ACK: [SRU][Xenial][PATCH 1/1] x86/vdso: Pass --eh-frame-hdr to the linker

[Connor Kuehl]

On 5/29/19 9:59 AM, Kleber Sacilotto de Souza wrote:
> From: Alistair Strachan <astrachan at google.com>
> 
> BugLink: https://bugs.launchpad.net/bugs/1830890
> 
> Commit
> 
>   379d98ddf413 ("x86: vdso: Use $LD instead of $CC to link")
> 
> accidentally broke unwinding from userspace, because ld would strip the
> .eh_frame sections when linking.
> 
> Originally, the compiler would implicitly add --eh-frame-hdr when
> invoking the linker, but when this Makefile was converted from invoking
> ld via the compiler, to invoking it directly (like vmlinux does),
> the flag was missed. (The EH_FRAME section is important for the VDSO
> shared libraries, but not for vmlinux.)
> 
> Fix the problem by explicitly specifying --eh-frame-hdr, which restores
> parity with the old method.
> 
> See relevant bug reports for additional info:
> 
>   https://bugzilla.kernel.org/show_bug.cgi?id=201741
>   https://bugzilla.redhat.com/show_bug.cgi?id=1659295
> 
> Fixes: 379d98ddf413 ("x86: vdso: Use $LD instead of $CC to link")
> Reported-by: Florian Weimer <fweimer at redhat.com>
> Reported-by: Carlos O'Donell <carlos at redhat.com>
> Reported-by: "H. J. Lu" <hjl.tools at gmail.com>
> Signed-off-by: Alistair Strachan <astrachan at google.com>
> Signed-off-by: Borislav Petkov <bp at suse.de>
> Tested-by: Laura Abbott <labbott at redhat.com>
> Cc: Andy Lutomirski <luto at kernel.org>
> Cc: Carlos O'Donell <carlos at redhat.com>
> Cc: "H. Peter Anvin" <hpa at zytor.com>
> Cc: Ingo Molnar <mingo at redhat.com>
> Cc: Joel Fernandes <joel at joelfernandes.org>
> Cc: kernel-team at android.com
> Cc: Laura Abbott <labbott at redhat.com>
> Cc: stable <stable at vger.kernel.org>
> Cc: Thomas Gleixner <tglx at linutronix.de>
> Cc: X86 ML <x86 at kernel.org>
> Link: https://lkml.kernel.org/r/20181214223637.35954-1-astrachan@google.com
> (cherry picked from commit cd01544a268ad8ee5b1dfe42c4393f1095f86879)
> Signed-off-by: Kleber Sacilotto de Souza <kleber.souza at canonical.com>
> ---

Acked-by: Connor Kuehl <connor.kuehl at canonical.com>

>  arch/x86/entry/vdso/Makefile | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile
> index 297dda4d5947..15ed35f5097d 100644
> --- a/arch/x86/entry/vdso/Makefile
> +++ b/arch/x86/entry/vdso/Makefile
> @@ -159,7 +159,8 @@ quiet_cmd_vdso = VDSO    $@
>  		 sh $(srctree)/$(src)/checkundef.sh '$(NM)' '$@'
>  
>  VDSO_LDFLAGS = -shared $(call ld-option, --hash-style=both) \
> -	$(call ld-option, --build-id) -Bsymbolic
> +	$(call ld-option, --build-id) $(call ld-option, --eh-frame-hdr) \
> +	-Bsymbolic
>  GCOV_PROFILE := n
>  
>  #
> 


-- 
Connor
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