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Commit c7bd4927 authored by Wolfram Sang's avatar Wolfram Sang Committed by Greg Kroah-Hartman
Browse files

docs: fault-injection: fix non-working usage of negative values 



[ Upstream commit 005747526d4f3c2ec995891e95cb7625161022f9 ]

Fault injection uses debugfs in a way that the provided values via sysfs
are interpreted as u64. Providing negative numbers results in an error:

/sys/kernel/debug/fail_function# echo -1 > times
sh: write error: Invalid argument

Update the docs and examples to use "printf %#x <val>" in these cases.
For "retval", reword the paragraph a little and fix a typo.

Signed-off-by: default avatarWolfram Sang <wsa+renesas@sang-engineering.com>
Link: https://lore.kernel.org/r/20210603125841.27436-1-wsa+renesas@sang-engineering.com


Signed-off-by: default avatarJonathan Corbet <corbet@lwn.net>
Stable-dep-of: d472cf797c4e ("debugfs: fix error when writing negative value to atomic_t debugfs file")
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 6865a549

Documentation/fault-injection/fault-injection.rst

+14 −10
Original line number Diff line number Diff line
@@ -74,8 +74,10 @@ configuration of fault-injection capabilities. 


- /sys/kernel/debug/fail*/times:



	specifies how many times failures may happen at most.

	A value of -1 means "no limit".

	specifies how many times failures may happen at most. A value of -1

	means "no limit". Note, though, that this file only accepts unsigned

	values. So, if you want to specify -1, you better use 'printf' instead

	of 'echo', e.g.: $ printf %#x -1 > times



- /sys/kernel/debug/fail*/space:
@@ -163,11 +165,13 @@ configuration of fault-injection capabilities. 
	- ERRNO: retval must be -1 to -MAX_ERRNO (-4096).

	- ERR_NULL: retval must be 0 or -1 to -MAX_ERRNO (-4096).



- /sys/kernel/debug/fail_function/<functiuon-name>/retval:

- /sys/kernel/debug/fail_function/<function-name>/retval:



	specifies the "error" return value to inject to the given

	function for given function. This will be created when

	user specifies new injection entry.

	specifies the "error" return value to inject to the given function.

	This will be created when the user specifies a new injection entry.

	Note that this file only accepts unsigned values. So, if you want to

	use a negative errno, you better use 'printf' instead of 'echo', e.g.:

	$ printf %#x -12 > retval



Boot option

^^^^^^^^^^^
@@ -250,7 +254,7 @@ Application Examples 
    echo Y > /sys/kernel/debug/$FAILTYPE/task-filter

    echo 10 > /sys/kernel/debug/$FAILTYPE/probability

    echo 100 > /sys/kernel/debug/$FAILTYPE/interval

    echo -1 > /sys/kernel/debug/$FAILTYPE/times

    printf %#x -1 > /sys/kernel/debug/$FAILTYPE/times

    echo 0 > /sys/kernel/debug/$FAILTYPE/space

    echo 2 > /sys/kernel/debug/$FAILTYPE/verbose

    echo 1 > /sys/kernel/debug/$FAILTYPE/ignore-gfp-wait
@@ -304,7 +308,7 @@ Application Examples 
    echo N > /sys/kernel/debug/$FAILTYPE/task-filter

    echo 10 > /sys/kernel/debug/$FAILTYPE/probability

    echo 100 > /sys/kernel/debug/$FAILTYPE/interval

    echo -1 > /sys/kernel/debug/$FAILTYPE/times

    printf %#x -1 > /sys/kernel/debug/$FAILTYPE/times

    echo 0 > /sys/kernel/debug/$FAILTYPE/space

    echo 2 > /sys/kernel/debug/$FAILTYPE/verbose

    echo 1 > /sys/kernel/debug/$FAILTYPE/ignore-gfp-wait
@@ -331,11 +335,11 @@ Application Examples 
    FAILTYPE=fail_function

    FAILFUNC=open_ctree

    echo $FAILFUNC > /sys/kernel/debug/$FAILTYPE/inject

    echo -12 > /sys/kernel/debug/$FAILTYPE/$FAILFUNC/retval

    printf %#x -12 > /sys/kernel/debug/$FAILTYPE/$FAILFUNC/retval

    echo N > /sys/kernel/debug/$FAILTYPE/task-filter

    echo 100 > /sys/kernel/debug/$FAILTYPE/probability

    echo 0 > /sys/kernel/debug/$FAILTYPE/interval

    echo -1 > /sys/kernel/debug/$FAILTYPE/times

    printf %#x -1 > /sys/kernel/debug/$FAILTYPE/times

    echo 0 > /sys/kernel/debug/$FAILTYPE/space

    echo 1 > /sys/kernel/debug/$FAILTYPE/verbose