asm_macros: set the default assembly code alignment to 4 byte
Assembly routines are usually defined by using "func" and "endfunc":
func foo
...
endfunc foo
Currently, the "func" macro does not specify ".align" directive
by default. It causes unaligned instruction under some circumstances.
As far as I tested, this problem happens for GCC 5 or older. It did
not happen for GCC 6 or newer. Taking into account that GCC 4.x / 5.x
is still used, make sure that assembly code is at least 4 byte aligned.
[ How to reproduce the problem ]
For example, use GCC 5.3 downloaded from Linaro:
http://releases.linaro.org/components/toolchain/binaries/5.3-2016.05/
aarch64-linux-gnu/gcc-linaro-5.3.1-2016.05-x86_64_aarch64-linux-gnu.tar.xz
Expand mbedtls-2.4.2 to the current directory.
Try the following:
$ git log --oneline -1
77544ef Merge pull request #1071 from jeenu-arm/syntax-fix
$ aarch64-linux-gnu-gcc --version | head -1
aarch64-linux-gnu-gcc (Linaro GCC 5.3-2016.05) 5.3.1 20160412
$ make CROSS_COMPILE=aarch64-linux-gnu- PLAT=uniphier \
TRUSTED_BOARD_BOOT=1 MBEDTLS_DIR=mbedtls-2.4.2
( snip build log )
$ aarch64-linux-gnu-nm build/uniphier/release/bl1/bl1.elf | grep handler
00000000800088f4 T bl1_fwu_smc_handler
00000000800084c8 T bl1_smc_handler
000000008000a6e0 t _panic_handler
000000008000a8e0 W plat_error_handler
000000008000a8e8 W plat_panic_handler
000000008000a8d8 W plat_reset_handler
000000008000a39f T reset_handler
000000008000a367 t smc_handler
000000008000a2ef t smc_handler64
You will notice "smc_handler64", "reset_handler", etc. are not properly
aligned.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/include/common/asm_macros_common.S b/include/common/asm_macros_common.S
index dbc9e2d..6a02e18 100644
--- a/include/common/asm_macros_common.S
+++ b/include/common/asm_macros_common.S
@@ -12,11 +12,12 @@
* to enable elimination of unused code during linking. It also adds
* basic debug information to enable call stack printing most of the
* time. The optional _align parameter can be used to force a
- * non-standard alignment (indicated in powers of 2). Do *not* try to
- * use a raw .align directive. Since func switches to a new section,
- * this would not have the desired effect.
+ * non-standard alignment (indicated in powers of 2). The default is
+ * _align=2 because both Aarch32 and Aarch64 instructions must be
+ * word aligned. Do *not* try to use a raw .align directive. Since func
+ * switches to a new section, this would not have the desired effect.
*/
- .macro func _name, _align=-1
+ .macro func _name, _align=2
/*
* Add Call Frame Information entry in the .debug_frame section for
* debugger consumption. This enables callstack printing in debuggers.
@@ -36,9 +37,7 @@
* .debug_frame
*/
.cfi_startproc
- .if (\_align) != -1
- .align \_align
- .endif
+ .align \_align
\_name:
.endm
