allocator: Deprecate use of base::ProtectedMemory

base::ProtectedMemory is being deprecated because it's not widely used
enough to make a security impact and justify its maintenance burden.
Replace use of base::ProtectedMemory with raw function pointers and add
an attribute to disable CFI-icall checking.

Bug: 1018834
Change-Id: Id6d956b02758aecaa0710aee56715429f5ffc267
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1884819
Commit-Queue: Primiano Tucci <primiano@chromium.org>
Auto-Submit: Vlad Tsyrklevich <vtsyrklevich@chromium.org>
Reviewed-by: Primiano Tucci <primiano@chromium.org>
Cr-Commit-Position: refs/heads/master@{#711201}

base/allocator/allocator_shim_default_dispatch_to_glibc.cc

@@ -3,7 +3,7 @@
 // found in the LICENSE file.
 
 #include "base/allocator/allocator_shim.h"
-#include "base/memory/protected_memory_cfi.h"
+#include "base/compiler_specific.h"
 
 #include <dlfcn.h>
 #include <malloc.h>
@@ -23,10 +23,6 @@ void __libc_free(void* ptr);
 namespace {
 
 using base::allocator::AllocatorDispatch;
-using MallocUsableSizeFunction = decltype(malloc_usable_size)*;
-
-PROTECTED_MEMORY_SECTION base::ProtectedMemory<MallocUsableSizeFunction>
-    g_MallocUsableSizeFunction;
 
 void* GlibcMalloc(const AllocatorDispatch*, size_t size, void* context) {
   return __libc_malloc(size);
@@ -57,6 +53,7 @@ void GlibcFree(const AllocatorDispatch*, void* address, void* context) {
   __libc_free(address);
 }
 
+NO_SANITIZE("cfi-icall")
 size_t GlibcGetSizeEstimate(const AllocatorDispatch*,
                             void* address,
                             void* context) {
@@ -64,11 +61,12 @@ size_t GlibcGetSizeEstimate(const AllocatorDispatch*,
   // resolve it instead. This should be safe because glibc (and hence dlfcn)
   // does not use malloc_size internally and so there should not be a risk of
   // recursion.
-  static base::ProtectedMemory<MallocUsableSizeFunction>::Initializer init(
-      &g_MallocUsableSizeFunction, reinterpret_cast<MallocUsableSizeFunction>(
-                                       dlsym(RTLD_NEXT, "malloc_usable_size")));
+  using MallocUsableSizeFunction = decltype(malloc_usable_size)*;
+  static MallocUsableSizeFunction fn_ptr =
+      reinterpret_cast<MallocUsableSizeFunction>(
+          dlsym(RTLD_NEXT, "malloc_usable_size"));
 
-  return base::UnsanitizedCfiCall(g_MallocUsableSizeFunction)(address);
+  return fn_ptr(address);
 }
 
 }  // namespace