50a81748fd
This patch adds the ability to attach a GDB host through the UART to a running payload. Libpayload implements a small stub that can parse and respond to the GDB remote protocol and provide the required primitives (reading/writing registers/memory, etc.) to allow GDB to control execution. The goal of this implementation is to be as small and uninvasive as possible. It implements only the minimum amount of primitives required, and relies on GDB's impressive workaround capabilities (such as emulating breakpoints by temporarily replacing instructions) for the more complicated features. This way, a relatively tiny amount of code on the firmware side opens a vast range of capabilities to the user, not just in debugging but also in remote-controlling the firmware to change its behavior (e.g. through GDBs ability to modify variables and call functions). By default, a system with the REMOTEGDB Kconfig will only trap into GDB when executing halt() (including the calls from die_if(), assert(), and exception handlers). In addition, payloads can manually call gdb_enter() if desired. It will print a final "Ready for GDB connection." on the serial, detach the normal serial output driver and wait for the commands that GDB starts sending on attach. Based on original implementation by Gabe Black <gabeblack@chromium.org>. BUG=chrome-os-partner:18390 TEST=Boot a GDB enabled image in recovery mode (or get it to hit a halt()), close your terminal, execute '<toolchain>-gdb --symbols /build/<board>/firmware/depthcharge_gdb/depthcharge.elf --directory ~/trunk/src/third_party/coreboot/payloads/libpayload --directory ~/trunk/src/platform/depthcharge --directory ~/trunk/src/platform/vboot_reference --ex "target remote <cpu_uart_pty>"' and behold the magic. (You can also SIGSTOP your terminal's parent shell and the terminal itself, and SIGCONT them in reverse order after GDB exits. More convenient wrapper tools to do all this automatically coming soon.) Original-Change-Id: Ib440d1804126cdfdac4a8801f5015b4487e25269 Original-Signed-off-by: Julius Werner <jwerner@chromium.org> Original-Reviewed-on: https://chromium-review.googlesource.com/202563 Original-Reviewed-by: Stefan Reinauer <reinauer@chromium.org> (cherry picked from commit 9c4a642c7be2faf122fef39bdfaddd64aec68b77) Signed-off-by: Marc Jones <marc.jones@se-eng.com> Change-Id: I9238b4eb19d3ab2c98e4e1c5946cd7d252ca3c3b Reviewed-on: http://review.coreboot.org/8119 Tested-by: build bot (Jenkins) Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org> |
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.. | ||
arch | ||
bin | ||
configs | ||
crypto | ||
curses | ||
drivers | ||
gdb | ||
include | ||
libc | ||
libcbfs | ||
liblzma | ||
libpci | ||
sample | ||
tests | ||
util | ||
Config.in | ||
Doxyfile | ||
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 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.