Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit e2414910 authored by Andi Kleen's avatar Andi Kleen Committed by Andi Kleen
Browse files

[PATCH] x86: Detect CFI support in the assembler at runtime 



... instead of using a CONFIG option. The config option still controls
if the resulting executable actually has unwind information.

This is useful to prevent compilation errors when users select
CONFIG_STACK_UNWIND on old binutils and also allows to use
CFI in the future for non kernel debugging applications.

Cc: jbeulich@novell.com
Cc: sam@ravnborg.org

Signed-off-by: default avatarAndi Kleen <ak@suse.de>
parent fe7414a2

Documentation/kbuild/makefiles.txt

+5 −0
Original line number Diff line number Diff line
@@ -421,6 +421,11 @@ more details, with real examples. 
	The second argument is optional, and if supplied will be used

	if first argument is not supported.



    as-instr

	as-instr checks if the assembler reports a specific instruction

	and then outputs either option1 or option2

	C escapes are supported in the test instruction



    cc-option

	cc-option is used to check if $(CC) supports a given option, and not

	supported to use an optional second option.

arch/i386/Makefile

+4 −0
Original line number Diff line number Diff line
@@ -46,6 +46,10 @@ cflags-y += -ffreestanding 
# a lot more stack due to the lack of sharing of stacklots:

CFLAGS				+= $(shell if [ $(call cc-version) -lt 0400 ] ; then echo $(call cc-option,-fno-unit-at-a-time); fi ;)



# do binutils support CFI?

cflags-y += $(call as-instr,.cfi_startproc\n.cfi_endproc,-DCONFIG_AS_CFI=1,)

AFLAGS += $(call as-instr,.cfi_startproc\n.cfi_endproc,-DCONFIG_AS_CFI=1,)



CFLAGS += $(cflags-y)



# Default subarch .c files

arch/x86_64/Makefile

+3 −0
Original line number Diff line number Diff line
@@ -54,6 +54,9 @@ endif 
cflags-y += $(call cc-option,-funit-at-a-time)

# prevent gcc from generating any FP code by mistake

cflags-y += $(call cc-option,-mno-sse -mno-mmx -mno-sse2 -mno-3dnow,)

# do binutils support CFI?

cflags-y += $(call as-instr,.cfi_startproc\n.cfi_endproc,-DCONFIG_AS_CFI=1,)

AFLAGS += $(call as-instr,.cfi_startproc\n.cfi_endproc,-DCONFIG_AS_CFI=1,)



CFLAGS += $(cflags-y)

CFLAGS_KERNEL += $(cflags-kernel-y)

include/asm-x86_64/dwarf2.h

+1 −1
Original line number Diff line number Diff line
@@ -13,7 +13,7 @@ 
   away for older version. 

 */



#ifdef CONFIG_UNWIND_INFO

#ifdef CONFIG_AS_CFI



#define CFI_STARTPROC .cfi_startproc

#define CFI_ENDPROC .cfi_endproc

scripts/Kbuild.include

+7 −0
Original line number Diff line number Diff line
@@ -63,6 +63,13 @@ as-option = $(shell if $(CC) $(CFLAGS) $(1) -Wa,-Z -c -o /dev/null \ 
	     -xassembler /dev/null > /dev/null 2>&1; then echo "$(1)"; \

	     else echo "$(2)"; fi ;)



# as-instr

# Usage: cflags-y += $(call as-instr, instr, option1, option2)



as-instr = $(shell if echo -e "$(1)" | $(AS) -Z -o astest$$$$.out \

		   2>&1 >/dev/null ; then echo "$(2)"; else echo "$(3)"; fi; \

	           rm -f astest$$$$.out)



# cc-option

# Usage: cflags-y += $(call cc-option, -march=winchip-c6, -march=i586)