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-rw-r--r--Documentation/dev-tools/gdb-kernel-debugging.rst6
-rw-r--r--Documentation/dev-tools/kgdb.rst11
2 files changed, 14 insertions, 3 deletions
diff --git a/Documentation/dev-tools/gdb-kernel-debugging.rst b/Documentation/dev-tools/gdb-kernel-debugging.rst
index 5e93c9bc6619..19df79286f00 100644
--- a/Documentation/dev-tools/gdb-kernel-debugging.rst
+++ b/Documentation/dev-tools/gdb-kernel-debugging.rst
@@ -31,11 +31,13 @@ Setup
CONFIG_DEBUG_INFO_REDUCED off. If your architecture supports
CONFIG_FRAME_POINTER, keep it enabled.
-- Install that kernel on the guest.
+- Install that kernel on the guest, turn off KASLR if necessary by adding
+ "nokaslr" to the kernel command line.
Alternatively, QEMU allows to boot the kernel directly using -kernel,
-append, -initrd command line switches. This is generally only useful if
you do not depend on modules. See QEMU documentation for more details on
- this mode.
+ this mode. In this case, you should build the kernel with
+ CONFIG_RANDOMIZE_BASE disabled if the architecture supports KASLR.
- Enable the gdb stub of QEMU/KVM, either
diff --git a/Documentation/dev-tools/kgdb.rst b/Documentation/dev-tools/kgdb.rst
index 75273203a35a..d38be58f872a 100644
--- a/Documentation/dev-tools/kgdb.rst
+++ b/Documentation/dev-tools/kgdb.rst
@@ -348,6 +348,15 @@ default behavior is always set to 0.
- ``echo 1 > /sys/module/debug_core/parameters/kgdbreboot``
- 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
=========
@@ -358,7 +367,7 @@ This is a quick example of how to use kdb.
1. Configure kgdboc at boot using kernel parameters::
- console=ttyS0,115200 kgdboc=ttyS0,115200
+ console=ttyS0,115200 kgdboc=ttyS0,115200 nokaslr
OR