541f2f74a3
The current initialization of the 'equals' counter is incorrect, so that when 'equals >= SSZ * SSZ', the pixels in the sample array might not be all the same, leading to a wrong pixel value being set in the framebuffer. The 'equals' counter stores the number of latest pixels that were exactly equal. Within the for loop of 'ox', the sample array is updated in a column-based order, and the 'equals' counter is updated accordingly. However, the 'equals' counter is initialized in a row-based order, which causes it to be set too large than it should be. Consider the example where sample[sx][sy] are initially: [X X X A A A] // sy = 0 [X X X B B B] [X X X B B B] [X X X B B B] [X X X B B B] [X X X B B B] // sy = SSZ Then, the correct implementation will initialize 'equals' to be 15, with last_equal being B. Suppose all of the remaining pixels are B. Then, at the end of the 'while (fpfloor(ixfp) > ix)' loop when ix = 4, or equivalently after 4 more columns of sample are updated, 'equals' will be 15 + 6 * 4 = 39, which is greater than SSZ * SSZ = 36, but we can see there are still 2 A's in the sample: [B B B B A A] [B B B B B B] [B B B B B B] [B B B B B B] [B B B B B B] [B B B B B B] Therefore, we must also initialize the 'equals' counter in a column-based order. BUG=b:167739127 TEST=emerge-puff libpayload TEST=Character 'k' is rendered correctly on puff BRANCH=zork Change-Id: Ibc91ad1af85adcf093eff40797cd54f32f57111d Signed-off-by: Yu-Ping Wu <yupingso@chromium.org> Reviewed-on: https://review.coreboot.org/c/coreboot/+/45235 Tested-by: build bot (Jenkins) <no-reply@coreboot.org> Reviewed-by: Julius Werner <jwerner@chromium.org> |
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| .. | ||
| arch | ||
| bin | ||
| configs | ||
| crypto | ||
| curses | ||
| drivers | ||
| gdb | ||
| include | ||
| libc | ||
| libcbfs | ||
| liblz4 | ||
| liblzma | ||
| libpci | ||
| sample | ||
| tests | ||
| Doxyfile | ||
| Kconfig | ||
| LICENSES | ||
| LICENSE_GPL | ||
| 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 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.