tor-browser

commit 9451691a420734a97d19391aca8eb345efb375a8
parent 4f27637b168c1fb8b5acb097535891359e13f93d
Author: Paul Bone <paul@bone.id.au>
Date:   Wed, 26 Nov 2025 02:46:46 +0000

Bug 1969856 - Limit PHC to 128MB of virtual address space r=gsvelto

Differential Revision: https://phabricator.services.mozilla.com/D273369

Diffstat:
M
memory/build/PHC.cpp
 | 
14
+++++++++++---
M
memory/build/test/gtest/TestPHC.cpp
 | 
6
+++++-

2 files changed, 16 insertions(+), 4 deletions(-)
diff --git a/memory/build/PHC.cpp b/memory/build/PHC.cpp
@@ -365,10 +365,18 @@ static_assert((kPhcAlign % kPageSize) == 0);
 
 // PHC will reserve some address space this large, then depending on runtime
 // configuration will use a smaller fraction of it.  Making
-// kPhcVirtualReservation the upper-bound of PHC's memory size.  On 32bit
-// systems with less available address space we choose a more moderate value.
+// kPhcVirtualReservation the upper-bound of PHC's memory size.
+//  * On 32bit systems with less available address space we choose a more
+//    moderate value.
+//  * On 64bit systems we set the limit to so that there are no more than 32,768
+//    mappings, half of Linux's default limit (Bug 1969856).  For 4KB pages
+//    that's 128MB.
 #ifdef HAVE_64BIT_BUILD
-static const size_t kPhcVirtualReservation = 1024 * 1024 * 1024;
+#  if defined(XP_DARWIN) && defined(__aarch64__)
+static const size_t kPhcVirtualReservation = 512 * 1024 * 1024;
+#  else
+static const size_t kPhcVirtualReservation = 128 * 1024 * 1024;
+#  endif
 #else
 static const size_t kPhcVirtualReservation = 2 * 1024 * 1024;
 #endif
diff --git a/memory/build/test/gtest/TestPHC.cpp b/memory/build/test/gtest/TestPHC.cpp
@@ -503,7 +503,11 @@ TEST(PHC, TestPHCLimit)
   // (see kPhcVirtualReservation)
   size_t limit =
 #ifdef HAVE_64BIT_BUILD
-      1024 * 1024 * 1024;
+#  if defined(XP_DARWIN) && defined(__aarch64__)
+      512 * 1024 * 1024;
+#  else
+      128 * 1024 * 1024;
+#  endif
 #else
       2 * 1024 * 1024;
 #endif