From: Matt Turner <[email protected]>
The kernel's 64-bit signal delivery (signal_64.c) uses:
newsp = frame - __SIGNAL_FRAMESIZE
while the 32-bit path (signal_32.c) uses:
newsp = frame - (__SIGNAL_FRAMESIZE + 16)
The extra 16 bytes in the 32-bit case is to place siginfo and ucontext
at the same offsets as older kernels (see the comment in signal_32.c).
The 64-bit rt_sigframe starts with ucontext directly and does not need
this adjustment.
QEMU's setup_rt_frame() unconditionally used (SIGNAL_FRAMESIZE + 16)
for both 32-bit and 64-bit, placing the handler's SP 16 bytes too low
on ppc64. Signal delivery and return still worked because do_rt_sigreturn
had the matching wrong offset, but the vDSO DWARF unwind info encodes
the correct kernel offset. This caused any DWARF unwinder (libunwind,
libgcc, etc.) to compute a CFA that is 16 bytes off, reading garbage
register values from the signal frame.
Define RT_SIGFRAME_ADJUST (0 on ppc64, 16 on ppc32) and use it in both
setup_rt_frame and do_rt_sigreturn to match the kernel.
This was verified by A/B testing with libunwind's test suite:
ppc64le: Gtest-bt, Ltest-bt, Gtest-concurrent, Ltest-concurrent,
and Ltest-sig-context all change from FAIL to PASS.
ppc64be: Gtest-bt, Ltest-bt, and Ltest-sig-context all change
from FAIL to PASS.
Signed-off-by: Matt Turner <[email protected]>
Reviewed-by: Peter Maydell <[email protected]>
Signed-off-by: Helge Deller <[email protected]>
Cc: [email protected]
(cherry picked from commit 654dce6c523612d38e8d53818dbc7c03cbe535a3)
Signed-off-by: Michael Tokarev <[email protected]>
diff --git a/linux-user/ppc/signal.c b/linux-user/ppc/signal.c
index 24e5a02a78..a9c10e0987 100644
--- a/linux-user/ppc/signal.c
+++ b/linux-user/ppc/signal.c
@@ -210,6 +210,18 @@ QEMU_BUILD_BUG_ON(offsetof(struct target_rt_sigframe,
uc.tuc_mcontext)
#endif
+#ifdef TARGET_PPC64
+#define RT_SIGFRAME_ADJUST 0
+#else
+/*
+ * For 32-bit rt sigframes we have an extra 16 bytes of gap
+ * on top of __SIGNAL_FRAMESIZE; this is to get the siginfo
+ * and ucontext in the same positions as in older kernels.
+ * See Linux's arch/powerpc/kernel/signal_32.c.
+ */
+#define RT_SIGFRAME_ADJUST 16
+#endif
+
#if defined(TARGET_PPC64)
struct target_func_ptr {
@@ -525,7 +537,7 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
env->fpscr = 0;
/* Create a stack frame for the caller of the handler. */
- newsp = rt_sf_addr - (SIGNAL_FRAMESIZE + 16);
+ newsp = rt_sf_addr - (SIGNAL_FRAMESIZE + RT_SIGFRAME_ADJUST);
err |= put_user(env->gpr[1], newsp, target_ulong);
if (err)
@@ -641,7 +653,7 @@ long do_rt_sigreturn(CPUPPCState *env)
struct target_rt_sigframe *rt_sf = NULL;
target_ulong rt_sf_addr;
- rt_sf_addr = env->gpr[1] + SIGNAL_FRAMESIZE + 16;
+ rt_sf_addr = env->gpr[1] + SIGNAL_FRAMESIZE + RT_SIGFRAME_ADJUST;
if (!lock_user_struct(VERIFY_READ, rt_sf, rt_sf_addr, 1))
goto sigsegv;
--
2.47.3
