The following commit has been merged into the locking/core branch of tip: Commit-ID: 566a9522381495d27b596ee3bdc9578ba02a895d Gitweb: https://git.kernel.org/tip/566a9522381495d27b596ee3bdc9578ba02a895d Author: Jason Gerecke <killertofu@xxxxxxxxx> AuthorDate: Thu, 11 Feb 2021 13:48:48 -08:00 Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx> CommitterDate: Tue, 02 Mar 2021 15:06:34 +01:00 x86/jump_label: Mark arguments as const to satisfy asm constraints When compiling an external kernel module with `-O0` or `-O1`, the following compile error may be reported: ./arch/x86/include/asm/jump_label.h:25:2: error: impossible constraint in ‘asm’ 25 | asm_volatile_goto("1:" | ^~~~~~~~~~~~~~~~~ It appears that these lower optimization levels prevent GCC from detecting that the key/branch arguments can be treated as constants and used as immediate operands. To work around this, explicitly add the `const` label. Signed-off-by: Jason Gerecke <jason.gerecke@xxxxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Reviewed-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx> Acked-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx> Link: https://lkml.kernel.org/r/20210211214848.536626-1-jason.gerecke@xxxxxxxxx --- arch/x86/include/asm/jump_label.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/include/asm/jump_label.h b/arch/x86/include/asm/jump_label.h index 06c3cc2..7f20066 100644 --- a/arch/x86/include/asm/jump_label.h +++ b/arch/x86/include/asm/jump_label.h @@ -20,7 +20,7 @@ #include <linux/stringify.h> #include <linux/types.h> -static __always_inline bool arch_static_branch(struct static_key *key, bool branch) +static __always_inline bool arch_static_branch(struct static_key * const key, const bool branch) { asm_volatile_goto("1:" ".byte " __stringify(STATIC_KEY_INIT_NOP) "\n\t" @@ -36,7 +36,7 @@ l_yes: return true; } -static __always_inline bool arch_static_branch_jump(struct static_key *key, bool branch) +static __always_inline bool arch_static_branch_jump(struct static_key * const key, const bool branch) { asm_volatile_goto("1:" ".byte 0xe9\n\t .long %l[l_yes] - 2f\n\t"
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