On Thu, Mar 5, 2015 at 12:13 AM, Jiri Slaby <jsl...@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 <jsl...@suse.cz> > Reported-by: Richard Biener <rguent...@suse.de> > Cc: sta...@vger.kernel.org > Cc: Andy Lutomirski <l...@amacapital.net> > Cc: Thomas Gleixner <t...@linutronix.de> > Cc: Ingo Molnar <mi...@redhat.com> > Cc: "H. Peter Anvin" <h...@zytor.com> > Cc: x...@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 <l...@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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
