coreboot-kgpe-d16/payloads/libpayload
Gabe Black c09cf0b7e1 libpayload: arm: Pass the coreboot table location to the payload.
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>
2014-12-09 18:38:48 +01:00
..
arch libpayload: arm: Pass the coreboot table location to the payload. 2014-12-09 18:38:48 +01:00
bin ARM: Generalize armv7 as arm. 2014-09-08 18:59:23 +02:00
configs libpayload: Remove config.panther 2014-11-13 06:22:25 +01:00
crypto libpayload: Change CONFIG_* to CONFIG_LP_* in the kconfig. 2014-08-05 18:44:08 +02:00
curses libpayload: Change CONFIG_* to CONFIG_LP_* in the kconfig. 2014-08-05 18:44:08 +02:00
drivers libpayload: Add minimal support for PL011 UART 2014-11-13 06:23:17 +01:00
include arm: Put assembly functions into separate sections 2014-11-13 06:49:41 +01:00
libc libpayload: Add a timer_us() function. 2014-09-15 19:01:03 +02:00
libcbfs cbfs: Fix overwalk on file scan 2014-08-10 22:25:07 +02:00
liblzma LZMA: Add a version of ulzma which takes the input and output buffer sizes. 2014-08-10 22:29:51 +02:00
libpci libpayload: minor cleanups 2012-04-04 00:40:31 +02:00
sample libpayload: Fix missed CONFIG_ -> CONFIG_LP_ substitutions 2014-10-17 11:24:15 +02:00
tests libpayload: Change CONFIG_X86_SERIAL_CONSOLE to CONFIG_8250_SERIAL_CONSOLE 2014-08-28 01:40:48 +02:00
util libpayload: also support armv7-a toolchain 2014-10-16 15:54:16 +02:00
Config.in libpayload: Add minimal support for PL011 UART 2014-11-13 06:23:17 +01:00
Doxyfile
LICENSES
Makefile libpayload: Don't use default path for kconfig 2014-10-17 11:25:10 +02:00
Makefile.inc libpayload: Build libpayload with debugging info turned up all the way. 2014-09-29 19:29:30 +02:00
README libpayload, superiotool: README: Prepend `coreboot/` to path of change directory line 2013-04-04 17:22:15 +02:00

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.