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author | 2015-08-28 09:58:54 +0800 | |
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committer | 2015-09-01 12:44:00 +0800 | |
commit | e44e3482bdb4d0ebde2d8b41830ac2cdb07948fb (patch) | |
tree | 66b09f592c55df2878107a468a91d21506104d3f /qemu/roms/seabios/docs/Debugging.md | |
parent | 9ca8dbcc65cfc63d6f5ef3312a33184e1d726e00 (diff) |
Add qemu 2.4.0
Change-Id: Ic99cbad4b61f8b127b7dc74d04576c0bcbaaf4f5
Signed-off-by: Yang Zhang <yang.z.zhang@intel.com>
Diffstat (limited to 'qemu/roms/seabios/docs/Debugging.md')
-rw-r--r-- | qemu/roms/seabios/docs/Debugging.md | 106 |
1 files changed, 106 insertions, 0 deletions
diff --git a/qemu/roms/seabios/docs/Debugging.md b/qemu/roms/seabios/docs/Debugging.md new file mode 100644 index 000000000..03567de4d --- /dev/null +++ b/qemu/roms/seabios/docs/Debugging.md @@ -0,0 +1,106 @@ +This page describes the process of obtaining diagnostic information +from SeaBIOS and for reporting problems. + +Diagnostic information +====================== + +SeaBIOS has the ability to output diagnostic messages. This is +implemented in the code via calls to the "dprintf()" C function. + +On QEMU these messages are written to a special debug port. One can +view these messages by adding '-chardev stdio,id=seabios -device +isa-debugcon,iobase=0x402,chardev=seabios' to the QEMU command line. +Once this is done, one should see status messages on the console. + +On coreboot these messages are generally written to the "cbmem" +console (CONFIG_DEBUG_COREBOOT). If SeaBIOS launches a Linux operating +system, one can obtain the cbmem tool from the coreboot repository and +run "cbmem -c" to view the SeaBIOS diagnostic messages. + +Additionally, if a serial port is available, one may compile SeaBIOS +to send the diagnostic messages to the serial port. See the SeaBIOS +CONFIG_DEBUG_SERIAL option. + +Trouble reporting +================= + +If you are experiencing problems with SeaBIOS, it's useful to increase +the debugging level. This is done by running "make menuconfig" and +setting CONFIG_DEBUG_LEVEL to a higher value. A debug level of 8 will +show a lot of diagnostic information without flooding the serial port +(levels above 8 will frequently cause too much data). + +To report an issue, please collect the serial boot log with SeaBIOS +set to a debug level of 8 and forward the full log along with a +description of the problem to the SeaBIOS [mailing list](Mailinglist). + +Timing debug messages +===================== + +The SeaBIOS repository has a tool (**scripts/readserial.py**) that can +timestamp each diagnostic message produced. The timestamps can provide +some additional information on how long internal processes take. It +also provides a simple profiling mechanism. + +The tool can be used on coreboot builds that have diagnostic messages +sent to a serial port. Make sure SeaBIOS is configured with +CONFIG_DEBUG_SERIAL and run the following on the host receiving serial +output: + +`/path/to/seabios/scripts/readserial.py /dev/ttyS0 115200` + +Update the above command with the appropriate serial device and baud +rate. + +The tool can also timestamp the messages from the QEMU debug port. To +use with QEMU run the following: + +`mkfifo qemudebugpipe`\ +`qemu -chardev pipe,path=qemudebugpipe,id=seabios -device isa-debugcon,iobase=0x402,chardev=seabios ...` + +and then in another session: + +`/path/to/seabios/scripts/readserial.py -nf qemudebugpipe` + +The mkfifo command only needs to be run once to create the pipe file. + +When readserial.py is running, it shows a timestamp with millisecond +precision of the amount of time since the start of the log. If one +presses the "enter" key in the readserial.py session it will add a +blank line to the screen and also reset the time back to zero. The +readserial.py program also keeps a log of all output in files that +look like "seriallog-YYYYMMDD_HHMMSS.log". + +Debugging with gdb on QEMU +========================== + +One can use gdb with QEMU to debug system images. To do this, add '-s +-S' to the qemu command line. For example: + +`qemu -bios out/bios.bin -fda myfdimage.img -s -S` + +Then, in another session, run gdb with either out/rom16.o (to debug +bios 16bit code) or out/rom.o (to debug bios 32bit code). For example: + +`gdb out/rom16.o` + +Once in gdb, use the command "target remote localhost:1234" to have +gdb connect to QEMU. See the QEMU documentation for more information +on using gdb and QEMU in this mode. + +When debugging 16bit code, also run the following commands in gdb: + +`set architecture i8086`\ +`add-symbol-file out/rom16.o 0xf0000` + +The second command loads the 16bit symbols a second time at an offset +of 0xf0000, which helps gdb set and catch breakpoints correctly. + +To debug a VGA BIOS image, run "gdb out/vgarom.o" add use the gdb +command "add-symbol-file out/vgarom.o 0xc0000" to load the 16bit VGA +BIOS symbols twice. + +If debugging the 32bit SeaBIOS initialization code with gdb, note that +SeaBIOS does self relocation by default. This relocation will alter +the location of initialization code symbols. Disable +CONFIG_RELOCATE_INIT to prevent SeaBIOS from doing this. |