[PATCH] D65245: [profile] In Android, do not mkdir() dirs in GCOV_PREFIX

[Pirama Arumuga Nainar via Phabricator via llvm-commits]

pirama created this revision.
pirama added reviewers: srhines, davidxl.
Herald added subscribers: Sanitizers, krytarowski.
Herald added projects: Sanitizers, LLVM.

In Android, attempting to mkdir() or even stat() top-level directories
like /data causes noisy selinux denials.  During whole-system coverage
instrumentation, this causes a deluge of noisy messages that drown out
legitimate selinux denials, that should be audited and fixed.

To avoid this, skip creating any directory in GCOV_PREFIX (thereby
assuming that it exists).

- Android platform ensures that the GCOV_PREFIX used in Android is

created and read/writable by all processes.

- This only affects the Android platform (by checking against

__ANDROID_API_FUTURE__) and for apps built with Clang coverage, the
runtime will still create any non-existent parent directories for the
coverage files.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D65245

Files:
  compiler-rt/lib/profile/InstrProfilingUtil.c


Index: compiler-rt/lib/profile/InstrProfilingUtil.c
===================================================================
--- compiler-rt/lib/profile/InstrProfilingUtil.c
+++ compiler-rt/lib/profile/InstrProfilingUtil.c
@@ -44,6 +44,17 @@
     char save = path[i];
     if (!IS_DIR_SEPARATOR(path[i]))
       continue;
+
+#if defined(__ANDROID__) && defined(__ANDROID_API__) && \
+    defined(__ANDROID_API_FUTURE__) && __ANDROID_API__==__ANDROID_API_FUTURE__
+    // Avoid spammy selinux denial messages in Android by not attempting to
+    // create directories in GCOV_PREFIX.  These denials occur when creating (or
+    // even attempting to stat()) top-level directories like "/data".
+    const char *gcov_prefix = getenv("GCOV_PREFIX");
+    if (gcov_prefix != NULL && strncmp(path, gcov_prefix, i) == 0)
+      continue;
+#endif
+
     path[i] = '\0';
 #ifdef _WIN32
     _mkdir(path);


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