diff mbox series

[v2,17/23] linux-user/ppc: Implement setup_sigtramp

Message ID 20210618192951.125651-18-richard.henderson@linaro.org
State Superseded
Headers show
Series linux-user: Move signal trampolines to new page | expand

Commit Message

Richard Henderson June 18, 2021, 7:29 p.m. UTC 
Create and record the two signal trampolines.

Cc: qemu-ppc@nongnu.org
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

---
 linux-user/ppc/target_signal.h |  2 ++
 linux-user/ppc/signal.c        | 34 ++++++++++++++++++----------------
 2 files changed, 20 insertions(+), 16 deletions(-)

-- 
2.25.1

Comments

Peter Maydell June 29, 2021, 2:52 p.m. UTC | #1 
On Fri, 18 Jun 2021 at 20:47, Richard Henderson
<richard.henderson@linaro.org> wrote:
>

> Create and record the two signal trampolines.

>

> Cc: qemu-ppc@nongnu.org

> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

> ---

>  linux-user/ppc/target_signal.h |  2 ++

>  linux-user/ppc/signal.c        | 34 ++++++++++++++++++----------------

>  2 files changed, 20 insertions(+), 16 deletions(-)


Reviewed-by: Peter Maydell <peter.maydell@linaro.org>


encode_trampoline() returns doing nothing if its first argument is zero.
It's not clear to me why it does that (it seems to have been that
way since the ppc signal handling code was added in 2009 in commit
bcd4933a23f1db). Is this because in some configurations there is no
NR_sigreturn syscall, only NR_rt_sigreturn (or vice-versa)? If so,
it would be better to handle that by not setting up the default_sigreturn
pointer, and assert()ing that it's not NULL if we ever try to use it.
(I would vaguely have expected that to result in NR_rt_whatever not
being defined, rather than it being defined to 0, though.)
If there is no way that the first argument to encode_trampoline()
can ever be non-zero, we should delete the unnecessary if().

thanks
-- PMM
diff mbox series

Patch

diff --git a/linux-user/ppc/target_signal.h b/linux-user/ppc/target_signal.h
index 72fcdd9bfa..82184ab8f2 100644
--- a/linux-user/ppc/target_signal.h
+++ b/linux-user/ppc/target_signal.h
@@ -24,4 +24,6 @@  typedef struct target_sigaltstack {
 #if !defined(TARGET_PPC64)
 #define TARGET_ARCH_HAS_SETUP_FRAME
 #endif
+#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 1
+
 #endif /* PPC_TARGET_SIGNAL_H */
diff --git a/linux-user/ppc/signal.c b/linux-user/ppc/signal.c
index edfad28a37..4ae35aaf6d 100644
--- a/linux-user/ppc/signal.c
+++ b/linux-user/ppc/signal.c
@@ -202,9 +202,6 @@  struct target_func_ptr {
 
 #endif
 
-/* We use the mc_pad field for the signal return trampoline.  */
-#define tramp mc_pad
-
 /* See arch/powerpc/kernel/signal.c.  */
 static target_ulong get_sigframe(struct target_sigaction *ka,
                                  CPUPPCState *env,
@@ -437,12 +434,7 @@  void setup_frame(int sig, struct target_sigaction *ka,
     /* Save user regs.  */
     save_user_regs(env, &frame->mctx);
 
-    /* Construct the trampoline code on the stack. */
-    encode_trampoline(TARGET_NR_sigreturn, (uint32_t *)&frame->mctx.tramp);
-
-    /* The kernel checks for the presence of a VDSO here.  We don't
-       emulate a vdso, so use a sigreturn system call.  */
-    env->lr = (target_ulong) h2g(frame->mctx.tramp);
+    env->lr = default_sigreturn;
 
     /* Turn off all fp exceptions.  */
     env->fpscr = 0;
@@ -478,7 +470,6 @@  void setup_rt_frame(int sig, struct target_sigaction *ka,
                     target_sigset_t *set, CPUPPCState *env)
 {
     struct target_rt_sigframe *rt_sf;
-    uint32_t *trampptr = 0;
     struct target_mcontext *mctx = 0;
     target_ulong rt_sf_addr, newsp = 0;
     int i, err = 0;
@@ -508,22 +499,17 @@  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;
 #endif
 
     save_user_regs(env, mctx);
-    encode_trampoline(TARGET_NR_rt_sigreturn, trampptr);
 
-    /* The kernel checks for the presence of a VDSO here.  We don't
-       emulate a vdso, so use a sigreturn system call.  */
-    env->lr = (target_ulong) h2g(trampptr);
+    env->lr = default_rt_sigreturn;
 
     /* Turn off all fp exceptions.  */
     env->fpscr = 0;
@@ -721,3 +707,19 @@  abi_long do_swapcontext(CPUArchState *env, abi_ulong uold_ctx,
 
     return 0;
 }
+
+void setup_sigtramp(abi_ulong sigtramp_page)
+{
+    uint32_t *tramp = lock_user(VERIFY_WRITE, sigtramp_page, 2 * 8, 0);
+    assert(tramp != NULL);
+
+#ifdef TARGET_ARCH_HAS_SETUP_FRAME
+    default_sigreturn = sigtramp_page;
+    encode_trampoline(TARGET_NR_sigreturn, tramp + 0);
+#endif
+
+    default_rt_sigreturn = sigtramp_page + 8;
+    encode_trampoline(TARGET_NR_rt_sigreturn, tramp + 2);
+
+    unlock_user(tramp, sigtramp_page, 2 * 8);
+}