From: Vincent Mailhol mailhol.vincent@wanadoo.fr
commit 9ce02f0fc68326dd1f87a0a3a4c6ae7fdd39e6f6 upstream.
The macro __WARN_FLAGS() uses a local variable named "f". This being a common name, there is a risk of shadowing other variables.
For example, GCC would yield:
| In file included from ./include/linux/bug.h:5, | from ./include/linux/cpumask.h:14, | from ./arch/x86/include/asm/cpumask.h:5, | from ./arch/x86/include/asm/msr.h:11, | from ./arch/x86/include/asm/processor.h:22, | from ./arch/x86/include/asm/timex.h:5, | from ./include/linux/timex.h:65, | from ./include/linux/time32.h:13, | from ./include/linux/time.h:60, | from ./include/linux/stat.h:19, | from ./include/linux/module.h:13, | from virt/lib/irqbypass.mod.c:1: | ./include/linux/rcupdate.h: In function 'rcu_head_after_call_rcu': | ./arch/x86/include/asm/bug.h:80:21: warning: declaration of 'f' shadows a parameter [-Wshadow] | 80 | __auto_type f = BUGFLAG_WARNING|(flags); \ | | ^ | ./include/asm-generic/bug.h:106:17: note: in expansion of macro '__WARN_FLAGS' | 106 | __WARN_FLAGS(BUGFLAG_ONCE | \ | | ^~~~~~~~~~~~ | ./include/linux/rcupdate.h:1007:9: note: in expansion of macro 'WARN_ON_ONCE' | 1007 | WARN_ON_ONCE(func != (rcu_callback_t)~0L); | | ^~~~~~~~~~~~ | In file included from ./include/linux/rbtree.h:24, | from ./include/linux/mm_types.h:11, | from ./include/linux/buildid.h:5, | from ./include/linux/module.h:14, | from virt/lib/irqbypass.mod.c:1: | ./include/linux/rcupdate.h:1001:62: note: shadowed declaration is here | 1001 | rcu_head_after_call_rcu(struct rcu_head *rhp, rcu_callback_t f) | | ~~~~~~~~~~~~~~~^
For reference, sparse also warns about it, c.f. [1].
This patch renames the variable from f to __flags (with two underscore prefixes as suggested in the Linux kernel coding style [2]) in order to prevent collisions.
[1] https://lore.kernel.org/all/CAFGhKbyifH1a+nAMCvWM88TK6fpNPdzFtUXPmRGnnQeePV+...
[2] Linux kernel coding style, section 12) Macros, Enums and RTL, paragraph 5) namespace collisions when defining local variables in macros resembling functions https://www.kernel.org/doc/html/latest/process/coding-style.html#macros-enum...
Fixes: bfb1a7c91fb7 ("x86/bug: Merge annotate_reachable() into_BUG_FLAGS() asm") Signed-off-by: Vincent Mailhol mailhol.vincent@wanadoo.fr Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Reviewed-by: Nick Desaulniers ndesaulniers@google.com Acked-by: Josh Poimboeuf jpoimboe@redhat.com Link: https://lkml.kernel.org/r/20220324023742.106546-1-mailhol.vincent@wanadoo.fr Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/include/asm/bug.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/arch/x86/include/asm/bug.h +++ b/arch/x86/include/asm/bug.h @@ -77,9 +77,9 @@ do { \ */ #define __WARN_FLAGS(flags) \ do { \ - __auto_type f = BUGFLAG_WARNING|(flags); \ + __auto_type __flags = BUGFLAG_WARNING|(flags); \ instrumentation_begin(); \ - _BUG_FLAGS(ASM_UD2, f, ASM_REACHABLE); \ + _BUG_FLAGS(ASM_UD2, __flags, ASM_REACHABLE); \ instrumentation_end(); \ } while (0)