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

[Roland McGrath <roland@redhat.com>]

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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