The Yocto project builds their aarch64 cross-compiler with the
configure knob --enable-standard-branch-protection, which means that
their gcc behaves as if -mbranch-protection=standard is passed; the
default (lacking that configure knob) is -mbranch-protection=none.
This means that when building U-Boot using the Yocto toolchain, most
functions end up containing paciasp/autiasp/bti instructions. However,
since U-Boot is not an ordinary userspace application, there's no OS
kernel which has set up the required authentication keys, so these
instructions do nothing at all (even on arm64 hardware that does have
the pointer authentication capability). They do however make the image
larger.
It is theoretically possible for U-Boot to make use of the pointer
authentication protection - cf. the linux kernel's
CONFIG_ARM64_PTR_AUTH_KERNEL - but it is far from trivial, and it's
hard to see just what threat model it would protect against in a
bootloader context. Regardless, we certainly have none of the required
infrastructure now, so explicitly pass -mbranch-protection=none to
ensure those useless instructions do not get emitted.
For a toolchain not configured with
--enable-standard-branch-protection, this changes nothing. For the
Yocto toolchain, this reduces the size of both SPL and U-Boot proper
by about 3% for my imx8mp target.
If you don't have a Yocto toolchain, the effect can easily be
reproduced by applying this patch and changing =none to =standard.
Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
Reviewed-by: Simon Glass <sjg@chromium.org>
When U-Boot started using SPDX tags we were among the early adopters and
there weren't a lot of other examples to borrow from. So we picked the
area of the file that usually had a full license text and replaced it
with an appropriate SPDX-License-Identifier: entry. Since then, the
Linux Kernel has adopted SPDX tags and they place it as the very first
line in a file (except where shebangs are used, then it's second line)
and with slightly different comment styles than us.
In part due to community overlap, in part due to better tag visibility
and in part for other minor reasons, switch over to that style.
This commit changes all instances where we have a single declared
license in the tag as both the before and after are identical in tag
contents. There's also a few places where I found we did not have a tag
and have introduced one.
Signed-off-by: Tom Rini <trini@konsulko.com>
Add support for EFI apps on aarch64. This includes start-up and relocation
code plus a link script.
Signed-off-by: Simon Glass <sjg@chromium.org>
[agraf: add kconfig dep]
Signed-off-by: Alexander Graf <agraf@suse.de>
My main motivations for this commit are:
[1] Follow the arch/arm/Makefile style of Linux Kernel
[2] Maintain compiler options systematically
Currently, we give -march=* and -mtune=* options inconsistently:
Only some of the CPUs pass -march=* and -mtune=* options.
By collecting such options into the single place arch/arm/Makefile
we can tell which options are missing at a glance.
[3] Prepare for deprecating arch/*/cpu/*/config.mk
Note:
This commit just moves the compiler options so as not to change
the behavior at all. It does not care about the correctness of
the given options. Fox example, "-march=armv5te" might be better
than "-march=armv4" for ARM946EJS, but it is beyond the scope this
commit. Also, filling the missing -march=* and -tune=* is left
to follow-up patches.
Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Acked-by: Marek Vasut <marex@denx.de>
Acked-by: Stefan Roese <sr@denx.de>
When we tell the compiler to optimize for ARMv7 (and ARMv6 for that
matter) it assumes a default of SCTRL.A being cleared and unaligned
accesses being allowed and fast at the hardware level. We set this bit
and must pass along -mno-unaligned-access so that the compiler will
still breakdown accesses and not trigger a data abort.
To better help understand the requirements of the project with respect
to unaligned memory access, the
Documentation/unaligned-memory-access.txt file has been added as
doc/README.unaligned-memory-access.txt and is taken from the v3.14-rc1
tag of the kernel.
Cc: Albert ARIBAUD <albert.u.boot@aribaud.net>
Cc: Mans Rullgard <mans@mansr.com>
Signed-off-by: Tom Rini <trini@ti.com>
Relocation code based on a patch by Scott Wood, which is:
Signed-off-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: David Feng <fenghua@phytium.com.cn>
