libs/libvmbase/sections.ld

/*
 * Copyright 2022 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*
 * Code will start running at this symbol which is placed at the start of the
 * image.
 */
ENTRY(entry)

/*
 * The following would be useful to check that .init code is not called back
 * into once it has completed but it isn't supported by ld.lld.
 *
 * NOCROSSREFS_TO(.init .text)
 */

SECTIONS
{
	/*
	 * Collect together the code. This is page aligned so it can be mapped
	 * as executable-only.
	 */
	.text : ALIGN(4096) {
		KEEP(*(.init.head));
		*(.init.head)
		text_begin = .;
		*(.init.entry)
		*(.init.*)
		*(.text.*)
	} >image
	text_end = .;

	/*
	 * Collect together read-only data. This is page aligned so it can be
	 * mapped as read-only and non-executable.
	 */
	.rodata : ALIGN(4096) {
		rodata_begin = .;
		*(.rodata.*)
	} >image
	.got : {
		*(.got)
	} >image
	rodata_end = .;

	.eh_stack (NOLOAD) : ALIGN(4096) {
		/*
		 * Get stack overflow guard from the previous page being from
		 * .rodata and mapped read-only or left unmapped.
		 */
		eh_stack_limit = .;
		. += 4096;
		. = ALIGN(4096);
		init_eh_stack_pointer = .;
	} >writable_data

	/*
	 * Collect together the read-write data including .bss at the end which
	 * will be zero'd by the entry code. This is page aligned so it can be
	 * mapped as non-executable.
	 */
	.data : ALIGN(4096) {
		data_begin = .;
		*(.data.*)
		/*
		 * The entry point code assumes that .data is a multiple of 32
		 * bytes long.
		 */
		. = ALIGN(32);
		data_end = .;
	} >writable_data AT>image
	data_lma = LOADADDR(.data);

	/* Everything beyond this point will not be included in the binary. */
	bin_end = data_lma + SIZEOF(.data);

	/* The entry point code assumes that .bss is 16-byte aligned. */
	.bss : ALIGN(16)  {
		bss_begin = .;
		*(.bss.*)
		*(COMMON)
		. = ALIGN(16);
		bss_end = .;
	} >writable_data

	/* Left unmapped, to catch overflows of the stack. */
	.stack_guard_page (NOLOAD) : ALIGN(4096) {
		. += 4096;
	} >writable_data

	/* Stack, mapped read-write (possibly partially). */
	.stack (NOLOAD) : ALIGN(4096) {
		stack_limit = .;
		. = ALIGN(LENGTH(writable_data));
		init_stack_pointer = .;
	} >writable_data

	/* Make our Bionic stack protector compatible with mainline LLVM */
	__stack_chk_guard = __bionic_tls + 40;

	/*
	 * Remove unused sections from the image.
	 */
	/DISCARD/ : {
		/* The image loads itself so doesn't need these sections. */
		*(.gnu.hash)
		*(.hash)
		*(.interp)
		*(.eh_frame_hdr)
		*(.eh_frame)
		*(.note.gnu.build-id)
	}
}