linux-kernel - [RFC 10/30] x86/vdso: Replace hex int80 CFI annotations with gas directives

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Message-Id: <3f0d54f4a1ec568a3cd320dbf0a2fece985dcb09.1441146105.git.luto@kernel.org>
Date:	Tue,  1 Sep 2015 15:41:10 -0700
From:	Andy Lutomirski <luto@...nel.org>
To:	x86@...nel.org, linux-kernel@...r.kernel.org
Cc:	Brian Gerst <brgerst@...il.com>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Borislav Petkov <bp@...en8.de>,
	Andy Lutomirski <luto@...nel.org>
Subject: [RFC 10/30] x86/vdso: Replace hex int80 CFI annotations with gas directives

Maintaining the current CFI annotations written in R'lyehian is
difficult for most of us.  Translate them to something a little
closer to English.

This will remove the CFI data for kernels built with extremely old
versions of binutils.  I think this is a fair tradeoff for the
ability for mortals to edit the asm.

Signed-off-by: Andy Lutomirski <luto@...nel.org>
---
 arch/x86/entry/vdso/vdso32/system_call.S | 48 ++++++--------------------------
 1 file changed, 8 insertions(+), 40 deletions(-)

diff --git a/arch/x86/entry/vdso/vdso32/system_call.S b/arch/x86/entry/vdso/vdso32/system_call.S
index b15b7c01aedb..b52cbfbe119e 100644
--- a/arch/x86/entry/vdso/vdso32/system_call.S
+++ b/arch/x86/entry/vdso/vdso32/system_call.S
@@ -1,6 +1,10 @@
 /*
  * Code for the vDSO.  This version uses the old int $0x80 method.
- *
+*/
+
+#include <asm/dwarf2.h>
+
+/*
  * First get the common code for the sigreturn entry points.
  * This must come first.
  */
@@ -11,46 +15,10 @@
 	.type __kernel_vsyscall,@function
 	ALIGN
 __kernel_vsyscall:
-.LSTART_vsyscall:
+	CFI_STARTPROC
 	int $0x80
 	ret
-.LEND_vsyscall:
-	.size __kernel_vsyscall,.-.LSTART_vsyscall
-	.previous
-
-	.section .eh_frame,"a",@progbits
-.LSTARTFRAMEDLSI:
-	.long .LENDCIEDLSI-.LSTARTCIEDLSI
-.LSTARTCIEDLSI:
-	.long 0			/* CIE ID */
-	.byte 1			/* Version number */
-	.string "zR"		/* NUL-terminated augmentation string */
-	.uleb128 1		/* Code alignment factor */
-	.sleb128 -4		/* Data alignment factor */
-	.byte 8			/* Return address register column */
-	.uleb128 1		/* Augmentation value length */
-	.byte 0x1b		/* DW_EH_PE_pcrel|DW_EH_PE_sdata4. */
-	.byte 0x0c		/* DW_CFA_def_cfa */
-	.uleb128 4
-	.uleb128 4
-	.byte 0x88		/* DW_CFA_offset, column 0x8 */
-	.uleb128 1
-	.align 4
-.LENDCIEDLSI:
-	.long .LENDFDEDLSI-.LSTARTFDEDLSI /* Length FDE */
-.LSTARTFDEDLSI:
-	.long .LSTARTFDEDLSI-.LSTARTFRAMEDLSI /* CIE pointer */
-	.long .LSTART_vsyscall-.	/* PC-relative start address */
-	.long .LEND_vsyscall-.LSTART_vsyscall
-	.uleb128 0
-	.align 4
-.LENDFDEDLSI:
-	.previous
+	CFI_ENDPROC
 
-	/*
-	 * Pad out the segment to match the size of the sysenter.S version.
-	 */
-VDSO32_vsyscall_eh_frame_size = 0x40
-	.section .data,"aw",@progbits
-	.space VDSO32_vsyscall_eh_frame_size-(.LENDFDEDLSI-.LSTARTFRAMEDLSI), 0
+	.size __kernel_vsyscall,.-__kernel_vsyscall
 	.previous
-- 
2.4.3

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