s390: Set psw addr field in getcontext and friends.
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Commit Message
So far if the ucontext structure was obtained by getcontext and co,
the return address was stored in general purpose register 14 as
it is defined as return address in the ABI.
In contrast, the context passed to a signal handler contains the address
in psw.addr field.
If somebody e.g. wants to dump the address of the context, the origin
needs to be known.
Now this patch adjusts getcontext and friends and stores the return address
also in psw.addr field.
Note that setcontext isn't adjusted and it is not supported to pass a
ucontext structure from signal-handler to setcontext. We are not able to
restore all registers and branching to psw.addr without clobbering one
register.
---
sysdeps/unix/sysv/linux/s390/s390-32/getcontext.S | 6 ++++++
sysdeps/unix/sysv/linux/s390/s390-32/makecontext.c | 5 +++++
sysdeps/unix/sysv/linux/s390/s390-32/swapcontext.S | 6 ++++++
sysdeps/unix/sysv/linux/s390/s390-64/getcontext.S | 6 ++++++
sysdeps/unix/sysv/linux/s390/s390-64/makecontext.c | 5 +++++
sysdeps/unix/sysv/linux/s390/s390-64/swapcontext.S | 6 ++++++
6 files changed, 34 insertions(+)
Comments
* Stefan Liebler:
> So far if the ucontext structure was obtained by getcontext and co,
> the return address was stored in general purpose register 14 as
> it is defined as return address in the ABI.
>
> In contrast, the context passed to a signal handler contains the address
> in psw.addr field.
>
> If somebody e.g. wants to dump the address of the context, the origin
> needs to be known.
>
> Now this patch adjusts getcontext and friends and stores the return address
> also in psw.addr field.
>
> Note that setcontext isn't adjusted and it is not supported to pass a
> ucontext structure from signal-handler to setcontext. We are not able to
> restore all registers and branching to psw.addr without clobbering one
> register.
> ---
> sysdeps/unix/sysv/linux/s390/s390-32/getcontext.S | 6 ++++++
> sysdeps/unix/sysv/linux/s390/s390-32/makecontext.c | 5 +++++
> sysdeps/unix/sysv/linux/s390/s390-32/swapcontext.S | 6 ++++++
> sysdeps/unix/sysv/linux/s390/s390-64/getcontext.S | 6 ++++++
> sysdeps/unix/sysv/linux/s390/s390-64/makecontext.c | 5 +++++
> sysdeps/unix/sysv/linux/s390/s390-64/swapcontext.S | 6 ++++++
> 6 files changed, 34 insertions(+)
I guess this makes sense. Please feel empowered to push this as the
S/390 maintainer.
Thanks,
Florian
On 18.12.23 15:18, Florian Weimer wrote:
> * Stefan Liebler:
>
>> So far if the ucontext structure was obtained by getcontext and co,
>> the return address was stored in general purpose register 14 as
>> it is defined as return address in the ABI.
>>
>> In contrast, the context passed to a signal handler contains the address
>> in psw.addr field.
>>
>> If somebody e.g. wants to dump the address of the context, the origin
>> needs to be known.
>>
>> Now this patch adjusts getcontext and friends and stores the return address
>> also in psw.addr field.
>>
>> Note that setcontext isn't adjusted and it is not supported to pass a
>> ucontext structure from signal-handler to setcontext. We are not able to
>> restore all registers and branching to psw.addr without clobbering one
>> register.
>> ---
>> sysdeps/unix/sysv/linux/s390/s390-32/getcontext.S | 6 ++++++
>> sysdeps/unix/sysv/linux/s390/s390-32/makecontext.c | 5 +++++
>> sysdeps/unix/sysv/linux/s390/s390-32/swapcontext.S | 6 ++++++
>> sysdeps/unix/sysv/linux/s390/s390-64/getcontext.S | 6 ++++++
>> sysdeps/unix/sysv/linux/s390/s390-64/makecontext.c | 5 +++++
>> sysdeps/unix/sysv/linux/s390/s390-64/swapcontext.S | 6 ++++++
>> 6 files changed, 34 insertions(+)
>
> I guess this makes sense. Please feel empowered to push this as the
> S/390 maintainer.
>
> Thanks,
> Florian
>
Sure. I've just committed it. Yes, even as maintainer, I post it and
wait a bit in order to give others the chance for review.
Thanks,
Stefan
@@ -71,6 +71,12 @@ ENTRY(__getcontext)
/* Store general purpose registers. */
stm %r0,%r15,SC_GPRS(%r1)
+ /* Store psw mask to 0x0 and addr to return address. Then the address
+ can be retrieved from the ucontext structure in the same way as if it
+ is created by kernel and passed to a signal-handler. */
+ st %r2,SC_PSW+0(%r1)
+ st %r14,SC_PSW+4(%r1)
+
/* Return. */
br %r14
END(__getcontext)
@@ -60,6 +60,11 @@ __makecontext (ucontext_t *ucp, void (*func) (void), int argc, ...)
/* Set the return address to trampoline. */
ucp->uc_mcontext.gregs[14] = (long int) __makecontext_ret;
+ /* Store psw mask to 0x0 and addr to trampoline. Then the address
+ can be retrieved from the ucontext structure in the same way as if it
+ is created by kernel and passed to a signal-handler. */
+ ucp->uc_mcontext.psw.addr = (long int) __makecontext_ret;
+ ucp->uc_mcontext.psw.mask = 0;
/* Set register parameters. */
va_start (ap, argc);
@@ -66,6 +66,12 @@ ENTRY(__swapcontext)
/* Store general purpose registers. */
stm %r0,%r15,SC_GPRS(%r1)
+ /* Store psw mask to 0x0 and addr to return address. Then the address
+ can be retrieved from the ucontext structure in the same way as if it
+ is created by kernel and passed to a signal-handler. */
+ st %r2,SC_PSW+0(%r1)
+ st %r14,SC_PSW+4(%r1)
+
/* rt_sigprocmask (SIG_SETMASK, &ucp->uc_sigmask, &oucp->uc_sigmask,
sigsetsize). */
la %r2,SIG_SETMASK
@@ -71,6 +71,12 @@ ENTRY(__getcontext)
/* Store general purpose registers. */
stmg %r0,%r15,SC_GPRS(%r1)
+ /* Store psw mask to 0x0 and addr to return address. Then the address
+ can be retrieved from the ucontext structure in the same way as if it
+ is created by kernel and passed to a signal-handler. */
+ stg %r2,SC_PSW+0(%r1)
+ stg %r14,SC_PSW+8(%r1)
+
/* Return. */
br %r14
END(__getcontext)
@@ -60,6 +60,11 @@ __makecontext (ucontext_t *ucp, void (*func) (void), int argc, ...)
/* Set the return address to trampoline. */
ucp->uc_mcontext.gregs[14] = (long int) __makecontext_ret;
+ /* Store psw mask to 0x0 and addr to trampoline. Then the address
+ can be retrieved from the ucontext structure in the same way as if it
+ is created by kernel and passed to a signal-handler. */
+ ucp->uc_mcontext.psw.addr = (long int) __makecontext_ret;
+ ucp->uc_mcontext.psw.mask = 0;
/* Set register parameters. */
va_start (ap, argc);
@@ -66,6 +66,12 @@ ENTRY(__swapcontext)
/* Store general purpose registers. */
stmg %r0,%r15,SC_GPRS(%r1)
+ /* Store psw mask to 0x0 and addr to return address. Then the address
+ can be retrieved from the ucontext structure in the same way as if it
+ is created by kernel and passed to a signal-handler. */
+ stg %r2,SC_PSW+0(%r1)
+ stg %r14,SC_PSW+8(%r1)
+
/* rt_sigprocmask (SIG_SETMASK, &ucp->uc_sigmask, &oucp->uc_sigmask,
sigsetsize). */
la %r2,SIG_SETMASK