Use DYNAMIC entries for MTE enablement
Adds support for the dynamic entries to specify MTE enablement. This is
now the preferred way for dynamically linked executables to specify to
the loader what mode MTE should be in, and whether stack MTE should be
enabled. In future, this is also needed for MTE globals support.
Leave the existing ELF note parsing as a backup option because dynamic
entries are not supported for fully static executables, and there's
still a bunch of glue sitting around in the build system and tests that
explicitly include the note. When -fsanitize=memtag* is specified, lld
will create the note implicitly (along with the new dynamic entries),
but at some point once we've cleaned up all the old references to the
note, we can remove the notegen from lld.
Bug: N/A
Test: atest bionic-unit-tests CtsBionicTestCases --test-filter=*Memtag*
Test: Build/boot the device under _fullmte.
Change-Id: I954b7e78afa5ff4274a3948b968cfad8eba94d88
diff --git a/linker/linker.cpp b/linker/linker.cpp
index 1553ba9..135eaa3 100644
--- a/linker/linker.cpp
+++ b/linker/linker.cpp
@@ -71,11 +71,12 @@
#include "linker_translate_path.h"
#include "linker_utils.h"
+#include "android-base/macros.h"
+#include "android-base/stringprintf.h"
+#include "android-base/strings.h"
+#include "private/bionic_asm_note.h"
#include "private/bionic_call_ifunc_resolver.h"
#include "private/bionic_globals.h"
-#include "android-base/macros.h"
-#include "android-base/strings.h"
-#include "android-base/stringprintf.h"
#include "ziparchive/zip_archive.h"
static std::unordered_map<void*, size_t> g_dso_handle_counters;
@@ -3194,13 +3195,32 @@
case DT_AARCH64_VARIANT_PCS:
// Ignored: AArch64 processor-specific dynamic array tags.
break;
- // TODO(mitchp): Add support to libc_init_mte to use these dynamic array entries instead of
- // the Android-specific ELF note.
case DT_AARCH64_MEMTAG_MODE:
+ memtag_dynamic_entries_.has_memtag_mode = true;
+ memtag_dynamic_entries_.memtag_mode = d->d_un.d_val;
+ break;
case DT_AARCH64_MEMTAG_HEAP:
+ memtag_dynamic_entries_.memtag_heap = d->d_un.d_val;
+ break;
+ // The AArch64 MemtagABI originally erroneously defined
+ // DT_AARCH64_MEMTAG_STACK as `d_ptr`, which is why the dynamic tag value
+ // is odd (`0x7000000c`). `d_val` is clearly the correct semantics, and so
+ // this was fixed in the ABI, but the value (0x7000000c) didn't change
+ // because we already had Android binaries floating around with dynamic
+ // entries, and didn't want to create a whole new dynamic entry and
+ // reserve a value just to fix that tiny mistake. P.S. lld was always
+ // outputting DT_AARCH64_MEMTAG_STACK as `d_val` anyway.
case DT_AARCH64_MEMTAG_STACK:
+ memtag_dynamic_entries_.memtag_stack = d->d_un.d_val;
+ break;
+ // Same as above, except DT_AARCH64_MEMTAG_GLOBALS was incorrectly defined
+ // as `d_val` (hence an even value of `0x7000000d`), when it should have
+ // been `d_ptr` all along. lld has always outputted this as `d_ptr`.
case DT_AARCH64_MEMTAG_GLOBALS:
+ memtag_dynamic_entries_.memtag_globals = reinterpret_cast<void*>(load_bias + d->d_un.d_ptr);
+ break;
case DT_AARCH64_MEMTAG_GLOBALSSZ:
+ memtag_dynamic_entries_.memtag_globalssz = d->d_un.d_val;
break;
#endif