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

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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: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Andi Kleen <ak@suse.de>
This commit is contained in:
Jan Beulich 2006-09-26 10:52:41 +02:00 committed by Andi Kleen
parent ab2e0b46cb
commit adf1423698
11 changed files with 73 additions and 9 deletions
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4
arch/i386/Makefile
View file

@ -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

4
arch/i386/kernel/entry.S
View file

@ -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

4
arch/x86_64/Makefile
View file

@ -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 )

4
arch/x86_64/ia32/ia32entry.S
View file

@ -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

4
arch/x86_64/kernel/entry.S
View file

@ -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

7
include/asm-i386/dwarf2.h
View file

@ -28,6 +28,12 @@
#define CFI_RESTORE_STATE .cfi_restore_state
#define CFI_UNDEFINED .cfi_undefined
#ifdef CONFIG_AS_CFI_SIGNAL_FRAME
#define CFI_SIGNAL_FRAME .cfi_signal_frame
#else
#define CFI_SIGNAL_FRAME
#endif
#else
/* Due to the structure of pre-exisiting code, don't use assembler line
@ -48,6 +54,7 @@
#define CFI_REMEMBER_STATE ignore
#define CFI_RESTORE_STATE ignore
#define CFI_UNDEFINED ignore
#define CFI_SIGNAL_FRAME ignore
#endif

5
include/asm-i386/unwind.h
View file

@ -18,6 +18,7 @@ struct unwind_frame_info
{
struct pt_regs regs;
struct task_struct *task;
unsigned call_frame:1;
};
#define UNW_PC(frame) (frame)->regs.eip
@ -44,6 +45,10 @@ struct unwind_frame_info
PTREGS_INFO(edi), \
PTREGS_INFO(eip)
#define UNW_DEFAULT_RA(raItem, dataAlign) \
((raItem).where == Memory && \
!((raItem).value * (dataAlign) + 4))
static inline void arch_unw_init_frame_info(struct unwind_frame_info *info,
/*const*/ struct pt_regs *regs)
{

6
include/asm-x86_64/dwarf2.h
View file

@ -28,6 +28,11 @@
#define CFI_REMEMBER_STATE .cfi_remember_state
#define CFI_RESTORE_STATE .cfi_restore_state
#define CFI_UNDEFINED .cfi_undefined
#ifdef CONFIG_AS_CFI_SIGNAL_FRAME
#define CFI_SIGNAL_FRAME .cfi_signal_frame
#else
#define CFI_SIGNAL_FRAME
#endif
#else
@ -45,6 +50,7 @@
#define CFI_REMEMBER_STATE #
#define CFI_RESTORE_STATE #
#define CFI_UNDEFINED #
#define CFI_SIGNAL_FRAME #
#endif

5
include/asm-x86_64/unwind.h
View file

@ -18,6 +18,7 @@ struct unwind_frame_info
{
struct pt_regs regs;
struct task_struct *task;
unsigned call_frame:1;
};
#define UNW_PC(frame) (frame)->regs.rip
@ -57,6 +58,10 @@ struct unwind_frame_info
PTREGS_INFO(r15), \
PTREGS_INFO(rip)
#define UNW_DEFAULT_RA(raItem, dataAlign) \
((raItem).where == Memory && \
!((raItem).value * (dataAlign) + 8))
static inline void arch_unw_init_frame_info(struct unwind_frame_info *info,
/*const*/ struct pt_regs *regs)
{

31
kernel/unwind.c
View file

@ -603,6 +603,7 @@ int unwind(struct unwind_frame_info *frame)
#define FRAME_REG(r, t) (((t *)frame)[reg_info[r].offs])
const u32 *fde = NULL, *cie = NULL;
const u8 *ptr = NULL, *end = NULL;
unsigned long pc = UNW_PC(frame) - frame->call_frame;
unsigned long startLoc = 0, endLoc = 0, cfa;
unsigned i;
signed ptrType = -1;
@ -612,7 +613,7 @@ int unwind(struct unwind_frame_info *frame)
if (UNW_PC(frame) == 0)
return -EINVAL;
if ((table = find_table(UNW_PC(frame))) != NULL
if ((table = find_table(pc)) != NULL
&& !(table->size & (sizeof(*fde) - 1))) {
unsigned long tableSize = table->size;
@ -647,7 +648,7 @@ int unwind(struct unwind_frame_info *frame)
ptrType & DW_EH_PE_indirect
? ptrType
: ptrType & (DW_EH_PE_FORM|DW_EH_PE_signed));
if (UNW_PC(frame) >= startLoc && UNW_PC(frame) < endLoc)
if (pc >= startLoc && pc < endLoc)
break;
cie = NULL;
}
@ -657,17 +658,29 @@ int unwind(struct unwind_frame_info *frame)
state.cieEnd = ptr; /* keep here temporarily */
ptr = (const u8 *)(cie + 2);
end = (const u8 *)(cie + 1) + *cie;
frame->call_frame = 1;
if ((state.version = *ptr) != 1)
cie = NULL; /* unsupported version */
else if (*++ptr) {
/* check if augmentation size is first (and thus present) */
if (*ptr == 'z') {
while (++ptr < end && *ptr) {
switch(*ptr) {
/* check for ignorable (or already handled)
* nul-terminated augmentation string */
while (++ptr < end && *ptr)
if (strchr("LPR", *ptr) == NULL)
case 'L':
case 'P':
case 'R':
continue;
case 'S':
frame->call_frame = 0;
continue;
default:
break;
}
break;
}
}
if (ptr >= end || *ptr)
cie = NULL;
}
@ -755,7 +768,7 @@ int unwind(struct unwind_frame_info *frame)
state.org = startLoc;
memcpy(&state.cfa, &badCFA, sizeof(state.cfa));
/* process instructions */
if (!processCFI(ptr, end, UNW_PC(frame), ptrType, &state)
if (!processCFI(ptr, end, pc, ptrType, &state)
|| state.loc > endLoc
|| state.regs[retAddrReg].where == Nowhere
|| state.cfa.reg >= ARRAY_SIZE(reg_info)
@ -763,6 +776,11 @@ int unwind(struct unwind_frame_info *frame)
|| state.cfa.offs % sizeof(unsigned long))
return -EIO;
/* update frame */
#ifndef CONFIG_AS_CFI_SIGNAL_FRAME
if(frame->call_frame
&& !UNW_DEFAULT_RA(state.regs[retAddrReg], state.dataAlign))
frame->call_frame = 0;
#endif
cfa = FRAME_REG(state.cfa.reg, unsigned long) + state.cfa.offs;
startLoc = min((unsigned long)UNW_SP(frame), cfa);
endLoc = max((unsigned long)UNW_SP(frame), cfa);
@ -866,6 +884,7 @@ int unwind_init_frame_info(struct unwind_frame_info *info,
/*const*/ struct pt_regs *regs)
{
info->task = tsk;
info->call_frame = 0;
arch_unw_init_frame_info(info, regs);
return 0;
@ -879,6 +898,7 @@ int unwind_init_blocked(struct unwind_frame_info *info,
struct task_struct *tsk)
{
info->task = tsk;
info->call_frame = 0;
arch_unw_init_blocked(info);
return 0;
@ -894,6 +914,7 @@ int unwind_init_running(struct unwind_frame_info *info,
void *arg)
{
info->task = current;
info->call_frame = 0;
return arch_unwind_init_running(info, callback, arg);
}

4
scripts/Kbuild.include
View file

@ -66,8 +66,8 @@ as-option = $(shell if $(CC) $(CFLAGS) $(1) -Wa,-Z -c -o /dev/null \
# as-instr
# Usage: cflags-y += $(call as-instr, instr, option1, option2)
as-instr = $(shell if echo -e "$(1)" | $(AS) -Z -o astest$$$$.out \
2>&1 >/dev/null ; then echo "$(2)"; else echo "$(3)"; fi; \
as-instr = $(shell if echo -e "$(1)" | $(AS) >/dev/null 2>&1 -W -Z -o astest$$$$.out ; \
then echo "$(2)"; else echo "$(3)"; fi; \
rm -f astest$$$$.out)
# cc-option