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Re: [Qemu-ppc] [Qemu-devel] [PATCH] linux-user: fill target sigcontext s
From: |
Laurent Vivier |
Subject: |
Re: [Qemu-ppc] [Qemu-devel] [PATCH] linux-user: fill target sigcontext struct accordingly |
Date: |
Wed, 1 Feb 2017 21:43:57 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.6.0 |
Le 31/01/2017 à 23:05, Jose Ricardo Ziviani a écrit :
> A segfault is noticed when an emulated program uses any of ucontext
> regs fields. Risu detected this issue in the following operation when
> handling a signal:
> ucontext_t *uc = (ucontext_t*)uc;
> uc->uc_mcontext.regs->nip += 4;
>
> but this works fine:
> uc->uc_mcontext.gp_regs[PT_NIP] += 4;
>
> This patch set regs to a valid location as well as other sigcontext
> fields.
>
> Signed-off-by: Jose Ricardo Ziviani <address@hidden>
> ---
> linux-user/signal.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/linux-user/signal.c b/linux-user/signal.c
> index 5064de0..8209539 100644
> --- a/linux-user/signal.c
> +++ b/linux-user/signal.c
> @@ -5155,6 +5155,7 @@ static void setup_rt_frame(int sig, struct
> target_sigaction *ka,
> target_ulong rt_sf_addr, newsp = 0;
> int i, err = 0;
> #if defined(TARGET_PPC64)
> + struct target_sigcontext *sc = 0;
> struct image_info *image = ((TaskState *)thread_cpu->opaque)->info;
> #endif
>
> @@ -5183,6 +5184,10 @@ static void setup_rt_frame(int sig, struct
> target_sigaction *ka,
> #if defined(TARGET_PPC64)
> mctx = &rt_sf->uc.tuc_sigcontext.mcontext;
> trampptr = &rt_sf->trampoline[0];
> +
> + sc = &rt_sf->uc.tuc_sigcontext;
> + __put_user(h2g(mctx), &sc->regs);
> + __put_user(sig, &sc->signal);
> #else
> mctx = &rt_sf->uc.tuc_mcontext;
> trampptr = (uint32_t *)&rt_sf->uc.tuc_mcontext.tramp;
>
Reviewed-by: Laurent Vivier <address@hidden>
This is correct, but QEMU and kernel implementation are really different.
In the kernel:
handle_rt_signal64()
...
frame = get_sigframe(ksig, get_tm_stackpointer(tsk),
sizeof(*frame), 0);
...
err |= setup_sigcontext(&frame->uc.uc_mcontext, tsk, ksig->sig,
NULL,
(unsigned long)ksig->ka.sa.sa_handler,
1);
static long setup_sigcontext(struct sigcontext __user *sc,
struct task_struct *tsk, int signr, sigset_t *set,
unsigned long handler, int ctx_has_vsx_region)
err |= __put_user(&sc->gp_regs, &sc->regs);
...
err |= __put_user(signr, &sc->signal);
...
According to kernel definition of ucontext:
struct ucontext {
...
#ifdef __powerpc64__
sigset_t __unused[15]; /* Allow for uc_sigmask growth */
struct sigcontext uc_mcontext; /* last for extensibility */
#else
...
}
kernel &frame->uc.uc_mcontext is qemu &rt_sf->uc.tuc_sigcontext
uc_sigcontext.mcontext doesn't exit in the kernel.
But QEMU code works because tuc_sigcontext.mcontext is where we have the
CPU registers in sigcontext:
kernel:
struct sigcontext {
unsigned long _unused[4];
int signal;
#ifdef __powerpc64__
int _pad0;
#endif
unsigned long handler;
unsigned long oldmask;
struct pt_regs __user *regs;
#ifdef __powerpc64__
elf_gregset_t gp_regs;
elf_fpregset_t fp_regs;
...
Qemu:
struct target_sigcontext {
target_ulong _unused[4];
int32_t signal;
#if defined(TARGET_PPC64)
int32_t pad0;
#endif
target_ulong handler;
target_ulong oldmask;
target_ulong regs; /* struct pt_regs __user * */
#if defined(TARGET_PPC64)
struct target_mcontext mcontext;
#endif
};
struct target_mcontext {
target_ulong mc_gregs[48];
/* Includes fpscr. */
uint64_t mc_fregs[33];
...
I think we do like that to use the same
save_user_regs()/save_user_regs() functions with PPC and PPC64... but
comparison with kernel becomes harder.
Laurent
- Re: [Qemu-ppc] [Qemu-devel] [PATCH] linux-user: fill target sigcontext struct accordingly,
Laurent Vivier <=