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>

1 files changed, 9 insertions, 17 deletions

diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 55828149e01e..ab115cd15fdf 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -17,20 +17,21 @@
 #include <linux/list.h>
 
 #include <asm/alternative.h>
+#include <asm/ftrace.h>
 
-#define CALL_BACK               5
 
 /* Long is fine, even if it is only 4 bytes ;-) */
 static long *ftrace_nop;
 
 union ftrace_code_union {
-        char code[5];
+        char code[MCOUNT_INSN_SIZE];
         struct {
                 char e8;
                 int offset;
         } __attribute__((packed));
 };
 
+
 static int notrace ftrace_calc_offset(long ip, long addr)
 {
         return (int)(addr - ip);
@@ -46,7 +47,7 @@ notrace unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
         static union ftrace_code_union calc;
 
         calc.e8         = 0xe8;
-        calc.offset     = ftrace_calc_offset(ip, addr);
+        calc.offset     = ftrace_calc_offset(ip + MCOUNT_INSN_SIZE, addr);
 
         /*
          * No locking needed, this must be called via kstop_machine
@@ -65,9 +66,6 @@ ftrace_modify_code(unsigned long ip, unsigned char *old_code,
         unsigned char newch = new_code[4];
         int faulted = 0;
 
-        /* move the IP back to the start of the call */
-        ip -= CALL_BACK;
-
         /*
          * Note: Due to modules and __init, code can
          *  disappear and change, we need to protect against faulting
@@ -102,12 +100,10 @@ ftrace_modify_code(unsigned long ip, unsigned char *old_code,
 notrace int ftrace_update_ftrace_func(ftrace_func_t func)
 {
         unsigned long ip = (unsigned long)(&ftrace_call);
-        unsigned char old[5], *new;
+        unsigned char old[MCOUNT_INSN_SIZE], *new;
         int ret;
 
-        ip += CALL_BACK;
-
-        memcpy(old, &ftrace_call, 5);
+        memcpy(old, &ftrace_call, MCOUNT_INSN_SIZE);
         new = ftrace_call_replace(ip, (unsigned long)func);
         ret = ftrace_modify_code(ip, old, new);
 
@@ -118,16 +114,13 @@ notrace int ftrace_mcount_set(unsigned long *data)
 {
         unsigned long ip = (long)(&mcount_call);
         unsigned long *addr = data;
-        unsigned char old[5], *new;
-
-        /* ip is at the location, but modify code will subtact this */
-        ip += CALL_BACK;
+        unsigned char old[MCOUNT_INSN_SIZE], *new;
 
         /*
          * Replace the mcount stub with a pointer to the
          * ip recorder function.
          */
-        memcpy(old, &mcount_call, 5);
+        memcpy(old, &mcount_call, MCOUNT_INSN_SIZE);
         new = ftrace_call_replace(ip, *addr);
         *addr = ftrace_modify_code(ip, old, new);
 
@@ -142,8 +135,7 @@ int __init ftrace_dyn_arch_init(void *data)
 
         ftrace_mcount_set(data);
 
-        ftrace_nop = (unsigned long *)noptable[CALL_BACK];
+        ftrace_nop = (unsigned long *)noptable[MCOUNT_INSN_SIZE];
 
         return 0;
 }
-