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Commit 3b6c223b authored by Rabin Vincent's avatar Rabin Vincent Committed by Russell King
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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: default avatarRabin Vincent <rabin@rab.in>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent f9810a82

arch/arm/include/asm/ftrace.h

+18 −1
Original line number Diff line number Diff line
@@ -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

arch/arm/kernel/entry-common.S

+28 −9
Original line number Diff line number Diff line
@@ -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

arch/arm/kernel/ftrace.c

+107 −48
Original line number Diff line number Diff line
@@ -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 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 (char *)&NOP;

	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;



	old = *(unsigned long *)old_code;

	new = *(unsigned long *)new_code;



	__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"



		".pushsection .fixup, \"ax\"\n"

		"4:  mov  %0, #1  \n"

		"    b    3b      \n"

		".popsection\n"



		".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))

	unsigned long replaced;



	if (probe_kernel_read(&replaced, (void *)pc, MCOUNT_INSN_SIZE))

		return -EFAULT;



	if (replaced != old)

		return -EINVAL;



	if (probe_kernel_write((void *)pc, &new, MCOUNT_INSN_SIZE))

		return -EPERM;



	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;

}

scripts/recordmcount.pl

+2 −0
Original line number Diff line number Diff line
@@ -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\$";