merge revision(s) 56030,56035: [Backport #12711]

	* vm_dump.c (backtrace): use rip in the saved context for the case
	  the SIGSEGV is received when the process is in userland.
	  Note that ip in the stack should be used if the signal is received
	  when it is in kernel (when it is calling syscall) [Bug #12711]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_3@56257 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 7 insertions, 3 deletions

diff --git a/vm_dump.c b/vm_dump.c
index df0d2413c9..01d15062fc 100644
--- a/vm_dump.c
+++ b/vm_dump.c
@@ -482,10 +482,14 @@ darwin_sigtramp:
 	unw_set_reg(&cursor, UNW_X86_64_R13, uctx->uc_mcontext->__ss.__r13);
 	unw_set_reg(&cursor, UNW_X86_64_R14, uctx->uc_mcontext->__ss.__r14);
 	unw_set_reg(&cursor, UNW_X86_64_R15, uctx->uc_mcontext->__ss.__r15);
-	ip = *(unw_word_t*)uctx->uc_mcontext->__ss.__rsp;
-	unw_set_reg(&cursor, UNW_REG_IP, ip);
-	trace[n++] = (void *)uctx->uc_mcontext->__ss.__rip;
+	ip = uctx->uc_mcontext->__ss.__rip;
+	if (((char*)ip)[-2] == 0x0f && ((char*)ip)[-1] == 5) {
+	    /* signal received in syscall */
+	    trace[n++] = (void *)ip;
+	    ip = *(unw_word_t*)uctx->uc_mcontext->__ss.__rsp;
+	}
 	trace[n++] = (void *)ip;
+	unw_set_reg(&cursor, UNW_REG_IP, ip);
     }
     while (unw_step(&cursor) > 0) {
 	unw_get_reg(&cursor, UNW_REG_IP, &ip);