110 lines
2.9 KiB
C
110 lines
2.9 KiB
C
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/*
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* Copyright (C) 2008 Matt Fleming <mjf@gentoo.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_nop[] = {
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0x09, 0x00, /* nop */
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0x09, 0x00, /* nop */
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};
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static unsigned char ftrace_replaced_code[MCOUNT_INSN_SIZE];
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unsigned char *ftrace_nop_replace(void)
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{
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return ftrace_nop;
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}
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static int is_sh_nop(unsigned char *ip)
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{
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return strncmp(ip, ftrace_nop, sizeof(ftrace_nop));
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}
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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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if (addr == CALLER_ADDR)
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__raw_writel(addr + MCOUNT_INSN_OFFSET, ftrace_replaced_code);
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else
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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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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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/*
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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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if (is_sh_nop(new_code) == 0)
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__raw_writel(ip + MCOUNT_INSN_SIZE, (unsigned long)new_code);
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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);
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unsigned char old[MCOUNT_INSN_SIZE], *new;
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memcpy(old, (unsigned char *)(ip + MCOUNT_INSN_OFFSET), MCOUNT_INSN_SIZE);
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new = ftrace_call_replace(ip, (unsigned long)func);
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return ftrace_modify_code(ip + MCOUNT_INSN_OFFSET, 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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