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Merge "[MTE] Relax ELF note." am: 24f9dab407

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Original change: https://android-review.googlesource.com/c/platform/bionic/+/1975286

Change-Id: I6389991190299c73b026685f6f189f7d27c3aeeb
This commit is contained in:
Treehugger Robot 2022-02-09 00:00:31 +00:00 committed by Automerger Merge Worker
commit 3354e0287a
3 changed files with 33 additions and 14 deletions
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37
libc/bionic/libc_init_static.cpp
View file

@ -191,14 +191,17 @@ bool get_config_from_env_or_sysprops(const char* env_var_name, const char* const
#ifdef __aarch64__
static bool __read_memtag_note(const ElfW(Nhdr)* note, const char* name, const char* desc,
unsigned* result) {
if (note->n_namesz != 8 || strncmp(name, "Android", 8) != 0) {
return false;
}
if (note->n_type != NT_ANDROID_TYPE_MEMTAG) {
return false;
}
if (note->n_descsz != 4) {
async_safe_fatal("unrecognized android.memtag note: n_descsz = %d, expected 4", note->n_descsz);
if (note->n_namesz != 8 || strncmp(name, "Android", 8) != 0) {
return false;
}
// Previously (in Android 12), if the note was != 4 bytes, we check-failed
// here. Let's be more permissive to allow future expansion.
if (note->n_descsz < 4) {
async_safe_fatal("unrecognized android.memtag note: n_descsz = %d, expected >= 4",
note->n_descsz);
}
*result = *reinterpret_cast<const ElfW(Word)*>(desc);
return true;
@ -285,21 +288,29 @@ static HeapTaggingLevel __get_heap_tagging_level(const void* phdr_start, size_t
unsigned note_val =
__get_memtag_note(reinterpret_cast<const ElfW(Phdr)*>(phdr_start), phdr_ct, load_bias);
if (note_val & ~(NT_MEMTAG_LEVEL_MASK | NT_MEMTAG_HEAP)) {
async_safe_fatal("unrecognized android.memtag note: desc = %d", note_val);
}
// Note, previously (in Android 12), any value outside of bits [0..3] resulted
// in a check-fail. In order to be permissive of further extensions, we
// relaxed this restriction. For now, we still only support MTE heap.
if (!(note_val & NT_MEMTAG_HEAP)) return M_HEAP_TAGGING_LEVEL_TBI;
unsigned memtag_level = note_val & NT_MEMTAG_LEVEL_MASK;
switch (memtag_level) {
unsigned mode = note_val & NT_MEMTAG_LEVEL_MASK;
switch (mode) {
case NT_MEMTAG_LEVEL_NONE:
// Note, previously (in Android 12), NT_MEMTAG_LEVEL_NONE was
// NT_MEMTAG_LEVEL_DEFAULT, which implied SYNC mode. This was never used
// by anyone, but we note it (heh) here for posterity, in case the zero
// level becomes meaningful, and binaries with this note can be executed
// on Android 12 devices.
return M_HEAP_TAGGING_LEVEL_TBI;
case NT_MEMTAG_LEVEL_ASYNC:
return M_HEAP_TAGGING_LEVEL_ASYNC;
case NT_MEMTAG_LEVEL_DEFAULT:
case NT_MEMTAG_LEVEL_SYNC:
return M_HEAP_TAGGING_LEVEL_SYNC;
default:
async_safe_fatal("unrecognized android.memtag note: level = %d", memtag_level);
// We allow future extensions to specify mode 3 (currently unused), with
// the idea that it might be used for ASYMM mode or something else. On
// this version of Android, it falls back to SYNC mode.
return M_HEAP_TAGGING_LEVEL_SYNC;
}
}

2
libc/private/bionic_asm_arm64.h
View file

@ -72,7 +72,7 @@
.popsection;
#define NT_MEMTAG_LEVEL_MASK 3
#define NT_MEMTAG_LEVEL_DEFAULT 0
#define NT_MEMTAG_LEVEL_NONE 0
#define NT_MEMTAG_LEVEL_ASYNC 1
#define NT_MEMTAG_LEVEL_SYNC 2
#define NT_MEMTAG_HEAP 4

8
tests/Android.bp
View file

@ -1122,6 +1122,14 @@ cc_test {
lto: {
never: true,
},
data_bins: [
"heap_tagging_async_helper",
"heap_tagging_disabled_helper",
"heap_tagging_static_async_helper",
"heap_tagging_static_disabled_helper",
"heap_tagging_static_sync_helper",
"heap_tagging_sync_helper",
],
}
// -----------------------------------------------------------------------------