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| author | Masami Hiramatsu <mhiramat@kernel.org> | 2020-02-20 13:18:42 +0100 |
|---|---|---|
| committer | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2020-02-20 23:52:34 +0100 |
| commit | 85c46b78da58398be1c5166f55063c0512decd39 (patch) | |
| tree | 61c46743c7f5dd9eaec9afa135020da8b5e66d04 /Documentation/admin-guide/bootconfig.rst | |
| parent | bootconfig: Set CONFIG_BOOT_CONFIG=n by default (diff) | |
| download | linux-85c46b78da58398be1c5166f55063c0512decd39.tar.xz linux-85c46b78da58398be1c5166f55063c0512decd39.zip | |
bootconfig: Add bootconfig magic word for indicating bootconfig explicitly
Add bootconfig magic word to the end of bootconfig on initrd
image for indicating explicitly the bootconfig is there.
Also tools/bootconfig treats wrong size or wrong checksum or
parse error as an error, because if there is a bootconfig magic
word, there must be a bootconfig.
The bootconfig magic word is "#BOOTCONFIG\n", 12 bytes word.
Thus the block image of the initrd file with bootconfig is
as follows.
[Initrd][bootconfig][size][csum][#BOOTCONFIG\n]
Link: http://lkml.kernel.org/r/158220112263.26565.3944814205960612841.stgit@devnote2
Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Diffstat (limited to 'Documentation/admin-guide/bootconfig.rst')
| -rw-r--r-- | Documentation/admin-guide/bootconfig.rst | 10 |
1 files changed, 7 insertions, 3 deletions
diff --git a/Documentation/admin-guide/bootconfig.rst b/Documentation/admin-guide/bootconfig.rst index b342a6796392..5e7609936507 100644 --- a/Documentation/admin-guide/bootconfig.rst +++ b/Documentation/admin-guide/bootconfig.rst @@ -102,9 +102,13 @@ Boot Kernel With a Boot Config ============================== Since the boot configuration file is loaded with initrd, it will be added -to the end of the initrd (initramfs) image file. The Linux kernel decodes -the last part of the initrd image in memory to get the boot configuration -data. +to the end of the initrd (initramfs) image file with size, checksum and +12-byte magic word as below. + +[initrd][bootconfig][size(u32)][checksum(u32)][#BOOTCONFIG\n] + +The Linux kernel decodes the last part of the initrd image in memory to +get the boot configuration data. Because of this "piggyback" method, there is no need to change or update the boot loader and the kernel image itself. |