[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>

diff --git a/arch/i386/Makefile b/arch/i386/Makefile
index 508cdbeb3a092845925cb3fb6a7ec39f514cf997..7cc0b189b82baa80d83d813a11ec256243a6cb0c 100644 (file)
--- a/arch/i386/Makefile
+++ b/arch/i386/Makefile
@@ -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

diff --git a/arch/i386/kernel/entry.S b/arch/i386/kernel/entry.S
index 284f2e908ad0c7c41efd7944c5ca4a4d8c43d8a9..5a63d6fdb70e4ff75d09b69874334b758d5af07a 100644 (file)
--- a/arch/i386/kernel/entry.S
+++ b/arch/i386/kernel/entry.S
@@ -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

diff --git a/arch/x86_64/Makefile b/arch/x86_64/Makefile
index 2b8d07c70106853fc0efecebae103c2313a82d2b..1c0f18d4f887a574734df7b6302ef8c362b8533d 100644 (file)
--- a/arch/x86_64/Makefile
+++ b/arch/x86_64/Makefile
@@ -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 )
 

diff --git a/arch/x86_64/ia32/ia32entry.S b/arch/x86_64/ia32/ia32entry.S
index 32fd32bea07c6e579baec44ddee5a6a6d7021f92..b4aa875e175becbaa59b27f6a1be2554b1f6aca1 100644 (file)
--- a/arch/x86_64/ia32/ia32entry.S
+++ b/arch/x86_64/ia32/ia32entry.S
@@ -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

diff --git a/arch/x86_64/kernel/entry.S b/arch/x86_64/kernel/entry.S
index ea32688386fd85148e2d466290bd32ef69707d4d..4cbc65290ae7599ed0dfa54d33b186f51182b756 100644 (file)
--- a/arch/x86_64/kernel/entry.S
+++ b/arch/x86_64/kernel/entry.S
@@ -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

diff --git a/include/asm-i386/dwarf2.h b/include/asm-i386/dwarf2.h
index 5d1a8db5a9b0c67291812c764f9df35107c1c8c2..6d66398a307d1dc16d271ec66d96fccbe949118f 100644 (file)
--- a/include/asm-i386/dwarf2.h
+++ b/include/asm-i386/dwarf2.h
@@ -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
 

diff --git a/include/asm-i386/unwind.h b/include/asm-i386/unwind.h
index f0ac399bae3c9e88204ec4e39c65089fe88835ed..5031d693b89d35fb3f7cfce8db78a79bb1db5503 100644 (file)
--- a/include/asm-i386/unwind.h
+++ b/include/asm-i386/unwind.h
@@ -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)
 {

diff --git a/include/asm-x86_64/dwarf2.h b/include/asm-x86_64/dwarf2.h
index 2b9368365fadca1531d5db27545e98de9aa85464..eedc08526b0b6d435d78626cb859156c51128677 100644 (file)
--- a/include/asm-x86_64/dwarf2.h
+++ b/include/asm-x86_64/dwarf2.h
@@ -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
 

diff --git a/include/asm-x86_64/unwind.h b/include/asm-x86_64/unwind.h
index 1f6e9bfb569e7ef6f645af572ee2a030c21f1a83..b8fa5cb7ff88e2f51efea28db8751bec6ecd989c 100644 (file)
--- a/include/asm-x86_64/unwind.h
+++ b/include/asm-x86_64/unwind.h
@@ -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)
 {

diff --git a/kernel/unwind.c b/kernel/unwind.c
index f69c804c8e620c5037ba5896a69568a426bca067..3430475fcd886d011c01370a558e0a5965dd950d 100644 (file)
--- 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);
 }

diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
index 7adef12a0c26f41e9db4359ef8d6b4cb0732bf92..4f5ff19b992b1f8a8db6f28a96cbace409db3baa 100644 (file)
--- a/scripts/Kbuild.include
+++ b/scripts/Kbuild.include
@@ -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