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/*
* Copyright (C) 2008 Imagination Technologies Ltd.
* Licensed under the GPL
*
* Dynamic ftrace support.
*/
#include <linux/ftrace.h>
#include <linux/io.h>
#include <linux/uaccess.h>
#include <asm/cacheflush.h>
#define D04_MOVT_TEMPLATE 0x02200005
#define D04_CALL_TEMPLATE 0xAC200005
#define D1RTP_MOVT_TEMPLATE 0x03200005
#define D1RTP_CALL_TEMPLATE 0xAC200006
static const unsigned long NOP[2] = {0xa0fffffe, 0xa0fffffe};
static unsigned long movt_and_call_insn[2];
static unsigned char *ftrace_nop_replace(void)
{
return (char *)&NOP[0];
}
static unsigned char *ftrace_call_replace(unsigned long pc, unsigned long addr)
{
unsigned long hi16, low16;
hi16 = (addr & 0xffff0000) >> 13;
low16 = (addr & 0x0000ffff) << 3;
/*
* The compiler makes the call to mcount_wrapper()
* (Meta's wrapper around mcount()) through the register
* D0.4. So whenever we're patching one of those compiler-generated
* calls we also need to go through D0.4. Otherwise use D1RtP.
*/
if (pc == (unsigned long)&ftrace_call) {
writel(D1RTP_MOVT_TEMPLATE | hi16, &movt_and_call_insn[0]);
writel(D1RTP_CALL_TEMPLATE | low16, &movt_and_call_insn[1]);
} else {
writel(D04_MOVT_TEMPLATE | hi16, &movt_and_call_insn[0]);
writel(D04_CALL_TEMPLATE | low16, &movt_and_call_insn[1]);
}
return (unsigned char *)&movt_and_call_insn[0];
}
static int ftrace_modify_code(unsigned long pc, unsigned char *old_code,
unsigned char *new_code)
{
unsigned char replaced[MCOUNT_INSN_SIZE];
/*
* Note:
* We are paranoid about modifying text, as if a bug was to happen, it
* could cause us to read or write to someplace that could cause harm.
* Carefully read and modify the code with probe_kernel_*(), and make
* sure what we read is what we expected it to be before modifying it.
*/
/* read the text we want to modify */
if (probe_kernel_read(replaced, (void *)pc, 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 *)pc, new_code, MCOUNT_INSN_SIZE))
return -EPERM;
flush_icache_range(pc, pc + MCOUNT_INSN_SIZE);
return 0;
}
int ftrace_update_ftrace_func(ftrace_func_t func)
{
int ret;
unsigned long pc;
unsigned char old[MCOUNT_INSN_SIZE], *new;
pc = (unsigned long)&ftrace_call;
memcpy(old, &ftrace_call, MCOUNT_INSN_SIZE);
new = ftrace_call_replace(pc, (unsigned long)func);
ret = ftrace_modify_code(pc, old, new);
return ret;
}
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();
return ftrace_modify_code(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();
new = ftrace_call_replace(ip, addr);
return ftrace_modify_code(ip, old, new);
}
int __init ftrace_dyn_arch_init(void)
{
return 0;
}
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