[MemProf] Add interface for reseting the profile file descriptor

[teresajohnson]

Add __memprof_profile_reset() interface which can be used to facilitate
dumping multiple rounds of profiles from a single binary run. This
closes the current file descriptor and resets the internal file
descriptor to invalid (-1), which ensures the underlying writer reopens
the recorded profile filename. This can be used once the client is done
moving or copying a dumped profile, to prepare for reinvoking profile
dumping.

[llvmbot]

@llvm/pr-subscribers-pgo

Author: Teresa Johnson (teresajohnson)

Changes

Add __memprof_profile_reset() interface which can be used to facilitate
dumping multiple rounds of profiles from a single binary run. This
closes the current file descriptor and resets the internal file
descriptor to invalid (-1), which ensures the underlying writer reopens
the recorded profile filename. This can be used once the client is done
moving or copying a dumped profile, to prepare for reinvoking profile
dumping.

---

Full diff: https://github.com/llvm/llvm-project/pull/73714.diff

4 Files Affected:

• (modified) compiler-rt/include/sanitizer/memprof_interface.h (+6)
• (modified) compiler-rt/lib/memprof/memprof_allocator.cpp (+8)
• (modified) compiler-rt/lib/memprof/memprof_interface_internal.h (+1)
• (added) compiler-rt/test/memprof/TestCases/profile_reset.cpp (+39)

diff --git a/compiler-rt/include/sanitizer/memprof_interface.h b/compiler-rt/include/sanitizer/memprof_interface.h
index fe0a2fc5ef025bf..4660a7818c92b3c 100644
--- a/compiler-rt/include/sanitizer/memprof_interface.h
+++ b/compiler-rt/include/sanitizer/memprof_interface.h
@@ -59,6 +59,12 @@ const char *SANITIZER_CDECL __memprof_default_options(void);
 /// \returns 0 on success.
 int SANITIZER_CDECL __memprof_profile_dump(void);
 
+/// Closes the existing file descriptor, if it is valid and not stdout or
+/// stderr, and resets the internal state such that the profile filename is
+/// reopened on the next profile dump attempt. This can be used to enable
+/// multiple rounds of profiling on the same binary.
+void SANITIZER_CDECL __memprof_profile_reset(void);
+
 #ifdef __cplusplus
 } // extern "C"
 #endif
diff --git a/compiler-rt/lib/memprof/memprof_allocator.cpp b/compiler-rt/lib/memprof/memprof_allocator.cpp
index efdfa5ad04a6917..12890fae101c3e7 100644
--- a/compiler-rt/lib/memprof/memprof_allocator.cpp
+++ b/compiler-rt/lib/memprof/memprof_allocator.cpp
@@ -738,3 +738,11 @@ int __memprof_profile_dump() {
   // detected during the dumping process.
   return 0;
 }
+
+void __memprof_profile_reset() {
+  if (report_file.fd != kInvalidFd && report_file.fd != kStdoutFd &&
+      report_file.fd != kStderrFd) {
+    CloseFile(report_file.fd);
+    report_file.fd = kInvalidFd;
+  }
+}
diff --git a/compiler-rt/lib/memprof/memprof_interface_internal.h b/compiler-rt/lib/memprof/memprof_interface_internal.h
index 0aca4afc9afa9b7..318bc410440562f 100644
--- a/compiler-rt/lib/memprof/memprof_interface_internal.h
+++ b/compiler-rt/lib/memprof/memprof_interface_internal.h
@@ -49,6 +49,7 @@ extern uptr __memprof_shadow_memory_dynamic_address;
 SANITIZER_INTERFACE_ATTRIBUTE SANITIZER_WEAK_ATTRIBUTE extern char
     __memprof_profile_filename[1];
 SANITIZER_INTERFACE_ATTRIBUTE int __memprof_profile_dump();
+SANITIZER_INTERFACE_ATTRIBUTE void __memprof_profile_reset();
 
 SANITIZER_INTERFACE_ATTRIBUTE void __memprof_load(uptr p);
 SANITIZER_INTERFACE_ATTRIBUTE void __memprof_store(uptr p);
diff --git a/compiler-rt/test/memprof/TestCases/profile_reset.cpp b/compiler-rt/test/memprof/TestCases/profile_reset.cpp
new file mode 100644
index 000000000000000..0130722eb2cf624
--- /dev/null
+++ b/compiler-rt/test/memprof/TestCases/profile_reset.cpp
@@ -0,0 +1,39 @@
+// Test to ensure that multiple rounds of dumping, using the
+// __memprof_profile_reset interface to close the initial file
+// and cause the profile to be reopened, works as expected.
+
+// RUN: %clangxx_memprof  %s -o %t
+
+// RUN: rm -f %t.log.*
+// RUN: %env_memprof_opts=print_text=true:log_path=%t.log %run %t
+
+// Check both outputs, starting with the renamed initial dump, then remove it so
+// that the second glob matches a single file.
+// RUN: FileCheck %s --dump-input=always < %t.log.*.sv
+// RUN: rm -f %t.log.*.sv
+// RUN: FileCheck %s --dump-input=always < %t.log.*
+// CHECK: Memory allocation stack id
+
+#include <sanitizer/memprof_interface.h>
+#include <stdio.h>
+
+#include <stdlib.h>
+#include <string.h>
+#include <string>
+int main(int argc, char **argv) {
+  char *x = (char *)malloc(10);
+  memset(x, 0, 10);
+  free(x);
+  __memprof_profile_dump();
+  // Save the initial dump in a different file.
+  std::string origname = __sanitizer_get_report_path();
+  std::string svname = origname + ".sv";
+  rename(origname.c_str(), svname.c_str());
+  // This should cause the current file descriptor to be closed and the
+  // the internal state reset so that the profile filename is reopened
+  // on the next write.
+  __memprof_profile_reset();
+  // This will dump to origname again.
+  __memprof_profile_dump();
+  return 0;
+}

[snehasish]

lgtm

[snehasish]

Is the dump-input left over from debugging? The default is on fail which seems fine.

[teresajohnson]

Looks like this came in when I copied from another test, where it is presumably leftover debugging. I removed from here.

[snehasish]

Can you add a comment why we need to set this to kInvalidFd?

[teresajohnson]

Done