Reduce space lost to object alignment
Currently, sections within .text/.rodata/.data/.bss are emitted in the
order they are seen by the linker. This leads to wasted space, when a
section with a larger alignment follows one with a smaller alignment.
We can avoid this wasted space by sorting the sections.
To take full advantage of this, we must disable generation of common
symbols, so "common" data can be sorted along with the rest of .bss.
An example of the improvement, from `make DEBUG=1 PLAT=sun50i_a64 bl31`:
.text => no change
.rodata => 16 bytes saved
.data => 11 bytes saved
.bss => 576 bytes saved
As a side effect, the addition of `-fno-common` in TF_CFLAGS makes it
easier to spot bugs in header files.
Signed-off-by: Samuel Holland <samuel@sholland.org>
Change-Id: I073630a9b0b84e7302a7a500d4bb4b547be01d51
diff --git a/bl2/bl2.ld.S b/bl2/bl2.ld.S
index 30cdf7d..6230562 100644
--- a/bl2/bl2.ld.S
+++ b/bl2/bl2.ld.S
@@ -1,5 +1,5 @@
/*
- * Copyright (c) 2013-2018, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2013-2019, ARM Limited and Contributors. All rights reserved.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
@@ -27,7 +27,7 @@
.text . : {
__TEXT_START__ = .;
*bl2_entrypoint.o(.text*)
- *(.text*)
+ *(SORT_BY_ALIGNMENT(.text*))
*(.vectors)
. = ALIGN(PAGE_SIZE);
__TEXT_END__ = .;
@@ -44,7 +44,7 @@
.rodata . : {
__RODATA_START__ = .;
- *(.rodata*)
+ *(SORT_BY_ALIGNMENT(.rodata*))
/* Ensure 8-byte alignment for descriptors and ensure inclusion */
. = ALIGN(8);
@@ -59,8 +59,8 @@
ro . : {
__RO_START__ = .;
*bl2_entrypoint.o(.text*)
- *(.text*)
- *(.rodata*)
+ *(SORT_BY_ALIGNMENT(.text*))
+ *(SORT_BY_ALIGNMENT(.rodata*))
/* Ensure 8-byte alignment for descriptors and ensure inclusion */
. = ALIGN(8);
@@ -93,7 +93,7 @@
*/
.data . : {
__DATA_START__ = .;
- *(.data*)
+ *(SORT_BY_ALIGNMENT(.data*))
__DATA_END__ = .;
} >RAM