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Subject[PATCH 6/6] reliable stack trace support (i386 entry.S annotations)
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>

Index: unwind-2.6.17-rc4/arch/i386/kernel/entry.S
===================================================================
--- unwind-2.6.17-rc4.orig/arch/i386/kernel/entry.S 2006-05-22 15:08:35.000000000 +0200
+++ unwind-2.6.17-rc4/arch/i386/kernel/entry.S 2006-05-22 15:08:38.000000000 +0200
@@ -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 s
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)
Index: unwind-2.6.17-rc4/include/asm-i386/dwarf2.h
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ unwind-2.6.17-rc4/include/asm-i386/dwarf2.h 2006-05-22 15:08:38.000000000 +0200
@@ -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

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