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Commit 620176f3 authored by Abel Vesa's avatar Abel Vesa Committed by Russell King
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ARM: 8678/1: ftrace: Adds support for CONFIG_DYNAMIC_FTRACE_WITH_REGS 



The DYNAMIC_FTRACE_WITH_REGS configuration makes it possible for a
ftrace operation to specify if registers need to saved/restored by
the ftrace handler. This is needed by kgraft and possibly other
ftrace-based tools, and the ARM architecture is currently lacking
this feature. It would also be the first step to support the
"Kprobes-on-ftrace" optimization on ARM.

This patch introduces a new ftrace handler that stores the registers
on the stack before calling the next stage. The registers are restored
from the stack before going back to the instrumented function.

A side-effect of this patch is to activate the support for
ftrace_modify_call() as it defines ARCH_SUPPORTS_FTRACE_OPS for the
ARM architecture.

Signed-off-by: default avatarAbel Vesa <abelvesa@linux.com>
Signed-off-by: default avatarRussell King <rmk+kernel@armlinux.org.uk>
parent 1515b186

arch/arm/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -56,6 +56,7 @@ config ARM 
	select HAVE_DMA_API_DEBUG

	select HAVE_DMA_CONTIGUOUS if MMU

	select HAVE_DYNAMIC_FTRACE if (!XIP_KERNEL) && !CPU_ENDIAN_BE32 && MMU

	select HAVE_DYNAMIC_FTRACE_WITH_REGS if HAVE_DYNAMIC_FTRACE

	select HAVE_EFFICIENT_UNALIGNED_ACCESS if (CPU_V6 || CPU_V6K || CPU_V7) && MMU

	select HAVE_EXIT_THREAD

	select HAVE_FTRACE_MCOUNT_RECORD if (!XIP_KERNEL)

arch/arm/include/asm/ftrace.h

+4 −0
Original line number Diff line number Diff line 
#ifndef _ASM_ARM_FTRACE

#define _ASM_ARM_FTRACE



#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS

#define ARCH_SUPPORTS_FTRACE_OPS 1

#endif



#ifdef CONFIG_FUNCTION_TRACER

#define MCOUNT_ADDR		((unsigned long)(__gnu_mcount_nc))

#define MCOUNT_INSN_SIZE	4 /* sizeof mcount call */

arch/arm/kernel/entry-ftrace.S

+100 −0
Original line number Diff line number Diff line
@@ -92,12 +92,95 @@ 
2:	mcount_exit

.endm



#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS



.macro __ftrace_regs_caller



	sub	sp, sp, #8	@ space for PC and CPSR OLD_R0,

				@ OLD_R0 will overwrite previous LR



	add 	ip, sp, #12	@ move in IP the value of SP as it was

				@ before the push {lr} of the mcount mechanism



	str     lr, [sp, #0]    @ store LR instead of PC



	ldr     lr, [sp, #8]    @ get previous LR



	str	r0, [sp, #8]	@ write r0 as OLD_R0 over previous LR



	stmdb   sp!, {ip, lr}

	stmdb   sp!, {r0-r11, lr}



	@ stack content at this point:

	@ 0  4          48   52       56            60   64    68       72

	@ R0 | R1 | ... | LR | SP + 4 | previous LR | LR | PSR | OLD_R0 |



	mov r3, sp				@ struct pt_regs*



	ldr r2, =function_trace_op

	ldr r2, [r2]				@ pointer to the current

						@ function tracing op



	ldr	r1, [sp, #S_LR]			@ lr of instrumented func



	ldr	lr, [sp, #S_PC]			@ get LR



	mcount_adjust_addr	r0, lr		@ instrumented function



	.globl ftrace_regs_call

ftrace_regs_call:

	bl	ftrace_stub



#ifdef CONFIG_FUNCTION_GRAPH_TRACER

	.globl ftrace_graph_regs_call

ftrace_graph_regs_call:

	mov	r0, r0

#endif



	@ pop saved regs

	ldmia   sp!, {r0-r12}			@ restore r0 through r12

	ldr	ip, [sp, #8]			@ restore PC

	ldr	lr, [sp, #4]			@ restore LR

	ldr	sp, [sp, #0]			@ restore SP

	mov	pc, ip				@ return

.endm



#ifdef CONFIG_FUNCTION_GRAPH_TRACER

.macro __ftrace_graph_regs_caller



	sub     r0, fp, #4              @ lr of instrumented routine (parent)



	@ called from __ftrace_regs_caller

	ldr     r1, [sp, #S_PC]		@ instrumented routine (func)

	mcount_adjust_addr	r1, r1



	mov	r2, fp			@ frame pointer

	bl	prepare_ftrace_return



	@ pop registers saved in ftrace_regs_caller

	ldmia   sp!, {r0-r12}			@ restore r0 through r12

	ldr	ip, [sp, #8]			@ restore PC

	ldr	lr, [sp, #4]			@ restore LR

	ldr	sp, [sp, #0]			@ restore SP

	mov	pc, ip				@ return



.endm

#endif

#endif



.macro __ftrace_caller suffix

	mcount_enter



	mcount_get_lr	r1			@ lr of instrumented func

	mcount_adjust_addr	r0, lr		@ instrumented function



#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS

	ldr r2, =function_trace_op

	ldr r2, [r2]				@ pointer to the current

						@ function tracing op

	mov r3, #0				@ regs is NULL

#endif



	.globl ftrace_call\suffix

ftrace_call\suffix:

	bl	ftrace_stub
@@ -212,6 +295,15 @@ UNWIND(.fnstart) 
	__ftrace_caller

UNWIND(.fnend)

ENDPROC(ftrace_caller)



#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS

ENTRY(ftrace_regs_caller)

UNWIND(.fnstart)

	__ftrace_regs_caller

UNWIND(.fnend)

ENDPROC(ftrace_regs_caller)

#endif



#endif



#ifdef CONFIG_FUNCTION_GRAPH_TRACER
@@ -220,6 +312,14 @@ UNWIND(.fnstart) 
	__ftrace_graph_caller

UNWIND(.fnend)

ENDPROC(ftrace_graph_caller)



#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS

ENTRY(ftrace_graph_regs_caller)

UNWIND(.fnstart)

	__ftrace_graph_regs_caller

UNWIND(.fnend)

ENDPROC(ftrace_graph_regs_caller)

#endif

#endif



.purgem mcount_enter

arch/arm/kernel/ftrace.c

+37 −0
Original line number Diff line number Diff line
@@ -141,6 +141,15 @@ int ftrace_update_ftrace_func(ftrace_func_t func) 


	ret = ftrace_modify_code(pc, 0, new, false);



#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS

	if (!ret) {

		pc = (unsigned long)&ftrace_regs_call;

		new = ftrace_call_replace(pc, (unsigned long)func);



		ret = ftrace_modify_code(pc, 0, new, false);

	}

#endif



#ifdef CONFIG_OLD_MCOUNT

	if (!ret) {

		pc = (unsigned long)&ftrace_call_old;
@@ -159,11 +168,29 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) 
	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, true);

}



#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS



int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,

				unsigned long addr)

{

	unsigned long new, old;

	unsigned long ip = rec->ip;



	old = ftrace_call_replace(ip, adjust_address(rec, old_addr));



	new = ftrace_call_replace(ip, adjust_address(rec, addr));



	return ftrace_modify_code(rec->ip, old, new, true);

}



#endif



int ftrace_make_nop(struct module *mod,

		    struct dyn_ftrace *rec, unsigned long addr)

{
@@ -231,6 +258,8 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr, 
extern unsigned long ftrace_graph_call;

extern unsigned long ftrace_graph_call_old;

extern void ftrace_graph_caller_old(void);

extern unsigned long ftrace_graph_regs_call;

extern void ftrace_graph_regs_caller(void);



static int __ftrace_modify_caller(unsigned long *callsite,

				  void (*func) (void), bool enable)
@@ -253,6 +282,14 @@ static int ftrace_modify_graph_caller(bool enable) 
				     ftrace_graph_caller,

				     enable);



#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS

	if (!ret)

		ret = __ftrace_modify_caller(&ftrace_graph_regs_call,

				     ftrace_graph_regs_caller,

				     enable);

#endif





#ifdef CONFIG_OLD_MCOUNT

	if (!ret)

		ret = __ftrace_modify_caller(&ftrace_graph_call_old,