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docs: disable KASLR when debugging kernel

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commit 6807c84652 ("x86: Enable KASLR by default") enables KASLR
by default on x86. While KASLR will confuse gdb which resolve kernel
symbol address from symbol table of vmlinux. We should turn off KASLR for
kernel debugging.

Signed-off-by: Zhouyi Zhou <zhouzhouyi@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
This commit is contained in:
Zhouyi Zhou 2017-07-07 15:11:46 +08:00 committed by Jonathan Corbet
parent 4c0477899f
commit 14994a9bb4
1 changed files with 10 additions and 1 deletions
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11
Documentation/dev-tools/kgdb.rst
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@ -348,6 +348,15 @@ default behavior is always set to 0.
- ``echo 1 > /sys/module/debug_core/parameters/kgdbreboot`` - ``echo 1 > /sys/module/debug_core/parameters/kgdbreboot``
- Enter the debugger on reboot notify. - Enter the debugger on reboot notify.
Kernel parameter: ``nokaslr``
-----------------------------
If the architecture that you are using enable KASLR by default,
you should consider turning it off. KASLR randomizes the
virtual address where the kernel image is mapped and confuse
gdb which resolve kernel symbol address from symbol table
of vmlinux.
Using kdb Using kdb
========= =========
@ -358,7 +367,7 @@ This is a quick example of how to use kdb.
1. Configure kgdboc at boot using kernel parameters:: 1. Configure kgdboc at boot using kernel parameters::
console=ttyS0,115200 kgdboc=ttyS0,115200 console=ttyS0,115200 kgdboc=ttyS0,115200 nokaslr
OR OR