ftrace: store mcount address in rec->ip

Record the address of the mcount call-site. Currently all archs except sparc64
record the address of the instruction following the mcount call-site. Some
general cleanups are entailed. Storing mcount addresses in rec->ip enables
looking them up in the kprobe hash table later on to check if they're kprobe'd.

Signed-off-by: Abhishek Sagar <sagar.abhishek@gmail.com>
Cc: davem@davemloft.net
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

3 files changed, 16 insertions, 14 deletions

diff --git a/arch/arm/kernel/armksyms.c b/arch/arm/kernel/armksyms.c
index 3b13221..cc7b246 100644
--- a/arch/arm/kernel/armksyms.c
+++ b/arch/arm/kernel/armksyms.c
@@ -18,6 +18,7 @@
 #include <asm/io.h>
 #include <asm/system.h>
 #include <asm/uaccess.h>
+#include <asm/ftrace.h>
 
 /*
  * libgcc functions - functions that are used internally by the
@@ -48,11 +49,6 @@ extern void __aeabi_ulcmp(void);
 extern void fpundefinstr(void);
 extern void fp_enter(void);
 
-#ifdef CONFIG_FTRACE
-extern void mcount(void);
-EXPORT_SYMBOL(mcount);
-#endif
-
 /*
  * This has a special calling convention; it doesn't
  * modify any of the usual registers, except for LR.
@@ -186,3 +182,7 @@ EXPORT_SYMBOL(_find_next_bit_be);
 #endif
 
 EXPORT_SYMBOL(copy_page);
+
+#ifdef CONFIG_FTRACE
+EXPORT_SYMBOL(mcount);
+#endif
diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index 8f79a47..84694e8 100644
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -9,6 +9,7 @@
  */
 
 #include <asm/unistd.h>
+#include <asm/ftrace.h>
 #include <asm/arch/entry-macro.S>
 
 #include "entry-header.S"
@@ -104,6 +105,7 @@ ENTRY(ret_from_fork)
 ENTRY(mcount)
 	stmdb sp!, {r0-r3, lr}
 	mov r0, lr
+	sub r0, r0, #MCOUNT_INSN_SIZE
 
 	.globl mcount_call
 mcount_call:
@@ -114,6 +116,7 @@ ENTRY(ftrace_caller)
 	stmdb sp!, {r0-r3, lr}
 	ldr r1, [fp, #-4]
 	mov r0, lr
+	sub r0, r0, #MCOUNT_INSN_SIZE
 
 	.globl ftrace_call
 ftrace_call:
@@ -134,6 +137,7 @@ ENTRY(mcount)
 trace:
 	ldr r1, [fp, #-4]
 	mov r0, lr
+	sub r0, r0, #MCOUNT_INSN_SIZE
 	mov lr, pc
 	mov pc, r2
 	ldmia sp!, {r0-r3, pc}
diff --git a/arch/arm/kernel/ftrace.c b/arch/arm/kernel/ftrace.c
index 22f3d6e..76d50e6 100644
--- a/arch/arm/kernel/ftrace.c
+++ b/arch/arm/kernel/ftrace.c
@@ -12,9 +12,10 @@
  */
 
 #include <linux/ftrace.h>
+
 #include <asm/cacheflush.h>
+#include <asm/ftrace.h>
 
-#define INSN_SIZE      4
 #define PC_OFFSET      8
 #define BL_OPCODE      0xeb000000
 #define BL_OFFSET_MASK 0x00ffffff
@@ -32,10 +33,10 @@ unsigned char *ftrace_call_replace(unsigned long pc, unsigned long addr)
 {
 	long offset;
 
-	offset = (long)addr - (long)(pc - INSN_SIZE + PC_OFFSET);
+	offset = (long)addr - (long)(pc + PC_OFFSET);
 	if (unlikely(offset < -33554432 || offset > 33554428)) {
 		/* Can't generate branches that far (from ARM ARM). Ftrace
-		 * doesn't generate branches outside of core kernel text.
+		 * doesn't generate branches outside of kernel text.
 		 */
 		WARN_ON_ONCE(1);
 		return NULL;
@@ -52,7 +53,6 @@ int ftrace_modify_code(unsigned long pc, unsigned char *old_code,
 
 	old = *(unsigned long *)old_code;
 	new = *(unsigned long *)new_code;
-	pc -= INSN_SIZE;
 
 	__asm__ __volatile__ (
 		"1:  ldr    %1, [%2]  \n"
@@ -77,7 +77,7 @@ int ftrace_modify_code(unsigned long pc, unsigned char *old_code,
 		: "memory");
 
 	if (!err && (replaced == old))
-		flush_icache_range(pc, pc + INSN_SIZE);
+		flush_icache_range(pc, pc + MCOUNT_INSN_SIZE);
 
 	return err;
 }
@@ -89,8 +89,7 @@ int ftrace_update_ftrace_func(ftrace_func_t func)
 	unsigned char *new;
 
 	pc = (unsigned long)&ftrace_call;
-	pc += INSN_SIZE;
-	memcpy(&old, &ftrace_call, INSN_SIZE);
+	memcpy(&old, &ftrace_call, MCOUNT_INSN_SIZE);
 	new = ftrace_call_replace(pc, (unsigned long)func);
 	ret = ftrace_modify_code(pc, (unsigned char *)&old, new);
 	return ret;
@@ -103,8 +102,7 @@ int ftrace_mcount_set(unsigned long *data)
 	unsigned char *new;
 
 	pc = (unsigned long)&mcount_call;
-	pc += INSN_SIZE;
-	memcpy(&old, &mcount_call, INSN_SIZE);
+	memcpy(&old, &mcount_call, MCOUNT_INSN_SIZE);
 	new = ftrace_call_replace(pc, *addr);
 	*addr = ftrace_modify_code(pc, (unsigned char *)&old, new);
 	return 0;