bionic: Refactor __get_elf_note()
Factor out generic __get_elf_note() logic and rename __get_elf_note() to
__find_elf_note(). Expose __get_elf_note() in libc/private/bionic_note.h
This will be used in the subsequent patch to test the presence of
NT_ANDROID_TYPE_PAD_SEGMENT note when loading segments.
Test: atest -c linker-unit-tests [Later patch]
Test: m && launch_cvd
Bug: 316403210
Change-Id: Ia7cb2f40b10cfaef402182a675087c8422b37e4d
Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
diff --git a/libc/bionic/elf_note.cpp b/libc/bionic/elf_note.cpp
new file mode 100644
index 0000000..d5cd5de
--- /dev/null
+++ b/libc/bionic/elf_note.cpp
@@ -0,0 +1,83 @@
+/*
+ * Copyright (C) 2024 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * * Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in
+ * the documentation and/or other materials provided with the
+ * distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include "platform/bionic/macros.h"
+#include "private/elf_note.h"
+
+#include <string.h>
+
+bool __get_elf_note(unsigned note_type, const char* note_name, const ElfW(Addr) note_addr,
+ const ElfW(Phdr)* phdr_note, const ElfW(Nhdr)** note_hdr,
+ const char** note_desc) {
+ if (phdr_note->p_type != PT_NOTE || !note_name || !note_addr) {
+ return false;
+ }
+
+ ElfW(Addr) p = note_addr;
+ ElfW(Addr) note_end = p + phdr_note->p_memsz;
+
+ while (p + sizeof(ElfW(Nhdr)) <= note_end) {
+ const ElfW(Nhdr)* note = reinterpret_cast<const ElfW(Nhdr)*>(p);
+ p += sizeof(ElfW(Nhdr));
+ const char* name = reinterpret_cast<const char*>(p);
+ p += align_up(note->n_namesz, 4);
+ const char* desc = reinterpret_cast<const char*>(p);
+ p += align_up(note->n_descsz, 4);
+ if (p > note_end) {
+ break;
+ }
+ if (note->n_type != note_type) {
+ continue;
+ }
+ size_t note_name_len = strlen(note_name) + 1;
+ if (note->n_namesz != note_name_len || strncmp(note_name, name, note_name_len) != 0) {
+ break;
+ }
+
+ *note_hdr = note;
+ *note_desc = desc;
+
+ return true;
+ }
+ return false;
+}
+
+bool __find_elf_note(unsigned int note_type, const char* note_name, const ElfW(Phdr)* phdr_start,
+ size_t phdr_ct, const ElfW(Nhdr)** note_hdr, const char** note_desc,
+ const ElfW(Addr) load_bias) {
+ for (size_t i = 0; i < phdr_ct; ++i) {
+ const ElfW(Phdr)* phdr = &phdr_start[i];
+
+ ElfW(Addr) note_addr = load_bias + phdr->p_vaddr;
+ if (__get_elf_note(note_type, note_name, note_addr, phdr, note_hdr, note_desc)) {
+ return true;
+ }
+ }
+
+ return false;
+}