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/*
* Dynamic function tracing support.
*
* Copyright (C) 2008 Shaohua Li <shaohua.li@intel.com>
*
* For licencing details, see COPYING.
*
* Defines low-level handling of mcount calls when the kernel
* is compiled with the -pg flag. When using dynamic ftrace, the
* mcount call-sites get patched lazily with NOP till they are
* enabled. All code mutation routines here take effect atomically.
*/
#include <linux/uaccess.h>
#include <linux/ftrace.h>
#include <asm/cacheflush.h>
#include <asm/patch.h>
/* In IA64, each function will be added below two bundles with -pg option */
static unsigned char __attribute__((aligned(8)))
ftrace_orig_code[MCOUNT_INSN_SIZE] = {
0x02, 0x40, 0x31, 0x10, 0x80, 0x05, /* alloc r40=ar.pfs,12,8,0 */
0xb0, 0x02, 0x00, 0x00, 0x42, 0x40, /* mov r43=r0;; */
0x05, 0x00, 0xc4, 0x00, /* mov r42=b0 */
0x11, 0x48, 0x01, 0x02, 0x00, 0x21, /* mov r41=r1 */
0x00, 0x00, 0x00, 0x02, 0x00, 0x00, /* nop.i 0x0 */
0x08, 0x00, 0x00, 0x50 /* br.call.sptk.many b0 = _mcount;; */
};
struct ftrace_orig_insn {
u64 dummy1, dummy2, dummy3;
u64 dummy4:64-41+13;
u64 imm20:20;
u64 dummy5:3;
u64 sign:1;
u64 dummy6:4;
};
/* mcount stub will be converted below for nop */
static unsigned char ftrace_nop_code[MCOUNT_INSN_SIZE] = {
0x00, 0x00, 0x00, 0x00, 0x01, 0x00, /* [MII] nop.m 0x0 */
0x30, 0x00, 0x00, 0x60, 0x00, 0x00, /* mov r3=ip */
0x00, 0x00, 0x04, 0x00, /* nop.i 0x0 */
0x05, 0x00, 0x00, 0x00, 0x01, 0x00, /* [MLX] nop.m 0x0 */
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* nop.x 0x0;; */
0x00, 0x00, 0x04, 0x00
};
static unsigned char *ftrace_nop_replace(void)
{
return ftrace_nop_code;
}
/*
* mcount stub will be converted below for call
* Note: Just the last instruction is changed against nop
* */
static unsigned char __attribute__((aligned(8)))
ftrace_call_code[MCOUNT_INSN_SIZE] = {
0x00, 0x00, 0x00, 0x00, 0x01, 0x00, /* [MII] nop.m 0x0 */
0x30, 0x00, 0x00, 0x60, 0x00, 0x00, /* mov r3=ip */
0x00, 0x00, 0x04, 0x00, /* nop.i 0x0 */
0x05, 0x00, 0x00, 0x00, 0x01, 0x00, /* [MLX] nop.m 0x0 */
0xff, 0xff, 0xff, 0xff, 0x7f, 0x00, /* brl.many .;;*/
0xf8, 0xff, 0xff, 0xc8
};
struct ftrace_call_insn {
u64 dummy1, dummy2;
u64 dummy3:48;
u64 imm39_l:16;
u64 imm39_h:23;
u64 dummy4:13;
u64 imm20:20;
u64 dummy5:3;
u64 i:1;
u64 dummy6:4;
};
static unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
{
struct ftrace_call_insn *code = (void *)ftrace_call_code;
unsigned long offset = addr - (ip + 0x10);
code->imm39_l = offset >> 24;
code->imm39_h = offset >> 40;
code->imm20 = offset >> 4;
code->i = offset >> 63;
return ftrace_call_code;
}
static int
ftrace_modify_code(unsigned long ip, unsigned char *old_code,
unsigned char *new_code, int do_check)
{
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.
*/
if (!do_check)
goto skip_check;
/* 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;
skip_check:
/* 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;
}
static int ftrace_make_nop_check(struct dyn_ftrace *rec, unsigned long addr)
{
unsigned char __attribute__((aligned(8))) replaced[MCOUNT_INSN_SIZE];
unsigned long ip = rec->ip;
if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
return -EFAULT;
if (rec->flags & FTRACE_FL_CONVERTED) {
struct ftrace_call_insn *call_insn, *tmp_call;
call_insn = (void *)ftrace_call_code;
tmp_call = (void *)replaced;
call_insn->imm39_l = tmp_call->imm39_l;
call_insn->imm39_h = tmp_call->imm39_h;
call_insn->imm20 = tmp_call->imm20;
call_insn->i = tmp_call->i;
if (memcmp(replaced, ftrace_call_code, MCOUNT_INSN_SIZE) != 0)
return -EINVAL;
return 0;
} else {
struct ftrace_orig_insn *call_insn, *tmp_call;
call_insn = (void *)ftrace_orig_code;
tmp_call = (void *)replaced;
call_insn->sign = tmp_call->sign;
call_insn->imm20 = tmp_call->imm20;
if (memcmp(replaced, ftrace_orig_code, MCOUNT_INSN_SIZE) != 0)
return -EINVAL;
return 0;
}
}
int ftrace_make_nop(struct module *mod,
struct dyn_ftrace *rec, unsigned long addr)
{
int ret;
char *new;
ret = ftrace_make_nop_check(rec, addr);
if (ret)
return ret;
new = ftrace_nop_replace();
return ftrace_modify_code(rec->ip, NULL, new, 0);
}
int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
unsigned long ip = rec->ip;
unsigned char *old, *new;
old= ftrace_nop_replace();
new = ftrace_call_replace(ip, addr);
return ftrace_modify_code(ip, old, new, 1);
}
/* in IA64, _mcount can't directly call ftrace_stub. Only jump is ok */
int ftrace_update_ftrace_func(ftrace_func_t func)
{
unsigned long ip;
unsigned long addr = ((struct fnptr *)ftrace_call)->ip;
if (func == ftrace_stub)
return 0;
ip = ((struct fnptr *)func)->ip;
ia64_patch_imm64(addr + 2, ip);
flush_icache_range(addr, addr + 16);
return 0;
}
/* run from kstop_machine */
int __init ftrace_dyn_arch_init(void)
{
return 0;
}
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