coreboot/payloads/libpayload
Julius Werner 84e000b88e libpayload: arm64: Fix alignment for exception_state
In the arm64 exception handler in libpayload, we use the banked
exception stack pointer (SP_EL2, as opposed to the normal SP_EL0) not as
a normal stack pointer, but simply as a pointer to the exception_state
struct. This makes it easy to dump all registers into that struct on
context switch. We then immediately switch back to SP_EL0.

Yet, even though it is not really a stack for us, the aarch64
architecture still requires that SP_EL2 is 16 byte aligned at function
boundaries. If the exception_state struct is not thus aligned,
exceptions are broken. (I don't know why nobody ever hit this before,
but I hit it now while trying to pull in zstd code. I guess we just
don't have unaligned BSS entries that often and simply got lucky for a
while. 3 hours wasted on debugging. :( )

Change-Id: Id19184656fb9da68fe4bfdbc240c0c25b9d24cd6
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/89926
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Yu-Ping Wu <yupingso@google.com>
2025-11-10 02:36:39 +00:00
..
arch libpayload: arm64: Fix alignment for exception_state 2025-11-10 02:36:39 +00:00
bin libpayload: Add x86_64 (64-bit) support 2024-05-26 01:26:31 +00:00
configs libpayload: configs: Add new config.featuretest to broaden CI 2024-12-04 22:25:34 +00:00
crypto payloads: Rename Makefiles from .inc to .mk 2024-01-24 10:15:10 +00:00
curses tree: Replace union {0} initializers with {} for C23 compliance 2025-08-11 16:40:34 +00:00
drivers libpayload/drivers/pci_qcom: Fix address during ATU config 2025-07-30 17:54:17 +00:00
gdb libpayload: gdb: Make die_if() format string a literal 2024-03-19 22:50:03 +00:00
include Revert "libpayload: Define UCHAR_MAX/CHAR_MIN/CHAR_MAX" 2025-10-14 09:58:49 +00:00
libc libpayload: Fix printf edge cases for precision 2025-11-04 23:14:13 +00:00
libcbfs libpayload: Remove legacy CBFS API 2024-02-22 21:18:39 +00:00
liblz4 payloads: Rename Makefiles from .inc to .mk 2024-01-24 10:15:10 +00:00
liblzma payloads: Rename Makefiles from .inc to .mk 2024-01-24 10:15:10 +00:00
libpci payloads: Rename Makefiles from .inc to .mk 2024-01-24 10:15:10 +00:00
sample libpayload: Add mock architecture 2021-10-11 12:59:57 +00:00
tests libpayload: Fix strsep() edge cases 2025-08-13 17:44:31 +00:00
vboot libpayload: Add x86_64 (64-bit) support 2024-05-26 01:26:31 +00:00
.gitignore .gitignore: Split into subdirectory files 2020-10-30 07:05:27 +00:00
Doxyfile payloads: Remove/fix trailing whitespace 2018-09-04 12:38:40 +00:00
Kconfig libpayload: Use Kconfig instead of weak symbol for arch_ndelay() 2025-05-22 19:27:30 +00:00
LICENSE_GPL libpayload: Introduce new Kconfig to explicitly allow GPL code 2015-01-09 07:06:27 +01:00
LICENSES libpayload: Add LZ4 decompression algorithm 2015-07-09 00:10:16 +02:00
Makefile tree: Replace scan-build by clang-tidy 2025-07-01 01:12:32 +00:00
Makefile.mk payloads/libpayload/Makefile.mk: Replace nm with $(NM) 2025-06-05 13:37:27 +00:00
Makefile.payload libpayload/Makefile.payload: Add lto flags 2024-08-27 09:08:07 +00:00
README payloads/libpayload: Update a Makefile for sample libpayload 2019-06-21 09:16:36 +00:00

-------------------------------------------------------------------------------
libpayload README
-------------------------------------------------------------------------------

libpayload is a minimal library to support standalone payloads
that can be booted with firmware like coreboot. It handles the setup
code, and provides common C library symbols such as malloc() and printf().

Note: This is _not_ a standard library for use with an operating system,
rather it's only useful for coreboot payload development!
See https://www.coreboot.org for details on coreboot.


Installation
------------

 $ git clone https://review.coreboot.org/coreboot.git

 $ cd coreboot/payloads/libpayload

 $ make menuconfig

 $ make

 $ make install (optional, will install into ./install per default)

On x86 systems, libpayload will always be 32-bit even if your host OS runs
in 64-bit, so you might have to install the 32-bit libgcc version.
On Debian systems you'd do 'apt-get install gcc-multilib' for example.

Run 'make distclean' before switching boards. This command will remove
your current .config file, so you need 'make menuconfig' again or
'make defconfig' in order to set up configuration. Default configuration
is based on 'configs/defconfig'. See the configs/ directory for examples
of configuration.


Usage
-----

Here's an example of a very simple payload (hello.c) and how to build it:

 #include <libpayload.h>

 int main(void)
 {
     printf("Hello, world!\n");
     return 0;
 }

Building the payload using the 'lpgcc' compiler wrapper:

 $ lpgcc -o hello.elf hello.c

Please see the sample/ directory for details.


Website and Mailing List
------------------------

The main website is https://www.coreboot.org/Libpayload.

For additional information, patches, and discussions, please join the
coreboot mailing list at https://www.coreboot.org/Mailinglist, where most
libpayload developers are subscribed.


Copyright and License
---------------------

See LICENSES.