[PATCH 19/19] [INCOMPLETE] ARM: make return_address available for ARM_UNWIND
From: arnd@arndb.de (Arnd Bergmann)
Date: 2014-01-07 15:48:47
Also in:
lkml
Subsystem:
arm port, function hooks (ftrace), the rest · Maintainers:
Russell King, Steven Rostedt, Masami Hiramatsu, Linus Torvalds
Possibly related (same subject, not in this thread)
- 2013-01-25 · [PATCH 19/19] [INCOMPLETE] ARM: make return_address available for ARM_UNWIND · Arnd Bergmann <arnd@arndb.de>
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:quoted
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);