Linux kernel - Revision history

Stefan at 09:13, 1 November 2023

2023-11-01T09:13:36Z

← Older revision		Revision as of 09:13, 1 November 2023
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	* Device trees: http://lwn.net/Articles/448502/		* Device trees: http://lwn.net/Articles/448502/
	* Nice intro guide: https://bootlin.com/doc/training/linux-kernel/linux-kernel-slides.pdf		* Nice intro guide: https://bootlin.com/doc/training/linux-kernel/linux-kernel-slides.pdf
			* More trainings: https://bootlin.com/training/

Stefan at 08:25, 1 November 2023

2023-11-01T08:25:22Z

← Older revision		Revision as of 08:25, 1 November 2023
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	* Kernel platform drivers: http://lwn.net/Articles/448499/		* Kernel platform drivers: http://lwn.net/Articles/448499/
	* Device trees: http://lwn.net/Articles/448502/		* Device trees: http://lwn.net/Articles/448502/
			* Nice intro guide: https://bootlin.com/doc/training/linux-kernel/linux-kernel-slides.pdf

Stefan: /* Other logging tips */

2019-10-24T12:51:20Z

Other logging tips

← Older revision		Revision as of 12:51, 24 October 2019
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	If you want to dump out a buffer or a bunch of registers, then you can use the excellent:		If you want to dump out a buffer or a bunch of registers, then you can use the excellent:
	print_hex_dump_bytes("HEX: ", DUMP_PREFIX_OFFSET, buf, size);		print_hex_dump_bytes("HEX: ", DUMP_PREFIX_OFFSET, buf, size);

			== Testing memory in Linux ==

			Enable the following kernel configs:
			CONFIG_MEMTEST=y
			CONFIG_DEBUG_MEMORY_INIT=y

			Add the following to the kernel command line:
			"memtest memblock=debug mminit_loglevel=10 loglevel=8"

Stefan: /* Step 6 - debugging initcalls */

2019-06-05T09:39:00Z

Step 6 - debugging initcalls

← Older revision		Revision as of 09:39, 5 June 2019
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	Other options that might be added can be found here: https://github.com/torvalds/linux/blob/master/Documentation/admin-guide/kernel-parameters.txt		Other options that might be added can be found here: https://github.com/torvalds/linux/blob/master/Documentation/admin-guide/kernel-parameters.txt

			=== Step 7 - overriding kernel command line ===
			For ARM64, if you have trouble with the bootloader overwriting your DTB kernel command line, you may add something like this to your kernel config to override it completely:

			CONFIG_CMDLINE="console=ttyLP0,115200 earlycon=lpuart32,0x3000000,115200 root=/dev/mmcblk1p2 rootwait rw initcall_debug ignore_loglevel"
			CONFIG_CMDLINE_FORCE=y
			# CONFIG_INITRAMFS_FORCE is not set

	=== Other logging tips ===		=== Other logging tips ===
	If you want to dump out a buffer or a bunch of registers, then you can use the excellent:		If you want to dump out a buffer or a bunch of registers, then you can use the excellent:
	print_hex_dump_bytes("HEX: ", DUMP_PREFIX_OFFSET, buf, size);		print_hex_dump_bytes("HEX: ", DUMP_PREFIX_OFFSET, buf, size);

Stefan: /* Tips for booting the kernel on a new ARM board */

2019-06-05T09:33:04Z

Tips for booting the kernel on a new ARM board

← Older revision		Revision as of 09:33, 5 June 2019
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	=== Step 6 - debugging initcalls ===		=== Step 6 - debugging initcalls ===
	If your kernel just stops or crashes in the later stages of kernel boot, it might be good to add the following option to the kernel command line: '''initcall_debug'''		If your kernel just stops or crashes in the later stages of kernel boot, it might be good to add the following option to the kernel command line: '''initcall_debug'''

			Note however that the prints are printed at DEBUG log level, so if you want to see them, you have to make sure that also DEBUG prints are printed. It might be worthwhile to also add '''ignore_loglevel'''

	Other options that might be added can be found here: https://github.com/torvalds/linux/blob/master/Documentation/admin-guide/kernel-parameters.txt		Other options that might be added can be found here: https://github.com/torvalds/linux/blob/master/Documentation/admin-guide/kernel-parameters.txt

Stefan: /* Step 5 - getting the serial running the proper way */

2019-06-05T09:24:53Z

Step 5 - getting the serial running the proper way

← Older revision		Revision as of 09:24, 5 June 2019
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	Then make sure you have set up the kernel command line to contain a ''console'' keyword with a suitable UART configuration, either in your device tree file (*.dts) or in your defconfig (CONFIG_CMDLINE="console=ttyAMA0,115200 earlyprintk init=/linuxrc") or that it is given from your bootloader. Make sure it is set up to the correct UART and speed.		Then make sure you have set up the kernel command line to contain a ''console'' keyword with a suitable UART configuration, either in your device tree file (*.dts) or in your defconfig (CONFIG_CMDLINE="console=ttyAMA0,115200 earlyprintk init=/linuxrc") or that it is given from your bootloader. Make sure it is set up to the correct UART and speed.

			=== Step 6 - debugging initcalls ===
			If your kernel just stops or crashes in the later stages of kernel boot, it might be good to add the following option to the kernel command line: '''initcall_debug'''

			Other options that might be added can be found here: https://github.com/torvalds/linux/blob/master/Documentation/admin-guide/kernel-parameters.txt

	=== Other logging tips ===		=== Other logging tips ===
	If you want to dump out a buffer or a bunch of registers, then you can use the excellent:		If you want to dump out a buffer or a bunch of registers, then you can use the excellent:
	print_hex_dump_bytes("HEX: ", DUMP_PREFIX_OFFSET, buf, size);		print_hex_dump_bytes("HEX: ", DUMP_PREFIX_OFFSET, buf, size);

Stefan: /* Step 1 - Uncompressing */

2018-01-11T15:01:08Z

Step 1 - Uncompressing

← Older revision		Revision as of 15:01, 11 January 2018
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	If you are working on a '''arm64''' architecture, DEBUG_LL is no longer available. The new way to do the same thing is to append something like the following to your kernel cmdline:		If you are working on a '''arm64''' architecture, DEBUG_LL is no longer available. The new way to do the same thing is to append something like the following to your kernel cmdline:
	earlycon=pl011,mmio32,0xF7800000		earlycon=pl011,mmio32,0xF7800000

			More info on earlycon and other kernel cmdline options: [https://www.kernel.org/doc/html/v4.14/admin-guide/kernel-parameters.html https://www.kernel.org/doc/html/v4.14/admin-guide/kernel-parameters.html]

	In both cases you have to adjust the UART config according to your platform! Now you should get the ''Uncompressing Linux...'' print, otherwise your bootloader has either:		In both cases you have to adjust the UART config according to your platform! Now you should get the ''Uncompressing Linux...'' print, otherwise your bootloader has either:

Stefan: /* Step 1 - Uncompressing */

2018-01-11T14:45:27Z

Step 1 - Uncompressing

← Older revision		Revision as of 14:45, 11 January 2018
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	CONFIG_DEBUG_UART_PHYS=0xF7800000		CONFIG_DEBUG_UART_PHYS=0xF7800000
	CONFIG_DEBUG_UART_VIRT=0xF7800000		CONFIG_DEBUG_UART_VIRT=0xF7800000
	~~You~~ have to adjust the UART config according to your platform! Now you should get the ''Uncompressing Linux...'' print, otherwise your bootloader has either:
			If you are working on a '''arm64''' architecture, DEBUG_LL is no longer available. The new way to do the same thing is to append something like the following to your kernel cmdline:
			earlycon=pl011,mmio32,0xF7800000

			In both cases you have to adjust the UART config according to your platform! Now you should get the ''Uncompressing Linux...'' print, otherwise your bootloader has either:
	* Not uploaded the kernel to RAM.		* Not uploaded the kernel to RAM.
	* Not jumped to the correct place in RAM to execute it.		* Not jumped to the correct place in RAM to execute it.

Stefan: /* Configure */

2017-05-30T09:34:27Z

Configure

← Older revision		Revision as of 09:34, 30 May 2017
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	== Building the kernel ==		== Building the kernel ==
	==== Configure ====		==== Configure ====
			===== config using defconfig =====
	To configure using a specified defconfig for a specified architecture		To configure using a specified defconfig for a specified architecture
	make ARCH=x86 i386_defconfig		make ARCH=x86 i386_defconfig

			===== menuconfig using defconfig =====
	To menuconfig starting from a specified defconfig for a specified architecture		To menuconfig starting from a specified defconfig for a specified architecture
	make menuconfig ARCH=x86 i386_defconfig		make menuconfig ARCH=x86 i386_defconfig
	Be sure to explicitly save the configuration.		Be sure to explicitly save the configuration.

			===== menuconfig using .config =====
			To menuconfig starting from a .config for a specified architecture
			make menuconfig ARCH=x86
			When inside menuconfig, choose "Load" and specify path to your .config Then edit the configuration as you see fit, then choose "Save" and save it as ".config" only. Then you can exit menuconfig and do:
			make savedefconfig ARCH=x86
			to save your updated, minimal defconfig. Be sure to specify your architecture at all times (if it is not the default x86).

	==== Build ====		==== Build ====

Stefan: /* Step 5 - getting the serial running the proper way */

2017-03-08T07:14:45Z

Step 5 - getting the serial running the proper way

← Older revision		Revision as of 07:14, 8 March 2017
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	Then make sure you have set up the kernel command line to contain a ''console'' keyword with a suitable UART configuration, either in your device tree file (*.dts) or in your defconfig (CONFIG_CMDLINE="console=ttyAMA0,115200 earlyprintk init=/linuxrc") or that it is given from your bootloader. Make sure it is set up to the correct UART and speed.		Then make sure you have set up the kernel command line to contain a ''console'' keyword with a suitable UART configuration, either in your device tree file (*.dts) or in your defconfig (CONFIG_CMDLINE="console=ttyAMA0,115200 earlyprintk init=/linuxrc") or that it is given from your bootloader. Make sure it is set up to the correct UART and speed.

			=== Other logging tips ===
			If you want to dump out a buffer or a bunch of registers, then you can use the excellent:
			print_hex_dump_bytes("HEX: ", DUMP_PREFIX_OFFSET, buf, size);