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/*
* Code for replacing ftrace calls with jumps.
*
* Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
*
* Thanks goes out to P.A. Semi, Inc for supplying me with a PPC64 box.
*
*/
#include <linux/spinlock.h>
#include <linux/hardirq.h>
#include <linux/uaccess.h>
#include <linux/ftrace.h>
#include <linux/percpu.h>
#include <linux/init.h>
#include <linux/list.h>
#include <asm/cacheflush.h>
#include <asm/ftrace.h>
static unsigned int ftrace_nop = 0x60000000;
#ifdef CONFIG_PPC32
# define GET_ADDR(addr) addr
#else
/* PowerPC64's functions are data that points to the functions */
# define GET_ADDR(addr) *(unsigned long *)addr
#endif
static unsigned int ftrace_calc_offset(long ip, long addr)
{
return (int)(addr - ip);
}
static unsigned char *ftrace_nop_replace(void)
{
return (char *)&ftrace_nop;
}
static unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
{
static unsigned int op;
/*
* It would be nice to just use create_function_call, but that will
* update the code itself. Here we need to just return the
* instruction that is going to be modified, without modifying the
* code.
*/
addr = GET_ADDR(addr);
/* Set to "bl addr" */
op = 0x48000001 | (ftrace_calc_offset(ip, addr) & 0x03fffffc);
/*
* No locking needed, this must be called via kstop_machine
* which in essence is like running on a uniprocessor machine.
*/
return (unsigned char *)&op;
}
#ifdef CONFIG_PPC64
# define _ASM_ALIGN " .align 3 "
# define _ASM_PTR " .llong "
#else
# define _ASM_ALIGN " .align 2 "
# define _ASM_PTR " .long "
#endif
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 + 8);
return 0;
}
static int test_24bit_addr(unsigned long ip, unsigned long addr)
{
long diff;
/*
* Can we get to addr from ip in 24 bits?
* (26 really, since we mulitply by 4 for 4 byte alignment)
*/
diff = addr - ip;
/*
* Return true if diff is less than 1 << 25
* and greater than -1 << 26.
*/
return (diff < (1 << 25)) && (diff > (-1 << 26));
}
int ftrace_make_nop(struct module *mod,
struct dyn_ftrace *rec, unsigned long addr)
{
unsigned char *old, *new;
/*
* If the calling address is more that 24 bits away,
* then we had to use a trampoline to make the call.
* Otherwise just update the call site.
*/
if (test_24bit_addr(rec->ip, addr)) {
/* within range */
old = ftrace_call_replace(rec->ip, addr);
new = ftrace_nop_replace();
return ftrace_modify_code(rec->ip, old, new);
}
return 0;
}
int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
unsigned char *old, *new;
/*
* If the calling address is more that 24 bits away,
* then we had to use a trampoline to make the call.
* Otherwise just update the call site.
*/
if (test_24bit_addr(rec->ip, addr)) {
/* within range */
old = ftrace_nop_replace();
new = ftrace_call_replace(rec->ip, addr);
return ftrace_modify_code(rec->ip, old, new);
}
return 0;
}
int ftrace_update_ftrace_func(ftrace_func_t func)
{
unsigned long ip = (unsigned long)(&ftrace_call);
unsigned char old[MCOUNT_INSN_SIZE], *new;
int ret;
memcpy(old, &ftrace_call, MCOUNT_INSN_SIZE);
new = ftrace_call_replace(ip, (unsigned long)func);
ret = ftrace_modify_code(ip, old, new);
return ret;
}
int __init ftrace_dyn_arch_init(void *data)
{
/* caller expects data to be zero */
unsigned long *p = data;
*p = 0;
return 0;
}
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