commit 7b13dd918e6e2c1638e6b137f27c80979a4ecd3f
author Peter Collingbourne <pcc@google.com> Mon Oct 29 21:48:38 2018 +0000
committer Peter Collingbourne <pcc@google.com> Mon Oct 29 21:48:59 2018 +0000
tree b7f8343a6fc3767bd968b68ba8b6be74466d027a
parent da1bc79f937225b1a048d9e5a03eca81680a17fd

Revert "bionic: Allocate a shadow call stack for each thread."

This reverts commit da1bc79f937225b1a048d9e5a03eca81680a17fd.

Reason for revert: Caused OOM in media process

Bug: 112907825
Bug: 118593766
Change-Id: I545663871d75889b209b9fd2131cdaa97166478f

libc/bionic/pthread_create.cpp

diff --git a/libc/bionic/pthread_create.cpp b/libc/bionic/pthread_create.cpp
index 3ba787b..543fdc5 100644
--- a/libc/bionic/pthread_create.cpp
+++ b/libc/bionic/pthread_create.cpp
@@ -32,7 +32,6 @@
 #include <string.h>
 #include <sys/mman.h>
 #include <sys/prctl.h>
-#include <sys/random.h>
 #include <unistd.h>
 
 #include "pthread_internal.h"
@@ -87,7 +86,7 @@
   thread->tls[TLS_SLOT_STACK_GUARD] = reinterpret_cast<void*>(__stack_chk_guard);
 }
 
-static void __init_alternate_signal_stack(pthread_internal_t* thread) {
+void __init_alternate_signal_stack(pthread_internal_t* thread) {
   // Create and set an alternate signal stack.
   void* stack_base = mmap(nullptr, SIGNAL_STACK_SIZE, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
   if (stack_base != MAP_FAILED) {
@@ -110,32 +109,6 @@
   }
 }
 
-static void __init_shadow_call_stack(pthread_internal_t* thread) {
-  (void)thread;
-#ifdef __aarch64__
-  char* scs_guard_region = reinterpret_cast<char*>(
-      mmap(nullptr, SCS_GUARD_REGION_SIZE, 0, MAP_PRIVATE | MAP_ANON, -1, 0));
-  thread->shadow_call_stack_guard_region = scs_guard_region;
-
-  // We need to page align scs_offset and ensure that [scs_offset,scs_offset+SCS_SIZE) is in the
-  // guard region. We can't use arc4random_uniform in init because /dev/urandom might not have
-  // been created yet.
-  size_t scs_offset =
-      (getpid() == 1) ? 0 : (arc4random_uniform(SCS_GUARD_REGION_SIZE / SCS_SIZE) * SCS_SIZE);
-
-  // Allocate the stack and store its address in register x18. This is deliberately the only place
-  // where the address is stored.
-  __asm__ __volatile__(
-      "mov x18, %0" ::"r"(mmap(scs_guard_region + scs_offset, SCS_SIZE, PROT_READ | PROT_WRITE,
-                               MAP_PRIVATE | MAP_ANON | MAP_FIXED, -1, 0)));
-#endif
-}
-
-void __init_additional_stacks(pthread_internal_t* thread) {
-  __init_alternate_signal_stack(thread);
-  __init_shadow_call_stack(thread);
-}
-
 int __init_thread(pthread_internal_t* thread) {
   thread->cleanup_stack = nullptr;
 
@@ -279,7 +252,7 @@
   // accesses previously made by the creating thread are visible to us.
   thread->startup_handshake_lock.lock();
 
-  __init_additional_stacks(thread);
+  __init_alternate_signal_stack(thread);
 
   void* result = thread->start_routine(thread->start_routine_arg);
   pthread_exit(result);