From: David Hildenbrand <david@redhat.com>
To: Andreas Krebbel <krebbel@linux.ibm.com>, qemu-devel@nongnu.org
Cc: qemu-s390x@nongnu.org
Subject: Re: [PATCH 1/1] linux-user/s390x: Apply h2g to address of sigreturn stub
Date: Wed, 24 Mar 2021 10:17:18 +0100 [thread overview]
Message-ID: <5070a253-cd95-59b0-dbdb-2eb549e9f61c@redhat.com> (raw)
In-Reply-To: <20210324085129.29684-1-krebbel@linux.ibm.com>
On 24.03.21 09:51, Andreas Krebbel wrote:
> The sigreturn SVC is put onto the stack by the emulation code. Hence
> the address of it should not be subject to guest_base transformation
> when fetching it.
>
> The fix applies h2g to the address when writing it into the return
> address register to nullify the transformation applied to it later.
>
> Note: This only caused problems if Qemu has been built with
> --disable-pie (as it is in distros nowadays). Otherwise guest_base
> defaults to 0 hiding the actual problem.
>
> Signed-off-by: Andreas Krebbel <krebbel@linux.ibm.com>
> ---
> linux-user/s390x/signal.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/linux-user/s390x/signal.c b/linux-user/s390x/signal.c
> index ecfa2a14a9..1412376958 100644
> --- a/linux-user/s390x/signal.c
> +++ b/linux-user/s390x/signal.c
> @@ -152,7 +152,7 @@ void setup_frame(int sig, struct target_sigaction *ka,
> env->regs[14] = (unsigned long)
> ka->sa_restorer | PSW_ADDR_AMODE;
> } else {
> - env->regs[14] = (frame_addr + offsetof(sigframe, retcode))
> + env->regs[14] = h2g(frame_addr + offsetof(sigframe, retcode))
> | PSW_ADDR_AMODE;
> __put_user(S390_SYSCALL_OPCODE | TARGET_NR_sigreturn,
> (uint16_t *)(frame->retcode));
> @@ -213,7 +213,7 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
> if (ka->sa_flags & TARGET_SA_RESTORER) {
> env->regs[14] = (unsigned long) ka->sa_restorer | PSW_ADDR_AMODE;
> } else {
> - env->regs[14] = (unsigned long) frame->retcode | PSW_ADDR_AMODE;
> + env->regs[14] = (unsigned long) h2g(frame->retcode) | PSW_ADDR_AMODE;
> __put_user(S390_SYSCALL_OPCODE | TARGET_NR_rt_sigreturn,
> (uint16_t *)(frame->retcode));
> }
>
Sounds sane to me, although I am not an expert on that code :)
Acked-by: David Hildenbrand <david@redhat.com>
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2021-03-24 9:20 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-24 8:51 [PATCH 1/1] linux-user/s390x: Apply h2g to address of sigreturn stub Andreas Krebbel
2021-03-24 9:17 ` David Hildenbrand [this message]
2021-03-24 10:28 ` Laurent Vivier
2021-03-24 11:26 ` Andreas Krebbel
2021-03-24 13:06 ` Laurent Vivier
2021-03-24 14:14 ` Andreas Krebbel
2021-03-24 14:34 ` Richard Henderson
2021-03-24 15:34 ` Laurent Vivier
2021-03-24 15:55 ` [PATCH v2] linux-user/s390x: Use the guest pointer for the " Andreas Krebbel
2021-03-24 17:53 ` Laurent Vivier
2021-03-24 18:48 ` Andreas Krebbel
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