From abc7da58c4b388ab9f6a756c0f297c29d3af665f Mon Sep 17 00:00:00 2001 From: Randy Dunlap Date: Wed, 23 Mar 2022 16:06:11 -0700 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@omprussia.ru Link: https://lkml.kernel.org/r/20220221050852.1147-1-rdunlap@infradead.org Signed-off-by: Randy Dunlap Reported-by: Igor Zhbanov Cc: Ingo Molnar Cc: Greg Kroah-Hartman Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/init.h | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) (limited to 'include') diff --git a/include/linux/init.h b/include/linux/init.h index d82b4b2e1d25..baf0b29a7010 100644 --- a/include/linux/init.h +++ b/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) -- cgit v1.2.3