Messages in this thread Patch in this message | | | From | Jason Gerecke <> | Subject | [PATCH] RFC: x86/jump_label: Mark arguments as const to satisfy asm constraints | Date | Thu, 11 Feb 2021 13:48:48 -0800 |
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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@wacom.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Ard Biesheuvel <ardb@kernel.org> --- Marked RFC since I'm not familiar with this subsystem or the asm blocks that are impacted. Extra-close inspection would be appreciated.
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 06c3cc22a058..7f2006645d84 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 @@ static __always_inline bool arch_static_branch(struct static_key *key, bool bran 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" -- 2.30.1
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