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authorMatt Fleming <mjf@gentoo.org>2008-11-12 06:11:47 -0500
committerPaul Mundt <lethal@linux-sh.org>2008-12-22 04:42:52 -0500
commitfad57feba77d2e5b183e068cb6b90693e4567b40 (patch)
tree478788d5a05a30f638540d345e9d09c5733687da /arch/sh/kernel/ftrace.c
parentef6aff6884408db95ceb0f678f583536e0bd48f8 (diff)
sh: dynamic ftrace support.
First cut at dynamic ftrace support. Signed-off-by: Matt Fleming <mjf@gentoo.org> Signed-off-by: Paul Mundt <lethal@linux-sh.org>
Diffstat (limited to 'arch/sh/kernel/ftrace.c')
-rw-r--r--arch/sh/kernel/ftrace.c109
1 files changed, 109 insertions, 0 deletions
diff --git a/arch/sh/kernel/ftrace.c b/arch/sh/kernel/ftrace.c
new file mode 100644
index 000000000000..6c193d56c2e7
--- /dev/null
+++ b/arch/sh/kernel/ftrace.c
@@ -0,0 +1,109 @@
1/*
2 * Copyright (C) 2008 Matt Fleming <mjf@gentoo.org>
3 *
4 * Code for replacing ftrace calls with jumps.
5 *
6 * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
7 *
8 * Thanks goes to Ingo Molnar, for suggesting the idea.
9 * Mathieu Desnoyers, for suggesting postponing the modifications.
10 * Arjan van de Ven, for keeping me straight, and explaining to me
11 * the dangers of modifying code on the run.
12 */
13#include <linux/uaccess.h>
14#include <linux/ftrace.h>
15#include <linux/string.h>
16#include <linux/init.h>
17#include <linux/io.h>
18#include <asm/ftrace.h>
19#include <asm/cacheflush.h>
20
21static unsigned char ftrace_nop[] = {
22 0x09, 0x00, /* nop */
23 0x09, 0x00, /* nop */
24};
25
26static unsigned char ftrace_replaced_code[MCOUNT_INSN_SIZE];
27
28unsigned char *ftrace_nop_replace(void)
29{
30 return ftrace_nop;
31}
32
33static int is_sh_nop(unsigned char *ip)
34{
35 return strncmp(ip, ftrace_nop, sizeof(ftrace_nop));
36}
37
38unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
39{
40 /* Place the address in the memory table. */
41 if (addr == CALLER_ADDR)
42 __raw_writel(addr + MCOUNT_INSN_OFFSET, ftrace_replaced_code);
43 else
44 __raw_writel(addr, ftrace_replaced_code);
45
46 /*
47 * No locking needed, this must be called via kstop_machine
48 * which in essence is like running on a uniprocessor machine.
49 */
50 return ftrace_replaced_code;
51}
52
53int ftrace_modify_code(unsigned long ip, unsigned char *old_code,
54 unsigned char *new_code)
55{
56 unsigned char replaced[MCOUNT_INSN_SIZE];
57
58 /*
59 * Note: Due to modules and __init, code can
60 * disappear and change, we need to protect against faulting
61 * as well as code changing. We do this by using the
62 * probe_kernel_* functions.
63 *
64 * No real locking needed, this code is run through
65 * kstop_machine, or before SMP starts.
66 */
67
68 /*
69 * If we're trying to nop out a call to a function, we instead
70 * place a call to the address after the memory table.
71 */
72 if (is_sh_nop(new_code) == 0)
73 __raw_writel(ip + MCOUNT_INSN_SIZE, (unsigned long)new_code);
74
75 /* read the text we want to modify */
76 if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
77 return -EFAULT;
78
79 /* Make sure it is what we expect it to be */
80 if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0)
81 return -EINVAL;
82
83 /* replace the text with the new text */
84 if (probe_kernel_write((void *)ip, new_code, MCOUNT_INSN_SIZE))
85 return -EPERM;
86
87 flush_icache_range(ip, ip + MCOUNT_INSN_SIZE);
88
89 return 0;
90}
91
92int ftrace_update_ftrace_func(ftrace_func_t func)
93{
94 unsigned long ip = (unsigned long)(&ftrace_call);
95 unsigned char old[MCOUNT_INSN_SIZE], *new;
96
97 memcpy(old, (unsigned char *)(ip + MCOUNT_INSN_OFFSET), MCOUNT_INSN_SIZE);
98 new = ftrace_call_replace(ip, (unsigned long)func);
99
100 return ftrace_modify_code(ip + MCOUNT_INSN_OFFSET, old, new);
101}
102
103int __init ftrace_dyn_arch_init(void *data)
104{
105 /* The return code is retured via data */
106 __raw_writel(0, (unsigned long)data);
107
108 return 0;
109}