Messages in this thread Patch in this message | | | From | Arnd Bergmann <> | Subject | Re: [PATCH 19/19] [INCOMPLETE] ARM: make return_address available for ARM_UNWIND | Date | Tue, 07 Jan 2014 16:48:25 +0100 |
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On Tuesday 07 January 2014 14:41:30 Russell King - ARM Linux wrote: > On Tue, Jan 07, 2014 at 03:33:34PM +0100, Arnd Bergmann wrote: > > > > > > It's been almost a year since we last discussed the patches that were > > posted by Dave and sahara, but nothing has changed in the mainline kernel. > > > > Any chance that someone could be motivated to pick this work up again > > and finally fix return_address(). > > I thought that we had _actively_ decided that we would not use the > unwinder for these paths - that it was too expensive for these paths, > and you had to use frame pointers instead.
I don't remember that discussion, but it may well be. What does that mean for the #warning in return_address.c then? Can we just use the frame pointer version based on CONFIG_FRAME_POINTER and ignore whether CONFIG_ARM_UNWIND is set as the patch below, or did I misunderstand?
Arnd
diff --git a/arch/arm/include/asm/ftrace.h b/arch/arm/include/asm/ftrace.h index f89515a..3247370 100644 --- a/arch/arm/include/asm/ftrace.h +++ b/arch/arm/include/asm/ftrace.h @@ -32,7 +32,7 @@ extern void ftrace_call_old(void); #ifndef __ASSEMBLY__ -#if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND) +#if defined(CONFIG_FRAME_POINTER) /* * return_address uses walk_stackframe to do it's work. If both * CONFIG_FRAME_POINTER=y and CONFIG_ARM_UNWIND=y walk_stackframe uses unwind diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile index a30fc9b..c713f46 100644 --- a/arch/arm/kernel/Makefile +++ b/arch/arm/kernel/Makefile @@ -16,13 +16,14 @@ CFLAGS_REMOVE_return_address.o = -pg # Object file lists. obj-y := elf.o entry-common.o irq.o opcodes.o \ - process.o ptrace.o return_address.o \ + process.o ptrace.o \ setup.o signal.o sigreturn_codes.o \ stacktrace.o sys_arm.o time.o traps.o obj-$(CONFIG_ATAGS) += atags_parse.o obj-$(CONFIG_ATAGS_PROC) += atags_proc.o obj-$(CONFIG_DEPRECATED_PARAM_STRUCT) += atags_compat.o +obj-$(CONFIG_FRAME_POINTER) += return_address.o ifeq ($(CONFIG_CPU_V7M),y) obj-y += entry-v7m.o v7m.o diff --git a/arch/arm/kernel/return_address.c b/arch/arm/kernel/return_address.c index fafedd8..d9f2c15 100644 --- a/arch/arm/kernel/return_address.c +++ b/arch/arm/kernel/return_address.c @@ -10,8 +10,6 @@ */ #include <linux/export.h> #include <linux/ftrace.h> - -#if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND) #include <linux/sched.h> #include <asm/stacktrace.h> @@ -56,18 +54,4 @@ void *return_address(unsigned int level) else return NULL; } - -#else /* if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND) */ - -#if defined(CONFIG_ARM_UNWIND) -#warning "TODO: return_address should use unwind tables" -#endif - -void *return_address(unsigned int level) -{ - return NULL; -} - -#endif /* if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND) / else */ - EXPORT_SYMBOL_GPL(return_address);
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