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authorLinus Torvalds <torvalds@linux-foundation.org>2021-09-09 13:11:15 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2021-09-09 13:11:15 -0700
commit43175623dd0dffccacbf014e368ee77f77c73898 (patch)
tree6d4e2cbcf7207bd4c98cb6b2b43330f507560290 /Documentation
parentf154c806676ad7153c6e161f30c53a44855329d6 (diff)
parentcfd799837dbc48499abb05d1891b3d9992354d3a (diff)
Merge tag 'trace-v5.15-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace
Pull more tracing updates from Steven Rostedt: - Add migrate-disable counter to tracing header - Fix error handling in event probes - Fix missed unlock in osnoise in error path - Fix merge issue with tools/bootconfig - Clean up bootconfig data when init memory is removed - Fix bootconfig to loop only on subkeys - Have kernel command lines override bootconfig options - Increase field counts for synthetic events - Have histograms dynamic allocate event elements to save space - Fixes in testing and documentation * tag 'trace-v5.15-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: tracing/boot: Fix to loop on only subkeys selftests/ftrace: Exclude "(fault)" in testing add/remove eprobe events tracing: Dynamically allocate the per-elt hist_elt_data array tracing: synth events: increase max fields count tools/bootconfig: Show whole test command for each test case bootconfig: Fix missing return check of xbc_node_compose_key function tools/bootconfig: Fix tracing_on option checking in ftrace2bconf.sh docs: bootconfig: Add how to use bootconfig for kernel parameters init/bootconfig: Reorder init parameter from bootconfig and cmdline init: bootconfig: Remove all bootconfig data when the init memory is removed tracing/osnoise: Fix missed cpus_read_unlock() in start_per_cpu_kthreads() tracing: Fix some alloc_event_probe() error handling bugs tracing: Add migrate-disabled counter to tracing output.
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/admin-guide/bootconfig.rst39
1 files changed, 38 insertions, 1 deletions
diff --git a/Documentation/admin-guide/bootconfig.rst b/Documentation/admin-guide/bootconfig.rst
index 6a79f2e59396..a1860fc0ca88 100644
--- a/Documentation/admin-guide/bootconfig.rst
+++ b/Documentation/admin-guide/bootconfig.rst
@@ -178,7 +178,7 @@ update the boot loader and the kernel image itself as long as the boot
loader passes the correct initrd file size. If by any chance, the boot
loader passes a longer size, the kernel fails to find the bootconfig data.
-To do this operation, Linux kernel provides "bootconfig" command under
+To do this operation, Linux kernel provides ``bootconfig`` command under
tools/bootconfig, which allows admin to apply or delete the config file
to/from initrd image. You can build it by the following command::
@@ -196,6 +196,43 @@ To remove the config from the image, you can use -d option as below::
Then add "bootconfig" on the normal kernel command line to tell the
kernel to look for the bootconfig at the end of the initrd file.
+
+Kernel parameters via Boot Config
+=================================
+
+In addition to the kernel command line, the boot config can be used for
+passing the kernel parameters. All the key-value pairs under ``kernel``
+key will be passed to kernel cmdline directly. Moreover, the key-value
+pairs under ``init`` will be passed to init process via the cmdline.
+The parameters are concatinated with user-given kernel cmdline string
+as the following order, so that the command line parameter can override
+bootconfig parameters (this depends on how the subsystem handles parameters
+but in general, earlier parameter will be overwritten by later one.)::
+
+ [bootconfig params][cmdline params] -- [bootconfig init params][cmdline init params]
+
+Here is an example of the bootconfig file for kernel/init parameters.::
+
+ kernel {
+ root = 01234567-89ab-cdef-0123-456789abcd
+ }
+ init {
+ splash
+ }
+
+This will be copied into the kernel cmdline string as the following::
+
+ root="01234567-89ab-cdef-0123-456789abcd" -- splash
+
+If user gives some other command line like,::
+
+ ro bootconfig -- quiet
+
+The final kernel cmdline will be the following::
+
+ root="01234567-89ab-cdef-0123-456789abcd" ro bootconfig -- splash quiet
+
+
Config File Limitation
======================