lkml.org 
[lkml]   [2015]   [Mar]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH 1/1] x86/vdso: fix a reference to a non-existing instruction
On Thu, Mar 5, 2015 at 12:13 AM, Jiri Slaby <jslaby@suse.cz> wrote:
> .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:

Acked-by: Andy Lutomirski <luto@amacapital.net>

Ingo or Thomas, can you apply this to tip:x86/urgent for this weekend?

Are we willing to depend on cfi-capable assemblers for 32-bit? If so,
could we rewrite this garbage with .cfi directives? The current code
is incomprehensible.

--Andy


\
 
 \ /
  Last update: 2015-03-06 00:41    [W:0.284 / U:0.020 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site