coreboot/payloads/libpayload
Julius Werner 4be8900ca3 libpayload: cbfs: Remove absolute pointer special case from ram_media
This patch changes the ram_media CBFS backend implementation to no
longer detect an absolute address that is inside the "memory region"
used to back the CBFS image (which on x86 is really just the
memory-mapped flash due to a depthcharge implementation detail). This
was (as far as I know only) used to support the ugly CBFS header pointer
situation with SeaBIOS, which is now resolved. It is a very dangerous
feature, since it's perfectly possible for a negative offset relative to
the end of the image to overlap that region. We only get lucky that in
our existing use cases the embedded CBFS is further away from the end of
the ROM than it's own size... if we instead had a 3MB image from
0xfffd0000 to 0xffff0000, then we might want to pass in an address like
0xfffe8000 (interpreted as a relative offset from the end) to refer to
the absolute address 0xfffd8000, but this feature would prevent that
since it fits inside the window when interpreted absolutely. (Also, it
is unlikely but possible that a non-memory-mapped architecture which
starts DRAM at 0x0 may put its bounce buffer within the first few
megabyte of the address space, so that a relative offset from the start
of the image could be interpreted as an absolute offset inside the
buffer.

CQ-DEPEND=CL:229962
BRANCH=None
BUG=None
TEST=Built and booted on Falco and Nyan_Blaze, confirmed that legacy
mode still works as well as before.

Change-Id: I0c9149d725adeecef2520342b307ce7ea52990c1
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/229976
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Stefan Reinauer <reinauer@chromium.org>
2014-12-03 06:09:59 +00:00
..
arch libpayload: arm64: don't modify cbtable entries 2014-11-18 21:11:52 +00:00
bin libpayload: Add support for arm64 in libpayload 2014-06-07 01:28:57 +00:00
configs libpayload: add veyron_mighty config 2014-11-21 04:37:51 +00:00
crypto libpayload: Change CONFIG_* to CONFIG_LP_* in the kconfig. 2013-08-14 17:05:33 -07:00
curses libpayload: Change CONFIG_* to CONFIG_LP_* in the kconfig. 2013-08-14 17:05:33 -07:00
drivers Revert "ryu: libpayload: Set fb address in dc register" 2014-11-14 19:39:26 +00:00
gdb libpayload: Let GDB stub read/write memory with aligned MMIO words 2014-07-22 01:24:00 +00:00
include CBFS: Automate ROM image layout and remove hardcoded offsets 2014-12-03 06:09:54 +00:00
libc libpayload: UTF-16LE to ASCII conversion 2014-11-25 03:47:18 +00:00
libcbfs libpayload: cbfs: Remove absolute pointer special case from ram_media 2014-12-03 06:09:59 +00:00
liblzma libpayload: Make lzma truncation non-fatal. 2013-08-19 19:04:35 -07:00
libpci libpayload: minor cleanups 2012-04-04 00:40:31 +02:00
sample fix compilation of hello.elf example payload. 2010-08-28 23:23:47 +00:00
tests libpayload: Change CONFIG_X86_SERIAL_CONSOLE to CONFIG_8250_SERIAL_CONSOLE 2013-09-27 14:05:53 +00:00
util libpayload: Add support for arm64 in libpayload 2014-06-07 01:28:57 +00:00
Config.in ryu: libpayload: Add CONFIG_LP_TEGRA_VIDEO_CONSOLE_INIT 2014-11-01 01:27:53 +00:00
Doxyfile Run doxygen -u on doxygen configuration files 2010-06-28 10:40:38 +00:00
LICENSE_GPL libpayload: Introduce new Kconfig to explicitly allow GPL code 2014-06-13 20:37:29 +00:00
LICENSES libpayload: Introduce new Kconfig to explicitly allow GPL code 2014-06-13 20:37:29 +00:00
Makefile libpayload: Add support for arm64 in libpayload 2014-06-07 01:28:57 +00:00
Makefile.inc Change GDB_DEBUG to SOURCE_DEBUG 2014-10-08 05:07:21 +00:00
README libpayload, superiotool: README: Prepend coreboot/ to path of change directory line 2013-04-04 17:22:15 +02:00

-------------------------------------------------------------------------------
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 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.