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.
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=201741
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1659295
Reported-by: Laura Abbott <[email protected]>
Fixes: 379d98ddf413 ("x86: vdso: Use $LD instead of $CC to link")
Cc: [email protected]
Cc: Andy Lutomirski <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: X86 ML <[email protected]>
Cc: Florian Weimer <[email protected]>,
Cc: Carlos O'Donell <[email protected]>,
Cc: "H. J. Lu" <[email protected]>
Cc: Joel Fernandes <[email protected]>
Cc: [email protected]
Signed-off-by: Alistair Strachan <[email protected]>
---
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 141d415a8c80..c3d7ccd25381 100644
--- a/arch/x86/entry/vdso/Makefile
+++ b/arch/x86/entry/vdso/Makefile
@@ -171,7 +171,8 @@ 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
#
--
2.20.0.405.gbc1bbc6f85-goog
On 12/14/18 2:27 PM, Alistair Strachan wrote:
> 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.
>
> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=201741
> Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1659295
> Reported-by: Laura Abbott <[email protected]>
You should probably use the bugzilla reporters instead
of me given I just did the boring part of sending an e-mail.
Instead you can use:
Tested-by: Laura Abbott <[email protected]>
> Fixes: 379d98ddf413 ("x86: vdso: Use $LD instead of $CC to link")
> Cc: [email protected]
> Cc: Andy Lutomirski <[email protected]>
> Cc: Thomas Gleixner <[email protected]>
> Cc: "H. Peter Anvin" <[email protected]>
> Cc: X86 ML <[email protected]>
> Cc: Florian Weimer <[email protected]>,
> Cc: Carlos O'Donell <[email protected]>,
> Cc: "H. J. Lu" <[email protected]>
> Cc: Joel Fernandes <[email protected]>
> Cc: [email protected]
> Signed-off-by: Alistair Strachan <[email protected]>
> ---
> 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 141d415a8c80..c3d7ccd25381 100644
> --- a/arch/x86/entry/vdso/Makefile
> +++ b/arch/x86/entry/vdso/Makefile
> @@ -171,7 +171,8 @@ 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
>
> #
>