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linux/arch/x86/vdso/vdso32
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Jiri Slaby e893286918 x86/vdso: Fix the build on GCC5 
On gcc5 the kernel does not link:

  ld: .eh_frame_hdr table[4] FDE at 0000000000000648 overlaps table[5] FDE at 0000000000000670.

Because prior GCC versions always emitted NOPs on ALIGN directives, but
gcc5 started omitting them.

.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 69d0627a7f ("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".

So fix this by adding to that point at least a single NOP and make the
function ALIGN possibly with more NOPs then.

Kudos for reporting and diagnosing should go to Richard.

Reported-by: Richard Biener <rguenther@suse.de>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Acked-by: Andy Lutomirski <luto@amacapital.net>
Cc: <stable@vger.kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1425543211-12542-1-git-send-email-jslaby@suse.cz
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-03-06 09:34:45 +01:00
..
.gitignore x86: gitignore arch/x86/vdso files 2008-01-30 13:32:32 +01:00
int80.S x86 vDSO: canonicalize sysenter .eh_frame 2008-01-30 13:30:44 +01:00
note.S x86 vDSO: i386 vdso32 2008-01-30 13:30:42 +01:00
sigreturn.S x86/vdso: Fix the build on GCC5 2015-03-06 09:34:45 +01:00
syscall.S x86 vDSO: canonicalize sysenter .eh_frame 2008-01-30 13:30:44 +01:00
sysenter.S x86-32, vdso: On system call restart after SYSENTER, use int $0x80 2011-08-23 16:20:10 -07:00
vclock_gettime.c x86, vdso: Add 32 bit VDSO time support for 64 bit kernel 2014-03-18 12:52:41 -07:00
vdso32.lds.S x86, vdso: Remove vestiges of VDSO_PRELINK and some outdated comments 2014-05-05 13:19:07 -07:00
vdso-fakesections.c x86/vdso: Improve the fake section headers 2014-06-19 15:45:12 -07:00