From: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
Subject: init.h: improve __setup and early_param documentation
Igor noted in [1] that there are quite a few __setup() handling functions
that return incorrect values. Doing this can be harmless, but it can also
cause strings to be added to init's argument or environment list,
polluting them.
Since __setup() handling and return values are not documented, first add
documentation for that. Also add more documentation for early_param()
handling and return values.
For __setup() functions, returning 0 (not handled) has questionable
value if it is just a malformed option value, as in
rodata=junk
since returning 0 would just cause "rodata=junk" to be added to init's
environment unnecessarily:
Run /sbin/init as init process
with arguments:
/sbin/init
with environment:
HOME=/
TERM=linux
splash=native
rodata=junk
Also, there are no recommendations on whether to print a warning when an
unknown parameter value is seen. I am not addressing that here.
[1] lore.kernel.org/r/64644a2f-4a20-bab3-1e15-3b2cdd0defe3@xxxxxxxxxxxx
Link: https://lkml.kernel.org/r/20220221050852.1147-1-rdunlap@xxxxxxxxxxxxx
Signed-off-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
Reported-by: Igor Zhbanov <i.zhbanov@xxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/init.h | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
--- a/include/linux/init.h~inith-improve-__setup-and-early_param-documentation
+++ a/include/linux/init.h
@@ -320,12 +320,19 @@ struct obs_kernel_param {
__aligned(__alignof__(struct obs_kernel_param)) \
= { __setup_str_##unique_id, fn, early }
+/*
+ * NOTE: __setup functions return values:
+ * @fn returns 1 (or non-zero) if the option argument is "handled"
+ * and returns 0 if the option argument is "not handled".
+ */
#define __setup(str, fn) \
__setup_param(str, fn, fn, 0)
/*
- * NOTE: fn is as per module_param, not __setup!
- * Emits warning if fn returns non-zero.
+ * NOTE: @fn is as per module_param, not __setup!
+ * I.e., @fn returns 0 for no error or non-zero for error
+ * (possibly @fn returns a -errno value, but it does not matter).
+ * Emits warning if @fn returns non-zero.
*/
#define early_param(str, fn) \
__setup_param(str, fn, fn, 1)
_
