On Fri, Oct 11, 2024 at 10:13:38AM +0000, Alice Ryhl wrote:
> +#[cfg(CONFIG_JUMP_LABEL)]
> +#[cfg(not(CONFIG_HAVE_JUMP_LABEL_HACK))]
> +macro_rules! arch_static_branch {
> + ($key:path, $keytyp:ty, $field:ident, $branch:expr) => {'my_label: {
> + $crate::asm!(
> + include!(concat!(env!("OBJTREE"), "/rust/kernel/arch_static_branch_asm.rs"));
> + l_yes = label {
> + break 'my_label true;
> + },
> + symb = sym $key,
> + off = const ::core::mem::offset_of!($keytyp, $field),
> + branch = const $crate::jump_label::bool_to_int($branch),
> + );
> +
> + break 'my_label false;
> + }};
> +}
> +
> +#[macro_export]
> +#[doc(hidden)]
> +#[cfg(CONFIG_JUMP_LABEL)]
> +#[cfg(CONFIG_HAVE_JUMP_LABEL_HACK)]
> +macro_rules! arch_static_branch {
> + ($key:path, $keytyp:ty, $field:ident, $branch:expr) => {'my_label: {
> + $crate::asm!(
> + include!(concat!(env!("OBJTREE"), "/rust/kernel/arch_static_branch_asm.rs"));
> + l_yes = label {
> + break 'my_label true;
> + },
> + symb = sym $key,
> + off = const ::core::mem::offset_of!($keytyp, $field),
> + branch = const 2 | $crate::jump_label::bool_to_int($branch),
> + );
> +
> + break 'my_label false;
> + }};
Ouch... could we get rid of all this duplication by containing the hack
bit to ARCH_STATIC_BRANCH_ASM() like so?
diff --git a/arch/x86/include/asm/jump_label.h b/arch/x86/include/asm/jump_label.h
index ffd0d1a1a4af..3f1c1d6c0da1 100644
--- a/arch/x86/include/asm/jump_label.h
+++ b/arch/x86/include/asm/jump_label.h
@@ -24,7 +24,7 @@
#ifdef CONFIG_HAVE_JUMP_LABEL_HACK
#define ARCH_STATIC_BRANCH_ASM(key, label) \
"1: jmp " label " # objtool NOPs this \n\t" \
- JUMP_TABLE_ENTRY(key, label)
+ JUMP_TABLE_ENTRY(key " + 2", label)
#else /* !CONFIG_HAVE_JUMP_LABEL_HACK */
#define ARCH_STATIC_BRANCH_ASM(key, label) \
"1: .byte " __stringify(BYTES_NOP5) "\n\t" \
@@ -33,10 +33,8 @@
static __always_inline bool arch_static_branch(struct static_key * const key, const bool branch)
{
- int hack_bit = IS_ENABLED(CONFIG_HAVE_JUMP_LABEL_HACK) ? 2 : 0;
-
asm goto(ARCH_STATIC_BRANCH_ASM("%c0 + %c1", "%l[l_yes]")
- : : "i" (key), "i" (hack_bit | branch) : : l_yes);
+ : : "i" (key), "i" (branch) : : l_yes);
return false;
l_yes:
