| From 9ce02f0fc68326dd1f87a0a3a4c6ae7fdd39e6f6 Mon Sep 17 00:00:00 2001 |
| From: Vincent Mailhol <mailhol.vincent@wanadoo.fr> |
| Date: Thu, 24 Mar 2022 11:37:42 +0900 |
| Subject: x86/bug: Prevent shadowing in __WARN_FLAGS |
| |
| 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+1sw@mail.gmail.com/ |
| |
| [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-enums-and-rtl |
| |
| 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) |
| |