c09cf0b7e1
To find the coreboot tables, the payload has historically searched for their signature in a predefined region of memory. This is a little clumsy on x86, but it works because you can assume certain regions are RAM. Also, there are areas which are set aside for the firmware by convention. On x86 there's a forwarding entry which goes in one of those fairly small conventional areas and which points to the CBMEM area at the end of memory. On ARM there aren't areas like that, so we've left out the forwarding entry and gone directly to CBMEM. RAM may not start at the beginning of the address space or go to its end, and that means there isn't really anywhere fixed you can put the coreboot tables. That's meant that libpayload has to be configured on a per board basis to know where to look for CBMEM. Now that we have boards that don't have fixed amounts of memory, the location of the end of RAM isn't fixed even on a per board level which means even that workaround will no longer cut it. This change makes coreboot pass the location of the coreboot tables to libpayload using r0, the first argument register. That means we'll be able to find them no matter where CBMEM is, and we can get rid of the per board search ranges. We can extend this mechanism to x86 as well, but there may be more complications and it's less necessary there. It would be a good thing to do eventually though. BUG=None TEST=Built and booted on nyan. Changed the size of memory and saw that the payload could still find the coreboot tables where before it couldn't. Built for pit, snow, and big. BRANCH=None Original-Change-Id: I7218afd999da1662b0db8172fd8125670ceac471 Original-Signed-off-by: Gabe Black <gabeblack@google.com> Original-Reviewed-on: https://chromium-review.googlesource.com/185572 Original-Reviewed-by: Julius Werner <jwerner@chromium.org> Original-Commit-Queue: Gabe Black <gabeblack@chromium.org> Original-Tested-by: Gabe Black <gabeblack@chromium.org> (cherry picked from commit ca88f39c21158b59abe3001f986207a292359cf5) Signed-off-by: Marc Jones <marc.jones@se-eng.com> Change-Id: Iab14e9502b6ce7a55f0a72e190fa582f89f11a1e Reviewed-on: http://review.coreboot.org/7655 Tested-by: build bot (Jenkins) Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net> Reviewed-by: Patrick Georgi <pgeorgi@google.com> |
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.. | ||
arch | ||
bin | ||
configs | ||
crypto | ||
curses | ||
drivers | ||
include | ||
libc | ||
libcbfs | ||
liblzma | ||
libpci | ||
sample | ||
tests | ||
util | ||
Config.in | ||
Doxyfile | ||
LICENSES | ||
Makefile | ||
Makefile.inc | ||
README |
README
------------------------------------------------------------------------------- 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 http://coreboot.org for details on coreboot. Installation ------------ $ git clone http://review.coreboot.org/p/coreboot.git $ cd coreboot/payloads/libpayload $ make menuconfig $ make $ sudo make install (optional, will install into /opt per default) As libpayload is for 32bit x86 systems only, you might have to install the 32bit libgcc version, otherwise your payloads will fail to compile. On Debian systems you'd do 'apt-get install gcc-multilib' for example. 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 http://www.coreboot.org/Libpayload. For additional information, patches, and discussions, please join the coreboot mailing list at http://coreboot.org/Mailinglist, where most libpayload developers are subscribed. Copyright and License --------------------- See LICENSES.