commit 965eb33c5e86
Author: Greg V <greg@unrelenting.technology>
Date:   Wed Jan 8 15:06:00 2020 -0800

    Bug 1550891 - re-add SHM_ANON support in IPC shared memory, freezing via capabilities
---
 config/system-headers.mozbuild               |  1 +
 ipc/chromium/src/base/shared_memory_posix.cc | 20 +++++++++++++++++---
 2 files changed, 18 insertions(+), 3 deletions(-)

diff --git config/system-headers.mozbuild config/system-headers.mozbuild
index 88afca1070f86..beff3e2542c9f 100644
--- config/system-headers.mozbuild
+++ config/system-headers.mozbuild
@@ -816,6 +816,7 @@ system_headers = [
     'sys/bitypes.h',
     'sys/byteorder.h',
     'syscall.h',
+    'sys/capsicum.h',
     'sys/cdefs.h',
     'sys/cfgodm.h',
     'sys/elf.h',
diff --git ipc/chromium/src/base/shared_memory_posix.cc ipc/chromium/src/base/shared_memory_posix.cc
index 0be9cce0b4bed..89e67483e4c16 100644
--- ipc/chromium/src/base/shared_memory_posix.cc
+++ ipc/chromium/src/base/shared_memory_posix.cc
@@ -16,6 +16,10 @@
 #  include "mozilla/Ashmem.h"
 #endif
 
+#ifdef __FreeBSD__
+#  include <sys/capsicum.h>
+#endif
+
 #include "base/eintr_wrapper.h"
 #include "base/logging.h"
 #include "base/string_util.h"
@@ -77,7 +81,7 @@ SharedMemoryHandle SharedMemory::NULLHandle() { return SharedMemoryHandle(); }
 
 // static
 bool SharedMemory::AppendPosixShmPrefix(std::string* str, pid_t pid) {
-#if defined(ANDROID)
+#if defined(ANDROID) || defined(__FreeBSD__)
   return false;
 #else
   *str += '/';
@@ -103,7 +107,7 @@ bool SharedMemory::AppendPosixShmPrefix(std::string* str, pid_t pid) {
   // enough for this.
   StringAppendF(str, "org.mozilla.ipc.%d.", static_cast<int>(pid));
   return true;
-#endif    // !ANDROID
+#endif    // !ANDROID && !__FreeBSD__
 }
 
 bool SharedMemory::CreateInternal(size_t size, bool freezeable) {
@@ -125,6 +129,9 @@ bool SharedMemory::CreateInternal(size_t size, bool freezeable) {
     return false;
   }
   needs_truncate = false;
+#elif defined(__FreeBSD__)
+  // FreeBSD supports anonymous shm_open
+  fd.reset(shm_open(SHM_ANON, O_RDWR, 0600));
 #else
   // Generic Unix: shm_open + shm_unlink
   do {
@@ -224,6 +231,14 @@ bool SharedMemory::ReadOnlyCopy(SharedMemory* ro_out) {
     return false;
   }
   ro_file = mapped_file_;
+#elif defined(__FreeBSD__)
+  cap_rights_t rights;
+  cap_rights_init(&rights, CAP_MMAP_R);
+  if (cap_rights_limit(mapped_file_, &rights) != 0) {
+    CHROMIUM_LOG(WARNING) << "failed to freeze shm: " << strerror(errno);
+    return false;
+  }
+  ro_file = mapped_file_;
 #else
   DCHECK(frozen_file_ >= 0);
   DCHECK(mapped_file_ >= 0);