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authorJan Beulich <jbeulich@novell.com>2006-09-26 10:52:41 +0200
committerAndi Kleen <andi@basil.nowhere.org>2006-09-26 10:52:41 +0200
commitadf1423698f00d00b267f7dca8231340ce7d65ef (patch)
treeec2e28a32d467cc3c618c8ee0cedd3d1a49f9c43 /kernel/unwind.c
parentab2e0b46cb9a197fab7d98e147cac7cd41a14047 (diff)
[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: Jan Beulich <jbeulich@novell.com> Signed-off-by: Andi Kleen <ak@suse.de>
Diffstat (limited to 'kernel/unwind.c')
-rw-r--r--kernel/unwind.c35
1 files changed, 28 insertions, 7 deletions
diff --git a/kernel/unwind.c b/kernel/unwind.c
index f69c804c8e62..3430475fcd88 100644
--- a/kernel/unwind.c
+++ b/kernel/unwind.c
@@ -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;
}
@@ -657,16 +658,28 @@ 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') {
- /* check for ignorable (or already handled)
- * nul-terminated augmentation string */
- while (++ptr < end && *ptr)
- if (strchr("LPR", *ptr) == NULL)
+ while (++ptr < end && *ptr) {
+ switch(*ptr) {
+ /* check for ignorable (or already handled)
+ * nul-terminated augmentation string */
+ 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);
}

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