From cc970aac70679288c24e7fbc080285e40743c5d2 Mon Sep 17 00:00:00 2001
From: Jonathan G Rennison <j.g.rennison@gmail.com>
Date: Tue, 23 Apr 2019 19:14:02 +0100
Subject: [PATCH] Add sigaltstack support to MacOS crashlog

---
 config.lib                     | 27 ++++++++++++
 src/os/macosx/crashlog_osx.cpp | 76 +++++++++++++++++++++++++++-------
 2 files changed, 87 insertions(+), 16 deletions(-)

diff --git a/config.lib b/config.lib
index 44758cbbea..f37e851af3 100644
--- a/config.lib
+++ b/config.lib
@@ -1956,6 +1956,33 @@ EOL
 			log 1 "checking ucontext... found"
 			CFLAGS="$CFLAGS -DWITH_UCONTEXT"
 		fi
+
+		log 2 "executing $cc_host $CFLAGS $CFLAGS_ENV $LDFLAGS $LDFLAGS_ENV $STATIC_FLAGS -o tmp.config.sigaltstack -x c++ - -ldl"
+		"$cc_host" $CFLAGS $CFLAGS_ENV $LDFLAGS $LDFLAGS_ENV $STATIC_FLAGS -o tmp.config.sigaltstack -x c++ - -ldl 2> /dev/null << EOL
+			#include <signal.h>
+			#include <stdlib.h>
+			#include <pthread.h>
+			int main() {
+				pthread_t self = pthread_self();
+				void *stacktop = pthread_get_stackaddr_np(self);
+				size_t stack_size = pthread_get_stacksize_np(self);
+				stack_t ss;
+				ss.ss_sp = calloc(SIGSTKSZ, 1);
+				ss.ss_size = SIGSTKSZ;
+				ss.ss_flags = 0;
+				sigaltstack(&ss, NULL);
+				return 0;
+			}
+EOL
+		ret=$?
+		rm -f tmp.config.sigaltstack
+		log 2 "  exit code $ret"
+		if [ $ret -ne 0 ]; then
+			log 1 "checking sigaltstack... no"
+		else
+			log 1 "checking sigaltstack... found"
+			CFLAGS="$CFLAGS -DWITH_SIGALTSTACK"
+		fi
 	fi
 
 	if [ "$os" = "HAIKU" ]; then
diff --git a/src/os/macosx/crashlog_osx.cpp b/src/os/macosx/crashlog_osx.cpp
index 3bad2e0f46..f2000d03fa 100644
--- a/src/os/macosx/crashlog_osx.cpp
+++ b/src/os/macosx/crashlog_osx.cpp
@@ -25,6 +25,9 @@
 #ifdef WITH_UCONTEXT
 #include <sys/ucontext.h>
 #endif
+#if defined(WITH_SIGALTSTACK) && defined(WITH_UCONTEXT)
+#include <pthread.h>
+#endif
 
 #include "../../safeguards.h"
 
@@ -174,22 +177,9 @@ class CrashLogOSX : public CrashLog {
 		buffer += seprintf(buffer, last, "\nStacktrace:\n");
 
 		void **frame;
-#if defined(__ppc__) || defined(__ppc64__)
-		/* Apple says __builtin_frame_address can be broken on PPC. */
-		__asm__ volatile("mr %0, r1" : "=r" (frame));
-#else
-		frame = (void **)__builtin_frame_address(0);
-#endif
-
-		for (int i = 0; frame != NULL && i < MAX_STACK_FRAMES; i++) {
-			/* Get IP for current stack frame. */
-#if defined(__ppc__) || defined(__ppc64__)
-			void *ip = frame[2];
-#else
-			void *ip = frame[1];
-#endif
-			if (ip == NULL) break;
+		int i = 0;
 
+		auto print_frame = [&](void *ip) {
 			/* Print running index. */
 			buffer += seprintf(buffer, last, " [%02d]", i);
 
@@ -221,6 +211,49 @@ class CrashLogOSX : public CrashLog {
 				free(func_name);
 			}
 			buffer += seprintf(buffer, last, "\n");
+		};
+
+#if defined(__ppc__) || defined(__ppc64__)
+		/* Apple says __builtin_frame_address can be broken on PPC. */
+		__asm__ volatile("mr %0, r1" : "=r" (frame));
+#elif defined(WITH_SIGALTSTACK) && defined(WITH_UCONTEXT) && (defined(__x86_64__) || defined(__i386))
+		if (this->signal_instruction_ptr_valid) {
+			print_frame(this->signal_instruction_ptr);
+			i++;
+		}
+
+		pthread_t self = pthread_self();
+		char *stacktop = (char *) pthread_get_stackaddr_np(self);
+		char *stackbot = stacktop - pthread_get_stacksize_np(self);
+		stacktop -= 2 * sizeof(void *);
+
+		ucontext_t *ucontext = static_cast<ucontext_t *>(context);
+#if defined(__x86_64__)
+		void **bp = (void **) ucontext->uc_mcontext->__ss.__rbp;
+		void **sp = (void **) ucontext->uc_mcontext->__ss.__rsp;
+#else
+		void **bp = (void **) ucontext->uc_mcontext->__ss.__ebp;
+		void **sp = (void **) ucontext->uc_mcontext->__ss.__esp;
+#endif
+		if (IS_ALIGNED(bp) && reinterpret_cast<uintptr_t>(bp) >= reinterpret_cast<uintptr_t>(sp) && reinterpret_cast<uintptr_t>(bp) >= reinterpret_cast<uintptr_t>(stackbot) && reinterpret_cast<uintptr_t>(bp) <= reinterpret_cast<uintptr_t>(stacktop)) {
+			frame = bp;
+		} else {
+			frame = nullptr;
+		}
+#else
+		frame = (void **)__builtin_frame_address(0);
+#endif
+
+		for (; frame != nullptr && i < MAX_STACK_FRAMES; i++) {
+			/* Get IP for current stack frame. */
+#if defined(__ppc__) || defined(__ppc64__)
+			void *ip = frame[2];
+#else
+			void *ip = frame[1];
+#endif
+			if (ip == nullptr) break;
+
+			print_frame(ip);
 
 			/* Get address of next stack frame. */
 			void **next = (void **)frame[0];
@@ -263,7 +296,7 @@ class CrashLogOSX : public CrashLog {
 		args.push_back("--batch");
 
 		args.push_back("-o");
-		args.push_back(IsNonMainThread() ? "bt all" : "bt");
+		args.push_back(IsNonMainThread() ? "bt all" : "bt 100");
 
 		if (this->GetMessage() == nullptr && this->signal_instruction_ptr_valid) {
 			seprintf(disasm_buffer, lastof(disasm_buffer), "disassemble -b -F intel -c 1 -s %p", this->signal_instruction_ptr);
@@ -448,10 +481,21 @@ void CDECL HandleCrash(int signum, siginfo_t *si, void *context)
 
 /* static */ void CrashLog::InitialiseCrashLog()
 {
+#if defined(WITH_SIGALTSTACK) && defined(WITH_UCONTEXT)
+	const size_t stack_size = max<size_t>(SIGSTKSZ, 512*1024);
+	stack_t ss;
+	ss.ss_sp = CallocT<byte>(stack_size);
+	ss.ss_size = stack_size;
+	ss.ss_flags = 0;
+	sigaltstack(&ss, nullptr);
+#endif
 	for (const int *i = _signals_to_handle; i != endof(_signals_to_handle); i++) {
 		struct sigaction sa;
 		memset(&sa, 0, sizeof(sa));
 		sa.sa_flags = SA_SIGINFO | SA_RESTART;
+#if defined(WITH_SIGALTSTACK) && defined(WITH_UCONTEXT)
+		sa.sa_flags |= SA_ONSTACK;
+#endif
 		sigemptyset(&sa.sa_mask);
 		sa.sa_sigaction = HandleCrash;
 		sigaction(*i, &sa, nullptr);