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Subject[PATCH 1/1] x86/vdso: fix a reference to a non-existing instruction
Date
.LSTARTFDEDLSI1 says:
/* HACK: The dwarf2 unwind routines will subtract 1 from the
return address to get an address in the middle of the
presumed call instruction. Since we didn't get here via
a call, we need to include the nop before the real start
to make up for it. */
.long .LSTART_sigreturn-1-. /* PC-relative start address */

But commit 69d0627a7f6e891189124d784d2fa90cae7c449a (x86 vDSO: reorder
vdso32 code) from 2.6.25 replaced
.org __kernel_vsyscall+32,0x90
by ALIGN right before __kernel_sigreturn. Of course, ALIGN need not
generate any nop in there. Esp. gcc5 collapses vclock_gettime.o and
int80.o together with no generated nops as "ALIGN". In that case
kernel does not even link:
ld: .eh_frame_hdr table[4] FDE at 0000000000000648 overlaps table[5] FDE at 0000000000000670.

So fix this by adding there at least a single nop and make the
function ALIGN possibly with more nops then.

Kudos for reporting and diagnosing should go to Richard.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Reported-by: Richard Biener <rguenther@suse.de>
Cc: stable@vger.kernel.org
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
---
arch/x86/vdso/vdso32/sigreturn.S | 1 +
1 file changed, 1 insertion(+)

diff --git a/arch/x86/vdso/vdso32/sigreturn.S b/arch/x86/vdso/vdso32/sigreturn.S
index 31776d0efc8c..d7ec4e251c0a 100644
--- a/arch/x86/vdso/vdso32/sigreturn.S
+++ b/arch/x86/vdso/vdso32/sigreturn.S
@@ -17,6 +17,7 @@
.text
.globl __kernel_sigreturn
.type __kernel_sigreturn,@function
+ nop /* this guy is needed for .LSTARTFDEDLSI1 below (watch for HACK) */
ALIGN
__kernel_sigreturn:
.LSTART_sigreturn:
--
2.3.0


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