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 <jos...@linux.vnet.ibm.com> > --- > 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 <laur...@vivier.eu> 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