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authorWolfram Sang <wsa+renesas@sang-engineering.com>2021-06-03 14:58:41 +0200
committerJonathan Corbet <corbet@lwn.net>2021-06-14 15:58:22 -0600
commit005747526d4f3c2ec995891e95cb7625161022f9 (patch)
tree012d3da858ae493cf64ccb040754a6bff528c9c8 /Documentation/fault-injection
parent91a1265cacdd96229304adddf18dcf64a4b8c040 (diff)
docs: fault-injection: fix non-working usage of negative values
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: Wolfram Sang <wsa+renesas@sang-engineering.com> Link: https://lore.kernel.org/r/20210603125841.27436-1-wsa+renesas@sang-engineering.com Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Diffstat (limited to 'Documentation/fault-injection')
-rw-r--r--Documentation/fault-injection/fault-injection.rst24
1 files changed, 14 insertions, 10 deletions
diff --git a/Documentation/fault-injection/fault-injection.rst b/Documentation/fault-injection/fault-injection.rst
index 31ecfe44e5b4..f47d05ed0d94 100644
--- a/Documentation/fault-injection/fault-injection.rst
+++ b/Documentation/fault-injection/fault-injection.rst
@@ -78,8 +78,10 @@ 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:
@@ -167,11 +169,13 @@ 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
^^^^^^^^^^^
@@ -255,7 +259,7 @@ 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
@@ -309,7 +313,7 @@ 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
@@ -336,11 +340,11 @@ 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