[PATCH] D39717: Always use prctl(PR_SET_PTRACER)

[Mike Hommey via Phabricator via cfe-commits]

glandium created this revision.
Herald added a subscriber: kubamracek.

Sufficiently old Linux kernel headers don't provide the PR_SET_PTRACER, but we can still call prctl with it if the runtime kernel is newer. Even if it's not, prctl will only return EINVAL.


https://reviews.llvm.org/D39717

Files:
  lib/sanitizer_common/sanitizer_stoptheworld_linux_libcdep.cc


Index: lib/sanitizer_common/sanitizer_stoptheworld_linux_libcdep.cc
===================================================================
--- lib/sanitizer_common/sanitizer_stoptheworld_linux_libcdep.cc
+++ lib/sanitizer_common/sanitizer_stoptheworld_linux_libcdep.cc
@@ -57,6 +57,13 @@
 #include "sanitizer_mutex.h"
 #include "sanitizer_placement_new.h"
 
+// Sufficiently old kernel header don't provide this value, but we can still
+// call prctl with it if the runtime kernel is newer. Even if it's not, prctl
+// will only return EINVAL.
+#ifndef PR_SET_PTRACER
+#define PR_SET_PTRACER 0x59616d61
+#endif
+
 // This module works by spawning a Linux task which then attaches to every
 // thread in the caller process with ptrace. This suspends the threads, and
 // PTRACE_GETREGS can then be used to obtain their register state. The callback
@@ -433,9 +440,7 @@
     ScopedSetTracerPID scoped_set_tracer_pid(tracer_pid);
     // On some systems we have to explicitly declare that we want to be traced
     // by the tracer thread.
-#ifdef PR_SET_PTRACER
     internal_prctl(PR_SET_PTRACER, tracer_pid, 0, 0, 0);
-#endif
     // Allow the tracer thread to start.
     tracer_thread_argument.mutex.Unlock();
     // NOTE: errno is shared between this thread and the tracer thread.


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