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doc: Add documentation for bootloader_{type,version}
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Add documentation for kernel/bootloader_type and
kernel/bootloader_version to sysctl/kernel.txt.  This should really
have been done a long time ago.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: Shen Feng <shen@cn.fujitsu.com>
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H. Peter Anvin committed Dec 11, 2009
1 parent 5054225 commit d75757a
Showing 1 changed file with 31 additions and 0 deletions.
31 changes: 31 additions & 0 deletions Documentation/sysctl/kernel.txt
Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,8 @@ Currently, these files might (depending on your configuration)
show up in /proc/sys/kernel:
- acpi_video_flags
- acct
- bootloader_type [ X86 only ]
- bootloader_version [ X86 only ]
- callhome [ S390 only ]
- auto_msgmni
- core_pattern
Expand Down Expand Up @@ -93,6 +95,35 @@ valid for 30 seconds.

==============================================================

bootloader_type:

x86 bootloader identification

This gives the bootloader type number as indicated by the bootloader,
shifted left by 4, and OR'd with the low four bits of the bootloader
version. The reason for this encoding is that this used to match the
type_of_loader field in the kernel header; the encoding is kept for
backwards compatibility. That is, if the full bootloader type number
is 0x15 and the full version number is 0x234, this file will contain
the value 340 = 0x154.

See the type_of_loader and ext_loader_type fields in
Documentation/x86/boot.txt for additional information.

==============================================================

bootloader_version:

x86 bootloader version

The complete bootloader version number. In the example above, this
file will contain the value 564 = 0x234.

See the type_of_loader and ext_loader_ver fields in
Documentation/x86/boot.txt for additional information.

==============================================================

callhome:

Controls the kernel's callhome behavior in case of a kernel panic.
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