[PATCH 1/4] ftrace: store mcount address in rec->ip

From: Abhishek Sagar
Date: Sat Jun 21 2008 - 14:18:41 EST


Record mcount call-site addresses. Tested on x86-32 and ARM. Would be a good
good idea to boot test it on sparc64, ppc and x86-64 before applying.

Signed-off-by: Abhishek Sagar <sagar.abhishek@xxxxxxxxx>
---

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.

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;
diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index 3b1dd29..7231a70 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 2c4d9e0..2f511a9 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 e12c593..3855ceb 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 c173731..4298d0a 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 8ac0b99..b80d982 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 04ea83c..95e6bbe 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 fe25e5f..b0f7308 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 5582814..ab115cd 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 29999db..dd7ebee 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 122885b..16ff4bf 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 0000000..584ef9a
--- /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 b1bfa70..de92132 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 0000000..f76a40a
--- /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 0000000..c184441
--- /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 20e14d0..366098d 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 0d5bcf6..f1e9e5c 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,
--
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