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/*
* Copyright (C) 2008 Matt Fleming <matt@console-pimps.org>
* Copyright (C) 2008 Paul Mundt <lethal@linux-sh.org>
*
* Code for replacing ftrace calls with jumps.
*
* Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
*
* Thanks goes to Ingo Molnar, for suggesting the idea.
* Mathieu Desnoyers, for suggesting postponing the modifications.
* Arjan van de Ven, for keeping me straight, and explaining to me
* the dangers of modifying code on the run.
*/
#include <linux/uaccess.h>
#include <linux/ftrace.h>
#include <linux/string.h>
#include <linux/init.h>
#include <linux/io.h>
#include <asm/ftrace.h>
#include <asm/cacheflush.h>
#include <asm/unistd.h>
#include <trace/syscall.h>
static unsigned char ftrace_replaced_code[MCOUNT_INSN_SIZE];
static unsigned char ftrace_nop[4];
/*
* If we're trying to nop out a call to a function, we instead
* place a call to the address after the memory table.
*
* 8c011060 <a>:
* 8c011060: 02 d1 mov.l 8c01106c <a+0xc>,r1
* 8c011062: 22 4f sts.l pr,@-r15
* 8c011064: 02 c7 mova 8c011070 <a+0x10>,r0
* 8c011066: 2b 41 jmp @r1
* 8c011068: 2a 40 lds r0,pr
* 8c01106a: 09 00 nop
* 8c01106c: 68 24 .word 0x2468 <--- ip
* 8c01106e: 1d 8c .word 0x8c1d
* 8c011070: 26 4f lds.l @r15+,pr <--- ip + MCOUNT_INSN_SIZE
*
* We write 0x8c011070 to 0x8c01106c so that on entry to a() we branch
* past the _mcount call and continue executing code like normal.
*/
static unsigned char *ftrace_nop_replace(unsigned long ip)
{
__raw_writel(ip + MCOUNT_INSN_SIZE, ftrace_nop);
return ftrace_nop;
}
static unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
{
/* Place the address in the memory table. */
__raw_writel(addr, ftrace_replaced_code);
/*
* No locking needed, this must be called via kstop_machine
* which in essence is like running on a uniprocessor machine.
*/
return ftrace_replaced_code;
}
static int ftrace_modify_code(unsigned long ip, unsigned char *old_code,
unsigned char *new_code)
{
unsigned char replaced[MCOUNT_INSN_SIZE];
/*
* Note: Due to modules and __init, code can
* disappear and change, we need to protect against faulting
* as well as code changing. We do this by using the
* probe_kernel_* functions.
*
* No real locking needed, this code is run through
* kstop_machine, or before SMP starts.
*/
/* read the text we want to modify */
if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
return -EFAULT;
/* Make sure it is what we expect it to be */
if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0)
return -EINVAL;
/* replace the text with the new text */
if (probe_kernel_write((void *)ip, new_code, MCOUNT_INSN_SIZE))
return -EPERM;
flush_icache_range(ip, ip + MCOUNT_INSN_SIZE);
return 0;
}
int ftrace_update_ftrace_func(ftrace_func_t func)
{
unsigned long ip = (unsigned long)(&ftrace_call) + MCOUNT_INSN_OFFSET;
unsigned char old[MCOUNT_INSN_SIZE], *new;
memcpy(old, (unsigned char *)ip, MCOUNT_INSN_SIZE);
new = ftrace_call_replace(ip, (unsigned long)func);
return ftrace_modify_code(ip, old, new);
}
int ftrace_make_nop(struct module *mod,
struct dyn_ftrace *rec, unsigned long addr)
{
unsigned char *new, *old;
unsigned long ip = rec->ip;
old = ftrace_call_replace(ip, addr);
new = ftrace_nop_replace(ip);
return ftrace_modify_code(rec->ip, old, new);
}
int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
unsigned char *new, *old;
unsigned long ip = rec->ip;
old = ftrace_nop_replace(ip);
new = ftrace_call_replace(ip, addr);
return ftrace_modify_code(rec->ip, old, new);
}
int __init ftrace_dyn_arch_init(void *data)
{
/* The return code is retured via data */
__raw_writel(0, (unsigned long)data);
return 0;
}
#ifdef CONFIG_FTRACE_SYSCALLS
extern unsigned long __start_syscalls_metadata[];
extern unsigned long __stop_syscalls_metadata[];
extern unsigned long *sys_call_table;
static struct syscall_metadata **syscalls_metadata;
static struct syscall_metadata *find_syscall_meta(unsigned long *syscall)
{
struct syscall_metadata *start;
struct syscall_metadata *stop;
char str[KSYM_SYMBOL_LEN];
start = (struct syscall_metadata *)__start_syscalls_metadata;
stop = (struct syscall_metadata *)__stop_syscalls_metadata;
kallsyms_lookup((unsigned long) syscall, NULL, NULL, NULL, str);
for ( ; start < stop; start++) {
if (start->name && !strcmp(start->name, str))
return start;
}
return NULL;
}
#define FTRACE_SYSCALL_MAX (NR_syscalls - 1)
struct syscall_metadata *syscall_nr_to_meta(int nr)
{
if (!syscalls_metadata || nr >= FTRACE_SYSCALL_MAX || nr < 0)
return NULL;
return syscalls_metadata[nr];
}
void arch_init_ftrace_syscalls(void)
{
int i;
struct syscall_metadata *meta;
unsigned long **psys_syscall_table = &sys_call_table;
static atomic_t refs;
if (atomic_inc_return(&refs) != 1)
goto end;
syscalls_metadata = kzalloc(sizeof(*syscalls_metadata) *
FTRACE_SYSCALL_MAX, GFP_KERNEL);
if (!syscalls_metadata) {
WARN_ON(1);
return;
}
for (i = 0; i < FTRACE_SYSCALL_MAX; i++) {
meta = find_syscall_meta(psys_syscall_table[i]);
syscalls_metadata[i] = meta;
}
return;
/* Paranoid: avoid overflow */
end:
atomic_dec(&refs);
}
#endif /* CONFIG_FTRACE_SYSCALLS */
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