Commit 31330e6cecfd ("linux-user/s390x: Implement setup_sigtramp")
removed an unused field from rt_sigframe, disturbing offsets of other
fields and breaking unwinding from signal handlers (e.g. libgcc's
s390_fallback_frame() relies on this struct having a specific layout).
Restore the field and add a comment.

Reported-by: Ulrich Weigand <ulrich.weigand@de.ibm.com>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Fixes: 31330e6cecfd ("linux-user/s390x: Implement setup_sigtramp")
---
 linux-user/s390x/signal.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/linux-user/s390x/signal.c b/linux-user/s390x/signal.c
index f47713e04a..4979c4b017 100644
--- a/linux-user/s390x/signal.c
+++ b/linux-user/s390x/signal.c
@@ -84,6 +84,11 @@ struct target_ucontext {
 
 typedef struct {
     uint8_t callee_used_stack[__SIGNAL_FRAMESIZE];
+    /*
+     * This field is no longer initialized by the kernel, but it's still a part
+     * of the ABI.
+     */
+    uint16_t svc_insn;
     struct target_siginfo info;
     struct target_ucontext uc;
 } rt_sigframe;
-- 
2.35.1

On 5/3/22 17:51, Ilya Leoshkevich wrote:
> Commit 31330e6cecfd ("linux-user/s390x: Implement setup_sigtramp")
> removed an unused field from rt_sigframe, disturbing offsets of other
> fields and breaking unwinding from signal handlers (e.g. libgcc's
> s390_fallback_frame() relies on this struct having a specific layout).
> Restore the field and add a comment.
> 
> Reported-by: Ulrich Weigand<ulrich.weigand@de.ibm.com>
> Signed-off-by: Ilya Leoshkevich<iii@linux.ibm.com>
> Fixes: 31330e6cecfd ("linux-user/s390x: Implement setup_sigtramp")
> ---
>   linux-user/s390x/signal.c | 5 +++++
>   1 file changed, 5 insertions(+)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

r~

On 04.05.22 00:51, Ilya Leoshkevich wrote:
> Commit 31330e6cecfd ("linux-user/s390x: Implement setup_sigtramp")
> removed an unused field from rt_sigframe, disturbing offsets of other
> fields and breaking unwinding from signal handlers (e.g. libgcc's
> s390_fallback_frame() relies on this struct having a specific layout).
> Restore the field and add a comment.
> 
> Reported-by: Ulrich Weigand <ulrich.weigand@de.ibm.com>
> Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
> Fixes: 31330e6cecfd ("linux-user/s390x: Implement setup_sigtramp")
> ---
>  linux-user/s390x/signal.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/linux-user/s390x/signal.c b/linux-user/s390x/signal.c
> index f47713e04a..4979c4b017 100644
> --- a/linux-user/s390x/signal.c
> +++ b/linux-user/s390x/signal.c
> @@ -84,6 +84,11 @@ struct target_ucontext {
>  
>  typedef struct {
>      uint8_t callee_used_stack[__SIGNAL_FRAMESIZE];
> +    /*
> +     * This field is no longer initialized by the kernel, but it's still a part
> +     * of the ABI.
> +     */
> +    uint16_t svc_insn;
>      struct target_siginfo info;
>      struct target_ucontext uc;
>  } rt_sigframe;


Reviewed-by: David Hildenbrand <david@redhat.com>

-- 
Thanks,

David / dhildenb