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Subject[PATCH x86/mm] x86 vDSO: canonicalize sysenter .eh_frame
Date

Some assembler versions automagically optimize .eh_frame contents,
changing their size. The CFI in sysenter.S was not using optimal
formatting, so it would be changed by newer/smarter assemblers.
This ran afoul of the wired constant for padding out the other vDSO
images to match its size. This changes the original hand-coded
source to use the optimal format encoding for its operations. That
leaves nothing more for a fancy assembler to do, so the sizes will
match the wired-in expected size regardless of the assembler version.

Signed-off-by: Roland McGrath <roland@redhat.com>
---
arch/x86/vdso/vdso32/int80.S | 2 +-
arch/x86/vdso/vdso32/syscall.S | 2 +-
arch/x86/vdso/vdso32/sysenter.S | 18 ++++++------------
3 files changed, 8 insertions(+), 14 deletions(-)

diff --git a/arch/x86/vdso/vdso32/int80.S b/arch/x86/vdso/vdso32/int80.S
index be4b7a9..b15b7c0 100644
--- a/arch/x86/vdso/vdso32/int80.S
+++ b/arch/x86/vdso/vdso32/int80.S
@@ -50,7 +50,7 @@ __kernel_vsyscall:
/*
* Pad out the segment to match the size of the sysenter.S version.
*/
-VDSO32_vsyscall_eh_frame_size = 0x44
+VDSO32_vsyscall_eh_frame_size = 0x40
.section .data,"aw",@progbits
.space VDSO32_vsyscall_eh_frame_size-(.LENDFDEDLSI-.LSTARTFRAMEDLSI), 0
.previous
diff --git a/arch/x86/vdso/vdso32/syscall.S b/arch/x86/vdso/vdso32/syscall.S
index fe88d34..5415b56 100644
--- a/arch/x86/vdso/vdso32/syscall.S
+++ b/arch/x86/vdso/vdso32/syscall.S
@@ -71,7 +71,7 @@ __kernel_vsyscall:
/*
* Pad out the segment to match the size of the sysenter.S version.
*/
-VDSO32_vsyscall_eh_frame_size = 0x44
+VDSO32_vsyscall_eh_frame_size = 0x40
.section .data,"aw",@progbits
.space VDSO32_vsyscall_eh_frame_size-(.LENDFDE1-.LSTARTFRAME), 0
.previous
diff --git a/arch/x86/vdso/vdso32/sysenter.S b/arch/x86/vdso/vdso32/sysenter.S
index 902d5fc..e2800af 100644
--- a/arch/x86/vdso/vdso32/sysenter.S
+++ b/arch/x86/vdso/vdso32/sysenter.S
@@ -84,31 +84,25 @@ VDSO32_SYSENTER_RETURN: /* Symbol used by sysenter.c via vdso32-syms.h */
.uleb128 0
/* What follows are the instructions for the table generation.
We have to record all changes of the stack pointer. */
- .byte 0x04 /* DW_CFA_advance_loc4 */
- .long .Lpush_ecx-.LSTART_vsyscall
+ .byte 0x40 + (.Lpush_ecx-.LSTART_vsyscall) /* DW_CFA_advance_loc */
.byte 0x0e /* DW_CFA_def_cfa_offset */
.byte 0x08 /* RA at offset 8 now */
- .byte 0x04 /* DW_CFA_advance_loc4 */
- .long .Lpush_edx-.Lpush_ecx
+ .byte 0x40 + (.Lpush_edx-.Lpush_ecx) /* DW_CFA_advance_loc */
.byte 0x0e /* DW_CFA_def_cfa_offset */
.byte 0x0c /* RA at offset 12 now */
- .byte 0x04 /* DW_CFA_advance_loc4 */
- .long .Lenter_kernel-.Lpush_edx
+ .byte 0x40 + (.Lenter_kernel-.Lpush_edx) /* DW_CFA_advance_loc */
.byte 0x0e /* DW_CFA_def_cfa_offset */
.byte 0x10 /* RA at offset 16 now */
.byte 0x85, 0x04 /* DW_CFA_offset %ebp -16 */
/* Finally the epilogue. */
- .byte 0x04 /* DW_CFA_advance_loc4 */
- .long .Lpop_ebp-.Lenter_kernel
+ .byte 0x40 + (.Lpop_ebp-.Lenter_kernel) /* DW_CFA_advance_loc */
.byte 0x0e /* DW_CFA_def_cfa_offset */
.byte 0x0c /* RA at offset 12 now */
.byte 0xc5 /* DW_CFA_restore %ebp */
- .byte 0x04 /* DW_CFA_advance_loc4 */
- .long .Lpop_edx-.Lpop_ebp
+ .byte 0x40 + (.Lpop_edx-.Lpop_ebp) /* DW_CFA_advance_loc */
.byte 0x0e /* DW_CFA_def_cfa_offset */
.byte 0x08 /* RA at offset 8 now */
- .byte 0x04 /* DW_CFA_advance_loc4 */
- .long .Lpop_ecx-.Lpop_edx
+ .byte 0x40 + (.Lpop_ecx-.Lpop_edx) /* DW_CFA_advance_loc */
.byte 0x0e /* DW_CFA_def_cfa_offset */
.byte 0x04 /* RA at offset 4 now */
.align 4

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