forked from Minki/linux
e4f5d5440b
To remove duplicate code, have the ftrace arch_ftrace_update_code() use the generic ftrace_modify_all_code(). This requires that the default ftrace_replace_code() becomes a weak function so that an arch may override it. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
620 lines
14 KiB
C
620 lines
14 KiB
C
/*
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* Code for replacing ftrace calls with jumps.
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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/init.h>
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#include <linux/list.h>
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#include <linux/module.h>
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#include <trace/syscall.h>
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#include <asm/cacheflush.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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#ifdef CONFIG_DYNAMIC_FTRACE
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int ftrace_arch_code_modify_prepare(void)
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{
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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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{
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set_all_modules_text_ro();
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set_kernel_text_ro();
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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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char e8;
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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 *ftrace_call_replace(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.e8 = 0xe8;
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calc.offset = ftrace_calc_offset(ip + MCOUNT_INSN_SIZE, addr);
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/*
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* No locking needed, this must be called via kstop_machine
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* which in essence is like running on a uniprocessor machine.
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*/
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return calc.code;
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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 int
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do_ftrace_mod_code(unsigned long ip, const void *new_code)
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{
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/*
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* On x86_64, kernel text mappings are mapped read-only with
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* CONFIG_DEBUG_RODATA. So we use the kernel identity mapping instead
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* of the kernel text mapping 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(ip));
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return probe_kernel_write((void *)ip, new_code, MCOUNT_INSN_SIZE);
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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(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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/*
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* Note: Due to modules and __init, code can
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* disappear and change, we need to protect against faulting
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* as well as code changing. We do this by using the
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* probe_kernel_* functions.
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*
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* No real locking needed, this code is run through
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* kstop_machine, or before SMP starts.
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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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/* replace the text with the new text */
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if (do_ftrace_mod_code(ip, new_code))
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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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return ftrace_modify_code(rec->ip, old, new);
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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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return ftrace_modify_code(rec->ip, old, new);
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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 old[MCOUNT_INSN_SIZE], *new;
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int ret;
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memcpy(old, &ftrace_call, MCOUNT_INSN_SIZE);
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new = ftrace_call_replace(ip, (unsigned long)func);
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ret = ftrace_modify_code(ip, old, new);
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return ret;
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}
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int modifying_ftrace_code __read_mostly;
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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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if (WARN_ON_ONCE(!regs))
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return 0;
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if (!ftrace_location(regs->ip - 1))
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return 0;
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regs->ip += MCOUNT_INSN_SIZE - 1;
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return 1;
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}
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static int ftrace_write(unsigned long ip, const char *val, int size)
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{
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/*
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* On x86_64, kernel text mappings are mapped read-only with
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* CONFIG_DEBUG_RODATA. So we use the kernel identity mapping instead
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* of the kernel text mapping 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(ip));
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return probe_kernel_write((void *)ip, val, size);
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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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/* 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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if (ftrace_write(ip, &brk, 1))
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return -EPERM;
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return 0;
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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, int 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 = (unsigned long)FTRACE_ADDR;
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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_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 -1;
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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 = (unsigned long)FTRACE_ADDR;
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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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return -EINVAL;
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}
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return probe_kernel_write((void *)ip, &nop[0], 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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if (ftrace_write(ip, new, MCOUNT_INSN_SIZE - 1))
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return -EPERM;
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return 0;
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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, int 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 = (unsigned long)FTRACE_ADDR;
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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_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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if (ftrace_write(ip, new, 1))
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return -EPERM;
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return 0;
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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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if (ftrace_write(ip, new, 1))
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return -EPERM;
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return 0;
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}
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static int finish_update(struct dyn_ftrace *rec, int 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 = (unsigned long)FTRACE_ADDR;
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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 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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}
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static void do_sync_core(void *data)
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{
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sync_core();
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}
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static void run_sync(void)
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{
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int enable_irqs = irqs_disabled();
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/* We may be called with interrupts disbled (on bootup). */
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if (enable_irqs)
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local_irq_enable();
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on_each_cpu(do_sync_core, NULL, 1);
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if (enable_irqs)
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local_irq_disable();
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}
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void ftrace_replace_code(int enable)
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{
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struct ftrace_rec_iter *iter;
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struct dyn_ftrace *rec;
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const char *report = "adding breakpoints";
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int count = 0;
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int ret;
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for_ftrace_rec_iter(iter) {
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rec = ftrace_rec_iter_record(iter);
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ret = add_breakpoints(rec, enable);
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if (ret)
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goto remove_breakpoints;
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count++;
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}
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run_sync();
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report = "updating code";
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for_ftrace_rec_iter(iter) {
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rec = ftrace_rec_iter_record(iter);
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ret = add_update(rec, enable);
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if (ret)
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goto remove_breakpoints;
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}
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run_sync();
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report = "removing breakpoints";
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for_ftrace_rec_iter(iter) {
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rec = ftrace_rec_iter_record(iter);
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ret = finish_update(rec, enable);
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if (ret)
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goto remove_breakpoints;
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}
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run_sync();
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return;
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remove_breakpoints:
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ftrace_bug(ret, rec ? rec->ip : 0);
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printk(KERN_WARNING "Failed on %s (%d):\n", report, count);
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for_ftrace_rec_iter(iter) {
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rec = ftrace_rec_iter_record(iter);
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remove_breakpoint(rec);
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}
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}
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void arch_ftrace_update_code(int command)
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{
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modifying_ftrace_code++;
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ftrace_modify_all_code(command);
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modifying_ftrace_code--;
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}
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int __init ftrace_dyn_arch_init(void *data)
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{
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/* The return code is retured via data */
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*(unsigned long *)data = 0;
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return 0;
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}
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#endif
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#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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#ifdef CONFIG_DYNAMIC_FTRACE
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extern void ftrace_graph_call(void);
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static int ftrace_mod_jmp(unsigned long ip,
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int old_offset, int new_offset)
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{
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unsigned char code[MCOUNT_INSN_SIZE];
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if (probe_kernel_read(code, (void *)ip, MCOUNT_INSN_SIZE))
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return -EFAULT;
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if (code[0] != 0xe9 || old_offset != *(int *)(&code[1]))
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return -EINVAL;
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*(int *)(&code[1]) = new_offset;
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if (do_ftrace_mod_code(ip, &code))
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return -EPERM;
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return 0;
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}
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int ftrace_enable_ftrace_graph_caller(void)
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{
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unsigned long ip = (unsigned long)(&ftrace_graph_call);
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int old_offset, new_offset;
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old_offset = (unsigned long)(&ftrace_stub) - (ip + MCOUNT_INSN_SIZE);
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new_offset = (unsigned long)(&ftrace_graph_caller) - (ip + MCOUNT_INSN_SIZE);
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return ftrace_mod_jmp(ip, old_offset, new_offset);
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}
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int ftrace_disable_ftrace_graph_caller(void)
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{
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unsigned long ip = (unsigned long)(&ftrace_graph_call);
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int old_offset, new_offset;
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old_offset = (unsigned long)(&ftrace_graph_caller) - (ip + MCOUNT_INSN_SIZE);
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new_offset = (unsigned long)(&ftrace_stub) - (ip + MCOUNT_INSN_SIZE);
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return ftrace_mod_jmp(ip, old_offset, new_offset);
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}
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#endif /* !CONFIG_DYNAMIC_FTRACE */
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/*
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* Hook the return address and push it in the stack of return addrs
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* in current thread info.
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*/
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void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
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unsigned long frame_pointer)
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{
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unsigned long old;
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int faulted;
|
|
struct ftrace_graph_ent trace;
|
|
unsigned long return_hooker = (unsigned long)
|
|
&return_to_handler;
|
|
|
|
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;
|
|
}
|
|
|
|
trace.func = self_addr;
|
|
trace.depth = current->curr_ret_stack + 1;
|
|
|
|
/* Only trace if the calling function expects to */
|
|
if (!ftrace_graph_entry(&trace)) {
|
|
*parent = old;
|
|
return;
|
|
}
|
|
|
|
if (ftrace_push_return_trace(old, self_addr, &trace.depth,
|
|
frame_pointer) == -EBUSY) {
|
|
*parent = old;
|
|
return;
|
|
}
|
|
}
|
|
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
|