[Qemu-devel] [PATCH] linux-user: fill target sigcontext struct accordingly

[Jose Ricardo Ziviani <joserz@linux.vnet.ibm.com>]

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 <joserz@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;
-- 
2.7.4