allow for heapprofd's signal to be multiplexed

This patch refactors heapprofd_malloc to make it easier to reuse the
reserved signal for multiple purposes. We define a new generic signal
handler for profilers, which dispatches to more specific logic based on
the signal's payload (si_value).

The profiler signal handler is installed during libc preinit, after
malloc initialization (so races against synchronous heapprofd
initialization need not be considered). In terms of code organization, I
copied the existing approach with a loosely referenced function in
bionic_globals.h. Do tell if you'd rather a different approach here.

The profileability of a process is quite tied to the malloc
files/interfaces in bionic - in particular, it's set through
android_mallopt. I do not change that, but instead introduce a new
android_mallopt option to be able to query profileability of the
process (which is now used by the new profiler signal handler). As part
of that, gZygoteChildProfileable is moved from heapprofd_malloc to
common (alongside gZygoteChild).

I've removed the masking and reraising of the heapprofd signal when
racing against malloc_limit init. We're ok with taking a simpler
approach and dropping the heapprofd signal in such an unlikely race.

Note: this requires a corresponding change in heapprofd to use sigqueue()
instead of kill(), as the latter leaves the si_value uninitialized(?) on
the receiving side.

Bug: 144281346
Change-Id: I93bb2e82cff5870e5ca499cf86439860aca9dfa5

1 files changed, 7 insertions, 2 deletions

diff --git a/tests/malloc_test.cpp b/tests/malloc_test.cpp
index ebbd24793..c7050dc68 100644
--- a/tests/malloc_test.cpp
+++ b/tests/malloc_test.cpp
@@ -18,14 +18,15 @@
 
 #include <elf.h>
 #include <limits.h>
+#include <malloc.h>
 #include <pthread.h>
+#include <signal.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/types.h>
 #include <sys/wait.h>
-#include <malloc.h>
 #include <unistd.h>
 
 #include <atomic>
@@ -962,7 +963,11 @@ static void SetAllocationLimitMultipleThreads() {
 
   // Let them go all at once.
   go = true;
-  ASSERT_EQ(0, kill(getpid(), __SIGRTMIN + 4));
+  // Send hardcoded signal (BIONIC_SIGNAL_PROFILER with value 0) to trigger
+  // heapprofd handler.
+  union sigval signal_value;
+  signal_value.sival_int = 0;
+  ASSERT_EQ(0, sigqueue(getpid(), __SIGRTMIN + 4, signal_value));
 
   size_t num_successful = 0;
   for (size_t i = 0; i < kNumThreads; i++) {