9e28c46b7d
Ftrace on sh handles nop'ing out trace function calls differently than other architectures. Instead of inserting NOP instructions in place of the call to the function tracer we branch over the call instructions and continue executing the main body of the function. This patch fixes a bug in the implementation of ftrace_modify_code() where we check that the old value of the code we're about to replace is an expected one. In the ftrace_make_call() code path ftrace_modify_code() was comparing the old instruction value with NOP instructions. The compare was failing because we never actually insert NOP instructions. It makes sense to just get rid of the NOP instructions in ftrace_nop and compare the old code with the address of the function body if we're expecting ftrace to have nop'd out the function trace call. Signed-off-by: Matt Fleming <matt@console-pimps.org>
133 lines
3.8 KiB
C
133 lines
3.8 KiB
C
/*
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* Copyright (C) 2008 Matt Fleming <matt@console-pimps.org>
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* Copyright (C) 2008 Paul Mundt <lethal@linux-sh.org>
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*
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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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#include <linux/uaccess.h>
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#include <linux/ftrace.h>
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#include <linux/string.h>
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#include <linux/init.h>
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#include <linux/io.h>
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#include <asm/ftrace.h>
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#include <asm/cacheflush.h>
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static unsigned char ftrace_replaced_code[MCOUNT_INSN_SIZE];
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static unsigned char ftrace_nop[4];
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/*
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* If we're trying to nop out a call to a function, we instead
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* place a call to the address after the memory table.
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*
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* 8c011060 <a>:
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* 8c011060: 02 d1 mov.l 8c01106c <a+0xc>,r1
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* 8c011062: 22 4f sts.l pr,@-r15
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* 8c011064: 02 c7 mova 8c011070 <a+0x10>,r0
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* 8c011066: 2b 41 jmp @r1
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* 8c011068: 2a 40 lds r0,pr
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* 8c01106a: 09 00 nop
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* 8c01106c: 68 24 .word 0x2468 <--- ip
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* 8c01106e: 1d 8c .word 0x8c1d
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* 8c011070: 26 4f lds.l @r15+,pr <--- ip + MCOUNT_INSN_SIZE
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*
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* We write 0x8c011070 to 0x8c01106c so that on entry to a() we branch
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* past the _mcount call and continue executing code like normal.
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*/
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static unsigned char *ftrace_nop_replace(unsigned long ip)
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{
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__raw_writel(ip + MCOUNT_INSN_SIZE, ftrace_nop);
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return ftrace_nop;
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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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/* Place the address in the memory table. */
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__raw_writel(addr, ftrace_replaced_code);
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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 ftrace_replaced_code;
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}
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static int ftrace_modify_code(unsigned long ip, unsigned char *old_code,
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unsigned 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 (probe_kernel_write((void *)ip, new_code, MCOUNT_INSN_SIZE))
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return -EPERM;
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flush_icache_range(ip, ip + MCOUNT_INSN_SIZE);
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return 0;
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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) + MCOUNT_INSN_OFFSET;
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unsigned char old[MCOUNT_INSN_SIZE], *new;
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memcpy(old, (unsigned char *)ip, MCOUNT_INSN_SIZE);
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new = ftrace_call_replace(ip, (unsigned long)func);
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return ftrace_modify_code(ip, old, new);
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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 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(ip);
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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 char *new, *old;
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unsigned long ip = rec->ip;
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old = ftrace_nop_replace(ip);
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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 __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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__raw_writel(0, (unsigned long)data);
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return 0;
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}
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