[PATCH] i386: reliable stack trace support i386 entry.S

To increase the usefulness of reliable stack unwinding, this adds CFI
unwind annotations to many low-level i386 routines.

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/arch/i386/kernel/entry.S b/arch/i386/kernel/entry.S
index e802f3c..e6e4506 100644 (file)
--- a/arch/i386/kernel/entry.S
+++ b/arch/i386/kernel/entry.S
@@ -48,6 +48,7 @@
 #include <asm/smp.h>
 #include <asm/page.h>
 #include <asm/desc.h>
+#include <asm/dwarf2.h>
 #include "irq_vectors.h"
 
 #define nr_syscalls ((syscall_table_size)/4)
@@ -85,31 +86,67 @@ VM_MASK             = 0x00020000
 #define SAVE_ALL \
        cld; \
        pushl %es; \
+       CFI_ADJUST_CFA_OFFSET 4;\
+       /*CFI_REL_OFFSET es, 0;*/\
        pushl %ds; \
+       CFI_ADJUST_CFA_OFFSET 4;\
+       /*CFI_REL_OFFSET ds, 0;*/\
        pushl %eax; \
+       CFI_ADJUST_CFA_OFFSET 4;\
+       CFI_REL_OFFSET eax, 0;\
        pushl %ebp; \
+       CFI_ADJUST_CFA_OFFSET 4;\
+       CFI_REL_OFFSET ebp, 0;\
        pushl %edi; \
+       CFI_ADJUST_CFA_OFFSET 4;\
+       CFI_REL_OFFSET edi, 0;\
        pushl %esi; \
+       CFI_ADJUST_CFA_OFFSET 4;\
+       CFI_REL_OFFSET esi, 0;\
        pushl %edx; \
+       CFI_ADJUST_CFA_OFFSET 4;\
+       CFI_REL_OFFSET edx, 0;\
        pushl %ecx; \
+       CFI_ADJUST_CFA_OFFSET 4;\
+       CFI_REL_OFFSET ecx, 0;\
        pushl %ebx; \
+       CFI_ADJUST_CFA_OFFSET 4;\
+       CFI_REL_OFFSET ebx, 0;\
        movl $(__USER_DS), %edx; \
        movl %edx, %ds; \
        movl %edx, %es;
 
 #define RESTORE_INT_REGS \
        popl %ebx;      \
+       CFI_ADJUST_CFA_OFFSET -4;\
+       CFI_RESTORE ebx;\
        popl %ecx;      \
+       CFI_ADJUST_CFA_OFFSET -4;\
+       CFI_RESTORE ecx;\
        popl %edx;      \
+       CFI_ADJUST_CFA_OFFSET -4;\
+       CFI_RESTORE edx;\
        popl %esi;      \
+       CFI_ADJUST_CFA_OFFSET -4;\
+       CFI_RESTORE esi;\
        popl %edi;      \
+       CFI_ADJUST_CFA_OFFSET -4;\
+       CFI_RESTORE edi;\
        popl %ebp;      \
-       popl %eax
+       CFI_ADJUST_CFA_OFFSET -4;\
+       CFI_RESTORE ebp;\
+       popl %eax;      \
+       CFI_ADJUST_CFA_OFFSET -4;\
+       CFI_RESTORE eax
 
 #define RESTORE_REGS   \
        RESTORE_INT_REGS; \
 1:     popl %ds;       \
+       CFI_ADJUST_CFA_OFFSET -4;\
+       /*CFI_RESTORE ds;*/\
 2:     popl %es;       \
+       CFI_ADJUST_CFA_OFFSET -4;\
+       /*CFI_RESTORE es;*/\
 .section .fixup,"ax";  \
 3:     movl $0,(%esp); \
        jmp 1b;         \
@@ -122,13 +159,43 @@ VM_MASK           = 0x00020000
        .long 2b,4b;    \
 .previous
 
+#define RING0_INT_FRAME \
+       CFI_STARTPROC simple;\
+       CFI_DEF_CFA esp, 3*4;\
+       /*CFI_OFFSET cs, -2*4;*/\
+       CFI_OFFSET eip, -3*4
+
+#define RING0_EC_FRAME \
+       CFI_STARTPROC simple;\
+       CFI_DEF_CFA esp, 4*4;\
+       /*CFI_OFFSET cs, -2*4;*/\
+       CFI_OFFSET eip, -3*4
+
+#define RING0_PTREGS_FRAME \
+       CFI_STARTPROC simple;\
+       CFI_DEF_CFA esp, OLDESP-EBX;\
+       /*CFI_OFFSET cs, CS-OLDESP;*/\
+       CFI_OFFSET eip, EIP-OLDESP;\
+       /*CFI_OFFSET es, ES-OLDESP;*/\
+       /*CFI_OFFSET ds, DS-OLDESP;*/\
+       CFI_OFFSET eax, EAX-OLDESP;\
+       CFI_OFFSET ebp, EBP-OLDESP;\
+       CFI_OFFSET edi, EDI-OLDESP;\
+       CFI_OFFSET esi, ESI-OLDESP;\
+       CFI_OFFSET edx, EDX-OLDESP;\
+       CFI_OFFSET ecx, ECX-OLDESP;\
+       CFI_OFFSET ebx, EBX-OLDESP
 
 ENTRY(ret_from_fork)
+       CFI_STARTPROC
        pushl %eax
+       CFI_ADJUST_CFA_OFFSET -4
        call schedule_tail
        GET_THREAD_INFO(%ebp)
        popl %eax
+       CFI_ADJUST_CFA_OFFSET -4
        jmp syscall_exit
+       CFI_ENDPROC
 
 /*
  * Return to user mode is not as complex as all this looks,
@@ -139,6 +206,7 @@ ENTRY(ret_from_fork)
 
        # userspace resumption stub bypassing syscall exit tracing
        ALIGN
+       RING0_PTREGS_FRAME
 ret_from_exception:
        preempt_stop
 ret_from_intr:
@@ -171,20 +239,33 @@ need_resched:
        call preempt_schedule_irq
        jmp need_resched
 #endif
+       CFI_ENDPROC
 
 /* SYSENTER_RETURN points to after the "sysenter" instruction in
    the vsyscall page.  See vsyscall-sysentry.S, which defines the symbol.  */
 
        # sysenter call handler stub
 ENTRY(sysenter_entry)
+       CFI_STARTPROC simple
+       CFI_DEF_CFA esp, 0
+       CFI_REGISTER esp, ebp
        movl TSS_sysenter_esp0(%esp),%esp
 sysenter_past_esp:
        sti
        pushl $(__USER_DS)
+       CFI_ADJUST_CFA_OFFSET 4
+       /*CFI_REL_OFFSET ss, 0*/
        pushl %ebp
+       CFI_ADJUST_CFA_OFFSET 4
+       CFI_REL_OFFSET esp, 0
        pushfl
+       CFI_ADJUST_CFA_OFFSET 4
        pushl $(__USER_CS)
+       CFI_ADJUST_CFA_OFFSET 4
+       /*CFI_REL_OFFSET cs, 0*/
        pushl $SYSENTER_RETURN
+       CFI_ADJUST_CFA_OFFSET 4
+       CFI_REL_OFFSET eip, 0
 
 /*
  * Load the potential sixth argument from user stack.
@@ -199,6 +280,7 @@ sysenter_past_esp:
 .previous
 
        pushl %eax
+       CFI_ADJUST_CFA_OFFSET 4
        SAVE_ALL
        GET_THREAD_INFO(%ebp)
 
@@ -219,11 +301,14 @@ sysenter_past_esp:
        xorl %ebp,%ebp
        sti
        sysexit
+       CFI_ENDPROC
 
 
        # system call handler stub
 ENTRY(system_call)
+       RING0_INT_FRAME                 # can't unwind into user space anyway
        pushl %eax                      # save orig_eax
+       CFI_ADJUST_CFA_OFFSET 4
        SAVE_ALL
        GET_THREAD_INFO(%ebp)
        testl $TF_MASK,EFLAGS(%esp)
@@ -256,10 +341,12 @@ restore_all:
        movb CS(%esp), %al
        andl $(VM_MASK | (4 << 8) | 3), %eax
        cmpl $((4 << 8) | 3), %eax
+       CFI_REMEMBER_STATE
        je ldt_ss                       # returning to user-space with LDT SS
 restore_nocheck:
        RESTORE_REGS
        addl $4, %esp
+       CFI_ADJUST_CFA_OFFSET -4
 1:     iret
 .section .fixup,"ax"
 iret_exc:
@@ -273,6 +360,7 @@ iret_exc:
        .long 1b,iret_exc
 .previous
 
+       CFI_RESTORE_STATE
 ldt_ss:
        larl OLDSS(%esp), %eax
        jnz restore_nocheck
@@ -285,11 +373,13 @@ ldt_ss:
         * CPUs, which we can try to work around to make
         * dosemu and wine happy. */
        subl $8, %esp           # reserve space for switch16 pointer
+       CFI_ADJUST_CFA_OFFSET 8
        cli
        movl %esp, %eax
        /* Set up the 16bit stack frame with switch32 pointer on top,
         * and a switch16 pointer on top of the current frame. */
        call setup_x86_bogus_stack
+       CFI_ADJUST_CFA_OFFSET -8        # frame has moved
        RESTORE_REGS
        lss 20+4(%esp), %esp    # switch to 16bit stack
 1:     iret
@@ -297,9 +387,11 @@ ldt_ss:
        .align 4
        .long 1b,iret_exc
 .previous
+       CFI_ENDPROC
 
        # perform work that needs to be done immediately before resumption
        ALIGN
+       RING0_PTREGS_FRAME              # can't unwind into user space anyway
 work_pending:
        testb $_TIF_NEED_RESCHED, %cl
        jz work_notifysig
@@ -329,8 +421,10 @@ work_notifysig:                            # deal with pending signals and
 work_notifysig_v86:
 #ifdef CONFIG_VM86
        pushl %ecx                      # save ti_flags for do_notify_resume
+       CFI_ADJUST_CFA_OFFSET 4
        call save_v86_state             # %eax contains pt_regs pointer
        popl %ecx
+       CFI_ADJUST_CFA_OFFSET -4
        movl %eax, %esp
        xorl %edx, %edx
        call do_notify_resume
@@ -363,19 +457,21 @@ syscall_exit_work:
        movl $1, %edx
        call do_syscall_trace
        jmp resume_userspace
+       CFI_ENDPROC
 
-       ALIGN
+       RING0_INT_FRAME                 # can't unwind into user space anyway
 syscall_fault:
        pushl %eax                      # save orig_eax
+       CFI_ADJUST_CFA_OFFSET 4
        SAVE_ALL
        GET_THREAD_INFO(%ebp)
        movl $-EFAULT,EAX(%esp)
        jmp resume_userspace
 
-       ALIGN
 syscall_badsys:
        movl $-ENOSYS,EAX(%esp)
        jmp resume_userspace
+       CFI_ENDPROC
 
 #define FIXUP_ESPFIX_STACK \
        movl %esp, %eax; \
@@ -387,16 +483,21 @@ syscall_badsys:
        movl %eax, %esp;
 #define UNWIND_ESPFIX_STACK \
        pushl %eax; \
+       CFI_ADJUST_CFA_OFFSET 4; \
        movl %ss, %eax; \
        /* see if on 16bit stack */ \
        cmpw $__ESPFIX_SS, %ax; \
-       jne 28f; \
-       movl $__KERNEL_DS, %edx; \
-       movl %edx, %ds; \
-       movl %edx, %es; \
+       je 28f; \
+27:    popl %eax; \
+       CFI_ADJUST_CFA_OFFSET -4; \
+.section .fixup,"ax"; \
+28:    movl $__KERNEL_DS, %eax; \
+       movl %eax, %ds; \
+       movl %eax, %es; \
        /* switch to 32bit stack */ \
-       FIXUP_ESPFIX_STACK \
-28:    popl %eax;
+       FIXUP_ESPFIX_STACK; \
+       jmp 27b; \
+.previous
 
 /*
  * Build the entry stubs and pointer table with
@@ -408,9 +509,14 @@ ENTRY(interrupt)
 
 vector=0
 ENTRY(irq_entries_start)
+       RING0_INT_FRAME
 .rept NR_IRQS
        ALIGN
+ .if vector
+       CFI_ADJUST_CFA_OFFSET -4
+ .endif
 1:     pushl $vector-256
+       CFI_ADJUST_CFA_OFFSET 4
        jmp common_interrupt
 .data
        .long 1b
@@ -424,60 +530,99 @@ common_interrupt:
        movl %esp,%eax
        call do_IRQ
        jmp ret_from_intr
+       CFI_ENDPROC
 
 #define BUILD_INTERRUPT(name, nr)      \
 ENTRY(name)                            \
+       RING0_INT_FRAME;                \
        pushl $nr-256;                  \
-       SAVE_ALL                        \
+       CFI_ADJUST_CFA_OFFSET 4;        \
+       SAVE_ALL;                       \
        movl %esp,%eax;                 \
        call smp_/**/name;              \
-       jmp ret_from_intr;
+       jmp ret_from_intr;      \
+       CFI_ENDPROC
 
 /* The include is where all of the SMP etc. interrupts come from */
 #include "entry_arch.h"
 
 ENTRY(divide_error)
+       RING0_INT_FRAME
        pushl $0                        # no error code
+       CFI_ADJUST_CFA_OFFSET 4
        pushl $do_divide_error
+       CFI_ADJUST_CFA_OFFSET 4
        ALIGN
 error_code:
        pushl %ds
+       CFI_ADJUST_CFA_OFFSET 4
+       /*CFI_REL_OFFSET ds, 0*/
        pushl %eax
+       CFI_ADJUST_CFA_OFFSET 4
+       CFI_REL_OFFSET eax, 0
        xorl %eax, %eax
        pushl %ebp
+       CFI_ADJUST_CFA_OFFSET 4
+       CFI_REL_OFFSET ebp, 0
        pushl %edi
+       CFI_ADJUST_CFA_OFFSET 4
+       CFI_REL_OFFSET edi, 0
        pushl %esi
+       CFI_ADJUST_CFA_OFFSET 4
+       CFI_REL_OFFSET esi, 0
        pushl %edx
+       CFI_ADJUST_CFA_OFFSET 4
+       CFI_REL_OFFSET edx, 0
        decl %eax                       # eax = -1
        pushl %ecx
+       CFI_ADJUST_CFA_OFFSET 4
+       CFI_REL_OFFSET ecx, 0
        pushl %ebx
+       CFI_ADJUST_CFA_OFFSET 4
+       CFI_REL_OFFSET ebx, 0
        cld
        pushl %es
+       CFI_ADJUST_CFA_OFFSET 4
+       /*CFI_REL_OFFSET es, 0*/
        UNWIND_ESPFIX_STACK
        popl %ecx
+       CFI_ADJUST_CFA_OFFSET -4
+       /*CFI_REGISTER es, ecx*/
        movl ES(%esp), %edi             # get the function address
        movl ORIG_EAX(%esp), %edx       # get the error code
        movl %eax, ORIG_EAX(%esp)
        movl %ecx, ES(%esp)
+       /*CFI_REL_OFFSET es, ES*/
        movl $(__USER_DS), %ecx
        movl %ecx, %ds
        movl %ecx, %es
        movl %esp,%eax                  # pt_regs pointer
        call *%edi
        jmp ret_from_exception
+       CFI_ENDPROC
 
 ENTRY(coprocessor_error)
+       RING0_INT_FRAME
        pushl $0
+       CFI_ADJUST_CFA_OFFSET 4
        pushl $do_coprocessor_error
+       CFI_ADJUST_CFA_OFFSET 4
        jmp error_code
+       CFI_ENDPROC
 
 ENTRY(simd_coprocessor_error)
+       RING0_INT_FRAME
        pushl $0
+       CFI_ADJUST_CFA_OFFSET 4
        pushl $do_simd_coprocessor_error
+       CFI_ADJUST_CFA_OFFSET 4
        jmp error_code
+       CFI_ENDPROC
 
 ENTRY(device_not_available)
+       RING0_INT_FRAME
        pushl $-1                       # mark this as an int
+       CFI_ADJUST_CFA_OFFSET 4
        SAVE_ALL
        movl %cr0, %eax
        testl $0x4, %eax                # EM (math emulation bit)
@@ -487,9 +632,12 @@ ENTRY(device_not_available)
        jmp ret_from_exception
 device_not_available_emulate:
        pushl $0                        # temporary storage for ORIG_EIP
+       CFI_ADJUST_CFA_OFFSET 4
        call math_emulate
        addl $4, %esp
+       CFI_ADJUST_CFA_OFFSET -4
        jmp ret_from_exception
+       CFI_ENDPROC
 
 /*
  * Debug traps and NMI can happen at the one SYSENTER instruction
@@ -514,16 +662,19 @@ label:                                            \
        pushl $sysenter_past_esp
 
 KPROBE_ENTRY(debug)
+       RING0_INT_FRAME
        cmpl $sysenter_entry,(%esp)
        jne debug_stack_correct
        FIX_STACK(12, debug_stack_correct, debug_esp_fix_insn)
 debug_stack_correct:
        pushl $-1                       # mark this as an int
+       CFI_ADJUST_CFA_OFFSET 4
        SAVE_ALL
        xorl %edx,%edx                  # error code 0
        movl %esp,%eax                  # pt_regs pointer
        call do_debug
        jmp ret_from_exception
+       CFI_ENDPROC
        .previous .text
 /*
  * NMI is doubly nasty. It can happen _while_ we're handling
@@ -534,14 +685,18 @@ debug_stack_correct:
  * fault happened on the sysenter path.
  */
 ENTRY(nmi)
+       RING0_INT_FRAME
        pushl %eax
+       CFI_ADJUST_CFA_OFFSET 4
        movl %ss, %eax
        cmpw $__ESPFIX_SS, %ax
        popl %eax
+       CFI_ADJUST_CFA_OFFSET -4
        je nmi_16bit_stack
        cmpl $sysenter_entry,(%esp)
        je nmi_stack_fixup
        pushl %eax
+       CFI_ADJUST_CFA_OFFSET 4
        movl %esp,%eax
        /* Do not access memory above the end of our stack page,
         * it might not exist.
@@ -549,16 +704,19 @@ ENTRY(nmi)
        andl $(THREAD_SIZE-1),%eax
        cmpl $(THREAD_SIZE-20),%eax
        popl %eax
+       CFI_ADJUST_CFA_OFFSET -4
        jae nmi_stack_correct
        cmpl $sysenter_entry,12(%esp)
        je nmi_debug_stack_check
 nmi_stack_correct:
        pushl %eax
+       CFI_ADJUST_CFA_OFFSET 4
        SAVE_ALL
        xorl %edx,%edx          # zero error code
        movl %esp,%eax          # pt_regs pointer
        call do_nmi
        jmp restore_all
+       CFI_ENDPROC
 
 nmi_stack_fixup:
        FIX_STACK(12,nmi_stack_correct, 1)
@@ -574,97 +732,150 @@ nmi_debug_stack_check:
        jmp nmi_stack_correct
 
 nmi_16bit_stack:
+       RING0_INT_FRAME
        /* create the pointer to lss back */
        pushl %ss
+       CFI_ADJUST_CFA_OFFSET 4
        pushl %esp
+       CFI_ADJUST_CFA_OFFSET 4
        movzwl %sp, %esp
        addw $4, (%esp)
        /* copy the iret frame of 12 bytes */
        .rept 3
        pushl 16(%esp)
+       CFI_ADJUST_CFA_OFFSET 4
        .endr
        pushl %eax
+       CFI_ADJUST_CFA_OFFSET 4
        SAVE_ALL
        FIXUP_ESPFIX_STACK              # %eax == %esp
+       CFI_ADJUST_CFA_OFFSET -20       # the frame has now moved
        xorl %edx,%edx                  # zero error code
        call do_nmi
        RESTORE_REGS
        lss 12+4(%esp), %esp            # back to 16bit stack
 1:     iret
+       CFI_ENDPROC
 .section __ex_table,"a"
        .align 4
        .long 1b,iret_exc
 .previous
 
 KPROBE_ENTRY(int3)
+       RING0_INT_FRAME
        pushl $-1                       # mark this as an int
+       CFI_ADJUST_CFA_OFFSET 4
        SAVE_ALL
        xorl %edx,%edx          # zero error code
        movl %esp,%eax          # pt_regs pointer
        call do_int3
        jmp ret_from_exception
+       CFI_ENDPROC
        .previous .text
 
 ENTRY(overflow)
+       RING0_INT_FRAME
        pushl $0
+       CFI_ADJUST_CFA_OFFSET 4
        pushl $do_overflow
+       CFI_ADJUST_CFA_OFFSET 4
        jmp error_code
+       CFI_ENDPROC
 
 ENTRY(bounds)
+       RING0_INT_FRAME
        pushl $0
+       CFI_ADJUST_CFA_OFFSET 4
        pushl $do_bounds
+       CFI_ADJUST_CFA_OFFSET 4
        jmp error_code
+       CFI_ENDPROC
 
 ENTRY(invalid_op)
+       RING0_INT_FRAME
        pushl $0
+       CFI_ADJUST_CFA_OFFSET 4
        pushl $do_invalid_op
+       CFI_ADJUST_CFA_OFFSET 4
        jmp error_code
+       CFI_ENDPROC
 
 ENTRY(coprocessor_segment_overrun)
+       RING0_INT_FRAME
        pushl $0
+       CFI_ADJUST_CFA_OFFSET 4
        pushl $do_coprocessor_segment_overrun
+       CFI_ADJUST_CFA_OFFSET 4
        jmp error_code
+       CFI_ENDPROC
 
 ENTRY(invalid_TSS)
+       RING0_EC_FRAME
        pushl $do_invalid_TSS
+       CFI_ADJUST_CFA_OFFSET 4
        jmp error_code
+       CFI_ENDPROC
 
 ENTRY(segment_not_present)
+       RING0_EC_FRAME
        pushl $do_segment_not_present
+       CFI_ADJUST_CFA_OFFSET 4
        jmp error_code
+       CFI_ENDPROC
 
 ENTRY(stack_segment)
+       RING0_EC_FRAME
        pushl $do_stack_segment
+       CFI_ADJUST_CFA_OFFSET 4
        jmp error_code
+       CFI_ENDPROC
 
 KPROBE_ENTRY(general_protection)
+       RING0_EC_FRAME
        pushl $do_general_protection
+       CFI_ADJUST_CFA_OFFSET 4
        jmp error_code
+       CFI_ENDPROC
        .previous .text
 
 ENTRY(alignment_check)
+       RING0_EC_FRAME
        pushl $do_alignment_check
+       CFI_ADJUST_CFA_OFFSET 4
        jmp error_code
+       CFI_ENDPROC
 
 KPROBE_ENTRY(page_fault)
+       RING0_EC_FRAME
        pushl $do_page_fault
+       CFI_ADJUST_CFA_OFFSET 4
        jmp error_code
+       CFI_ENDPROC
        .previous .text
 
 #ifdef CONFIG_X86_MCE
 ENTRY(machine_check)
+       RING0_INT_FRAME
        pushl $0
+       CFI_ADJUST_CFA_OFFSET 4
        pushl machine_check_vector
+       CFI_ADJUST_CFA_OFFSET 4
        jmp error_code
+       CFI_ENDPROC
 #endif
 
 ENTRY(spurious_interrupt_bug)
+       RING0_INT_FRAME
        pushl $0
+       CFI_ADJUST_CFA_OFFSET 4
        pushl $do_spurious_interrupt_bug
+       CFI_ADJUST_CFA_OFFSET 4
        jmp error_code
+       CFI_ENDPROC
 
 #ifdef CONFIG_STACK_UNWIND
 ENTRY(arch_unwind_init_running)
+       CFI_STARTPROC
        movl    4(%esp), %edx
        movl    (%esp), %ecx
        leal    4(%esp), %eax
@@ -689,6 +900,7 @@ ENTRY(arch_unwind_init_running)
        movl    EBX(%edx), %ebx
        movl    $__KERNEL_DS, OLDSS(%edx)
        jmpl    *%eax
+       CFI_ENDPROC
 ENDPROC(arch_unwind_init_running)
 #endif
 

diff --git a/include/asm-i386/dwarf2.h b/include/asm-i386/dwarf2.h
new file mode 100644 (file)
index 0000000..2280f62
--- /dev/null
+++ b/include/asm-i386/dwarf2.h
@@ -0,0 +1,54 @@
+#ifndef _DWARF2_H
+#define _DWARF2_H
+
+#include <linux/config.h>
+
+#ifndef __ASSEMBLY__
+#warning "asm/dwarf2.h should be only included in pure assembly files"
+#endif
+
+/*
+   Macros for dwarf2 CFI unwind table entries.
+   See "as.info" for details on these pseudo ops. Unfortunately
+   they are only supported in very new binutils, so define them
+   away for older version.
+ */
+
+#ifdef CONFIG_UNWIND_INFO
+
+#define CFI_STARTPROC .cfi_startproc
+#define CFI_ENDPROC .cfi_endproc
+#define CFI_DEF_CFA .cfi_def_cfa
+#define CFI_DEF_CFA_REGISTER .cfi_def_cfa_register
+#define CFI_DEF_CFA_OFFSET .cfi_def_cfa_offset
+#define CFI_ADJUST_CFA_OFFSET .cfi_adjust_cfa_offset
+#define CFI_OFFSET .cfi_offset
+#define CFI_REL_OFFSET .cfi_rel_offset
+#define CFI_REGISTER .cfi_register
+#define CFI_RESTORE .cfi_restore
+#define CFI_REMEMBER_STATE .cfi_remember_state
+#define CFI_RESTORE_STATE .cfi_restore_state
+
+#else
+
+/* Due to the structure of pre-exisiting code, don't use assembler line
+   comment character # to ignore the arguments. Instead, use a dummy macro. */
+.macro ignore a=0, b=0, c=0, d=0
+.endm
+
+#define CFI_STARTPROC  ignore
+#define CFI_ENDPROC    ignore
+#define CFI_DEF_CFA    ignore
+#define CFI_DEF_CFA_REGISTER   ignore
+#define CFI_DEF_CFA_OFFSET     ignore
+#define CFI_ADJUST_CFA_OFFSET  ignore
+#define CFI_OFFSET     ignore
+#define CFI_REL_OFFSET ignore
+#define CFI_REGISTER   ignore
+#define CFI_RESTORE    ignore
+#define CFI_REMEMBER_STATE ignore
+#define CFI_RESTORE_STATE ignore
+
+#endif
+
+#endif