aboutsummaryrefslogtreecommitdiff
path: root/arch/sh/kernel/ftrace.c
diff options
context:
space:
mode:
Diffstat (limited to 'arch/sh/kernel/ftrace.c')
-rw-r--r--arch/sh/kernel/ftrace.c58
1 files changed, 29 insertions, 29 deletions
diff --git a/arch/sh/kernel/ftrace.c b/arch/sh/kernel/ftrace.c
index 040cdc6a67e..066f37dc32a 100644
--- a/arch/sh/kernel/ftrace.c
+++ b/arch/sh/kernel/ftrace.c
@@ -19,30 +19,37 @@
#include <asm/ftrace.h>
#include <asm/cacheflush.h>
-static unsigned char ftrace_nop[] = {
- 0x09, 0x00, /* nop */
- 0x09, 0x00, /* nop */
-};
-
static unsigned char ftrace_replaced_code[MCOUNT_INSN_SIZE];
-unsigned char *ftrace_nop_replace(void)
+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 int is_sh_nop(unsigned char *ip)
-{
- return strncmp(ip, ftrace_nop, sizeof(ftrace_nop));
-}
-
-unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
+static unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
{
/* Place the address in the memory table. */
- if (addr == CALLER_ADDR)
- __raw_writel(addr + MCOUNT_INSN_OFFSET, ftrace_replaced_code);
- else
- __raw_writel(addr, ftrace_replaced_code);
+ __raw_writel(addr, ftrace_replaced_code);
/*
* No locking needed, this must be called via kstop_machine
@@ -51,7 +58,7 @@ unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
return ftrace_replaced_code;
}
-int ftrace_modify_code(unsigned long ip, unsigned char *old_code,
+static int ftrace_modify_code(unsigned long ip, unsigned char *old_code,
unsigned char *new_code)
{
unsigned char replaced[MCOUNT_INSN_SIZE];
@@ -66,13 +73,6 @@ int ftrace_modify_code(unsigned long ip, unsigned char *old_code,
* kstop_machine, or before SMP starts.
*/
- /*
- * If we're trying to nop out a call to a function, we instead
- * place a call to the address after the memory table.
- */
- if (is_sh_nop(new_code) == 0)
- __raw_writel(ip + MCOUNT_INSN_SIZE, (unsigned long)new_code);
-
/* read the text we want to modify */
if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
return -EFAULT;
@@ -92,13 +92,13 @@ int ftrace_modify_code(unsigned long ip, unsigned char *old_code,
int ftrace_update_ftrace_func(ftrace_func_t func)
{
- unsigned long ip = (unsigned long)(&ftrace_call);
+ unsigned long ip = (unsigned long)(&ftrace_call) + MCOUNT_INSN_OFFSET;
unsigned char old[MCOUNT_INSN_SIZE], *new;
- memcpy(old, (unsigned char *)(ip + MCOUNT_INSN_OFFSET), MCOUNT_INSN_SIZE);
+ memcpy(old, (unsigned char *)ip, MCOUNT_INSN_SIZE);
new = ftrace_call_replace(ip, (unsigned long)func);
- return ftrace_modify_code(ip + MCOUNT_INSN_OFFSET, old, new);
+ return ftrace_modify_code(ip, old, new);
}
int ftrace_make_nop(struct module *mod,
@@ -108,7 +108,7 @@ int ftrace_make_nop(struct module *mod,
unsigned long ip = rec->ip;
old = ftrace_call_replace(ip, addr);
- new = ftrace_nop_replace();
+ new = ftrace_nop_replace(ip);
return ftrace_modify_code(rec->ip, old, new);
}
@@ -118,7 +118,7 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
unsigned char *new, *old;
unsigned long ip = rec->ip;
- old = ftrace_nop_replace();
+ old = ftrace_nop_replace(ip);
new = ftrace_call_replace(ip, addr);
return ftrace_modify_code(rec->ip, old, new);