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ARM: 6318/1: ftrace: fix and update dynamic ftrace 

This adds mcount recording and updates dynamic ftrace for ARM to work
with the new ftrace dyamic tracing implementation.  It also adds support
for the mcount format used by newer ARM compilers.

With dynamic tracing, mcount() is implemented as a nop.  Callsites are
patched on startup with nops, and dynamically patched to call to the
ftrace_caller() routine as needed.

Acked-by: Steven Rostedt <rostedt@goodmis.org> [recordmcount.pl change]
Signed-off-by: Rabin Vincent <rabin@rab.in>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Rabin Vincent 2010-08-10 19:43:28 +01:00 committed by Russell King
parent f9810a8253
commit 3b6c223b1b
4 changed files with 155 additions and 58 deletions
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19
arch/arm/include/asm/ftrace.h
View File

@ -2,12 +2,29 @@
#define _ASM_ARM_FTRACE
#ifdef CONFIG_FUNCTION_TRACER
#define MCOUNT_ADDR ((long)(mcount))
#define MCOUNT_ADDR ((unsigned long)(__gnu_mcount_nc))
#define MCOUNT_INSN_SIZE 4 /* sizeof mcount call */
#ifndef __ASSEMBLY__
extern void mcount(void);
extern void __gnu_mcount_nc(void);
#ifdef CONFIG_DYNAMIC_FTRACE
struct dyn_arch_ftrace {
#ifdef CONFIG_OLD_MCOUNT
bool old_mcount;
#endif
};
static inline unsigned long ftrace_call_adjust(unsigned long addr)
{
return addr;
}
extern void ftrace_caller_old(void);
extern void ftrace_call_old(void);
#endif
#endif
#endif

37
arch/arm/kernel/entry-common.S
View File

@ -127,6 +127,10 @@ ENDPROC(ret_from_fork)
* clobber the ip register. This is OK because the ARM calling convention
* allows it to be clobbered in subroutines and doesn't use it to hold
* parameters.)
*
* When using dynamic ftrace, we patch out the mcount call by a "mov r0, r0"
* for the mcount case, and a "pop {lr}" for the __gnu_mcount_nc case (see
* arch/arm/kernel/ftrace.c).
*/
#ifndef CONFIG_OLD_MCOUNT
@ -136,30 +140,45 @@ ENDPROC(ret_from_fork)
#endif
#ifdef CONFIG_DYNAMIC_FTRACE
ENTRY(mcount)
ENTRY(__gnu_mcount_nc)
mov ip, lr
ldmia sp!, {lr}
mov pc, ip
ENDPROC(__gnu_mcount_nc)
ENTRY(ftrace_caller)
stmdb sp!, {r0-r3, lr}
mov r0, lr
sub r0, r0, #MCOUNT_INSN_SIZE
ldr r1, [sp, #20]
.globl mcount_call
mcount_call:
.global ftrace_call
ftrace_call:
bl ftrace_stub
ldr lr, [fp, #-4] @ restore lr
ldmia sp!, {r0-r3, pc}
ldmia sp!, {r0-r3, ip, lr}
mov pc, ip
ENDPROC(ftrace_caller)
#ifdef CONFIG_OLD_MCOUNT
ENTRY(mcount)
stmdb sp!, {lr}
ldr lr, [fp, #-4]
ldmia sp!, {pc}
ENDPROC(mcount)
ENTRY(ftrace_caller)
ENTRY(ftrace_caller_old)
stmdb sp!, {r0-r3, lr}
ldr r1, [fp, #-4]
mov r0, lr
sub r0, r0, #MCOUNT_INSN_SIZE
.globl ftrace_call
ftrace_call:
.globl ftrace_call_old
ftrace_call_old:
bl ftrace_stub
ldr lr, [fp, #-4] @ restore lr
ldmia sp!, {r0-r3, pc}
ENDPROC(ftrace_caller)
ENDPROC(ftrace_caller_old)
#endif
#else

153
arch/arm/kernel/ftrace.c
View File

@ -2,102 +2,161 @@
* Dynamic function tracing support.
*
* Copyright (C) 2008 Abhishek Sagar <sagar.abhishek@gmail.com>
* Copyright (C) 2010 Rabin Vincent <rabin@rab.in>
*
* For licencing details, see COPYING.
*
* Defines low-level handling of mcount calls when the kernel
* is compiled with the -pg flag. When using dynamic ftrace, the
* mcount call-sites get patched lazily with NOP till they are
* enabled. All code mutation routines here take effect atomically.
* mcount call-sites get patched with NOP till they are enabled.
* All code mutation routines here are called under stop_machine().
*/
#include <linux/ftrace.h>
#include <linux/uaccess.h>
#include <asm/cacheflush.h>
#include <asm/ftrace.h>
#define PC_OFFSET 8
#define BL_OPCODE 0xeb000000
#define BL_OFFSET_MASK 0x00ffffff
#define NOP 0xe8bd4000 /* pop {lr} */
static unsigned long bl_insn;
static const unsigned long NOP = 0xe1a00000; /* mov r0, r0 */
#ifdef CONFIG_OLD_MCOUNT
#define OLD_MCOUNT_ADDR ((unsigned long) mcount)
#define OLD_FTRACE_ADDR ((unsigned long) ftrace_caller_old)
unsigned char *ftrace_nop_replace(void)
#define OLD_NOP 0xe1a00000 /* mov r0, r0 */
static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec)
{
return (char *)&NOP;
return rec->arch.old_mcount ? OLD_NOP : NOP;
}
static unsigned long adjust_address(struct dyn_ftrace *rec, unsigned long addr)
{
if (!rec->arch.old_mcount)
return addr;
if (addr == MCOUNT_ADDR)
addr = OLD_MCOUNT_ADDR;
else if (addr == FTRACE_ADDR)
addr = OLD_FTRACE_ADDR;
return addr;
}
#else
static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec)
{
return NOP;
}
static unsigned long adjust_address(struct dyn_ftrace *rec, unsigned long addr)
{
return addr;
}
#endif
/* construct a branch (BL) instruction to addr */
unsigned char *ftrace_call_replace(unsigned long pc, unsigned long addr)
static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr)
{
long offset;
offset = (long)addr - (long)(pc + PC_OFFSET);
offset = (long)addr - (long)(pc + 8);
if (unlikely(offset < -33554432 || offset > 33554428)) {
/* Can't generate branches that far (from ARM ARM). Ftrace
* doesn't generate branches outside of kernel text.
*/
WARN_ON_ONCE(1);
return NULL;
return 0;
}
offset = (offset >> 2) & BL_OFFSET_MASK;
bl_insn = BL_OPCODE | offset;
return (unsigned char *)&bl_insn;
offset = (offset >> 2) & 0x00ffffff;
return 0xeb000000 | offset;
}
int ftrace_modify_code(unsigned long pc, unsigned char *old_code,
unsigned char *new_code)
static int ftrace_modify_code(unsigned long pc, unsigned long old,
unsigned long new)
{
unsigned long err = 0, replaced = 0, old, new;
unsigned long replaced;
old = *(unsigned long *)old_code;
new = *(unsigned long *)new_code;
if (probe_kernel_read(&replaced, (void *)pc, MCOUNT_INSN_SIZE))
return -EFAULT;
__asm__ __volatile__ (
"1: ldr %1, [%2] \n"
" cmp %1, %4 \n"
"2: streq %3, [%2] \n"
" cmpne %1, %3 \n"
" movne %0, #2 \n"
"3:\n"
if (replaced != old)
return -EINVAL;
".pushsection .fixup, \"ax\"\n"
"4: mov %0, #1 \n"
" b 3b \n"
".popsection\n"
if (probe_kernel_write((void *)pc, &new, MCOUNT_INSN_SIZE))
return -EPERM;
".pushsection __ex_table, \"a\"\n"
" .long 1b, 4b \n"
" .long 2b, 4b \n"
".popsection\n"
: "=r"(err), "=r"(replaced)
: "r"(pc), "r"(new), "r"(old), "0"(err), "1"(replaced)
: "memory");
if (!err && (replaced == old))
flush_icache_range(pc, pc + MCOUNT_INSN_SIZE);
return err;
return 0;
}
int ftrace_update_ftrace_func(ftrace_func_t func)
{
int ret;
unsigned long pc, old;
unsigned char *new;
unsigned long new;
int ret;
pc = (unsigned long)&ftrace_call;
memcpy(&old, &ftrace_call, MCOUNT_INSN_SIZE);
new = ftrace_call_replace(pc, (unsigned long)func);
ret = ftrace_modify_code(pc, (unsigned char *)&old, new);
ret = ftrace_modify_code(pc, old, new);
#ifdef CONFIG_OLD_MCOUNT
if (!ret) {
pc = (unsigned long)&ftrace_call_old;
memcpy(&old, &ftrace_call_old, MCOUNT_INSN_SIZE);
new = ftrace_call_replace(pc, (unsigned long)func);
ret = ftrace_modify_code(pc, old, new);
}
#endif
return ret;
}
int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
unsigned long new, old;
unsigned long ip = rec->ip;
old = ftrace_nop_replace(rec);
new = ftrace_call_replace(ip, adjust_address(rec, addr));
return ftrace_modify_code(rec->ip, old, new);
}
int ftrace_make_nop(struct module *mod,
struct dyn_ftrace *rec, unsigned long addr)
{
unsigned long ip = rec->ip;
unsigned long old;
unsigned long new;
int ret;
old = ftrace_call_replace(ip, adjust_address(rec, addr));
new = ftrace_nop_replace(rec);
ret = ftrace_modify_code(ip, old, new);
#ifdef CONFIG_OLD_MCOUNT
if (ret == -EINVAL && addr == MCOUNT_ADDR) {
rec->arch.old_mcount = true;
old = ftrace_call_replace(ip, adjust_address(rec, addr));
new = ftrace_nop_replace(rec);
ret = ftrace_modify_code(ip, old, new);
}
#endif
return ret;
}
/* run from ftrace_init with irqs disabled */
int __init ftrace_dyn_arch_init(void *data)
{
ftrace_mcount_set(data);
*(unsigned long *)data = 0;
return 0;
}

2
scripts/recordmcount.pl
View File

@ -270,6 +270,8 @@ if ($arch eq "x86_64") {
} elsif ($arch eq "arm") {
$alignment = 2;
$section_type = '%progbits';
$mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_ARM_(CALL|PC24)" .
"\\s+(__gnu_mcount_nc|mcount)\$";
} elsif ($arch eq "ia64") {
$mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";