[PATCH] D84262: Avoid failing a CHECK in `DlAddrSymbolizer::SymbolizePC`.

[Dan Liew via Phabricator via llvm-commits]

delcypher updated this revision to Diff 279611.
delcypher added a comment.

Fix failing test due to LSan.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D84262/new/

https://reviews.llvm.org/D84262

Files:
  compiler-rt/lib/sanitizer_common/sanitizer_symbolizer_mac.cpp
  compiler-rt/test/asan/TestCases/Darwin/symbolizer-function-offset-dladdr.cpp


Index: compiler-rt/test/asan/TestCases/Darwin/symbolizer-function-offset-dladdr.cpp
===================================================================
--- /dev/null
+++ compiler-rt/test/asan/TestCases/Darwin/symbolizer-function-offset-dladdr.cpp
@@ -0,0 +1,44 @@
+// FIXME(dliew): Duplicated from `test/sanitizer_common/TestCases/Darwin/symbolizer-function-offset-dladdr.cpp`.
+// This case can be dropped once sanitizer_common tests work on iOS devices (rdar://problem/47333049).
+
+// NOTE: `detect_leaks=0` is necessary because with LSan enabled the dladdr
+// symbolizer actually leaks memory because the call to
+// `__sanitizer::DemangleCXXABI` leaks memory which LSan detects
+// (rdar://problem/42868950).
+
+// RUN: %clangxx_asan %s -O0 -o %t
+// RUN: %env_asan_opts=detect_leaks=0,verbosity=2,external_symbolizer_path=,stack_trace_format='"function_name_%f___function_offset_%q"' %run %t > %t.output 2>&1
+// RUN: FileCheck -input-file=%t.output %s
+#include <sanitizer/common_interface_defs.h>
+#include <stdio.h>
+
+void baz() {
+  printf("Do stuff in baz\n");
+  __sanitizer_print_stack_trace();
+}
+
+void bar() {
+  printf("Do stuff in bar\n");
+  baz();
+}
+
+void foo() {
+  printf("Do stuff in foo\n");
+  bar();
+}
+
+int main() {
+  printf("Do stuff in main\n");
+  foo();
+  return 0;
+}
+
+// CHECK: External symbolizer is explicitly disabled
+// CHECK: Using dladdr symbolizer
+
+// These `function_offset` patterns are designed to disallow `0x0` which is the
+// value printed for `kUnknown`.
+// CHECK: function_name_baz{{(\(\))?}}___function_offset_0x{{0*[1-9a-f][0-9a-f]*$}}
+// CHECK: function_name_bar{{(\(\))?}}___function_offset_0x{{0*[1-9a-f][0-9a-f]*$}}
+// CHECK: function_name_foo{{(\(\))?}}___function_offset_0x{{0*[1-9a-f][0-9a-f]*$}}
+// CHECK: function_name_main{{(\(\))?}}___function_offset_0x{{0*[1-9a-f][0-9a-f]*$}}
Index: compiler-rt/lib/sanitizer_common/sanitizer_symbolizer_mac.cpp
===================================================================
--- compiler-rt/lib/sanitizer_common/sanitizer_symbolizer_mac.cpp
+++ compiler-rt/lib/sanitizer_common/sanitizer_symbolizer_mac.cpp
@@ -33,8 +33,15 @@
   int result = dladdr((const void *)addr, &info);
   if (!result) return false;
 
-  CHECK(addr >= reinterpret_cast<uptr>(info.dli_saddr));
-  stack->info.function_offset = addr - reinterpret_cast<uptr>(info.dli_saddr);
+  // Compute offset if possible. `dladdr()` doesn't always ensure that `addr >=
+  // sym_addr` so only compute the offset when this holds. Failure to find the
+  // function offset is not treated as a failure because it might still be
+  // possible to get the symbol name.
+  uptr sym_addr = reinterpret_cast<uptr>(info.dli_saddr);
+  if (addr >= sym_addr) {
+    stack->info.function_offset = addr - sym_addr;
+  }
+
   const char *demangled = DemangleSwiftAndCXX(info.dli_sname);
   if (!demangled) return false;
   stack->info.function = internal_strdup(demangled);
@@ -219,10 +226,10 @@
       start_address = reinterpret_cast<uptr>(info.dli_saddr);
   }
 
-  // Only assig to `function_offset` if we were able to get the function's
-  // start address.
-  if (start_address != AddressInfo::kUnknown) {
-    CHECK(addr >= start_address);
+  // Only assign to `function_offset` if we were able to get the function's
+  // start address and we got a sensible `start_address` (dladdr doesn't always
+  // ensure that `addr >= sym_addr`).
+  if (start_address != AddressInfo::kUnknown && addr >= start_address) {
     stack->info.function_offset = addr - start_address;
   }
   return true;


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