Commit adf14236 authored by Jan Beulich's avatar Jan Beulich Committed by Andi Kleen
Browse files

[PATCH] i386/x86-64: Work around gcc bug with noreturn functions in unwinder 



Current gcc generates calls not jumps to noreturn functions. When that happens the
return address can point to the next function, which confuses the unwinder.

This patch works around it by marking asynchronous exception
frames in contrast normal call frames in the unwind information.  Then teach
the unwinder to decode this.

For normal call frames the unwinder now subtracts one from the address which avoids
this problem.  The standard libgcc unwinder uses the same trick.

It doesn't include adjustment of the printed address (i.e. for the original
example, it'd still be kernel_math_error+0 that gets displayed, but the
unwinder wouldn't get confused anymore.

This only works with binutils 2.6.17+ and some versions of H.J.Lu's 2.6.16
unfortunately because earlier binutils don't support .cfi_signal_frame

[AK: added automatic detection of the new binutils and wrote description]

Signed-off-by: default avatarJan Beulich <jbeulich@novell.com>
Signed-off-by: default avatarAndi Kleen <ak@suse.de>
parent ab2e0b46

arch/i386/Makefile

+4 −0
Original line number Diff line number Diff line
@@ -50,6 +50,10 @@ CFLAGS += $(shell if [ $(call cc-version) -lt 0400 ] ; then echo $(call cc-op 
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,)



# is .cfi_signal_frame supported too?

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/i386/kernel/entry.S

+4 −0
Original line number Diff line number Diff line
@@ -183,18 +183,21 @@ VM_MASK = 0x00020000 


#define RING0_INT_FRAME \

	CFI_STARTPROC simple;\

	CFI_SIGNAL_FRAME;\

	CFI_DEF_CFA esp, 3*4;\

	/*CFI_OFFSET cs, -2*4;*/\

	CFI_OFFSET eip, -3*4



#define RING0_EC_FRAME \

	CFI_STARTPROC simple;\

	CFI_SIGNAL_FRAME;\

	CFI_DEF_CFA esp, 4*4;\

	/*CFI_OFFSET cs, -2*4;*/\

	CFI_OFFSET eip, -3*4



#define RING0_PTREGS_FRAME \

	CFI_STARTPROC simple;\

	CFI_SIGNAL_FRAME;\

	CFI_DEF_CFA esp, OLDESP-EBX;\

	/*CFI_OFFSET cs, CS-OLDESP;*/\

	CFI_OFFSET eip, EIP-OLDESP;\
@@ -275,6 +278,7 @@ need_resched: 
	# sysenter call handler stub

ENTRY(sysenter_entry)

	CFI_STARTPROC simple

	CFI_SIGNAL_FRAME

	CFI_DEF_CFA esp, 0

	CFI_REGISTER esp, ebp

	movl TSS_sysenter_esp0(%esp),%esp

arch/x86_64/Makefile

+4 −0
Original line number Diff line number Diff line
@@ -58,6 +58,10 @@ cflags-y += $(call cc-option,-mno-sse -mno-mmx -mno-sse2 -mno-3dnow,) 
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,)



# is .cfi_signal_frame supported too?

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

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



cflags-$(CONFIG_CC_STACKPROTECTOR) += $(shell $(CONFIG_SHELL) $(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC) -fstack-protector )

cflags-$(CONFIG_CC_STACKPROTECTOR_ALL) += $(shell $(CONFIG_SHELL) $(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC) -fstack-protector-all )

arch/x86_64/ia32/ia32entry.S

+4 −0
Original line number Diff line number Diff line
@@ -71,6 +71,7 @@ 
 */ 	

ENTRY(ia32_sysenter_target)

	CFI_STARTPROC32	simple

	CFI_SIGNAL_FRAME

	CFI_DEF_CFA	rsp,0

	CFI_REGISTER	rsp,rbp

	swapgs
@@ -186,6 +187,7 @@ ENDPROC(ia32_sysenter_target) 
 */ 	

ENTRY(ia32_cstar_target)

	CFI_STARTPROC32	simple

	CFI_SIGNAL_FRAME

	CFI_DEF_CFA	rsp,PDA_STACKOFFSET

	CFI_REGISTER	rip,rcx

	/*CFI_REGISTER	rflags,r11*/
@@ -293,6 +295,7 @@ ia32_badarg: 


ENTRY(ia32_syscall)

	CFI_STARTPROC	simple

	CFI_SIGNAL_FRAME

	CFI_DEF_CFA	rsp,SS+8-RIP

	/*CFI_REL_OFFSET	ss,SS-RIP*/

	CFI_REL_OFFSET	rsp,RSP-RIP
@@ -370,6 +373,7 @@ ENTRY(ia32_ptregs_common) 
	popq %r11

	CFI_ENDPROC

	CFI_STARTPROC32	simple

	CFI_SIGNAL_FRAME

	CFI_DEF_CFA	rsp,SS+8-ARGOFFSET

	CFI_REL_OFFSET	rax,RAX-ARGOFFSET

	CFI_REL_OFFSET	rcx,RCX-ARGOFFSET

arch/x86_64/kernel/entry.S

+4 −0
Original line number Diff line number Diff line
@@ -123,6 +123,7 @@ 
	.macro	CFI_DEFAULT_STACK start=1

	.if \start

	CFI_STARTPROC	simple

	CFI_SIGNAL_FRAME

	CFI_DEF_CFA	rsp,SS+8

	.else

	CFI_DEF_CFA_OFFSET SS+8
@@ -207,6 +208,7 @@ END(ret_from_fork) 


ENTRY(system_call)

	CFI_STARTPROC	simple

	CFI_SIGNAL_FRAME

	CFI_DEF_CFA	rsp,PDA_STACKOFFSET

	CFI_REGISTER	rip,rcx

	/*CFI_REGISTER	rflags,r11*/
@@ -324,6 +326,7 @@ END(system_call) 
 */ 	

ENTRY(int_ret_from_sys_call)

	CFI_STARTPROC	simple

	CFI_SIGNAL_FRAME

	CFI_DEF_CFA	rsp,SS+8-ARGOFFSET

	/*CFI_REL_OFFSET	ss,SS-ARGOFFSET*/

	CFI_REL_OFFSET	rsp,RSP-ARGOFFSET
@@ -484,6 +487,7 @@ END(stub_rt_sigreturn) 
 */

	.macro _frame ref

	CFI_STARTPROC simple

	CFI_SIGNAL_FRAME

	CFI_DEF_CFA rsp,SS+8-\ref

	/*CFI_REL_OFFSET ss,SS-\ref*/

	CFI_REL_OFFSET rsp,RSP-\ref

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