diff options
Diffstat (limited to 'arch/x86/kernel/ftrace.c')
| -rw-r--r-- | arch/x86/kernel/ftrace.c | 1081 |
1 files changed, 1081 insertions, 0 deletions
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c new file mode 100644 index 000000000..32b63b30e --- /dev/null +++ b/arch/x86/kernel/ftrace.c @@ -0,0 +1,1081 @@ +// 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 <trace/syscall.h> + +#include <asm/set_memory.h> +#include <asm/kprobes.h> +#include <asm/ftrace.h> +#include <asm/nops.h> +#include <asm/text-patching.h> + +#ifdef CONFIG_DYNAMIC_FTRACE + +int ftrace_arch_code_modify_prepare(void) + __acquires(&text_mutex) +{ + mutex_lock(&text_mutex); + set_kernel_text_rw(); + set_all_modules_text_rw(); + return 0; +} + +int ftrace_arch_code_modify_post_process(void) + __releases(&text_mutex) +{ + set_all_modules_text_ro(); + set_kernel_text_ro(); + mutex_unlock(&text_mutex); + return 0; +} + +union ftrace_code_union { + char code[MCOUNT_INSN_SIZE]; + struct { + unsigned char op; + int offset; + } __attribute__((packed)); +}; + +static int ftrace_calc_offset(long ip, long addr) +{ + return (int)(addr - ip); +} + +static unsigned char * +ftrace_text_replace(unsigned char op, unsigned long ip, unsigned long addr) +{ + static union ftrace_code_union calc; + + calc.op = op; + calc.offset = ftrace_calc_offset(ip + MCOUNT_INSN_SIZE, addr); + + return calc.code; +} + +static unsigned char * +ftrace_call_replace(unsigned long ip, unsigned long addr) +{ + return ftrace_text_replace(0xe8, ip, addr); +} + +static inline int +within(unsigned long addr, unsigned long start, unsigned long end) +{ + return addr >= start && addr < end; +} + +static unsigned long text_ip_addr(unsigned long ip) +{ + /* + * On x86_64, kernel text mappings are mapped read-only, so we use + * the kernel identity mapping instead of the kernel text mapping + * to modify the kernel text. + * + * For 32bit kernels, these mappings are same and we can use + * kernel identity mapping to modify code. + */ + if (within(ip, (unsigned long)_text, (unsigned long)_etext)) + ip = (unsigned long)__va(__pa_symbol(ip)); + + return ip; +} + +static const unsigned char *ftrace_nop_replace(void) +{ + return ideal_nops[NOP_ATOMIC5]; +} + +static int +ftrace_modify_code_direct(unsigned long ip, unsigned const char *old_code, + unsigned const char *new_code) +{ + unsigned char replaced[MCOUNT_INSN_SIZE]; + + ftrace_expected = old_code; + + /* + * 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 (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE)) + return -EFAULT; + + /* Make sure it is what we expect it to be */ + if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0) + return -EINVAL; + + ip = text_ip_addr(ip); + + /* replace the text with the new text */ + if (probe_kernel_write((void *)ip, new_code, MCOUNT_INSN_SIZE)) + return -EPERM; + + sync_core(); + + return 0; +} + +int ftrace_make_nop(struct module *mod, + struct dyn_ftrace *rec, unsigned long addr) +{ + unsigned const char *new, *old; + unsigned long ip = rec->ip; + + 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(rec->ip, old, new); + + ftrace_expected = NULL; + + /* Normal cases use add_brk_on_nop */ + WARN_ONCE(1, "invalid use of ftrace_make_nop"); + return -EINVAL; +} + +int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) +{ + unsigned const char *new, *old; + unsigned long ip = rec->ip; + + 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); +} + +/* + * The modifying_ftrace_code is used to tell the breakpoint + * handler to call ftrace_int3_handler(). If it fails to + * call this handler for a breakpoint added by ftrace, then + * the kernel may crash. + * + * As atomic_writes on x86 do not need a barrier, we do not + * need to add smp_mb()s for this to work. It is also considered + * that we can not read the modifying_ftrace_code before + * executing the breakpoint. That would be quite remarkable if + * it could do that. Here's the flow that is required: + * + * CPU-0 CPU-1 + * + * atomic_inc(mfc); + * write int3s + * <trap-int3> // implicit (r)mb + * if (atomic_read(mfc)) + * call ftrace_int3_handler() + * + * Then when we are finished: + * + * atomic_dec(mfc); + * + * If we hit a breakpoint that was not set by ftrace, it does not + * matter if ftrace_int3_handler() is called or not. It will + * simply be ignored. But it is crucial that a ftrace nop/caller + * breakpoint is handled. No other user should ever place a + * breakpoint on an ftrace nop/caller location. It must only + * be done by this code. + */ +atomic_t modifying_ftrace_code __read_mostly; + +static int +ftrace_modify_code(unsigned long ip, unsigned const char *old_code, + unsigned const char *new_code); + +/* + * 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); + ftrace_expected = NULL; + return -EINVAL; +} + +static unsigned long ftrace_update_func; +static unsigned long ftrace_update_func_call; + +static int update_ftrace_func(unsigned long ip, void *new) +{ + unsigned char old[MCOUNT_INSN_SIZE]; + int ret; + + memcpy(old, (void *)ip, MCOUNT_INSN_SIZE); + + ftrace_update_func = ip; + /* Make sure the breakpoints see the ftrace_update_func update */ + smp_wmb(); + + /* See comment above by declaration of modifying_ftrace_code */ + atomic_inc(&modifying_ftrace_code); + + ret = ftrace_modify_code(ip, old, new); + + atomic_dec(&modifying_ftrace_code); + + return ret; +} + +int ftrace_update_ftrace_func(ftrace_func_t func) +{ + unsigned long ip = (unsigned long)(&ftrace_call); + unsigned char *new; + int ret; + + ftrace_update_func_call = (unsigned long)func; + + new = ftrace_call_replace(ip, (unsigned long)func); + ret = update_ftrace_func(ip, new); + + /* Also update the regs callback function */ + if (!ret) { + ip = (unsigned long)(&ftrace_regs_call); + new = ftrace_call_replace(ip, (unsigned long)func); + ret = update_ftrace_func(ip, new); + } + + return ret; +} + +static int is_ftrace_caller(unsigned long ip) +{ + if (ip == ftrace_update_func) + return 1; + + return 0; +} + +/* + * A breakpoint was added to the code address we are about to + * modify, and this is the handle that will just skip over it. + * We are either changing a nop into a trace call, or a trace + * call to a nop. While the change is taking place, we treat + * it just like it was a nop. + */ +int ftrace_int3_handler(struct pt_regs *regs) +{ + unsigned long ip; + + if (WARN_ON_ONCE(!regs)) + return 0; + + ip = regs->ip - INT3_INSN_SIZE; + +#ifdef CONFIG_X86_64 + if (ftrace_location(ip)) { + int3_emulate_call(regs, (unsigned long)ftrace_regs_caller); + return 1; + } else if (is_ftrace_caller(ip)) { + if (!ftrace_update_func_call) { + int3_emulate_jmp(regs, ip + CALL_INSN_SIZE); + return 1; + } + int3_emulate_call(regs, ftrace_update_func_call); + return 1; + } +#else + if (ftrace_location(ip) || is_ftrace_caller(ip)) { + int3_emulate_jmp(regs, ip + CALL_INSN_SIZE); + return 1; + } +#endif + + return 0; +} + +static int ftrace_write(unsigned long ip, const char *val, int size) +{ + ip = text_ip_addr(ip); + + if (probe_kernel_write((void *)ip, val, size)) + return -EPERM; + + return 0; +} + +static int add_break(unsigned long ip, const char *old) +{ + unsigned char replaced[MCOUNT_INSN_SIZE]; + unsigned char brk = BREAKPOINT_INSTRUCTION; + + if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE)) + return -EFAULT; + + ftrace_expected = old; + + /* Make sure it is what we expect it to be */ + if (memcmp(replaced, old, MCOUNT_INSN_SIZE) != 0) + return -EINVAL; + + return ftrace_write(ip, &brk, 1); +} + +static int add_brk_on_call(struct dyn_ftrace *rec, unsigned long addr) +{ + unsigned const char *old; + unsigned long ip = rec->ip; + + old = ftrace_call_replace(ip, addr); + + return add_break(rec->ip, old); +} + + +static int add_brk_on_nop(struct dyn_ftrace *rec) +{ + unsigned const char *old; + + old = ftrace_nop_replace(); + + return add_break(rec->ip, old); +} + +static int add_breakpoints(struct dyn_ftrace *rec, int enable) +{ + unsigned long ftrace_addr; + int ret; + + ftrace_addr = ftrace_get_addr_curr(rec); + + ret = ftrace_test_record(rec, enable); + + switch (ret) { + case FTRACE_UPDATE_IGNORE: + return 0; + + case FTRACE_UPDATE_MAKE_CALL: + /* converting nop to call */ + return add_brk_on_nop(rec); + + case FTRACE_UPDATE_MODIFY_CALL: + case FTRACE_UPDATE_MAKE_NOP: + /* converting a call to a nop */ + return add_brk_on_call(rec, ftrace_addr); + } + return 0; +} + +/* + * On error, we need to remove breakpoints. This needs to + * be done caefully. If the address does not currently have a + * breakpoint, we know we are done. Otherwise, we look at the + * remaining 4 bytes of the instruction. If it matches a nop + * we replace the breakpoint with the nop. Otherwise we replace + * it with the call instruction. + */ +static int remove_breakpoint(struct dyn_ftrace *rec) +{ + unsigned char ins[MCOUNT_INSN_SIZE]; + unsigned char brk = BREAKPOINT_INSTRUCTION; + const unsigned char *nop; + unsigned long ftrace_addr; + unsigned long ip = rec->ip; + + /* If we fail the read, just give up */ + if (probe_kernel_read(ins, (void *)ip, MCOUNT_INSN_SIZE)) + return -EFAULT; + + /* If this does not have a breakpoint, we are done */ + if (ins[0] != brk) + return 0; + + nop = ftrace_nop_replace(); + + /* + * If the last 4 bytes of the instruction do not match + * a nop, then we assume that this is a call to ftrace_addr. + */ + if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) != 0) { + /* + * For extra paranoidism, we check if the breakpoint is on + * a call that would actually jump to the ftrace_addr. + * If not, don't touch the breakpoint, we make just create + * a disaster. + */ + ftrace_addr = ftrace_get_addr_new(rec); + nop = ftrace_call_replace(ip, ftrace_addr); + + if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) == 0) + goto update; + + /* Check both ftrace_addr and ftrace_old_addr */ + ftrace_addr = ftrace_get_addr_curr(rec); + nop = ftrace_call_replace(ip, ftrace_addr); + + ftrace_expected = nop; + + if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) != 0) + return -EINVAL; + } + + update: + return ftrace_write(ip, nop, 1); +} + +static int add_update_code(unsigned long ip, unsigned const char *new) +{ + /* skip breakpoint */ + ip++; + new++; + return ftrace_write(ip, new, MCOUNT_INSN_SIZE - 1); +} + +static int add_update_call(struct dyn_ftrace *rec, unsigned long addr) +{ + unsigned long ip = rec->ip; + unsigned const char *new; + + new = ftrace_call_replace(ip, addr); + return add_update_code(ip, new); +} + +static int add_update_nop(struct dyn_ftrace *rec) +{ + unsigned long ip = rec->ip; + unsigned const char *new; + + new = ftrace_nop_replace(); + return add_update_code(ip, new); +} + +static int add_update(struct dyn_ftrace *rec, int enable) +{ + unsigned long ftrace_addr; + int ret; + + ret = ftrace_test_record(rec, enable); + + ftrace_addr = ftrace_get_addr_new(rec); + + switch (ret) { + case FTRACE_UPDATE_IGNORE: + return 0; + + case FTRACE_UPDATE_MODIFY_CALL: + case FTRACE_UPDATE_MAKE_CALL: + /* converting nop to call */ + return add_update_call(rec, ftrace_addr); + + case FTRACE_UPDATE_MAKE_NOP: + /* converting a call to a nop */ + return add_update_nop(rec); + } + + return 0; +} + +static int finish_update_call(struct dyn_ftrace *rec, unsigned long addr) +{ + unsigned long ip = rec->ip; + unsigned const char *new; + + new = ftrace_call_replace(ip, addr); + + return ftrace_write(ip, new, 1); +} + +static int finish_update_nop(struct dyn_ftrace *rec) +{ + unsigned long ip = rec->ip; + unsigned const char *new; + + new = ftrace_nop_replace(); + + return ftrace_write(ip, new, 1); +} + +static int finish_update(struct dyn_ftrace *rec, int enable) +{ + unsigned long ftrace_addr; + int ret; + + ret = ftrace_update_record(rec, enable); + + ftrace_addr = ftrace_get_addr_new(rec); + + switch (ret) { + case FTRACE_UPDATE_IGNORE: + return 0; + + case FTRACE_UPDATE_MODIFY_CALL: + case FTRACE_UPDATE_MAKE_CALL: + /* converting nop to call */ + return finish_update_call(rec, ftrace_addr); + + case FTRACE_UPDATE_MAKE_NOP: + /* converting a call to a nop */ + return finish_update_nop(rec); + } + + return 0; +} + +static void do_sync_core(void *data) +{ + sync_core(); +} + +static void run_sync(void) +{ + int enable_irqs; + + /* No need to sync if there's only one CPU */ + if (num_online_cpus() == 1) + return; + + enable_irqs = irqs_disabled(); + + /* We may be called with interrupts disabled (on bootup). */ + if (enable_irqs) + local_irq_enable(); + on_each_cpu(do_sync_core, NULL, 1); + if (enable_irqs) + local_irq_disable(); +} + +void ftrace_replace_code(int enable) +{ + struct ftrace_rec_iter *iter; + struct dyn_ftrace *rec; + const char *report = "adding breakpoints"; + int count = 0; + int ret; + + for_ftrace_rec_iter(iter) { + rec = ftrace_rec_iter_record(iter); + + ret = add_breakpoints(rec, enable); + if (ret) + goto remove_breakpoints; + count++; + } + + run_sync(); + + report = "updating code"; + count = 0; + + for_ftrace_rec_iter(iter) { + rec = ftrace_rec_iter_record(iter); + + ret = add_update(rec, enable); + if (ret) + goto remove_breakpoints; + count++; + } + + run_sync(); + + report = "removing breakpoints"; + count = 0; + + for_ftrace_rec_iter(iter) { + rec = ftrace_rec_iter_record(iter); + + ret = finish_update(rec, enable); + if (ret) + goto remove_breakpoints; + count++; + } + + run_sync(); + + return; + + remove_breakpoints: + pr_warn("Failed on %s (%d):\n", report, count); + ftrace_bug(ret, rec); + for_ftrace_rec_iter(iter) { + rec = ftrace_rec_iter_record(iter); + /* + * Breakpoints are handled only when this function is in + * progress. The system could not work with them. + */ + if (remove_breakpoint(rec)) + BUG(); + } + run_sync(); +} + +static int +ftrace_modify_code(unsigned long ip, unsigned const char *old_code, + unsigned const char *new_code) +{ + int ret; + + ret = add_break(ip, old_code); + if (ret) + goto out; + + run_sync(); + + ret = add_update_code(ip, new_code); + if (ret) + goto fail_update; + + run_sync(); + + ret = ftrace_write(ip, new_code, 1); + /* + * The breakpoint is handled only when this function is in progress. + * The system could not work if we could not remove it. + */ + BUG_ON(ret); + out: + run_sync(); + return ret; + + fail_update: + /* Also here the system could not work with the breakpoint */ + if (ftrace_write(ip, old_code, 1)) + BUG(); + goto out; +} + +void arch_ftrace_update_code(int command) +{ + /* See comment above by declaration of modifying_ftrace_code */ + atomic_inc(&modifying_ftrace_code); + + ftrace_modify_all_code(command); + + atomic_dec(&modifying_ftrace_code); +} + +int __init ftrace_dyn_arch_init(void) +{ + return 0; +} + +/* 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, int size) +{ + int npages = PAGE_ALIGN(size) >> PAGE_SHIFT; + + set_memory_nx((unsigned long)tramp, npages); + set_memory_rw((unsigned long)tramp, npages); + 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, int size) { } +#endif + +/* Defined as markers to the end of the ftrace default trampolines */ +extern void ftrace_regs_caller_end(void); +extern void ftrace_epilogue(void); +extern void ftrace_caller_op_ptr(void); +extern void ftrace_regs_caller_op_ptr(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 1 + +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 offset; + unsigned long npages; + unsigned long size; + unsigned long retq; + unsigned long *ptr; + void *trampoline; + void *ip; + /* 48 8b 15 <offset> is movq <offset>(%rip), %rdx */ + unsigned const char op_ref[] = { 0x48, 0x8b, 0x15 }; + 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; + } else { + start_offset = (unsigned long)ftrace_caller; + end_offset = (unsigned long)ftrace_epilogue; + op_offset = (unsigned long)ftrace_caller_op_ptr; + } + + 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 = probe_kernel_read(trampoline, (void *)start_offset, size); + if (WARN_ON(ret < 0)) + goto fail; + + ip = trampoline + size; + + /* The trampoline ends with ret(q) */ + retq = (unsigned long)ftrace_stub; + ret = probe_kernel_read(ip, (void *)retq, RET_SIZE); + if (WARN_ON(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); + + /* ALLOC_TRAMP flags lets us know we created it */ + ops->flags |= FTRACE_OPS_FL_ALLOC_TRAMP; + + /* + * Module allocation needs to be completed by making the page + * executable. The page is still writable, which is a security hazard, + * but anyhow ftrace breaks W^X completely. + */ + set_memory_x((unsigned long)trampoline, npages); + return (unsigned long)trampoline; +fail: + tramp_free(trampoline, *tramp_size); + return 0; +} + +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 char *new; + unsigned long offset; + unsigned long ip; + unsigned int size; + int ret, npages; + + if (ops->trampoline) { + /* + * 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; + npages = PAGE_ALIGN(ops->trampoline_size) >> PAGE_SHIFT; + set_memory_rw(ops->trampoline, npages); + } else { + ops->trampoline = create_trampoline(ops, &size); + if (!ops->trampoline) + return; + ops->trampoline_size = size; + npages = PAGE_ALIGN(size) >> PAGE_SHIFT; + } + + offset = calc_trampoline_call_offset(ops->flags & FTRACE_OPS_FL_SAVE_REGS); + ip = ops->trampoline + offset; + + func = ftrace_ops_get_func(ops); + + ftrace_update_func_call = (unsigned long)func; + + /* Do a safe modify in case the trampoline is executing */ + new = ftrace_call_replace(ip, (unsigned long)func); + ret = update_ftrace_func(ip, new); + set_memory_ro(ops->trampoline, npages); + + /* The update should never fail */ + WARN_ON(ret); +} + +/* Return the address of the function the trampoline calls */ +static void *addr_from_call(void *ptr) +{ + union ftrace_code_union calc; + int ret; + + ret = probe_kernel_read(&calc, ptr, MCOUNT_INSN_SIZE); + if (WARN_ON_ONCE(ret < 0)) + return NULL; + + /* Make sure this is a call */ + if (WARN_ON_ONCE(calc.op != 0xe8)) { + pr_warn("Expected e8, got %x\n", calc.op); + return NULL; + } + + return ptr + MCOUNT_INSN_SIZE + calc.offset; +} + +void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent, + unsigned long frame_pointer); + +/* + * 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) { +#ifdef 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_size); + ops->trampoline = 0; +} + +#endif /* CONFIG_X86_64 */ +#endif /* CONFIG_DYNAMIC_FTRACE */ + +#ifdef CONFIG_FUNCTION_GRAPH_TRACER + +#ifdef CONFIG_DYNAMIC_FTRACE +extern void ftrace_graph_call(void); + +static unsigned char *ftrace_jmp_replace(unsigned long ip, unsigned long addr) +{ + return ftrace_text_replace(0xe9, ip, addr); +} + +static int ftrace_mod_jmp(unsigned long ip, void *func) +{ + unsigned char *new; + + ftrace_update_func_call = 0UL; + new = ftrace_jmp_replace(ip, (unsigned long)func); + + return update_ftrace_func(ip, new); +} + +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 */ + +/* + * Hook the return address and push it in the stack of return addrs + * in current thread info. + */ +void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent, + unsigned long frame_pointer) +{ + unsigned long old; + int faulted; + unsigned long return_hooker = (unsigned long) + &return_to_handler; + + /* + * 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; + + /* + * Protect against fault, even if it shouldn't + * happen. This tool is too much intrusive to + * ignore such a protection. + */ + asm volatile( + "1: " _ASM_MOV " (%[parent]), %[old]\n" + "2: " _ASM_MOV " %[return_hooker], (%[parent])\n" + " movl $0, %[faulted]\n" + "3:\n" + + ".section .fixup, \"ax\"\n" + "4: movl $1, %[faulted]\n" + " jmp 3b\n" + ".previous\n" + + _ASM_EXTABLE(1b, 4b) + _ASM_EXTABLE(2b, 4b) + + : [old] "=&r" (old), [faulted] "=r" (faulted) + : [parent] "r" (parent), [return_hooker] "r" (return_hooker) + : "memory" + ); + + if (unlikely(faulted)) { + ftrace_graph_stop(); + WARN_ON(1); + return; + } + + if (function_graph_enter(old, self_addr, frame_pointer, parent)) + *parent = old; +} +#endif /* CONFIG_FUNCTION_GRAPH_TRACER */ |