debuggerd_handler: increase thread stack size.

1 page isn't enough to log on AArch64, and clean pages are free, so
increase the stack size to 8 pages.

Bug: http://b/144887737
Test: treehugger
Change-Id: I731b3bc27ab37f4b830a9478a04cd34d4f7648d3

1 files changed, 5 insertions, 4 deletions

diff --git a/debuggerd/handler/debuggerd_handler.cpp b/debuggerd/handler/debuggerd_handler.cpp
index 6e0128993..f8192b52d 100644
--- a/debuggerd/handler/debuggerd_handler.cpp
+++ b/debuggerd/handler/debuggerd_handler.cpp
@@ -592,19 +592,20 @@ void debuggerd_init(debuggerd_callbacks_t* callbacks) {
     g_callbacks = *callbacks;
   }
 
-  void* thread_stack_allocation =
-    mmap(nullptr, PAGE_SIZE * 3, PROT_NONE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+  size_t thread_stack_pages = 8;
+  void* thread_stack_allocation = mmap(nullptr, PAGE_SIZE * (thread_stack_pages + 2), PROT_NONE,
+                                       MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
   if (thread_stack_allocation == MAP_FAILED) {
     fatal_errno("failed to allocate debuggerd thread stack");
   }
 
   char* stack = static_cast<char*>(thread_stack_allocation) + PAGE_SIZE;
-  if (mprotect(stack, PAGE_SIZE, PROT_READ | PROT_WRITE) != 0) {
+  if (mprotect(stack, PAGE_SIZE * thread_stack_pages, PROT_READ | PROT_WRITE) != 0) {
     fatal_errno("failed to mprotect debuggerd thread stack");
   }
 
   // Stack grows negatively, set it to the last byte in the page...
-  stack = (stack + PAGE_SIZE - 1);
+  stack = (stack + thread_stack_pages * PAGE_SIZE - 1);
   // and align it.
   stack -= 15;
   pseudothread_stack = stack;