[ubsan] Fall back to the fast unwinder when print_stacktrace=1

[vsk]

Summary

This makes it possible to get stacktrace info when print_stacktrace=1 on
Darwin (where the slow unwinder is not currently supported [1]). This
should not regress any other platforms.

[1] The thread about r300295 has a relatively recent discusion about
this. We should be able to enable the existing slow unwind functionality
for Darwin, but this needs more testing.

[eugenis]

lib/ubsan/ubsan_diag.cc

43

This would use fast unwinder on linux, even when the slow one is available.
I think we should prefer slow, as before.

[vsk]

Fall back to the fast unwinder, instead of making it the preferred choice.

[eugenis]

lib/ubsan/ubsan_diag.cc

37

use common_flags()->fast_unwind_on_fatal here

test/ubsan/TestCases/Misc/missing_return.cpp

9

This is unnecessarily complex. Remove () and (void), we don't really care about the exact function signature.

[vsk]

lib/ubsan/ubsan_diag.cc

37

Ok. I think it would also make sense to enable the fast unwinder when fast_unwind_on_check is set, then.

[eugenis]

lib/ubsan/ubsan_diag.cc

37

No, fast_unwind_on_check is for internal CHECK(...) failures.

test/ubsan/TestCases/Misc/missing_return.cpp

9

And now there is no need to keep 3 separate check lines.

[vsk]

Will update shortly.

lib/ubsan/ubsan_diag.cc

37

I see, those failures are not surfaced through this function.

[eugenis]

LGTM

test/ubsan/TestCases/TypeCheck/misaligned.cpp

51

Here as well, no need for %os.
Will this pass on, say, FreeBSD, without the corresponding CHECK line?

[vsk]

test/ubsan/TestCases/TypeCheck/misaligned.cpp

51

I expect this to pass on FreeBSD. I will remove the '%os' stuff in this test before committing.

lib/ubsan/ubsan_diag.cc

 
 using namespace __ubsan;
 
 static void MaybePrintStackTrace(uptr pc, uptr bp) {
   // We assume that flags are already parsed, as UBSan runtime
   // will definitely be called when we print the first diagnostics message.
   if (!flags()->print_stacktrace)
     return;
-  // We can only use slow unwind, as we don't have any information about stack
-  // top/bottom.
-  // FIXME: It's better to respect "fast_unwind_on_fatal" runtime flag and
-  // fetch stack top/bottom information if we have it (e.g. if we're running
-  // under ASan).
-  if (StackTrace::WillUseFastUnwind(false))
-    return;
+
+  uptr top = 0;
+  uptr bottom = 0;
+  const bool request_fast_unwind = false;
+  if (StackTrace::WillUseFastUnwind(request_fast_unwind))
+    __sanitizer::GetThreadStackTopAndBottom(false, &top, &bottom);
+
   BufferedStackTrace stack;
-  stack.Unwind(kStackTraceMax, pc, bp, 0, 0, 0, false);
+  stack.Unwind(kStackTraceMax, pc, bp, nullptr, top, bottom,
+               request_fast_unwind);
   stack.Print();
 }
 
 static const char *ConvertTypeToString(ErrorType Type) {
   switch (Type) {
 #define UBSAN_CHECK(Name, SummaryKind, FSanitizeFlagName)                      \
   case ErrorType::Name:                                                        \
     return SummaryKind;

test/ubsan/TestCases/Misc/missing_return.cpp

 // RUN: %clangxx -fsanitize=return -g %s -O3 -o %t
 // RUN: not %run %t 2>&1 | FileCheck %s
 // RUN: %env_ubsan_opts=print_stacktrace=1 not %run %t 2>&1 | FileCheck %s --check-prefix=CHECK --check-prefix=CHECK-%os-STACKTRACE
 
 // CHECK: missing_return.cpp:[[@LINE+1]]:5: runtime error: execution reached the end of a value-returning function without returning a value
 int f() {
-// Slow stack unwinding is not available on Darwin for now, see
-// https://code.google.com/p/address-sanitizer/issues/detail?id=137
-// CHECK-Linux-STACKTRACE: #0 {{.*}}f(){{.*}}missing_return.cpp:[[@LINE-3]]
-// CHECK-FreeBSD-STACKTRACE: #0 {{.*}}f(void){{.*}}missing_return.cpp:[[@LINE-4]]
+// CHECK-Linux-STACKTRACE: #0 {{.*}}f(){{.*}}missing_return.cpp:[[@LINE-1]]
+// CHECK-FreeBSD-STACKTRACE: #0 {{.*}}f(void){{.*}}missing_return.cpp:[[@LINE-2]]
+// CHECK-Darwin-STACKTRACE: #0 {{.*}}f(){{.*}}missing_return.cpp:[[@LINE-3]]
 }
 
 int main(int, char **argv) {
   return f();
 }

test/ubsan/TestCases/TypeCheck/misaligned.cpp

int main(int, char **argv) {
 
   switch (argv[1][0]) {
   case 'l':
     // CHECK-LOAD: misaligned.cpp:[[@LINE+4]]{{(:12)?}}: runtime error: load of misaligned address [[PTR:0x[0-9a-f]*]] for type 'int', which requires 4 byte alignment
     // CHECK-LOAD-NEXT: [[PTR]]: note: pointer points here
     // CHECK-LOAD-NEXT: {{^ 00 00 00 01 02 03 04  05}}
     // CHECK-LOAD-NEXT: {{^             \^}}
     return *p && 0;
-    // Slow stack unwinding is disabled on Darwin for now, see
-    // https://code.google.com/p/address-sanitizer/issues/detail?id=137
     // CHECK-Linux-STACK-LOAD: #0 {{.*}}main{{.*}}misaligned.cpp
-    // Check for the already checked line to avoid lit error reports.
-    // CHECK-Darwin-STACK-LOAD: {{ }}
+    // CHECK-Darwin-STACK-LOAD: #0 {{.*}}main{{.*}}misaligned.cpp
 
   case 's':
     // CHECK-STORE: misaligned.cpp:[[@LINE+4]]{{(:5)?}}: runtime error: store to misaligned address [[PTR:0x[0-9a-f]*]] for type 'int', which requires 4 byte alignment
     // CHECK-STORE-NEXT: [[PTR]]: note: pointer points here
     // CHECK-STORE-NEXT: {{^ 00 00 00 01 02 03 04  05}}
     // CHECK-STORE-NEXT: {{^             \^}}
     *p = 1;
     break;