No description
2fe505bd9a
The console output driver framework in libpayload is currently built on
the putchar primitive, meaning that every driver's function gets called
one character at a time. This becomes an issue when we add drivers that
could output multiple characters at a time, but have a high constant
overhead per invocation (such as the planned GDB stub, which needs to
wrap a special frame around output strings and wait for an
acknowledgement from the server).
This patch adds a new 'write' function pointer to the
console_output_driver structure as an alternative to 'putchar'. Output
drivers need to provide at least one of the two ('write' is preferred if
available). The CBMEM console driver is ported as a proof of concept
(since it's our most performace-critical driver and should in theory
benefit the most from less function pointer invocations, although it's
probably still negligible compared to the big sprawling mess that is
printf()).
Even with this fix, the problem remains that printf() was written with
the putchar primitive in mind. Even though normal text already contains
an optimization to allow multiple characters at a time, almost all
formatting directives cause their output (including things like
padding whitespace) to be putchar()ed one character at a time.
Therefore, this patch reworks parts of the output code (especially
number printing) to all but remove that inefficiency (directives still
invoke an extra write() call, but at least not one per character). Since
I'm touching printf() core code anyway, I also tried to salvage what I
could from that weird, broken "return negative on error" code path (not
that any of our current output drivers can trigger it anyway).
A final consequence of this patch is that the responsibility to prepend
line feeds with carriage returns is moved into the output driver
implementations. Doing this only makes sense for drivers with explicit
cursor position control (i.e. serial or video), and things like the
CBMEM console that appears like a normal file to the system really have
no business containing carriage returns (we don't want people to
accidentally associate us with Windows, now, do we?).
BUG=chrome-os-partner:18390
TEST=Made sure video and CBMEM console still look good, tried printf()
with as many weird edge-case strings as I could find and compared serial
output as well as sprintf() return value.
Original-Change-Id: Ie05ae489332a0103461620f5348774b6d4afd91a
Original-Signed-off-by: Julius Werner <jwerner@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/196384
Original-Reviewed-by: Hung-Te Lin <hungte@chromium.org>
Original-Reviewed-by: David Hendricks <dhendrix@chromium.org>
(cherry picked from commit ab1ef0c07736fe1aa3e0baaf02d258731e6856c0)
Signed-off-by: Marc Jones <marc.jones@se-eng.com>
Change-Id: I78f5aedf6d0c3665924995cdab691ee0162de404
Reviewed-on: http://review.coreboot.org/7880
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
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| 3rdparty@a8b0c52850 | ||
| documentation | ||
| payloads | ||
| src | ||
| util | ||
| .gitignore | ||
| .gitmodules | ||
| .gitreview | ||
| COPYING | ||
| Makefile | ||
| Makefile.inc | ||
| README | ||
| toolchain.inc | ||
------------------------------------------------------------------------------- coreboot README ------------------------------------------------------------------------------- coreboot is a Free Software project aimed at replacing the proprietary BIOS (firmware) found in most computers. coreboot performs a little bit of hardware initialization and then executes additional boot logic, called a payload. With the separation of hardware initialization and later boot logic, coreboot can scale from specialized applications that run directly firmware, run operating systems in flash, load custom bootloaders, or implement firmware standards, like PC BIOS services or UEFI. This allows for systems to only include the features necessary in the target application, reducing the amount of code and flash space required. coreboot was formerly known as LinuxBIOS. Payloads -------- After the basic initialization of the hardware has been performed, any desired "payload" can be started by coreboot. See http://www.coreboot.org/Payloads for a list of supported payloads. Supported Hardware ------------------ coreboot supports a wide range of chipsets, devices, and mainboards. For details please consult: * http://www.coreboot.org/Supported_Motherboards * http://www.coreboot.org/Supported_Chipsets_and_Devices Build Requirements ------------------ * gcc / g++ * make Optional: * doxygen (for generating/viewing documentation) * iasl (for targets with ACPI support) * gdb (for better debugging facilities on some targets) * ncurses (for 'make menuconfig') * flex and bison (for regenerating parsers) Building coreboot ----------------- Please consult http://www.coreboot.org/Build_HOWTO for details. Testing coreboot Without Modifying Your Hardware ------------------------------------------------ If you want to test coreboot without any risks before you really decide to use it on your hardware, you can use the QEMU system emulator to run coreboot virtually in QEMU. Please see http://www.coreboot.org/QEMU for details. Website and Mailing List ------------------------ Further details on the project, a FAQ, many HOWTOs, news, development guidelines and more can be found on the coreboot website: http://www.coreboot.org You can contact us directly on the coreboot mailing list: http://www.coreboot.org/Mailinglist Copyright and License --------------------- The copyright on coreboot is owned by quite a large number of individual developers and companies. Please check the individual source files for details. coreboot is licensed under the terms of the GNU General Public License (GPL). Some files are licensed under the "GPL (version 2, or any later version)", and some files are licensed under the "GPL, version 2". For some parts, which were derived from other projects, other (GPL-compatible) licenses may apply. Please check the individual source files for details. This makes the resulting coreboot images licensed under the GPL, version 2.