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>

19 files changed, 110 insertions, 56 deletions

diff --git a/arch/arm/kernel/armksyms.c b/arch/arm/kernel/armksyms.c
index 3b132215cbf8..cc7b246e9652 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 8f79a4789ed4..84694e88b428 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 22f3d6e309f9..76d50e6091bc 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;
diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index 3b1dd29d9f91..7231a708af0d 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -30,6 +30,7 @@
 #include <asm/ppc_asm.h>
 #include <asm/asm-offsets.h>
 #include <asm/unistd.h>
+#include <asm/ftrace.h>
 
 #undef SHOW_SYSCALLS
 #undef SHOW_SYSCALLS_TASK
@@ -1053,6 +1054,7 @@ _GLOBAL(_mcount)
         stw     r10,40(r1)
         stw     r3, 44(r1)
         stw     r5, 8(r1)
+        subi    r3, r3, MCOUNT_INSN_SIZE
         .globl mcount_call
 mcount_call:
         bl      ftrace_stub
@@ -1090,6 +1092,7 @@ _GLOBAL(ftrace_caller)
         stw     r10,40(r1)
         stw     r3, 44(r1)
         stw     r5, 8(r1)
+        subi    r3, r3, MCOUNT_INSN_SIZE
 .globl ftrace_call
 ftrace_call:
         bl      ftrace_stub
@@ -1128,6 +1131,7 @@ _GLOBAL(_mcount)
         stw     r3, 44(r1)
         stw     r5, 8(r1)
 
+        subi    r3, r3, MCOUNT_INSN_SIZE
         LOAD_REG_ADDR(r5, ftrace_trace_function)
         lwz     r5,0(r5)
 
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index 2c4d9e056ead..2f511a969d2c 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -31,6 +31,7 @@
 #include <asm/bug.h>
 #include <asm/ptrace.h>
 #include <asm/irqflags.h>
+#include <asm/ftrace.h>
 
 /*
  * System calls.
@@ -879,6 +880,7 @@ _GLOBAL(_mcount)
         mflr    r3
         stdu    r1, -112(r1)
         std     r3, 128(r1)
+        subi    r3, r3, MCOUNT_INSN_SIZE
         .globl mcount_call
 mcount_call:
         bl      ftrace_stub
@@ -895,6 +897,7 @@ _GLOBAL(ftrace_caller)
         stdu    r1, -112(r1)
         std     r3, 128(r1)
         ld      r4, 16(r11)
+        subi    r3, r3, MCOUNT_INSN_SIZE
 .globl ftrace_call
 ftrace_call:
         bl      ftrace_stub
@@ -916,7 +919,7 @@ _GLOBAL(_mcount)
         std     r3, 128(r1)
         ld      r4, 16(r11)
 
-
+        subi    r3, r3, MCOUNT_INSN_SIZE
         LOAD_REG_ADDR(r5,ftrace_trace_function)
         ld      r5,0(r5)
         ld      r5,0(r5)
diff --git a/arch/powerpc/kernel/ftrace.c b/arch/powerpc/kernel/ftrace.c
index e12c593ab9ca..3855ceb937b0 100644
--- a/arch/powerpc/kernel/ftrace.c
+++ b/arch/powerpc/kernel/ftrace.c
@@ -15,8 +15,8 @@
 #include <linux/list.h>
 
 #include <asm/cacheflush.h>
+#include <asm/ftrace.h>
 
-#define CALL_BACK               4
 
 static unsigned int ftrace_nop = 0x60000000;
 
@@ -27,9 +27,10 @@ static unsigned int ftrace_nop = 0x60000000;
 # define GET_ADDR(addr) *(unsigned long *)addr
 #endif
 
+
 static unsigned int notrace ftrace_calc_offset(long ip, long addr)
 {
-        return (int)((addr + CALL_BACK) - ip);
+        return (int)(addr - ip);
 }
 
 notrace unsigned char *ftrace_nop_replace(void)
@@ -76,9 +77,6 @@ ftrace_modify_code(unsigned long ip, unsigned char *old_code,
         unsigned new = *(unsigned *)new_code;
         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
@@ -118,12 +116,10 @@ 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[4], *new;
+        unsigned char old[MCOUNT_INSN_SIZE], *new;
         int ret;
 
-        ip += CALL_BACK;
-
-        memcpy(old, &ftrace_call, 4);
+        memcpy(old, &ftrace_call, MCOUNT_INSN_SIZE);
         new = ftrace_call_replace(ip, (unsigned long)func);
         ret = ftrace_modify_code(ip, old, new);
 
@@ -134,16 +130,13 @@ notrace int ftrace_mcount_set(unsigned long *data)
 {
         unsigned long ip = (long)(&mcount_call);
         unsigned long *addr = data;
-        unsigned char old[4], *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, 4);
+        memcpy(old, &mcount_call, MCOUNT_INSN_SIZE);
         new = ftrace_call_replace(ip, *addr);
         *addr = ftrace_modify_code(ip, old, new);
 
diff --git a/arch/sparc64/kernel/ftrace.c b/arch/sparc64/kernel/ftrace.c
index c17373195b1e..4298d0aee713 100644
--- a/arch/sparc64/kernel/ftrace.c
+++ b/arch/sparc64/kernel/ftrace.c
@@ -5,6 +5,8 @@
 #include <linux/init.h>
 #include <linux/list.h>
 
+#include <asm/ftrace.h>
+
 static const u32 ftrace_nop = 0x01000000;
 
 notrace unsigned char *ftrace_nop_replace(void)
@@ -60,9 +62,9 @@ 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[4], *new;
+        unsigned char old[MCOUNT_INSN_SIZE], *new;
 
-        memcpy(old, &ftrace_call, 4);
+        memcpy(old, &ftrace_call, MCOUNT_INSN_SIZE);
         new = ftrace_call_replace(ip, (unsigned long)func);
         return ftrace_modify_code(ip, old, new);
 }
@@ -71,13 +73,13 @@ notrace int ftrace_mcount_set(unsigned long *data)
 {
         unsigned long ip = (long)(&mcount_call);
         unsigned long *addr = data;
-        unsigned char old[4], *new;
+        unsigned char old[MCOUNT_INSN_SIZE], *new;
 
         /*
          * Replace the mcount stub with a pointer to the
          * ip recorder function.
          */
-        memcpy(old, &mcount_call, 4);
+        memcpy(old, &mcount_call, MCOUNT_INSN_SIZE);
         new = ftrace_call_replace(ip, *addr);
         *addr = ftrace_modify_code(ip, old, new);
 
diff --git a/arch/sparc64/kernel/sparc64_ksyms.c b/arch/sparc64/kernel/sparc64_ksyms.c
index 8ac0b99f2c55..b80d982a29c6 100644
--- a/arch/sparc64/kernel/sparc64_ksyms.c
+++ b/arch/sparc64/kernel/sparc64_ksyms.c
@@ -53,6 +53,7 @@
 #include <asm/ns87303.h>
 #include <asm/timer.h>
 #include <asm/cpudata.h>
+#include <asm/ftrace.h>
 
 struct poll {
         int fd;
@@ -112,7 +113,6 @@ EXPORT_SYMBOL(smp_call_function);
 #endif /* CONFIG_SMP */
 
 #if defined(CONFIG_MCOUNT)
-extern void _mcount(void);
 EXPORT_SYMBOL(_mcount);
 #endif
 
diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S
index 04ea83ccb979..95e6bbe3665e 100644
--- a/arch/x86/kernel/entry_32.S
+++ b/arch/x86/kernel/entry_32.S
@@ -51,6 +51,7 @@
 #include <asm/percpu.h>
 #include <asm/dwarf2.h>
 #include <asm/processor-flags.h>
+#include <asm/ftrace.h>
 #include "irq_vectors.h"
 
 /*
@@ -1118,6 +1119,7 @@ ENTRY(mcount)
         pushl %ecx
         pushl %edx
         movl 0xc(%esp), %eax
+        subl $MCOUNT_INSN_SIZE, %eax
 
 .globl mcount_call
 mcount_call:
@@ -1136,6 +1138,7 @@ ENTRY(ftrace_caller)
         pushl %edx
         movl 0xc(%esp), %eax
         movl 0x4(%ebp), %edx
+        subl $MCOUNT_INSN_SIZE, %eax
 
 .globl ftrace_call
 ftrace_call:
@@ -1166,6 +1169,7 @@ trace:
         pushl %edx
         movl 0xc(%esp), %eax
         movl 0x4(%ebp), %edx
+        subl $MCOUNT_INSN_SIZE, %eax
 
         call *ftrace_trace_function
 
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index fe25e5febca3..b0f7308f78a6 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -51,6 +51,7 @@
 #include <asm/page.h>
 #include <asm/irqflags.h>
 #include <asm/paravirt.h>
+#include <asm/ftrace.h>
 
         .code64
 
@@ -68,6 +69,7 @@ ENTRY(mcount)
         movq %r9, 48(%rsp)
 
         movq 0x38(%rsp), %rdi
+        subq $MCOUNT_INSN_SIZE, %rdi
 
 .globl mcount_call
 mcount_call:
@@ -99,6 +101,7 @@ ENTRY(ftrace_caller)
 
         movq 0x38(%rsp), %rdi
         movq 8(%rbp), %rsi
+        subq $MCOUNT_INSN_SIZE, %rdi
 
 .globl ftrace_call
 ftrace_call:
@@ -139,6 +142,7 @@ trace:
 
         movq 0x38(%rsp), %rdi
         movq 8(%rbp), %rsi
+        subq $MCOUNT_INSN_SIZE, %rdi
 
         call   *ftrace_trace_function
 
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;
 }
-
diff --git a/arch/x86/kernel/i386_ksyms_32.c b/arch/x86/kernel/i386_ksyms_32.c
index 29999dbb754c..dd7ebee446af 100644
--- a/arch/x86/kernel/i386_ksyms_32.c
+++ b/arch/x86/kernel/i386_ksyms_32.c
@@ -1,9 +1,9 @@
-#include <linux/ftrace.h>
 #include <linux/module.h>
 
 #include <asm/checksum.h>
 #include <asm/pgtable.h>
 #include <asm/desc.h>
+#include <asm/ftrace.h>
 
 #ifdef CONFIG_FTRACE
 /* mcount is defined in assembly */
diff --git a/arch/x86/kernel/x8664_ksyms_64.c b/arch/x86/kernel/x8664_ksyms_64.c
index 122885bc5f3b..16ff4bf418d9 100644
--- a/arch/x86/kernel/x8664_ksyms_64.c
+++ b/arch/x86/kernel/x8664_ksyms_64.c
@@ -1,7 +1,6 @@
 /* Exports for assembly files.
    All C exports should go in the respective C files. */
 
-#include <linux/ftrace.h>
 #include <linux/module.h>
 #include <linux/smp.h>
 
@@ -11,6 +10,7 @@
 #include <asm/pgtable.h>
 #include <asm/uaccess.h>
 #include <asm/desc.h>
+#include <asm/ftrace.h>
 
 #ifdef CONFIG_FTRACE
 /* mcount is defined in assembly */
diff --git a/include/asm-arm/ftrace.h b/include/asm-arm/ftrace.h
new file mode 100644
index 000000000000..584ef9a8e5a5
--- /dev/null
+++ b/include/asm-arm/ftrace.h
@@ -0,0 +1,14 @@
+#ifndef _ASM_ARM_FTRACE
+#define _ASM_ARM_FTRACE
+
+#ifdef CONFIG_FTRACE
+#define MCOUNT_ADDR             ((long)(mcount))
+#define MCOUNT_INSN_SIZE        4 /* sizeof mcount call */
+
+#ifndef __ASSEMBLY__
+extern void mcount(void);
+#endif
+
+#endif
+
+#endif /* _ASM_ARM_FTRACE */
diff --git a/include/asm-powerpc/ftrace.h b/include/asm-powerpc/ftrace.h
index b1bfa704b6e5..de921326cca8 100644
--- a/include/asm-powerpc/ftrace.h
+++ b/include/asm-powerpc/ftrace.h
@@ -1,6 +1,14 @@
 #ifndef _ASM_POWERPC_FTRACE
 #define _ASM_POWERPC_FTRACE
 
+#ifdef CONFIG_FTRACE
+#define MCOUNT_ADDR             ((long)(_mcount))
+#define MCOUNT_INSN_SIZE        4 /* sizeof mcount call */
+
+#ifndef __ASSEMBLY__
 extern void _mcount(void);
+#endif
 
 #endif
+
+#endif /* _ASM_POWERPC_FTRACE */
diff --git a/include/asm-sparc64/ftrace.h b/include/asm-sparc64/ftrace.h
new file mode 100644
index 000000000000..f76a40a338bb
--- /dev/null
+++ b/include/asm-sparc64/ftrace.h
@@ -0,0 +1,14 @@
+#ifndef _ASM_SPARC64_FTRACE
+#define _ASM_SPARC64_FTRACE
+
+#ifdef CONFIG_FTRACE
+#define MCOUNT_ADDR             ((long)(_mcount))
+#define MCOUNT_INSN_SIZE        4 /* sizeof mcount call */
+
+#ifndef __ASSEMBLY__
+extern void _mcount(void);
+#endif
+
+#endif
+
+#endif /* _ASM_SPARC64_FTRACE */
diff --git a/include/asm-x86/ftrace.h b/include/asm-x86/ftrace.h
new file mode 100644
index 000000000000..c184441133f2
--- /dev/null
+++ b/include/asm-x86/ftrace.h
@@ -0,0 +1,14 @@
+#ifndef _ASM_X86_FTRACE
+#define _ASM_SPARC64_FTRACE
+
+#ifdef CONFIG_FTRACE
+#define MCOUNT_ADDR             ((long)(mcount))
+#define MCOUNT_INSN_SIZE        5 /* sizeof mcount call */
+
+#ifndef __ASSEMBLY__
+extern void mcount(void);
+#endif
+
+#endif /* CONFIG_FTRACE */
+
+#endif /* _ASM_X86_FTRACE */
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 20e14d0093c7..366098d591de 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -31,7 +31,6 @@ int unregister_ftrace_function(struct ftrace_ops *ops);
 void clear_ftrace_function(void);
 
 extern void ftrace_stub(unsigned long a0, unsigned long a1);
-extern void mcount(void);
 
 #else /* !CONFIG_FTRACE */
 # define register_ftrace_function(ops) do { } while (0)
@@ -54,7 +53,7 @@ enum {
 
 struct dyn_ftrace {
         struct hlist_node node;
-        unsigned long     ip;
+        unsigned long     ip; /* address of mcount call-site */
         unsigned long     flags;
 };
 
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 0d5bcf69952d..f1e9e5c74e64 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -27,6 +27,8 @@
 #include <linux/hash.h>
 #include <linux/list.h>
 
+#include <asm/ftrace.h>
+
 #include "trace.h"
 
 /* ftrace_enabled is a method to turn ftrace on or off */
@@ -329,7 +331,6 @@ ftrace_record_ip(unsigned long ip)
 }
 
 #define FTRACE_ADDR ((long)(ftrace_caller))
-#define MCOUNT_ADDR ((long)(mcount))
 
 static int
 __ftrace_replace_code(struct dyn_ftrace *rec,