insn insn; + int len, ret; + u8 bytes[16]; + u8 op1, op2; + + ret = insn_decode_kernel(&insn, addr); + if (WARN_ON_ONCE(ret < 0)) + continue; + + op1 = insn.opcode.bytes[0]; + op2 = insn.opcode.bytes[1]; + + switch (op1) { + case CALL_INSN_OPCODE: + case JMP32_INSN_OPCODE: + break; + + case 0x0f: /* escape */ + if (op2 >= 0x80 && op2 <= 0x8f) + break; + fallthrough; + default: + WARN_ON_ONCE(1); + continue; + } + + DPRINTK("retpoline at: %pS (%px) len: %d to: %pS", + addr, addr, insn.length, + addr + insn.length + insn.immediate.value); + + len = patch_retpoline(addr, &insn, bytes); + if (len == insn.length) { + optimize_nops(bytes, len); + DUMP_BYTES(((u8*)addr), len, "%px: orig: ", addr); + DUMP_BYTES(((u8*)bytes), len, "%px: repl: ", addr); + text_poke_early(addr, bytes, len); + } + } +} + +#ifdef CONFIG_RETHUNK +/* + * Rewrite the compiler generated return thunk tail-calls. + * + * For example, convert: + * + * JMP __x86_return_thunk + * + * into: + * + * RET + */ +static int patch_return(void *addr, struct insn *insn, u8 *bytes) +{ + int i = 0; + + if (cpu_feature_enabled(X86_FEATURE_RETHUNK)) + return -1; + + bytes[i++] = RET_INSN_OPCODE; + + for (; i < insn->length;) + bytes[i++] = INT3_INSN_OPCODE; + + return i; +} + +void __init_or_module noinline apply_returns(s32 *start, s32 *end) +{ + s32 *s; + + for (s = start; s < end; s++) { + void *dest = NULL, *addr = (void *)s + *s; + struct insn insn; + int len, ret; + u8 bytes[16]; + u8 op; + + ret = insn_decode_kernel(&insn, addr); + if (WARN_ON_ONCE(ret < 0)) + continue; + + op = insn.opcode.bytes[0]; + if (op == JMP32_INSN_OPCODE) + dest = addr + insn.length + insn.immediate.value; + + if (__static_call_fixup(addr, op, dest) || + WARN_ONCE(dest != &__x86_return_thunk, + "missing return thunk: %pS-%pS: %*ph", + addr, dest, 5, addr)) + continue; + + DPRINTK("return thunk at: %pS (%px) len: %d to: %pS", + addr, addr, insn.length, + addr + insn.length + insn.immediate.value); + + len = patch_return(addr, &insn, bytes); + if (len == insn.length) { + DUMP_BYTES(((u8*)addr), len, "%px: orig: ", addr); + DUMP_BYTES(((u8*)bytes), len, "%px: repl: ", addr); + text_poke_early(addr, bytes, len); + } + } +} +#else +void __init_or_module noinline apply_returns(s32 *start, s32 *end) { } +#endif /* CONFIG_RETHUNK */ + +#else /* !CONFIG_RETPOLINE || !CONFIG_OBJTOOL */ + +void __init_or_module noinline apply_retpolines(s32 *start, s32 *end) { } +void __init_or_module noinline apply_returns(s32 *start, s32 *end) { } + +#endif /* CONFIG_RETPOLINE && CONFIG_OBJTOOL */ + +#ifdef CONFIG_X86_KERNEL_IBT + +/* + * Generated by: objtool --ibt + */ +void __init_or_module noinline apply_ibt_endbr(s32 *start, s32 *end) +{ + s32 *s; + + for (s = start; s < end; s++) { + u32 endbr, poison = gen_endbr_poison(); + void *addr = (void *)s + *s; + + if (WARN_ON_ONCE(get_kernel_nofault(endbr, addr))) + continue; + + if (WARN_ON_ONCE(!is_endbr(endbr))) + continue; + + DPRINTK("ENDBR at: %pS (%px)", addr, addr); + + /* + * When we have IBT, the lack of ENDBR will trigger #CP + */ + DUMP_BYTES(((u8*)addr), 4, "%px: orig: ", addr); + DUMP_BYTES(((u8*)&poison), 4, "%px: repl: ", addr); + text_poke_early(addr, &poison, 4); + } +} + +#else + +void __init_or_module noinline apply_ibt_endbr(s32 *start, s32 *end) { } + +#endif /* CONFIG_X86_KERNEL_IBT */ + +#ifdef CONFIG_SMP +static void alternatives_smp_lock(const s32 *start, const s32 *end, + u8 *text, u8 *text_end) +{ + const s32 *poff; + + for (poff = start; poff < end; poff++) { + u8 *ptr = (u8 *)poff + *poff; + + if (!*poff || ptr < text || ptr >= text_end) + continue; + /* turn DS segment override prefix into lock prefix */ + if (*ptr == 0x3e) + text_poke(ptr, ((unsigned char []){0xf0}), 1); + } +} + +static void alternatives_smp_unlock(const s32 *start, const s32 *end, + u8 *text, u8 *text_end) +{ + const s32 *poff; + + for (poff = start; poff < end; poff++) { + u8 *ptr = (u8 *)poff + *poff; + + if (!*poff || ptr < text || ptr >= text_end) + continue; + /* turn lock prefix into DS segment override prefix */ + if (*ptr == 0xf0) + text_poke(ptr, ((unsigned char []){0x3E}), 1); + } +} + +struct smp_alt_module { + /* what is this ??? */ + struct module *mod; + char *name; + + /* ptrs to lock prefixes */ + const s32 *locks; + const s32 *locks_end; + + /* .text segment, needed to avoid patching init code ;) */ + u8 *text; + u8 *text_end; + + struct list_head next; +}; +static LIST_HEAD(smp_alt_modules); +static bool uniproc_patched = false; /* protected by text_mutex */ + +void __init_or_module alternatives_smp_module_add(struct module *mod, + char *name, + void *locks, void *locks_end, + void *text, void *text_end) +{ + struct smp_alt_module *smp; + + mutex_lock(&text_mutex); + if (!uniproc_patched) + goto unlock; + + if (num_possible_cpus() == 1) + /* Don't bother remembering, we'll never have to undo it. */ + goto smp_unlock; + + smp = kzalloc(sizeof(*smp), GFP_KERNEL); + if (NULL == smp) + /* we'll run the (safe but slow) SMP code then ... */ + goto unlock; + + smp->mod = mod; + smp->name = name; + smp->locks = locks; + smp->locks_end = locks_end; + smp->text = text; + smp->text_end = text_end; + DPRINTK("locks %p -> %p, text %p -> %p, name %s\n", + smp->locks, smp->locks_end, + smp->text, smp->text_end, smp->name); + + list_add_tail(&smp->next, &smp_alt_modules); +smp_unlock: + alternatives_smp_unlock(locks, locks_end, text, text_end); +unlock: + mutex_unlock(&text_mutex); +} + +void __init_or_module alternatives_smp_module_del(struct module *mod) +{ + struct smp_alt_module *item; + + mutex_lock(&text_mutex); + list_for_each_entry(item, &smp_alt_modules, next) { + if (mod != item->mod) + continue; + list_del(&item->next); + kfree(item); + break; + } + mutex_unlock(&text_mutex); +} + +void alternatives_enable_smp(void) +{ + struct smp_alt_module *mod; + + /* Why bother if there are no other CPUs? */ + BUG_ON(num_possible_cpus() == 1); + + mutex_lock(&text_mutex); + + if (uniproc_patched) { + pr_info("switching to SMP code\n"); + BUG_ON(num_online_cpus() != 1); + clear_cpu_cap(&boot_cpu_data, X86_FEATURE_UP); + clear_cpu_cap(&cpu_data(0), X86_FEATURE_UP); + list_for_each_entry(mod, &smp_alt_modules, next) + alternatives_smp_lock(mod->locks, mod->locks_end, + mod->text, mod->text_end); + uniproc_patched = false; + } + mutex_unlock(&text_mutex); +} + +/* + * Return 1 if the address range is reserved for SMP-alternatives. + * Must hold text_mutex. + */ +int alternatives_text_reserved(void *start, void *end) +{ + struct smp_alt_module *mod; + const s32 *poff; + u8 *text_start = start; + u8 *text_end = end; + + lockdep_assert_held(&text_mutex); + + list_for_each_entry(mod, &smp_alt_modules, next) { + if (mod->text > text_end || mod->text_end < text_start) + continue; + for (poff = mod->locks; poff < mod->locks_end; poff++) { + const u8 *ptr = (const u8 *)poff + *poff; + + if (text_start <= ptr && text_end > ptr) + return 1; + } + } + + return 0; +} +#endif /* CONFIG_SMP */ + +#ifdef CONFIG_PARAVIRT +void __init_or_module apply_paravirt(struct paravirt_patch_site *start, + struct paravirt_patch_site *end) +{ + struct paravirt_patch_site *p; + char insn_buff[MAX_PATCH_LEN]; + + for (p = start; p < end; p++) { + unsigned int used; + + BUG_ON(p->len > MAX_PATCH_LEN); + /* prep the buffer with the original instructions */ + memcpy(insn_buff, p->instr, p->len); + used = paravirt_patch(p->type, insn_buff, (unsigned long)p->instr, p->len); + + BUG_ON(used > p->len); + + /* Pad the rest with nops */ + add_nops(insn_buff + used, p->len - used); + text_poke_early(p->instr, insn_buff, p->len); + } +} +extern struct paravirt_patch_site __start_parainstructions[], + __stop_parainstructions[]; +#endif /* CONFIG_PARAVIRT */ + +/* + * Self-test for the INT3 based CALL emulation code. + * + * This exercises int3_emulate_call() to make sure INT3 pt_regs are set up + * properly and that there is a stack gap between the INT3 frame and the + * previous context. Without this gap doing a virtual PUSH on the interrupted + * stack would corrupt the INT3 IRET frame. + * + * See entry_{32,64}.S for more details. + */ + +/* + * We define the int3_magic() function in assembly to control the calling + * convention such that we can 'call' it from assembly. + */ + +extern void int3_magic(unsigned int *ptr); /* defined in asm */ + +asm ( +" .pushsection .init.text, \"ax\", @progbits\n" +" .type int3_magic, @function\n" +"int3_magic:\n" + ANNOTATE_NOENDBR +" movl $1, (%" _ASM_ARG1 ")\n" + ASM_RET +" .size int3_magic, .-int3_magic\n" +" .popsection\n" +); + +extern void int3_selftest_ip(void); /* defined in asm below */ + +static int __init +int3_exception_notify(struct notifier_block *self, unsigned long val, void *data) +{ + unsigned long selftest = (unsigned long)&int3_selftest_ip; + struct die_args *args = data; + struct pt_regs *regs = args->regs; + + OPTIMIZER_HIDE_VAR(selftest); + + if (!regs || user_mode(regs)) + return NOTIFY_DONE; + + if (val != DIE_INT3) + return NOTIFY_DONE; + + if (regs->ip - INT3_INSN_SIZE != selftest) + return NOTIFY_DONE; + + int3_emulate_call(regs, (unsigned long)&int3_magic); + return NOTIFY_STOP; +} + +/* Must be noinline to ensure uniqueness of int3_selftest_ip. */ +static noinline void __init int3_selftest(void) +{ + static __initdata struct notifier_block int3_exception_nb = { + .notifier_call = int3_exception_notify, + .priority = INT_MAX-1, /* last */ + }; + unsigned int val = 0; + + BUG_ON(register_die_notifier(&int3_exception_nb)); + + /* + * Basically: int3_magic(&val); but really complicated :-) + * + * INT3 padded with NOP to CALL_INSN_SIZE. The int3_exception_nb + * notifier above will emulate CALL for us. + */ + asm volatile ("int3_selftest_ip:\n\t" + ANNOTATE_NOENDBR + " int3; nop; nop; nop; nop\n\t" + : ASM_CALL_CONSTRAINT + : __ASM_SEL_RAW(a, D) (&val) + : "memory"); + + BUG_ON(val != 1); + + unregister_die_notifier(&int3_exception_nb); +} + +void __init alternative_instructions(void) +{ + int3_selftest(); + + /* + * The patching is not fully atomic, so try to avoid local + * interruptions that might execute the to be patched code. + * Other CPUs are not running. + */ + stop_nmi(); + + /* + * Don't stop machine check exceptions while patching. + * MCEs only happen when something got corrupted and in this + * case we must do something about the corruption. + * Ignoring it is worse than an unlikely patching race. + * Also machine checks tend to be broadcast and if one CPU + * goes into machine check the others follow quickly, so we don't + * expect a machine check to cause undue problems during to code + * patching. + */ + + /* + * Paravirt patching and alternative patching can be combined to + * replace a function call with a short direct code sequence (e.g. + * by setting a constant return value instead of doing that in an + * external function). + * In order to make this work the following sequence is required: + * 1. set (artificial) features depending on used paravirt + * functions which can later influence alternative patching + * 2. apply paravirt patching (generally replacing an indirect + * function call with a direct one) + * 3. apply alternative patching (e.g. replacing a direct function + * call with a custom code sequence) + * Doing paravirt patching after alternative patching would clobber + * the optimization of the custom code with a function call again. + */ + paravirt_set_cap(); + + /* + * First patch paravirt functions, such that we overwrite the indirect + * call with the direct call. + */ + apply_paravirt(__parainstructions, __parainstructions_end); + + /* + * Rewrite the retpolines, must be done before alternatives since + * those can rewrite the retpoline thunks. + */ + apply_retpolines(__retpoline_sites, __retpoline_sites_end); + apply_returns(__return_sites, __return_sites_end); + + /* + * Then patch alternatives, such that those paravirt calls that are in + * alternatives can be overwritten by their immediate fragments. + */ + apply_alternatives(__alt_instructions, __alt_instructions_end); + + apply_ibt_endbr(__ibt_endbr_seal, __ibt_endbr_seal_end); + +#ifdef CONFIG_SMP + /* Patch to UP if other cpus not imminent. */ + if (!noreplace_smp && (num_present_cpus() == 1 || setup_max_cpus <= 1)) { + uniproc_patched = true; + alternatives_smp_module_add(NULL, "core kernel", + __smp_locks, __smp_locks_end, + _text, _etext); + } + + if (!uniproc_patched || num_possible_cpus() == 1) { + free_init_pages("SMP alternatives", + (unsigned long)__smp_locks, + (unsigned long)__smp_locks_end); + } +#endif + + restart_nmi(); + alternatives_patched = 1; +} + +/** + * text_poke_early - Update instructions on a live kernel at boot time + * @addr: address to modify + * @opcode: source of the copy + * @len: length to copy + * + * When you use this code to patch more than one byte of an instruction + * you need to make sure that other CPUs cannot execute this code in parallel. + * Also no thread must be currently preempted in the middle of these + * instructions. And on the local CPU you need to be protected against NMI or + * MCE handlers seeing an inconsistent instruction while you patch. + */ +void __init_or_module text_poke_early(void *addr, const void *opcode, + size_t len) +{ + unsigned long flags; + + if (boot_cpu_has(X86_FEATURE_NX) && + is_module_text_address((unsigned long)addr)) { + /* + * Modules text is marked initially as non-executable, so the + * code cannot be running and speculative code-fetches are + * prevented. Just change the code. + */ + memcpy(addr, opcode, len); + } else { + local_irq_save(flags); + memcpy(addr, opcode, len); + sync_core(); + local_irq_restore(flags); + + /* + * Could also do a CLFLUSH here to speed up CPU recovery; but + * that causes hangs on some VIA CPUs. + */ + } +} + +typedef struct { + struct mm_struct *mm; +} temp_mm_state_t; + +/* + * Using a temporary mm allows to set temporary mappings that are not accessible + * by other CPUs. Such mappings are needed to perform sensitive memory writes + * that override the kernel memory protections (e.g., W^X), without exposing the + * temporary page-table mappings that are required for these write operations to + * other CPUs. Using a temporary mm also allows to avoid TLB shootdowns when the + * mapping is torn down. + * + * Context: The temporary mm needs to be used exclusively by a single core. To + * harden security IRQs must be disabled while the temporary mm is + * loaded, thereby preventing interrupt handler bugs from overriding + * the kernel memory protection. + */ +static inline temp_mm_state_t use_temporary_mm(struct mm_struct *mm) +{ + temp_mm_state_t temp_state; + + lockdep_assert_irqs_disabled(); + + /* + * Make sure not to be in TLB lazy mode, as otherwise we'll end up + * with a stale address space WITHOUT being in lazy mode after + * restoring the previous mm. + */ + if (this_cpu_read(cpu_tlbstate_shared.is_lazy)) + leave_mm(smp_processor_id()); + + temp_state.mm = this_cpu_read(cpu_tlbstate.loaded_mm); + switch_mm_irqs_off(NULL, mm, current); + + /* + * If breakpoints are enabled, disable them while the temporary mm is + * used. Userspace might set up watchpoints on addresses that are used + * in the temporary mm, which would lead to wrong signals being sent or + * crashes. + * + * Note that breakpoints are not disabled selectively, which also causes + * kernel breakpoints (e.g., perf's) to be disabled. This might be + * undesirable, but still seems reasonable as the code that runs in the + * temporary mm should be short. + */ + if (hw_breakpoint_active()) + hw_breakpoint_disable(); + + return temp_state; +} + +static inline void unuse_temporary_mm(temp_mm_state_t prev_state) +{ + lockdep_assert_irqs_disabled(); + switch_mm_irqs_off(NULL, prev_state.mm, current); + + /* + * Restore the breakpoints if they were disabled before the temporary mm + * was loaded. + */ + if (hw_breakpoint_active()) + hw_breakpoint_restore(); +} + +__ro_after_init struct mm_struct *poking_mm; +__ro_after_init unsigned long poking_addr; + +static void text_poke_memcpy(void *dst, const void *src, size_t len) +{ + memcpy(dst, src, len); +} + +static void text_poke_memset(void *dst, const void *src, size_t len) +{ + int c = *(const int *)src; + + memset(dst, c, len); +} + +typedef void text_poke_f(void *dst, const void *src, size_t len); + +static void *__text_poke(text_poke_f func, void *addr, const void *src, size_t len) +{ + bool cross_page_boundary = offset_in_page(addr) + len > PAGE_SIZE; + struct page *pages[2] = {NULL}; + temp_mm_state_t prev; + unsigned long flags; + pte_t pte, *ptep; + spinlock_t *ptl; + pgprot_t pgprot; + + /* + * While boot memory allocator is running we cannot use struct pages as + * they are not yet initialized. There is no way to recover. + */ + BUG_ON(!after_bootmem); + + if (!core_kernel_text((unsigned long)addr)) { + pages[0] = vmalloc_to_page(addr); + if (cross_page_boundary) + pages[1] = vmalloc_to_page(addr + PAGE_SIZE); + } else { + pages[0] = virt_to_page(addr); + WARN_ON(!PageReserved(pages[0])); + if (cross_page_boundary) + pages[1] = virt_to_page(addr + PAGE_SIZE); + } + /* + * If something went wrong, crash and burn since recovery paths are not + * implemented. + */ + BUG_ON(!pages[0] || (cross_page_boundary && !pages[1])); + + /* + * Map the page without the global bit, as TLB flushing is done with + * flush_tlb_mm_range(), which is intended for non-global PTEs. + */ + pgprot = __pgprot(pgprot_val(PAGE_KERNEL) & ~_PAGE_GLOBAL); + + /* + * The lock is not really needed, but this allows to avoid open-coding. + */ + ptep = get_locked_pte(poking_mm, poking_addr, &ptl); + + /* + * This must not fail; preallocated in poking_init(). + */ + VM_BUG_ON(!ptep); + + local_irq_save(flags); + + pte = mk_pte(pages[0], pgprot); + set_pte_at(poking_mm, poking_addr, ptep, pte); + + if (cross_page_boundary) { + pte = mk_pte(pages[1], pgprot); + set_pte_at(poking_mm, poking_addr + PAGE_SIZE, ptep + 1, pte); + } + + /* + * Loading the temporary mm behaves as a compiler barrier, which + * guarantees that the PTE will be set at the time memcpy() is done. + */ + prev = use_temporary_mm(poking_mm); + + kasan_disable_current(); + func((u8 *)poking_addr + offset_in_page(addr), src, len); + kasan_enable_current(); + + /* + * Ensure that the PTE is only cleared after the instructions of memcpy + * were issued by using a compiler barrier. + */ + barrier(); + + pte_clear(poking_mm, poking_addr, ptep); + if (cross_page_boundary) + pte_clear(poking_mm, poking_addr + PAGE_SIZE, ptep + 1); + + /* + * Loading the previous page-table hierarchy requires a serializing + * instruction that already allows the core to see the updated version. + * Xen-PV is assumed to serialize execution in a similar manner. + */ + unuse_temporary_mm(prev); + + /* + * Flushing the TLB might involve IPIs, which would require enabled + * IRQs, but not if the mm is not used, as it is in this point. + */ + flush_tlb_mm_range(poking_mm, poking_addr, poking_addr + + (cross_page_boundary ? 2 : 1) * PAGE_SIZE, + PAGE_SHIFT, false); + + if (func == text_poke_memcpy) { + /* + * If the text does not match what we just wrote then something is + * fundamentally screwy; there's nothing we can really do about that. + */ + BUG_ON(memcmp(addr, src, len)); + } + + local_irq_restore(flags); + pte_unmap_unlock(ptep, ptl); + return addr; +} + +/** + * text_poke - Update instructions on a live kernel + * @addr: address to modify + * @opcode: source of the copy + * @len: length to copy + * + * Only atomic text poke/set should be allowed when not doing early patching. + * It means the size must be writable atomically and the address must be aligned + * in a way that permits an atomic write. It also makes sure we fit on a single + * page. + * + * Note that the caller must ensure that if the modified code is part of a + * module, the module would not be removed during poking. This can be achieved + * by registering a module notifier, and ordering module removal and patching + * trough a mutex. + */ +void *text_poke(void *addr, const void *opcode, size_t len) +{ + lockdep_assert_held(&text_mutex); + + return __text_poke(text_poke_memcpy, addr, opcode, len); +} + +/** + * text_poke_kgdb - Update instructions on a live kernel by kgdb + * @addr: address to modify + * @opcode: source of the copy + * @len: length to copy + * + * Only atomic text poke/set should be allowed when not doing early patching. + * It means the size must be writable atomically and the address must be aligned + * in a way that permits an atomic write. It also makes sure we fit on a single + * page. + * + * Context: should only be used by kgdb, which ensures no other core is running, + * despite the fact it does not hold the text_mutex. + */ +void *text_poke_kgdb(void *addr, const void *opcode, size_t len) +{ + return __text_poke(text_poke_memcpy, addr, opcode, len); +} + +/** + * text_poke_copy - Copy instructions into (an unused part of) RX memory + * @addr: address to modify + * @opcode: source of the copy + * @len: length to copy, could be more than 2x PAGE_SIZE + * + * Not safe against concurrent execution; useful for JITs to dump + * new code blocks into unused regions of RX memory. Can be used in + * conjunction with synchronize_rcu_tasks() to wait for existing + * execution to quiesce after having made sure no existing functions + * pointers are live. + */ +void *text_poke_copy(void *addr, const void *opcode, size_t len) +{ + unsigned long start = (unsigned long)addr; + size_t patched = 0; + + if (WARN_ON_ONCE(core_kernel_text(start))) + return NULL; + + mutex_lock(&text_mutex); + while (patched < len) { + unsigned long ptr = start + patched; + size_t s; + + s = min_t(size_t, PAGE_SIZE * 2 - offset_in_page(ptr), len - patched); + + __text_poke(text_poke_memcpy, (void *)ptr, opcode + patched, s); + patched += s; + } + mutex_unlock(&text_mutex); + return addr; +} + +/** + * text_poke_set - memset into (an unused part of) RX memory + * @addr: address to modify + * @c: the byte to fill the area with + * @len: length to copy, could be more than 2x PAGE_SIZE + * + * This is useful to overwrite unused regions of RX memory with illegal + * instructions. + */ +void *text_poke_set(void *addr, int c, size_t len) +{ + unsigned long start = (unsigned long)addr; + size_t patched = 0; + + if (WARN_ON_ONCE(core_kernel_text(start))) + return NULL; + + mutex_lock(&text_mutex); + while (patched < len) { + unsigned long ptr = start + patched; + size_t s; + + s = min_t(size_t, PAGE_SIZE * 2 - offset_in_page(ptr), len - patched); + + __text_poke(text_poke_memset, (void *)ptr, (void *)&c, s); + patched += s; + } + mutex_unlock(&text_mutex); + return addr; +} + +static void do_sync_core(void *info) +{ + sync_core(); +} + +void text_poke_sync(void) +{ + on_each_cpu(do_sync_core, NULL, 1); +} + +/* + * NOTE: crazy scheme to allow patching Jcc.d32 but not increase the size of + * this thing. When len == 6 everything is prefixed with 0x0f and we map + * opcode to Jcc.d8, using len to distinguish. + */ +struct text_poke_loc { + /* addr := _stext + rel_addr */ + s32 rel_addr; + s32 disp; + u8 len; + u8 opcode; + const u8 text[POKE_MAX_OPCODE_SIZE]; + /* see text_poke_bp_batch() */ + u8 old; +}; + +struct bp_patching_desc { + struct text_poke_loc *vec; + int nr_entries; + atomic_t refs; +}; + +static struct bp_patching_desc bp_desc; + +static __always_inline +struct bp_patching_desc *try_get_desc(void) +{ + struct bp_patching_desc *desc = &bp_desc; + + if (!arch_atomic_inc_not_zero(&desc->refs)) + return NULL; + + return desc; +} + +static __always_inline void put_desc(void) +{ + struct bp_patching_desc *desc = &bp_desc; + + smp_mb__before_atomic(); + arch_atomic_dec(&desc->refs); +} + +static __always_inline void *text_poke_addr(struct text_poke_loc *tp) +{ + return _stext + tp->rel_addr; +} + +static __always_inline int patch_cmp(const void *key, const void *elt) +{ + struct text_poke_loc *tp = (struct text_poke_loc *) elt; + + if (key < text_poke_addr(tp)) + return -1; + if (key > text_poke_addr(tp)) + return 1; + return 0; +} + +noinstr int poke_int3_handler(struct pt_regs *regs) +{ + struct bp_patching_desc *desc; + struct text_poke_loc *tp; + int ret = 0; + void *ip; + + if (user_mode(regs)) + return 0; + + /* + * Having observed our INT3 instruction, we now must observe + * bp_desc with non-zero refcount: + * + * bp_desc.refs = 1 INT3 + * WMB RMB + * write INT3 if (bp_desc.refs != 0) + */ + smp_rmb(); + + desc = try_get_desc(); + if (!desc) + return 0; + + /* + * Discount the INT3. See text_poke_bp_batch(). + */ + ip = (void *) regs->ip - INT3_INSN_SIZE; + + /* + * Skip the binary search if there is a single member in the vector. + */ + if (unlikely(desc->nr_entries > 1)) { + tp = __inline_bsearch(ip, desc->vec, desc->nr_entries, + sizeof(struct text_poke_loc), + patch_cmp); + if (!tp) + goto out_put; + } else { + tp = desc->vec; + if (text_poke_addr(tp) != ip) + goto out_put; + } + + ip += tp->len; + + switch (tp->opcode) { + case INT3_INSN_OPCODE: + /* + * Someone poked an explicit INT3, they'll want to handle it, + * do not consume. + */ + goto out_put; + + case RET_INSN_OPCODE: + int3_emulate_ret(regs); + break; + + case CALL_INSN_OPCODE: + int3_emulate_call(regs, (long)ip + tp->disp); + break; + + case JMP32_INSN_OPCODE: + case JMP8_INSN_OPCODE: + int3_emulate_jmp(regs, (long)ip + tp->disp); + break; + + case 0x70 ... 0x7f: /* Jcc */ + int3_emulate_jcc(regs, tp->opcode & 0xf, (long)ip, tp->disp); + break; + + default: + BUG(); + } + + ret = 1; + +out_put: + put_desc(); + return ret; +} + +#define TP_VEC_MAX (PAGE_SIZE / sizeof(struct text_poke_loc)) +static struct text_poke_loc tp_vec[TP_VEC_MAX]; +static int tp_vec_nr; + +/** + * text_poke_bp_batch() -- update instructions on live kernel on SMP + * @tp: vector of instructions to patch + * @nr_entries: number of entries in the vector + * + * Modify multi-byte instruction by using int3 breakpoint on SMP. + * We completely avoid stop_machine() here, and achieve the + * synchronization using int3 breakpoint. + * + * The way it is done: + * - For each entry in the vector: + * - add a int3 trap to the address that will be patched + * - sync cores + * - For each entry in the vector: + * - update all but the first byte of the patched range + * - sync cores + * - For each entry in the vector: + * - replace the first byte (int3) by the first byte of + * replacing opcode + * - sync cores + */ +static void text_poke_bp_batch(struct text_poke_loc *tp, unsigned int nr_entries) +{ + unsigned char int3 = INT3_INSN_OPCODE; + unsigned int i; + int do_sync; + + lockdep_assert_held(&text_mutex); + + bp_desc.vec = tp; + bp_desc.nr_entries = nr_entries; + + /* + * Corresponds to the implicit memory barrier in try_get_desc() to + * ensure reading a non-zero refcount provides up to date bp_desc data. + */ + atomic_set_release(&bp_desc.refs, 1); + + /* + * Corresponding read barrier in int3 notifier for making sure the + * nr_entries and handler are correctly ordered wrt. patching. + */ + smp_wmb(); + + /* + * First step: add a int3 trap to the address that will be patched. + */ + for (i = 0; i < nr_entries; i++) { + tp[i].old = *(u8 *)text_poke_addr(&tp[i]); + text_poke(text_poke_addr(&tp[i]), &int3, INT3_INSN_SIZE); + } + + text_poke_sync(); + + /* + * Second step: update all but the first byte of the patched range. + */ + for (do_sync = 0, i = 0; i < nr_entries; i++) { + u8 old[POKE_MAX_OPCODE_SIZE+1] = { tp[i].old, }; + u8 _new[POKE_MAX_OPCODE_SIZE+1]; + const u8 *new = tp[i].text; + int len = tp[i].len; + + if (len - INT3_INSN_SIZE > 0) { + memcpy(old + INT3_INSN_SIZE, + text_poke_addr(&tp[i]) + INT3_INSN_SIZE, + len - INT3_INSN_SIZE); + + if (len == 6) { + _new[0] = 0x0f; + memcpy(_new + 1, new, 5); + new = _new; + } + + text_poke(text_poke_addr(&tp[i]) + INT3_INSN_SIZE, + new + INT3_INSN_SIZE, + len - INT3_INSN_SIZE); + + do_sync++; + } + + /* + * Emit a perf event to record the text poke, primarily to + * support Intel PT decoding which must walk the executable code + * to reconstruct the trace. The flow up to here is: + * - write INT3 byte + * - IPI-SYNC + * - write instruction tail + * At this point the actual control flow will be through the + * INT3 and handler and not hit the old or new instruction. + * Intel PT outputs FUP/TIP packets for the INT3, so the flow + * can still be decoded. Subsequently: + * - emit RECORD_TEXT_POKE with the new instruction + * - IPI-SYNC + * - write first byte + * - IPI-SYNC + * So before the text poke event timestamp, the decoder will see + * either the old instruction flow or FUP/TIP of INT3. After the + * text poke event timestamp, the decoder will see either the + * new instruction flow or FUP/TIP of INT3. Thus decoders can + * use the timestamp as the point at which to modify the + * executable code. + * The old instruction is recorded so that the event can be + * processed forwards or backwards. + */ + perf_event_text_poke(text_poke_addr(&tp[i]), old, len, new, len); + } + + if (do_sync) { + /* + * According to Intel, this core syncing is very likely + * not necessary and we'd be safe even without it. But + * better safe than sorry (plus there's not only Intel). + */ + text_poke_sync(); + } + + /* + * Third step: replace the first byte (int3) by the first byte of + * replacing opcode. + */ + for (do_sync = 0, i = 0; i < nr_entries; i++) { + u8 byte = tp[i].text[0]; + + if (tp[i].len == 6) + byte = 0x0f; + + if (byte == INT3_INSN_OPCODE) + continue; + + text_poke(text_poke_addr(&tp[i]), &byte, INT3_INSN_SIZE); + do_sync++; + } + + if (do_sync) + text_poke_sync(); + + /* + * Remove and wait for refs to be zero. + */ + if (!atomic_dec_and_test(&bp_desc.refs)) + atomic_cond_read_acquire(&bp_desc.refs, !VAL); +} + +static void text_poke_loc_init(struct text_poke_loc *tp, void *addr, + const void *opcode, size_t len, const void *emulate) +{ + struct insn insn; + int ret, i = 0; + + if (len == 6) + i = 1; + memcpy((void *)tp->text, opcode+i, len-i); + if (!emulate) + emulate = opcode; + + ret = insn_decode_kernel(&insn, emulate); + BUG_ON(ret < 0); + + tp->rel_addr = addr - (void *)_stext; + tp->len = len; + tp->opcode = insn.opcode.bytes[0]; + + if (is_jcc32(&insn)) { + /* + * Map Jcc.d32 onto Jcc.d8 and use len to distinguish. + */ + tp->opcode = insn.opcode.bytes[1] - 0x10; + } + + switch (tp->opcode) { + case RET_INSN_OPCODE: + case JMP32_INSN_OPCODE: + case JMP8_INSN_OPCODE: + /* + * Control flow instructions without implied execution of the + * next instruction can be padded with INT3. + */ + for (i = insn.length; i < len; i++) + BUG_ON(tp->text[i] != INT3_INSN_OPCODE); + break; + + default: + BUG_ON(len != insn.length); + }; + + switch (tp->opcode) { + case INT3_INSN_OPCODE: + case RET_INSN_OPCODE: + break; + + case CALL_INSN_OPCODE: + case JMP32_INSN_OPCODE: + case JMP8_INSN_OPCODE: + case 0x70 ... 0x7f: /* Jcc */ + tp->disp = insn.immediate.value; + break; + + default: /* assume NOP */ + switch (len) { + case 2: /* NOP2 -- emulate as JMP8+0 */ + BUG_ON(memcmp(emulate, x86_nops[len], len)); + tp->opcode = JMP8_INSN_OPCODE; + tp->disp = 0; + break; + + case 5: /* NOP5 -- emulate as JMP32+0 */ + BUG_ON(memcmp(emulate, x86_nops[len], len)); + tp->opcode = JMP32_INSN_OPCODE; + tp->disp = 0; + break; + + default: /* unknown instruction */ + BUG(); + } + break; + } +} + +/* + * We hard rely on the tp_vec being ordered; ensure this is so by flushing + * early if needed. + */ +static bool tp_order_fail(void *addr) +{ + struct text_poke_loc *tp; + + if (!tp_vec_nr) + return false; + + if (!addr) /* force */ + return true; + + tp = &tp_vec[tp_vec_nr - 1]; + if ((unsigned long)text_poke_addr(tp) > (unsigned long)addr) + return true; + + return false; +} + +static void text_poke_flush(void *addr) +{ + if (tp_vec_nr == TP_VEC_MAX || tp_order_fail(addr)) { + text_poke_bp_batch(tp_vec, tp_vec_nr); + tp_vec_nr = 0; + } +} + +void text_poke_finish(void) +{ + text_poke_flush(NULL); +} + +void __ref text_poke_queue(void *addr, const void *opcode, size_t len, const void *emulate) +{ + struct text_poke_loc *tp; + + if (unlikely(system_state == SYSTEM_BOOTING)) { + text_poke_early(addr, opcode, len); + return; + } + + text_poke_flush(addr); + + tp = &tp_vec[tp_vec_nr++]; + text_poke_loc_init(tp, addr, opcode, len, emulate); +} + +/** + * text_poke_bp() -- update instructions on live kernel on SMP + * @addr: address to patch + * @opcode: opcode of new instruction + * @len: length to copy + * @emulate: instruction to be emulated + * + * Update a single instruction with the vector in the stack, avoiding + * dynamically allocated memory. This function should be used when it is + * not possible to allocate memory. + */ +void __ref text_poke_bp(void *addr, const void *opcode, size_t len, const void *emulate) +{ + struct text_poke_loc tp; + + if (unlikely(system_state == SYSTEM_BOOTING)) { + text_poke_early(addr, opcode, len); + return; + } + + text_poke_loc_init(&tp, addr, opcode, len, emulate); + text_poke_bp_batch(&tp, 1); +} |