coreboot/payloads/libpayload
Julius Werner aedc177f00 libpayload: arm64: Reduce DMA allocator space to 1MB
On arm64 device libpayload reserves 32MB of space for the DMA allocator.
DMA allocators are usually just used for small bounce buffers or DMA
descriptors for SPI, I2C or USB transfers, nothing that should get
anywhere near the size of megabytes.

Presumably the original number was just made arbitrarily large because
it didn't matter. But more recently we have had security applications
(guarding secrets that get received over SPI/I2C from firmware and must
not be visible to the OS after handoff) that made us want to erase the
entire DMA heap just to be sure no driver left a copy of any secret
lying around there. This means the size is no longer fully harmless
because erasing a larger heap takes more time.

Change the default to 1MB which should still be more than more than
enough for any real applications, but should bring the time required to
erase it back into negligible territory.

BUG=b:418942992
TEST=Booted Trogdor from USB.

Change-Id: Id56486203c512d7ff08909cac1a016adc44d8e68
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/87780
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Yu-Ping Wu <yupingso@google.com>
2025-05-22 20:56:14 +00:00
..
arch libpayload: Use Kconfig instead of weak symbol for arch_ndelay() 2025-05-22 19:27:30 +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 payloads: Rename Makefiles from .inc to .mk 2024-01-24 10:15:10 +00:00
drivers cbgfx: Prevent divide-by-zero edge case in Lanczos kernel 2025-05-06 21:04:04 +00:00
gdb libpayload: gdb: Make die_if() format string a literal 2024-03-19 22:50:03 +00:00
include libpayload: arm64: Reduce DMA allocator space to 1MB 2025-05-22 20:56:14 +00:00
libc libpayload: Use Kconfig instead of weak symbol for arch_ndelay() 2025-05-22 19:27:30 +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: Use Kconfig instead of weak symbol for arch_ndelay() 2025-05-22 19:27:30 +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 libpayload: Add x86_64 (64-bit) support 2024-05-26 01:26:31 +00:00
Makefile.mk payloads/libpayload: Add Wno-address-of-packed-member flag 2024-10-15 18:55:32 +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.