diff options
Diffstat (limited to 'arch/x86/kernel/ftrace.c')
| -rw-r--r-- | arch/x86/kernel/ftrace.c | 666 |
1 files changed, 666 insertions, 0 deletions
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c new file mode 100644 index 000000000..12df54ff0 --- /dev/null +++ b/arch/x86/kernel/ftrace.c @@ -0,0 +1,666 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Dynamic function tracing support. + * + * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com> + * + * Thanks goes to Ingo Molnar, for suggesting the idea. + * Mathieu Desnoyers, for suggesting postponing the modifications. + * Arjan van de Ven, for keeping me straight, and explaining to me + * the dangers of modifying code on the run. + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include <linux/spinlock.h> +#include <linux/hardirq.h> +#include <linux/uaccess.h> +#include <linux/ftrace.h> +#include <linux/percpu.h> +#include <linux/sched.h> +#include <linux/slab.h> +#include <linux/init.h> +#include <linux/list.h> +#include <linux/module.h> +#include <linux/memory.h> +#include <linux/vmalloc.h> +#include <linux/set_memory.h> + +#include <trace/syscall.h> + +#include <asm/kprobes.h> +#include <asm/ftrace.h> +#include <asm/nops.h> +#include <asm/text-patching.h> + +#ifdef CONFIG_DYNAMIC_FTRACE + +static int ftrace_poke_late = 0; + +void ftrace_arch_code_modify_prepare(void) + __acquires(&text_mutex) +{ + /* + * Need to grab text_mutex to prevent a race from module loading + * and live kernel patching from changing the text permissions while + * ftrace has it set to "read/write". + */ + mutex_lock(&text_mutex); + ftrace_poke_late = 1; +} + +void ftrace_arch_code_modify_post_process(void) + __releases(&text_mutex) +{ + /* + * ftrace_make_{call,nop}() may be called during + * module load, and we need to finish the text_poke_queue() + * that they do, here. + */ + text_poke_finish(); + ftrace_poke_late = 0; + mutex_unlock(&text_mutex); +} + +static const char *ftrace_nop_replace(void) +{ + return x86_nops[5]; +} + +static const char *ftrace_call_replace(unsigned long ip, unsigned long addr) +{ + /* + * No need to translate into a callthunk. The trampoline does + * the depth accounting itself. + */ + return text_gen_insn(CALL_INSN_OPCODE, (void *)ip, (void *)addr); +} + +static int ftrace_verify_code(unsigned long ip, const char *old_code) +{ + char cur_code[MCOUNT_INSN_SIZE]; + + /* + * Note: + * We are paranoid about modifying text, as if a bug was to happen, it + * could cause us to read or write to someplace that could cause harm. + * Carefully read and modify the code with probe_kernel_*(), and make + * sure what we read is what we expected it to be before modifying it. + */ + /* read the text we want to modify */ + if (copy_from_kernel_nofault(cur_code, (void *)ip, MCOUNT_INSN_SIZE)) { + WARN_ON(1); + return -EFAULT; + } + + /* Make sure it is what we expect it to be */ + if (memcmp(cur_code, old_code, MCOUNT_INSN_SIZE) != 0) { + ftrace_expected = old_code; + WARN_ON(1); + return -EINVAL; + } + + return 0; +} + +/* + * Marked __ref because it calls text_poke_early() which is .init.text. That is + * ok because that call will happen early, during boot, when .init sections are + * still present. + */ +static int __ref +ftrace_modify_code_direct(unsigned long ip, const char *old_code, + const char *new_code) +{ + int ret = ftrace_verify_code(ip, old_code); + if (ret) + return ret; + + /* replace the text with the new text */ + if (ftrace_poke_late) + text_poke_queue((void *)ip, new_code, MCOUNT_INSN_SIZE, NULL); + else + text_poke_early((void *)ip, new_code, MCOUNT_INSN_SIZE); + return 0; +} + +int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr) +{ + unsigned long ip = rec->ip; + const char *new, *old; + + old = ftrace_call_replace(ip, addr); + new = ftrace_nop_replace(); + + /* + * On boot up, and when modules are loaded, the MCOUNT_ADDR + * is converted to a nop, and will never become MCOUNT_ADDR + * again. This code is either running before SMP (on boot up) + * or before the code will ever be executed (module load). + * We do not want to use the breakpoint version in this case, + * just modify the code directly. + */ + if (addr == MCOUNT_ADDR) + return ftrace_modify_code_direct(ip, old, new); + + /* + * x86 overrides ftrace_replace_code -- this function will never be used + * in this case. + */ + WARN_ONCE(1, "invalid use of ftrace_make_nop"); + return -EINVAL; +} + +int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) +{ + unsigned long ip = rec->ip; + const char *new, *old; + + old = ftrace_nop_replace(); + new = ftrace_call_replace(ip, addr); + + /* Should only be called when module is loaded */ + return ftrace_modify_code_direct(rec->ip, old, new); +} + +/* + * Should never be called: + * As it is only called by __ftrace_replace_code() which is called by + * ftrace_replace_code() that x86 overrides, and by ftrace_update_code() + * which is called to turn mcount into nops or nops into function calls + * but not to convert a function from not using regs to one that uses + * regs, which ftrace_modify_call() is for. + */ +int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr, + unsigned long addr) +{ + WARN_ON(1); + return -EINVAL; +} + +int ftrace_update_ftrace_func(ftrace_func_t func) +{ + unsigned long ip; + const char *new; + + ip = (unsigned long)(&ftrace_call); + new = ftrace_call_replace(ip, (unsigned long)func); + text_poke_bp((void *)ip, new, MCOUNT_INSN_SIZE, NULL); + + ip = (unsigned long)(&ftrace_regs_call); + new = ftrace_call_replace(ip, (unsigned long)func); + text_poke_bp((void *)ip, new, MCOUNT_INSN_SIZE, NULL); + + return 0; +} + +void ftrace_replace_code(int enable) +{ + struct ftrace_rec_iter *iter; + struct dyn_ftrace *rec; + const char *new, *old; + int ret; + + for_ftrace_rec_iter(iter) { + rec = ftrace_rec_iter_record(iter); + + switch (ftrace_test_record(rec, enable)) { + case FTRACE_UPDATE_IGNORE: + default: + continue; + + case FTRACE_UPDATE_MAKE_CALL: + old = ftrace_nop_replace(); + break; + + case FTRACE_UPDATE_MODIFY_CALL: + case FTRACE_UPDATE_MAKE_NOP: + old = ftrace_call_replace(rec->ip, ftrace_get_addr_curr(rec)); + break; + } + + ret = ftrace_verify_code(rec->ip, old); + if (ret) { + ftrace_expected = old; + ftrace_bug(ret, rec); + ftrace_expected = NULL; + return; + } + } + + for_ftrace_rec_iter(iter) { + rec = ftrace_rec_iter_record(iter); + + switch (ftrace_test_record(rec, enable)) { + case FTRACE_UPDATE_IGNORE: + default: + continue; + + case FTRACE_UPDATE_MAKE_CALL: + case FTRACE_UPDATE_MODIFY_CALL: + new = ftrace_call_replace(rec->ip, ftrace_get_addr_new(rec)); + break; + + case FTRACE_UPDATE_MAKE_NOP: + new = ftrace_nop_replace(); + break; + } + + text_poke_queue((void *)rec->ip, new, MCOUNT_INSN_SIZE, NULL); + ftrace_update_record(rec, enable); + } + text_poke_finish(); +} + +void arch_ftrace_update_code(int command) +{ + ftrace_modify_all_code(command); +} + +/* Currently only x86_64 supports dynamic trampolines */ +#ifdef CONFIG_X86_64 + +#ifdef CONFIG_MODULES +#include <linux/moduleloader.h> +/* Module allocation simplifies allocating memory for code */ +static inline void *alloc_tramp(unsigned long size) +{ + return module_alloc(size); +} +static inline void tramp_free(void *tramp) +{ + module_memfree(tramp); +} +#else +/* Trampolines can only be created if modules are supported */ +static inline void *alloc_tramp(unsigned long size) +{ + return NULL; +} +static inline void tramp_free(void *tramp) { } +#endif + +/* Defined as markers to the end of the ftrace default trampolines */ +extern void ftrace_regs_caller_end(void); +extern void ftrace_caller_end(void); +extern void ftrace_caller_op_ptr(void); +extern void ftrace_regs_caller_op_ptr(void); +extern void ftrace_regs_caller_jmp(void); + +/* movq function_trace_op(%rip), %rdx */ +/* 0x48 0x8b 0x15 <offset-to-ftrace_trace_op (4 bytes)> */ +#define OP_REF_SIZE 7 + +/* + * The ftrace_ops is passed to the function callback. Since the + * trampoline only services a single ftrace_ops, we can pass in + * that ops directly. + * + * The ftrace_op_code_union is used to create a pointer to the + * ftrace_ops that will be passed to the callback function. + */ +union ftrace_op_code_union { + char code[OP_REF_SIZE]; + struct { + char op[3]; + int offset; + } __attribute__((packed)); +}; + +#define RET_SIZE (IS_ENABLED(CONFIG_RETPOLINE) ? 5 : 1 + IS_ENABLED(CONFIG_SLS)) + +static unsigned long +create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size) +{ + unsigned long start_offset; + unsigned long end_offset; + unsigned long op_offset; + unsigned long call_offset; + unsigned long jmp_offset; + unsigned long offset; + unsigned long npages; + unsigned long size; + unsigned long *ptr; + void *trampoline; + void *ip, *dest; + /* 48 8b 15 <offset> is movq <offset>(%rip), %rdx */ + unsigned const char op_ref[] = { 0x48, 0x8b, 0x15 }; + unsigned const char retq[] = { RET_INSN_OPCODE, INT3_INSN_OPCODE }; + union ftrace_op_code_union op_ptr; + int ret; + + if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) { + start_offset = (unsigned long)ftrace_regs_caller; + end_offset = (unsigned long)ftrace_regs_caller_end; + op_offset = (unsigned long)ftrace_regs_caller_op_ptr; + call_offset = (unsigned long)ftrace_regs_call; + jmp_offset = (unsigned long)ftrace_regs_caller_jmp; + } else { + start_offset = (unsigned long)ftrace_caller; + end_offset = (unsigned long)ftrace_caller_end; + op_offset = (unsigned long)ftrace_caller_op_ptr; + call_offset = (unsigned long)ftrace_call; + jmp_offset = 0; + } + + size = end_offset - start_offset; + + /* + * Allocate enough size to store the ftrace_caller code, + * the iret , as well as the address of the ftrace_ops this + * trampoline is used for. + */ + trampoline = alloc_tramp(size + RET_SIZE + sizeof(void *)); + if (!trampoline) + return 0; + + *tramp_size = size + RET_SIZE + sizeof(void *); + npages = DIV_ROUND_UP(*tramp_size, PAGE_SIZE); + + /* Copy ftrace_caller onto the trampoline memory */ + ret = copy_from_kernel_nofault(trampoline, (void *)start_offset, size); + if (WARN_ON(ret < 0)) + goto fail; + + ip = trampoline + size; + if (cpu_feature_enabled(X86_FEATURE_RETHUNK)) + __text_gen_insn(ip, JMP32_INSN_OPCODE, ip, x86_return_thunk, JMP32_INSN_SIZE); + else + memcpy(ip, retq, sizeof(retq)); + + /* No need to test direct calls on created trampolines */ + if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) { + /* NOP the jnz 1f; but make sure it's a 2 byte jnz */ + ip = trampoline + (jmp_offset - start_offset); + if (WARN_ON(*(char *)ip != 0x75)) + goto fail; + ret = copy_from_kernel_nofault(ip, x86_nops[2], 2); + if (ret < 0) + goto fail; + } + + /* + * The address of the ftrace_ops that is used for this trampoline + * is stored at the end of the trampoline. This will be used to + * load the third parameter for the callback. Basically, that + * location at the end of the trampoline takes the place of + * the global function_trace_op variable. + */ + + ptr = (unsigned long *)(trampoline + size + RET_SIZE); + *ptr = (unsigned long)ops; + + op_offset -= start_offset; + memcpy(&op_ptr, trampoline + op_offset, OP_REF_SIZE); + + /* Are we pointing to the reference? */ + if (WARN_ON(memcmp(op_ptr.op, op_ref, 3) != 0)) + goto fail; + + /* Load the contents of ptr into the callback parameter */ + offset = (unsigned long)ptr; + offset -= (unsigned long)trampoline + op_offset + OP_REF_SIZE; + + op_ptr.offset = offset; + + /* put in the new offset to the ftrace_ops */ + memcpy(trampoline + op_offset, &op_ptr, OP_REF_SIZE); + + /* put in the call to the function */ + mutex_lock(&text_mutex); + call_offset -= start_offset; + /* + * No need to translate into a callthunk. The trampoline does + * the depth accounting before the call already. + */ + dest = ftrace_ops_get_func(ops); + memcpy(trampoline + call_offset, + text_gen_insn(CALL_INSN_OPCODE, trampoline + call_offset, dest), + CALL_INSN_SIZE); + mutex_unlock(&text_mutex); + + /* ALLOC_TRAMP flags lets us know we created it */ + ops->flags |= FTRACE_OPS_FL_ALLOC_TRAMP; + + set_memory_rox((unsigned long)trampoline, npages); + return (unsigned long)trampoline; +fail: + tramp_free(trampoline); + return 0; +} + +void set_ftrace_ops_ro(void) +{ + struct ftrace_ops *ops; + unsigned long start_offset; + unsigned long end_offset; + unsigned long npages; + unsigned long size; + + do_for_each_ftrace_op(ops, ftrace_ops_list) { + if (!(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP)) + continue; + + if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) { + start_offset = (unsigned long)ftrace_regs_caller; + end_offset = (unsigned long)ftrace_regs_caller_end; + } else { + start_offset = (unsigned long)ftrace_caller; + end_offset = (unsigned long)ftrace_caller_end; + } + size = end_offset - start_offset; + size = size + RET_SIZE + sizeof(void *); + npages = DIV_ROUND_UP(size, PAGE_SIZE); + set_memory_ro((unsigned long)ops->trampoline, npages); + } while_for_each_ftrace_op(ops); +} + +static unsigned long calc_trampoline_call_offset(bool save_regs) +{ + unsigned long start_offset; + unsigned long call_offset; + + if (save_regs) { + start_offset = (unsigned long)ftrace_regs_caller; + call_offset = (unsigned long)ftrace_regs_call; + } else { + start_offset = (unsigned long)ftrace_caller; + call_offset = (unsigned long)ftrace_call; + } + + return call_offset - start_offset; +} + +void arch_ftrace_update_trampoline(struct ftrace_ops *ops) +{ + ftrace_func_t func; + unsigned long offset; + unsigned long ip; + unsigned int size; + const char *new; + + if (!ops->trampoline) { + ops->trampoline = create_trampoline(ops, &size); + if (!ops->trampoline) + return; + ops->trampoline_size = size; + return; + } + + /* + * The ftrace_ops caller may set up its own trampoline. + * In such a case, this code must not modify it. + */ + if (!(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP)) + return; + + offset = calc_trampoline_call_offset(ops->flags & FTRACE_OPS_FL_SAVE_REGS); + ip = ops->trampoline + offset; + func = ftrace_ops_get_func(ops); + + mutex_lock(&text_mutex); + /* Do a safe modify in case the trampoline is executing */ + new = ftrace_call_replace(ip, (unsigned long)func); + text_poke_bp((void *)ip, new, MCOUNT_INSN_SIZE, NULL); + mutex_unlock(&text_mutex); +} + +/* Return the address of the function the trampoline calls */ +static void *addr_from_call(void *ptr) +{ + union text_poke_insn call; + int ret; + + ret = copy_from_kernel_nofault(&call, ptr, CALL_INSN_SIZE); + if (WARN_ON_ONCE(ret < 0)) + return NULL; + + /* Make sure this is a call */ + if (WARN_ON_ONCE(call.opcode != CALL_INSN_OPCODE)) { + pr_warn("Expected E8, got %x\n", call.opcode); + return NULL; + } + + return ptr + CALL_INSN_SIZE + call.disp; +} + +/* + * If the ops->trampoline was not allocated, then it probably + * has a static trampoline func, or is the ftrace caller itself. + */ +static void *static_tramp_func(struct ftrace_ops *ops, struct dyn_ftrace *rec) +{ + unsigned long offset; + bool save_regs = rec->flags & FTRACE_FL_REGS_EN; + void *ptr; + + if (ops && ops->trampoline) { +#if !defined(CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS) && \ + defined(CONFIG_FUNCTION_GRAPH_TRACER) + /* + * We only know about function graph tracer setting as static + * trampoline. + */ + if (ops->trampoline == FTRACE_GRAPH_ADDR) + return (void *)prepare_ftrace_return; +#endif + return NULL; + } + + offset = calc_trampoline_call_offset(save_regs); + + if (save_regs) + ptr = (void *)FTRACE_REGS_ADDR + offset; + else + ptr = (void *)FTRACE_ADDR + offset; + + return addr_from_call(ptr); +} + +void *arch_ftrace_trampoline_func(struct ftrace_ops *ops, struct dyn_ftrace *rec) +{ + unsigned long offset; + + /* If we didn't allocate this trampoline, consider it static */ + if (!ops || !(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP)) + return static_tramp_func(ops, rec); + + offset = calc_trampoline_call_offset(ops->flags & FTRACE_OPS_FL_SAVE_REGS); + return addr_from_call((void *)ops->trampoline + offset); +} + +void arch_ftrace_trampoline_free(struct ftrace_ops *ops) +{ + if (!ops || !(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP)) + return; + + tramp_free((void *)ops->trampoline); + ops->trampoline = 0; +} + +#endif /* CONFIG_X86_64 */ +#endif /* CONFIG_DYNAMIC_FTRACE */ + +#ifdef CONFIG_FUNCTION_GRAPH_TRACER + +#if defined(CONFIG_DYNAMIC_FTRACE) && !defined(CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS) +extern void ftrace_graph_call(void); +static const char *ftrace_jmp_replace(unsigned long ip, unsigned long addr) +{ + return text_gen_insn(JMP32_INSN_OPCODE, (void *)ip, (void *)addr); +} + +static int ftrace_mod_jmp(unsigned long ip, void *func) +{ + const char *new; + + new = ftrace_jmp_replace(ip, (unsigned long)func); + text_poke_bp((void *)ip, new, MCOUNT_INSN_SIZE, NULL); + return 0; +} + +int ftrace_enable_ftrace_graph_caller(void) +{ + unsigned long ip = (unsigned long)(&ftrace_graph_call); + + return ftrace_mod_jmp(ip, &ftrace_graph_caller); +} + +int ftrace_disable_ftrace_graph_caller(void) +{ + unsigned long ip = (unsigned long)(&ftrace_graph_call); + + return ftrace_mod_jmp(ip, &ftrace_stub); +} +#endif /* CONFIG_DYNAMIC_FTRACE && !CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS */ + +/* + * Hook the return address and push it in the stack of return addrs + * in current thread info. + */ +void prepare_ftrace_return(unsigned long ip, unsigned long *parent, + unsigned long frame_pointer) +{ + unsigned long return_hooker = (unsigned long)&return_to_handler; + int bit; + + /* + * When resuming from suspend-to-ram, this function can be indirectly + * called from early CPU startup code while the CPU is in real mode, + * which would fail miserably. Make sure the stack pointer is a + * virtual address. + * + * This check isn't as accurate as virt_addr_valid(), but it should be + * good enough for this purpose, and it's fast. + */ + if (unlikely((long)__builtin_frame_address(0) >= 0)) + return; + + if (unlikely(ftrace_graph_is_dead())) + return; + + if (unlikely(atomic_read(¤t->tracing_graph_pause))) + return; + + bit = ftrace_test_recursion_trylock(ip, *parent); + if (bit < 0) + return; + + if (!function_graph_enter(*parent, ip, frame_pointer, parent)) + *parent = return_hooker; + + ftrace_test_recursion_unlock(bit); +} + +#ifdef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS +void ftrace_graph_func(unsigned long ip, unsigned long parent_ip, + struct ftrace_ops *op, struct ftrace_regs *fregs) +{ + struct pt_regs *regs = &fregs->regs; + unsigned long *stack = (unsigned long *)kernel_stack_pointer(regs); + + prepare_ftrace_return(ip, (unsigned long *)stack, 0); +} +#endif + +#endif /* CONFIG_FUNCTION_GRAPH_TRACER */ |