1079 lines
25 KiB
C
1079 lines
25 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Dynamic function tracing support.
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*
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* Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
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*
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* Thanks goes to Ingo Molnar, for suggesting the idea.
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* Mathieu Desnoyers, for suggesting postponing the modifications.
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* Arjan van de Ven, for keeping me straight, and explaining to me
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* the dangers of modifying code on the run.
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/spinlock.h>
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#include <linux/hardirq.h>
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#include <linux/uaccess.h>
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#include <linux/ftrace.h>
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#include <linux/percpu.h>
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#include <linux/sched.h>
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#include <linux/slab.h>
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#include <linux/init.h>
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#include <linux/list.h>
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#include <linux/module.h>
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#include <linux/memory.h>
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#include <trace/syscall.h>
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#include <asm/set_memory.h>
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#include <asm/kprobes.h>
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#include <asm/ftrace.h>
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#include <asm/nops.h>
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#include <asm/text-patching.h>
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#ifdef CONFIG_DYNAMIC_FTRACE
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int ftrace_arch_code_modify_prepare(void)
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__acquires(&text_mutex)
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{
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/*
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* Need to grab text_mutex to prevent a race from module loading
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* and live kernel patching from changing the text permissions while
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* ftrace has it set to "read/write".
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*/
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mutex_lock(&text_mutex);
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set_kernel_text_rw();
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set_all_modules_text_rw();
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return 0;
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}
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int ftrace_arch_code_modify_post_process(void)
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__releases(&text_mutex)
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{
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set_all_modules_text_ro();
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set_kernel_text_ro();
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mutex_unlock(&text_mutex);
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return 0;
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}
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union ftrace_code_union {
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char code[MCOUNT_INSN_SIZE];
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struct {
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unsigned char op;
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int offset;
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} __attribute__((packed));
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};
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static int ftrace_calc_offset(long ip, long addr)
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{
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return (int)(addr - ip);
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}
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static unsigned char *
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ftrace_text_replace(unsigned char op, unsigned long ip, unsigned long addr)
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{
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static union ftrace_code_union calc;
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calc.op = op;
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calc.offset = ftrace_calc_offset(ip + MCOUNT_INSN_SIZE, addr);
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return calc.code;
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}
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static unsigned char *
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ftrace_call_replace(unsigned long ip, unsigned long addr)
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{
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return ftrace_text_replace(0xe8, ip, addr);
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}
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static inline int
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within(unsigned long addr, unsigned long start, unsigned long end)
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{
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return addr >= start && addr < end;
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}
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static unsigned long text_ip_addr(unsigned long ip)
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{
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/*
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* On x86_64, kernel text mappings are mapped read-only, so we use
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* the kernel identity mapping instead of the kernel text mapping
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* to modify the kernel text.
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*
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* For 32bit kernels, these mappings are same and we can use
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* kernel identity mapping to modify code.
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*/
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if (within(ip, (unsigned long)_text, (unsigned long)_etext))
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ip = (unsigned long)__va(__pa_symbol(ip));
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return ip;
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}
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static const unsigned char *ftrace_nop_replace(void)
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{
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return ideal_nops[NOP_ATOMIC5];
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}
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static int
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ftrace_modify_code_direct(unsigned long ip, unsigned const char *old_code,
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unsigned const char *new_code)
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{
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unsigned char replaced[MCOUNT_INSN_SIZE];
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ftrace_expected = old_code;
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/*
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* Note:
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* We are paranoid about modifying text, as if a bug was to happen, it
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* could cause us to read or write to someplace that could cause harm.
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* Carefully read and modify the code with probe_kernel_*(), and make
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* sure what we read is what we expected it to be before modifying it.
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*/
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/* read the text we want to modify */
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if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
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return -EFAULT;
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/* Make sure it is what we expect it to be */
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if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0)
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return -EINVAL;
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ip = text_ip_addr(ip);
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/* replace the text with the new text */
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if (probe_kernel_write((void *)ip, new_code, MCOUNT_INSN_SIZE))
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return -EPERM;
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sync_core();
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return 0;
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}
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int ftrace_make_nop(struct module *mod,
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struct dyn_ftrace *rec, unsigned long addr)
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{
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unsigned const char *new, *old;
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unsigned long ip = rec->ip;
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old = ftrace_call_replace(ip, addr);
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new = ftrace_nop_replace();
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/*
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* On boot up, and when modules are loaded, the MCOUNT_ADDR
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* is converted to a nop, and will never become MCOUNT_ADDR
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* again. This code is either running before SMP (on boot up)
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* or before the code will ever be executed (module load).
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* We do not want to use the breakpoint version in this case,
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* just modify the code directly.
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*/
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if (addr == MCOUNT_ADDR)
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return ftrace_modify_code_direct(rec->ip, old, new);
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ftrace_expected = NULL;
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/* Normal cases use add_brk_on_nop */
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WARN_ONCE(1, "invalid use of ftrace_make_nop");
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return -EINVAL;
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}
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int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
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{
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unsigned const char *new, *old;
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unsigned long ip = rec->ip;
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old = ftrace_nop_replace();
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new = ftrace_call_replace(ip, addr);
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/* Should only be called when module is loaded */
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return ftrace_modify_code_direct(rec->ip, old, new);
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}
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/*
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* The modifying_ftrace_code is used to tell the breakpoint
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* handler to call ftrace_int3_handler(). If it fails to
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* call this handler for a breakpoint added by ftrace, then
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* the kernel may crash.
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*
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* As atomic_writes on x86 do not need a barrier, we do not
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* need to add smp_mb()s for this to work. It is also considered
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* that we can not read the modifying_ftrace_code before
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* executing the breakpoint. That would be quite remarkable if
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* it could do that. Here's the flow that is required:
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*
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* CPU-0 CPU-1
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*
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* atomic_inc(mfc);
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* write int3s
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* <trap-int3> // implicit (r)mb
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* if (atomic_read(mfc))
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* call ftrace_int3_handler()
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*
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* Then when we are finished:
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*
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* atomic_dec(mfc);
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*
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* If we hit a breakpoint that was not set by ftrace, it does not
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* matter if ftrace_int3_handler() is called or not. It will
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* simply be ignored. But it is crucial that a ftrace nop/caller
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* breakpoint is handled. No other user should ever place a
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* breakpoint on an ftrace nop/caller location. It must only
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* be done by this code.
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*/
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atomic_t modifying_ftrace_code __read_mostly;
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static int
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ftrace_modify_code(unsigned long ip, unsigned const char *old_code,
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unsigned const char *new_code);
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/*
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* Should never be called:
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* As it is only called by __ftrace_replace_code() which is called by
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* ftrace_replace_code() that x86 overrides, and by ftrace_update_code()
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* which is called to turn mcount into nops or nops into function calls
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* but not to convert a function from not using regs to one that uses
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* regs, which ftrace_modify_call() is for.
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*/
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int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
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unsigned long addr)
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{
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WARN_ON(1);
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ftrace_expected = NULL;
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return -EINVAL;
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}
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static unsigned long ftrace_update_func;
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static unsigned long ftrace_update_func_call;
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static int update_ftrace_func(unsigned long ip, void *new)
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{
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unsigned char old[MCOUNT_INSN_SIZE];
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int ret;
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memcpy(old, (void *)ip, MCOUNT_INSN_SIZE);
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ftrace_update_func = ip;
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/* Make sure the breakpoints see the ftrace_update_func update */
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smp_wmb();
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/* See comment above by declaration of modifying_ftrace_code */
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atomic_inc(&modifying_ftrace_code);
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ret = ftrace_modify_code(ip, old, new);
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atomic_dec(&modifying_ftrace_code);
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return ret;
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}
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int ftrace_update_ftrace_func(ftrace_func_t func)
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{
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unsigned long ip = (unsigned long)(&ftrace_call);
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unsigned char *new;
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int ret;
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ftrace_update_func_call = (unsigned long)func;
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new = ftrace_call_replace(ip, (unsigned long)func);
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ret = update_ftrace_func(ip, new);
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/* Also update the regs callback function */
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if (!ret) {
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ip = (unsigned long)(&ftrace_regs_call);
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new = ftrace_call_replace(ip, (unsigned long)func);
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ret = update_ftrace_func(ip, new);
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}
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return ret;
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}
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static nokprobe_inline int is_ftrace_caller(unsigned long ip)
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{
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if (ip == ftrace_update_func)
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return 1;
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return 0;
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}
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/*
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* A breakpoint was added to the code address we are about to
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* modify, and this is the handle that will just skip over it.
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* We are either changing a nop into a trace call, or a trace
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* call to a nop. While the change is taking place, we treat
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* it just like it was a nop.
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*/
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int ftrace_int3_handler(struct pt_regs *regs)
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{
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unsigned long ip;
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if (WARN_ON_ONCE(!regs))
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return 0;
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ip = regs->ip - INT3_INSN_SIZE;
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if (ftrace_location(ip)) {
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int3_emulate_call(regs, (unsigned long)ftrace_regs_caller);
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return 1;
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} else if (is_ftrace_caller(ip)) {
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if (!ftrace_update_func_call) {
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int3_emulate_jmp(regs, ip + CALL_INSN_SIZE);
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return 1;
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}
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int3_emulate_call(regs, ftrace_update_func_call);
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return 1;
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}
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return 0;
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}
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NOKPROBE_SYMBOL(ftrace_int3_handler);
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static int ftrace_write(unsigned long ip, const char *val, int size)
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{
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ip = text_ip_addr(ip);
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if (probe_kernel_write((void *)ip, val, size))
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return -EPERM;
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return 0;
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}
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static int add_break(unsigned long ip, const char *old)
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{
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unsigned char replaced[MCOUNT_INSN_SIZE];
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unsigned char brk = BREAKPOINT_INSTRUCTION;
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if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
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return -EFAULT;
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ftrace_expected = old;
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/* Make sure it is what we expect it to be */
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if (memcmp(replaced, old, MCOUNT_INSN_SIZE) != 0)
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return -EINVAL;
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return ftrace_write(ip, &brk, 1);
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}
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static int add_brk_on_call(struct dyn_ftrace *rec, unsigned long addr)
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{
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unsigned const char *old;
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unsigned long ip = rec->ip;
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old = ftrace_call_replace(ip, addr);
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return add_break(rec->ip, old);
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}
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static int add_brk_on_nop(struct dyn_ftrace *rec)
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{
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unsigned const char *old;
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old = ftrace_nop_replace();
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return add_break(rec->ip, old);
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}
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static int add_breakpoints(struct dyn_ftrace *rec, bool enable)
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{
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unsigned long ftrace_addr;
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int ret;
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ftrace_addr = ftrace_get_addr_curr(rec);
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ret = ftrace_test_record(rec, enable);
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switch (ret) {
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case FTRACE_UPDATE_IGNORE:
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return 0;
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case FTRACE_UPDATE_MAKE_CALL:
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/* converting nop to call */
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return add_brk_on_nop(rec);
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case FTRACE_UPDATE_MODIFY_CALL:
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case FTRACE_UPDATE_MAKE_NOP:
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/* converting a call to a nop */
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return add_brk_on_call(rec, ftrace_addr);
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}
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return 0;
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}
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/*
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* On error, we need to remove breakpoints. This needs to
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* be done caefully. If the address does not currently have a
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* breakpoint, we know we are done. Otherwise, we look at the
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* remaining 4 bytes of the instruction. If it matches a nop
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* we replace the breakpoint with the nop. Otherwise we replace
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* it with the call instruction.
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*/
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static int remove_breakpoint(struct dyn_ftrace *rec)
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{
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unsigned char ins[MCOUNT_INSN_SIZE];
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unsigned char brk = BREAKPOINT_INSTRUCTION;
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const unsigned char *nop;
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unsigned long ftrace_addr;
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unsigned long ip = rec->ip;
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/* If we fail the read, just give up */
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if (probe_kernel_read(ins, (void *)ip, MCOUNT_INSN_SIZE))
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return -EFAULT;
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/* If this does not have a breakpoint, we are done */
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if (ins[0] != brk)
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return 0;
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nop = ftrace_nop_replace();
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/*
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* If the last 4 bytes of the instruction do not match
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* a nop, then we assume that this is a call to ftrace_addr.
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*/
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if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) != 0) {
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/*
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* For extra paranoidism, we check if the breakpoint is on
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* a call that would actually jump to the ftrace_addr.
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* If not, don't touch the breakpoint, we make just create
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* a disaster.
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*/
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ftrace_addr = ftrace_get_addr_new(rec);
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nop = ftrace_call_replace(ip, ftrace_addr);
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if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) == 0)
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goto update;
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/* Check both ftrace_addr and ftrace_old_addr */
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ftrace_addr = ftrace_get_addr_curr(rec);
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nop = ftrace_call_replace(ip, ftrace_addr);
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ftrace_expected = nop;
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if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) != 0)
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return -EINVAL;
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}
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update:
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return ftrace_write(ip, nop, 1);
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}
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static int add_update_code(unsigned long ip, unsigned const char *new)
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{
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/* skip breakpoint */
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ip++;
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new++;
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return ftrace_write(ip, new, MCOUNT_INSN_SIZE - 1);
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}
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static int add_update_call(struct dyn_ftrace *rec, unsigned long addr)
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{
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unsigned long ip = rec->ip;
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unsigned const char *new;
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new = ftrace_call_replace(ip, addr);
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return add_update_code(ip, new);
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}
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static int add_update_nop(struct dyn_ftrace *rec)
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{
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unsigned long ip = rec->ip;
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unsigned const char *new;
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new = ftrace_nop_replace();
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return add_update_code(ip, new);
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}
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static int add_update(struct dyn_ftrace *rec, bool enable)
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{
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unsigned long ftrace_addr;
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int ret;
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ret = ftrace_test_record(rec, enable);
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ftrace_addr = ftrace_get_addr_new(rec);
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switch (ret) {
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case FTRACE_UPDATE_IGNORE:
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return 0;
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case FTRACE_UPDATE_MODIFY_CALL:
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case FTRACE_UPDATE_MAKE_CALL:
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/* converting nop to call */
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return add_update_call(rec, ftrace_addr);
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case FTRACE_UPDATE_MAKE_NOP:
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/* converting a call to a nop */
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return add_update_nop(rec);
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}
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return 0;
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}
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static int finish_update_call(struct dyn_ftrace *rec, unsigned long addr)
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{
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unsigned long ip = rec->ip;
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unsigned const char *new;
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new = ftrace_call_replace(ip, addr);
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return ftrace_write(ip, new, 1);
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}
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static int finish_update_nop(struct dyn_ftrace *rec)
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{
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unsigned long ip = rec->ip;
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unsigned const char *new;
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new = ftrace_nop_replace();
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return ftrace_write(ip, new, 1);
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}
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static int finish_update(struct dyn_ftrace *rec, bool enable)
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{
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unsigned long ftrace_addr;
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int ret;
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ret = ftrace_update_record(rec, enable);
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ftrace_addr = ftrace_get_addr_new(rec);
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switch (ret) {
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case FTRACE_UPDATE_IGNORE:
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return 0;
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case FTRACE_UPDATE_MODIFY_CALL:
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case FTRACE_UPDATE_MAKE_CALL:
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/* converting nop to call */
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return finish_update_call(rec, ftrace_addr);
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case FTRACE_UPDATE_MAKE_NOP:
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/* converting a call to a nop */
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return finish_update_nop(rec);
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}
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return 0;
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}
|
|
|
|
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)
|
|
{
|
|
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_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;
|
|
|
|
set_vm_flush_reset_perms(trampoline);
|
|
|
|
/*
|
|
* 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);
|
|
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 = 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 */
|