[ASan] Fix the log_path option to use different log files for parent and child processes after fork().

llvm-svn: 172828

2 files changed, 47 insertions, 9 deletions

diff --git a/compiler-rt/lib/asan/lit_tests/log_path_fork_test.cc b/compiler-rt/lib/asan/lit_tests/log_path_fork_test.cc
new file mode 100644
index 00000000000..c6c1b49e994
--- /dev/null
+++ b/compiler-rt/lib/asan/lit_tests/log_path_fork_test.cc
@@ -0,0 +1,22 @@
+// RUN: %clangxx_asan  %s -o %t
+// RUN: rm -f %t.log.*
+// Set verbosity to 1 so that the log files are opened prior to fork().
+// RUN: ASAN_OPTIONS="log_path=%t.log verbosity=1" not %t 2> %t.out
+// RUN: for f in %t.log.* ; do FileCheck %s < $f; done
+// RUN: [ `ls %t.log.* | wc -l` == 2 ]
+
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+int main(int argc, char **argv) {
+  void *x = malloc(10);
+  free(x);
+  if (fork() == -1) return 1;
+  // There are two processes at this point, thus there should be two distinct
+  // error logs.
+  free(x);
+  return 0;
+}
+
+// CHECK: ERROR: AddressSanitizer
diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_common.cc b/compiler-rt/lib/sanitizer_common/sanitizer_common.cc
index 4b1ddae7237..4a8d9a749bf 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_common.cc
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_common.cc
@@ -23,10 +23,16 @@ uptr GetPageSizeCached() {
   return PageSize;
 }
 
-// By default, dump to stderr. If report_fd is kInvalidFd, try to obtain file
-// descriptor by opening file in report_path.
+static bool log_to_file = false;  // Set to true by __sanitizer_set_report_path
+
+// By default, dump to stderr. If |log_to_file| is true and |report_fd_pid|
+// isn't equal to the current PID, try to obtain file descriptor by opening
+// file "report_path_prefix.<PID>".
 static fd_t report_fd = kStderrFd;
-static char report_path[4096];  // Set via __sanitizer_set_report_path.
+static char report_path_prefix[4096];  // Set via __sanitizer_set_report_path.
+// PID of process that opened |report_fd|. If a fork() occurs, the PID of the
+// child thread will be different from |report_fd_pid|.
+static int report_fd_pid = 0;
 
 static void (*DieCallback)(void);
 void SetDieCallback(void (*callback)(void)) {
@@ -56,15 +62,23 @@ void NORETURN CheckFailed(const char *file, int line, const char *cond,
 }
 
 static void MaybeOpenReportFile() {
-  if (report_fd != kInvalidFd)
-    return;
-  fd_t fd = internal_open(report_path, true);
+  if (!log_to_file || (report_fd_pid == GetPid())) return;
+  char report_path_full[4096];
+  internal_snprintf(report_path_full, sizeof(report_path_full),
+                    "%s.%d", report_path_prefix, GetPid());
+  fd_t fd = internal_open(report_path_full, true);
   if (fd == kInvalidFd) {
     report_fd = kStderrFd;
-    Report("ERROR: Can't open file: %s\n", report_path);
+    log_to_file = false;
+    Report("ERROR: Can't open file: %s\n", report_path_full);
     Die();
   }
+  if (report_fd != kInvalidFd) {
+    // We're in the child. Close the parent's log.
+    internal_close(report_fd);
+  }
   report_fd = fd;
+  report_fd_pid = GetPid();
 }
 
 bool PrintsToTty() {
@@ -184,14 +198,16 @@ extern "C" {
 void __sanitizer_set_report_path(const char *path) {
   if (!path) return;
   uptr len = internal_strlen(path);
-  if (len > sizeof(report_path) - 100) {
+  if (len > sizeof(report_path_prefix) - 100) {
     Report("ERROR: Path is too long: %c%c%c%c%c%c%c%c...\n",
            path[0], path[1], path[2], path[3],
            path[4], path[5], path[6], path[7]);
     Die();
   }
-  internal_snprintf(report_path, sizeof(report_path), "%s.%d", path, GetPid());
+  internal_strncpy(report_path_prefix, path, sizeof(report_path_prefix));
+  report_path_prefix[len] = '\0';
   report_fd = kInvalidFd;
+  log_to_file = true;
 }
 
 void __sanitizer_set_report_fd(int fd) {