We've had a report[1] of d-bus getting a SEGV only on i686 machines
with the 3.16 kernel. It's a bit light on specifics, but the relevant
detail seems to be:
"I'm pretty sure kernel is to blame here.
The crash occurs when signal handler for RT signal 33 (used internaly
by NPTL/pthreads) returns to address zero (not sure why).
This only happens with 3.16 kernel, works fine with 3.15."
and
"Seems to be related to v3.16's arch/x86 VDSO changes. Works fine when
booting with vdso=0."
There isn't an actual backtrace for the SEGV in the bug, but we can
ask for one. The kernels in question should be very recent, but lack
the 5 patch series Andy recently sent as those aren't in Linus' tree
yet. Not sure if those would impact anything or not.
josh
[1] https://bugzilla.redhat.com/show_bug.cgi?id=1110968
This commit:
commit 6f121e548f83674ab4920a4e60afb58d4f61b829
Author: Andy Lutomirski <[email protected]>
Date: Mon May 5 12:19:34 2014 -0700
x86, vdso: Reimplement vdso.so preparation in build-time C
Contained this obvious typo:
- restorer = VDSO32_SYMBOL(current->mm->context.vdso, rt_sigreturn);
+ restorer = current->mm->context.vdso +
+ selected_vdso32->sym___kernel_sigreturn;
Note the missing 'rt_' in the new code. Fix it.
Signed-off-by: Andy Lutomirski <[email protected]>
---
Compile-tested only. I bet that someone will test it here far more quickly
than I can figure out how to test it:
https://bugzilla.redhat.com/show_bug.cgi?id=1110968
arch/x86/kernel/signal.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index a0da58d..2851d63 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -363,7 +363,7 @@ static int __setup_rt_frame(int sig, struct ksignal *ksig,
/* Set up to return from userspace. */
restorer = current->mm->context.vdso +
- selected_vdso32->sym___kernel_sigreturn;
+ selected_vdso32->sym___kernel_rt_sigreturn;
if (ksig->ka.sa.sa_flags & SA_RESTORER)
restorer = ksig->ka.sa.sa_restorer;
put_user_ex(restorer, &frame->pretcode);
--
1.9.3
On Sat, Jun 21, 2014 at 7:31 AM, Andy Lutomirski <[email protected]> wrote:
> This commit:
>
> commit 6f121e548f83674ab4920a4e60afb58d4f61b829
> Author: Andy Lutomirski <[email protected]>
> Date: Mon May 5 12:19:34 2014 -0700
>
> x86, vdso: Reimplement vdso.so preparation in build-time C
>
> Contained this obvious typo:
>
> - restorer = VDSO32_SYMBOL(current->mm->context.vdso, rt_sigreturn);
> + restorer = current->mm->context.vdso +
> + selected_vdso32->sym___kernel_sigreturn;
>
> Note the missing 'rt_' in the new code. Fix it.
>
> Signed-off-by: Andy Lutomirski <[email protected]>
> ---
>
> Compile-tested only. I bet that someone will test it here far more quickly
> than I can figure out how to test it:
>
> https://bugzilla.redhat.com/show_bug.cgi?id=1110968
Tested now at the link above.
--Andy
Commit-ID: 6ba19a670c8b604e9802d30b511e6a4778118592
Gitweb: http://git.kernel.org/tip/6ba19a670c8b604e9802d30b511e6a4778118592
Author: Andy Lutomirski <[email protected]>
AuthorDate: Sat, 21 Jun 2014 07:31:55 -0700
Committer: H. Peter Anvin <[email protected]>
CommitDate: Mon, 23 Jun 2014 15:54:42 -0700
x86_32, signal: Fix vdso rt_sigreturn
This commit:
commit 6f121e548f83674ab4920a4e60afb58d4f61b829
Author: Andy Lutomirski <[email protected]>
Date: Mon May 5 12:19:34 2014 -0700
x86, vdso: Reimplement vdso.so preparation in build-time C
Contained this obvious typo:
- restorer = VDSO32_SYMBOL(current->mm->context.vdso, rt_sigreturn);
+ restorer = current->mm->context.vdso +
+ selected_vdso32->sym___kernel_sigreturn;
Note the missing 'rt_' in the new code. Fix it.
Signed-off-by: Andy Lutomirski <[email protected]>
Link: http://lkml.kernel.org/r/1eb40ad923acde2e18357ef2832867432e70ac42.1403361010.git.luto@amacapital.net
Signed-off-by: H. Peter Anvin <[email protected]>
---
arch/x86/kernel/signal.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index a0da58d..2851d63 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -363,7 +363,7 @@ static int __setup_rt_frame(int sig, struct ksignal *ksig,
/* Set up to return from userspace. */
restorer = current->mm->context.vdso +
- selected_vdso32->sym___kernel_sigreturn;
+ selected_vdso32->sym___kernel_rt_sigreturn;
if (ksig->ka.sa.sa_flags & SA_RESTORER)
restorer = ksig->ka.sa.sa_restorer;
put_user_ex(restorer, &frame->pretcode);