[PATCH] Unwinding CFI for x86_64 signal frame (__restore_rt)
Jan Kratochvil
jan.kratochvil@redhat.com
Wed Nov 29 10:16:00 GMT 2006
Hi Jakub,
On Wed, 29 Nov 2006 00:44:09 +0100, Jakub Jelinek wrote:
...
> Not sure, but perhaps it would be more readable if the .eh_frame asm
> wasn't in the macro, but just an extra asm () below the RESTORE.
> There is just one RESTORE, you'd just add the nop and .LSTART_restore_rt
> and .LEND_restore_rt symbols to the RESTORE macro, and you could get rid of
> all the \'s at the end of the lines, #name uglification etc.
> Perhaps the RESTORE macro could be dropped altogether, all we need
> is something like CFI_STRINGIFY which would be defined unconditionally
> and use it for the syscall number.
> Guess Ulrich should decide how he wants it to look like.
this idea was dropped as we discussed before.
Other suggested changes were integrated. Minor .byte->.uleb128 length
fix+change, I hope it does not violate the intended coding style.
Tested with libunwind run-ptrace-stepper.
Best Regards,
Jan
-------------- next part --------------
2006-11-29 Daniel Jacobowitz <dan@codesourcery.com>
Jakub Jelinek <jakub@redhat.com>
Jan Kratochvil <jan.kratochvil@redhat.com>
* sysdeps/unix/sysv/linux/x86_64/sigaction.c (restore_rt): Add correct
unwind information.
* sysdeps/unix/sysv/linux/x86_64/Makefile: Prvide symbols for
`restore_rt' even in the `signal' directory.
* sysdeps/unix/sysv/linux/x86_64/ucontext_i.sym: Extend the regs list.
diff -u -rup glibc-20061120T1000-orig/sysdeps/unix/sysv/linux/x86_64/Makefile glibc-20061120T1000/sysdeps/unix/sysv/linux/x86_64/Makefile
--- glibc-20061120T1000-orig/sysdeps/unix/sysv/linux/x86_64/Makefile 2005-12-22 05:57:36.000000000 +0100
+++ glibc-20061120T1000/sysdeps/unix/sysv/linux/x86_64/Makefile 2006-11-28 23:47:15.000000000 +0100
@@ -8,8 +8,9 @@ endif
ifeq ($(subdir),stdlib)
sysdep_routines += __start_context
+gen-as-const-headers += ucontext_i.sym
endif
-ifeq ($(subdir),stdlib)
+ifeq ($(subdir),signal)
gen-as-const-headers += ucontext_i.sym
endif
diff -u -rup glibc-20061120T1000-orig/sysdeps/unix/sysv/linux/x86_64/sigaction.c glibc-20061120T1000/sysdeps/unix/sysv/linux/x86_64/sigaction.c
--- glibc-20061120T1000-orig/sysdeps/unix/sysv/linux/x86_64/sigaction.c 2006-10-28 08:44:03.000000000 +0200
+++ glibc-20061120T1000/sysdeps/unix/sysv/linux/x86_64/sigaction.c 2006-11-29 11:01:09.000000000 +0100
@@ -33,6 +33,8 @@
translate it here. */
#include <kernel_sigaction.h>
+#include "ucontext_i.h"
+
/* We do not globally define the SA_RESTORER flag so do it here. */
#define SA_RESTORER 0x04000000
@@ -90,18 +92,94 @@ weak_alias (__libc_sigaction, sigaction)
signal handlers work right. Important are both the names
(__restore_rt) and the exact instruction sequence.
If you ever feel the need to make any changes, please notify the
- appropriate GDB maintainer. */
+ appropriate GDB maintainer.
+
+ The unwind information starts a byte before __restore_rt, so that
+ it is found when unwinding, to get an address the unwinder assumes
+ will be in the middle of a call instruction. See the Linux kernel
+ (the i386 vsyscall, in particular) for an explanation of the complex
+ unwind information used here in order to get the traditional CFA.
+ We do not restore cs - it's only stored as two bytes here so that's
+ a bit tricky. We don't use the gas cfi directives, so that we can
+ reliably add .cfi_signal_frame. */
+
+#define do_cfa_expr \
+ " .byte 0x0f\n" /* DW_CFA_def_cfa_expression */ \
+ " .uleb128 2f-1f\n" /* length */ \
+ "1: .byte 0x77\n" /* DW_OP_breg8 */ \
+ " .sleb128 " CFI_STRINGIFY (oRSP) "\n" \
+ " .byte 0x06\n" /* DW_OP_deref */ \
+ "2:"
+
+#define do_expr(regno, offset) \
+ " .byte 0x10\n" /* DW_CFA_expression */ \
+ " .uleb128 " CFI_STRINGIFY (regno) "\n" \
+ " .uleb128 2f-1f\n" /* length */ \
+ "1: .byte 0x77\n" /* DW_OP_breg8 */ \
+ " .sleb128 " CFI_STRINGIFY (offset) "\n" \
+ "2:"
#define RESTORE(name, syscall) RESTORE2 (name, syscall)
# define RESTORE2(name, syscall) \
-asm \
- ( \
- ".align 16\n" \
- CFI_STARTPROC "\n" \
- "__" #name ":\n" \
- " movq $" #syscall ", %rax\n" \
- " syscall\n" \
- CFI_ENDPROC "\n" \
+asm \
+ ( \
+ /* `nop' for debuggers assuming `call' should not disalign the code. */ \
+ " nop\n" \
+ ".align 16\n" \
+ ".LSTART_" #name ":\n" \
+ " .type __" #name ",@function\n" \
+ "__" #name ":\n" \
+ " movq $" #syscall ", %rax\n" \
+ " syscall\n" \
+ ".LEND_" #name ":\n" \
+ ".section .eh_frame,\"a\",@progbits\n" \
+ ".LSTARTFRAME_" #name ":\n" \
+ " .long .LENDCIE_" #name "-.LSTARTCIE_" #name "\n" \
+ ".LSTARTCIE_" #name ":\n" \
+ " .long 0\n" /* CIE ID */ \
+ " .byte 1\n" /* Version number */ \
+ " .string \"zRS\"\n" /* NUL-terminated augmentation string */ \
+ " .uleb128 1\n" /* Code alignment factor */ \
+ " .sleb128 -8\n" /* Data alignment factor */ \
+ " .uleb128 16\n" /* Return address register column (rip) */ \
+ /* Augmentation value length */ \
+ " .uleb128 .LENDAUGMNT_" #name "-.LSTARTAUGMNT_" #name "\n" \
+ ".LSTARTAUGMNT_" #name ":\n" \
+ " .byte 0x1b\n" /* DW_EH_PE_pcrel|DW_EH_PE_sdata4. */ \
+ ".LENDAUGMNT_" #name ":\n" \
+ " .align 8\n" \
+ ".LENDCIE_" #name ":\n" \
+ " .long .LENDFDE_" #name "-.LSTARTFDE_" #name "\n" /* FDE len */ \
+ ".LSTARTFDE_" #name ":\n" \
+ " .long .LSTARTFDE_" #name "-.LSTARTFRAME_" #name "\n" /* CIE */ \
+ /* `LSTART_' is subtracted 1 as debuggers assume a `call' here. */ \
+ " .long (.LSTART_" #name "-1)-.\n" /* PC-relative start addr. */ \
+ " .long .LEND_" #name "-(.LSTART_" #name "-1)\n" \
+ " .uleb128 0\n" /* FDE augmentation length */ \
+ do_cfa_expr \
+ do_expr (8 /* r8 */, oR8) \
+ do_expr (9 /* r9 */, oR9) \
+ do_expr (10 /* r10 */, oR10) \
+ do_expr (11 /* r11 */, oR11) \
+ do_expr (12 /* r12 */, oR12) \
+ do_expr (13 /* r13 */, oR13) \
+ do_expr (14 /* r14 */, oR14) \
+ do_expr (15 /* r15 */, oR15) \
+ do_expr (5 /* rdi */, oRDI) \
+ do_expr (4 /* rsi */, oRSI) \
+ do_expr (6 /* rbp */, oRBP) \
+ do_expr (3 /* rbx */, oRBX) \
+ do_expr (1 /* rdx */, oRDX) \
+ do_expr (0 /* rax */, oRAX) \
+ do_expr (2 /* rcx */, oRCX) \
+ do_expr (7 /* rsp */, oRSP) \
+ do_expr (16 /* rip */, oRIP) \
+ do_expr (49 /* rflags */, oEFL) \
+ /* `cs'/`ds'/`fs' are unaligned and a different size. */ \
+ /* gas: Error: register save offset not a multiple of 8 */ \
+ " .align 8\n" \
+ ".LENDFDE_" #name ":\n" \
+ " .previous\n" \
);
/* The return code for realtime-signals. */
RESTORE (restore_rt, __NR_rt_sigreturn)
diff -u -rup glibc-20061120T1000-orig/sysdeps/unix/sysv/linux/x86_64/ucontext_i.sym glibc-20061120T1000/sysdeps/unix/sysv/linux/x86_64/ucontext_i.sym
--- glibc-20061120T1000-orig/sysdeps/unix/sysv/linux/x86_64/ucontext_i.sym 2005-12-22 05:57:36.000000000 +0100
+++ glibc-20061120T1000/sysdeps/unix/sysv/linux/x86_64/ucontext_i.sym 2006-11-28 23:12:37.000000000 +0100
@@ -18,6 +18,8 @@ oRSP mreg (RSP)
oRBX mreg (RBX)
oR8 mreg (R8)
oR9 mreg (R9)
+oR10 mreg (R10)
+oR11 mreg (R11)
oR12 mreg (R12)
oR13 mreg (R13)
oR14 mreg (R14)
@@ -28,6 +30,7 @@ oRDX mreg (RDX)
oRAX mreg (RAX)
oRCX mreg (RCX)
oRIP mreg (RIP)
+oEFL mreg (EFL)
oFPREGS mcontext (fpregs)
oSIGMASK ucontext (uc_sigmask)
oFPREGSMEM ucontext (__fpregs_mem)
-------------- next part --------------
@@ -55,16 +55,16 @@
+ " .byte 0x0f\n" /* DW_CFA_def_cfa_expression */ \
+ " .uleb128 2f-1f\n" /* length */ \
+ "1: .byte 0x77\n" /* DW_OP_breg8 */ \
-+ " .sleb128 " CFI_STRINGIFY(oRSP) "\n" \
++ " .sleb128 " CFI_STRINGIFY (oRSP) "\n" \
+ " .byte 0x06\n" /* DW_OP_deref */ \
+ "2:"
+
+#define do_expr(regno, offset) \
+ " .byte 0x10\n" /* DW_CFA_expression */ \
-+ " .uleb128 " CFI_STRINGIFY(regno) "\n" \
++ " .uleb128 " CFI_STRINGIFY (regno) "\n" \
+ " .uleb128 2f-1f\n" /* length */ \
+ "1: .byte 0x77\n" /* DW_OP_breg8 */ \
-+ " .sleb128 " CFI_STRINGIFY(offset) "\n" \
++ " .sleb128 " CFI_STRINGIFY (offset) "\n" \
+ "2:"
#define RESTORE(name, syscall) RESTORE2 (name, syscall)
@@ -83,7 +83,6 @@
+ " nop\n" \
+ ".align 16\n" \
+ ".LSTART_" #name ":\n" \
-+ " nop\n" \
+ " .type __" #name ",@function\n" \
+ "__" #name ":\n" \
+ " movq $" #syscall ", %rax\n" \
@@ -98,10 +97,12 @@
+ " .string \"zRS\"\n" /* NUL-terminated augmentation string */ \
+ " .uleb128 1\n" /* Code alignment factor */ \
+ " .sleb128 -8\n" /* Data alignment factor */ \
-+ " .byte 0x10\n" /* Return address register column */ \
-+ " .uleb128 1\n" /* Augmentation value length */ \
++ " .uleb128 16\n" /* Return address register column (rip) */ \
++ /* Augmentation value length */ \
++ " .uleb128 .LENDAUGMNT_" #name "-.LSTARTAUGMNT_" #name "\n" \
++ ".LSTARTAUGMNT_" #name ":\n" \
+ " .byte 0x1b\n" /* DW_EH_PE_pcrel|DW_EH_PE_sdata4. */ \
-+ " .byte 0\n" /* DW_CFA_nop */ \
++ ".LENDAUGMNT_" #name ":\n" \
+ " .align 8\n" \
+ ".LENDCIE_" #name ":\n" \
+ " .long .LENDFDE_" #name "-.LSTARTFDE_" #name "\n" /* FDE len */ \
@@ -110,7 +111,7 @@
+ /* `LSTART_' is subtracted 1 as debuggers assume a `call' here. */ \
+ " .long (.LSTART_" #name "-1)-.\n" /* PC-relative start addr. */ \
+ " .long .LEND_" #name "-(.LSTART_" #name "-1)\n" \
-+ " .uleb128 0\n" /* Augmentation */ \
++ " .uleb128 0\n" /* FDE augmentation length */ \
+ do_cfa_expr \
+ do_expr (8 /* r8 */, oR8) \
+ do_expr (9 /* r9 */, oR9) \
@@ -129,12 +130,11 @@
+ do_expr (2 /* rcx */, oRCX) \
+ do_expr (7 /* rsp */, oRSP) \
+ do_expr (16 /* rip */, oRIP) \
-+ /* Older gas(1) does not support `rflags'. */ \
+ do_expr (49 /* rflags */, oEFL) \
+ /* `cs'/`ds'/`fs' are unaligned and a different size. */ \
+ /* gas: Error: register save offset not a multiple of 8 */ \
-+ " .align 4\n" \
-+ " .LENDFDE_" #name ":\n" \
++ " .align 8\n" \
++ ".LENDFDE_" #name ":\n" \
+ " .previous\n" \
);
/* The return code for realtime-signals. */
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