Re: [PATCH v9 4/5] jump_label: adjust inline asm to be consistent

From: Steven Rostedt
Date: Tue Oct 01 2024 - 10:17:15 EST


Can I get some more acks from the arch maintainers? So far there's only one
ack from Peter Zijlstra for x86. But this touches arm, arm64, loongarch and
riscv too.

-- Steve


On Tue, 01 Oct 2024 13:30:01 +0000
Alice Ryhl <aliceryhl@xxxxxxxxxx> wrote:

> To avoid duplication of inline asm between C and Rust, we need to
> import the inline asm from the relevant `jump_label.h` header into Rust.
> To make that easier, this patch updates the header files to expose the
> inline asm via a new ARCH_STATIC_BRANCH_ASM macro.
>
> The header files are all updated to define a ARCH_STATIC_BRANCH_ASM that
> takes the same arguments in a consistent order so that Rust can use the
> same logic for every architecture.
>
> Suggested-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
> Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
> Co-developed-by: Miguel Ojeda <ojeda@xxxxxxxxxx>
> Signed-off-by: Miguel Ojeda <ojeda@xxxxxxxxxx>
> Signed-off-by: Alice Ryhl <aliceryhl@xxxxxxxxxx>
> ---
> arch/arm/include/asm/jump_label.h | 14 +++++----
> arch/arm64/include/asm/jump_label.h | 20 ++++++++-----
> arch/loongarch/include/asm/jump_label.h | 16 +++++++----
> arch/riscv/include/asm/jump_label.h | 50 ++++++++++++++++++---------------
> arch/x86/include/asm/jump_label.h | 38 ++++++++++---------------
> 5 files changed, 75 insertions(+), 63 deletions(-)
>
> diff --git a/arch/arm/include/asm/jump_label.h b/arch/arm/include/asm/jump_label.h
> index e4eb54f6cd9f..a35aba7f548c 100644
> --- a/arch/arm/include/asm/jump_label.h
> +++ b/arch/arm/include/asm/jump_label.h
> @@ -9,13 +9,17 @@
>
> #define JUMP_LABEL_NOP_SIZE 4
>
> +/* This macro is also expanded on the Rust side. */
> +#define ARCH_STATIC_BRANCH_ASM(key, label) \
> + "1:\n\t" \
> + WASM(nop) "\n\t" \
> + ".pushsection __jump_table, \"aw\"\n\t" \
> + ".word 1b, " label ", " key "\n\t" \
> + ".popsection\n\t" \
> +
> static __always_inline bool arch_static_branch(struct static_key *key, bool branch)
> {
> - asm goto("1:\n\t"
> - WASM(nop) "\n\t"
> - ".pushsection __jump_table, \"aw\"\n\t"
> - ".word 1b, %l[l_yes], %c0\n\t"
> - ".popsection\n\t"
> + asm goto(ARCH_STATIC_BRANCH_ASM("%c0", "%l[l_yes]")
> : : "i" (&((char *)key)[branch]) : : l_yes);
>
> return false;
> diff --git a/arch/arm64/include/asm/jump_label.h b/arch/arm64/include/asm/jump_label.h
> index a0a5bbae7229..424ed421cd97 100644
> --- a/arch/arm64/include/asm/jump_label.h
> +++ b/arch/arm64/include/asm/jump_label.h
> @@ -19,10 +19,14 @@
> #define JUMP_TABLE_ENTRY(key, label) \
> ".pushsection __jump_table, \"aw\"\n\t" \
> ".align 3\n\t" \
> - ".long 1b - ., %l["#label"] - .\n\t" \
> - ".quad %c0 - .\n\t" \
> - ".popsection\n\t" \
> - : : "i"(key) : : label
> + ".long 1b - ., " label " - .\n\t" \
> + ".quad " key " - .\n\t" \
> + ".popsection\n\t"
> +
> +/* This macro is also expanded on the Rust side. */
> +#define ARCH_STATIC_BRANCH_ASM(key, label) \
> + "1: nop\n\t" \
> + JUMP_TABLE_ENTRY(key, label)
>
> static __always_inline bool arch_static_branch(struct static_key * const key,
> const bool branch)
> @@ -30,8 +34,8 @@ static __always_inline bool arch_static_branch(struct static_key * const key,
> char *k = &((char *)key)[branch];
>
> asm goto(
> - "1: nop \n\t"
> - JUMP_TABLE_ENTRY(k, l_yes)
> + ARCH_STATIC_BRANCH_ASM("%c0", "%l[l_yes]")
> + : : "i"(k) : : l_yes
> );
>
> return false;
> @@ -43,9 +47,11 @@ static __always_inline bool arch_static_branch_jump(struct static_key * const ke
> const bool branch)
> {
> char *k = &((char *)key)[branch];
> +
> asm goto(
> "1: b %l[l_yes] \n\t"
> - JUMP_TABLE_ENTRY(k, l_yes)
> + JUMP_TABLE_ENTRY("%c0", "%l[l_yes]")
> + : : "i"(k) : : l_yes
> );
> return false;
> l_yes:
> diff --git a/arch/loongarch/include/asm/jump_label.h b/arch/loongarch/include/asm/jump_label.h
> index 29acfe3de3fa..8a924bd69d19 100644
> --- a/arch/loongarch/include/asm/jump_label.h
> +++ b/arch/loongarch/include/asm/jump_label.h
> @@ -13,18 +13,22 @@
>
> #define JUMP_LABEL_NOP_SIZE 4
>
> -#define JUMP_TABLE_ENTRY \
> +/* This macro is also expanded on the Rust side. */
> +#define JUMP_TABLE_ENTRY(key, label) \
> ".pushsection __jump_table, \"aw\" \n\t" \
> ".align 3 \n\t" \
> - ".long 1b - ., %l[l_yes] - . \n\t" \
> - ".quad %0 - . \n\t" \
> + ".long 1b - ., " label " - . \n\t" \
> + ".quad " key " - . \n\t" \
> ".popsection \n\t"
>
> +#define ARCH_STATIC_BRANCH_ASM(key, label) \
> + "1: nop \n\t" \
> + JUMP_TABLE_ENTRY(key, label)
> +
> static __always_inline bool arch_static_branch(struct static_key * const key, const bool branch)
> {
> asm goto(
> - "1: nop \n\t"
> - JUMP_TABLE_ENTRY
> + ARCH_STATIC_BRANCH_ASM("%0", "%l[l_yes]")
> : : "i"(&((char *)key)[branch]) : : l_yes);
>
> return false;
> @@ -37,7 +41,7 @@ static __always_inline bool arch_static_branch_jump(struct static_key * const ke
> {
> asm goto(
> "1: b %l[l_yes] \n\t"
> - JUMP_TABLE_ENTRY
> + JUMP_TABLE_ENTRY("%0", "%l[l_yes]")
> : : "i"(&((char *)key)[branch]) : : l_yes);
>
> return false;
> diff --git a/arch/riscv/include/asm/jump_label.h b/arch/riscv/include/asm/jump_label.h
> index 1c768d02bd0c..87a71cc6d146 100644
> --- a/arch/riscv/include/asm/jump_label.h
> +++ b/arch/riscv/include/asm/jump_label.h
> @@ -16,21 +16,28 @@
>
> #define JUMP_LABEL_NOP_SIZE 4
>
> +#define JUMP_TABLE_ENTRY(key, label) \
> + ".pushsection __jump_table, \"aw\" \n\t" \
> + ".align " RISCV_LGPTR " \n\t" \
> + ".long 1b - ., " label " - . \n\t" \
> + "" RISCV_PTR " " key " - . \n\t" \
> + ".popsection \n\t"
> +
> +/* This macro is also expanded on the Rust side. */
> +#define ARCH_STATIC_BRANCH_ASM(key, label) \
> + " .align 2 \n\t" \
> + " .option push \n\t" \
> + " .option norelax \n\t" \
> + " .option norvc \n\t" \
> + "1: nop \n\t" \
> + " .option pop \n\t" \
> + JUMP_TABLE_ENTRY(key, label)
> +
> static __always_inline bool arch_static_branch(struct static_key * const key,
> const bool branch)
> {
> asm goto(
> - " .align 2 \n\t"
> - " .option push \n\t"
> - " .option norelax \n\t"
> - " .option norvc \n\t"
> - "1: nop \n\t"
> - " .option pop \n\t"
> - " .pushsection __jump_table, \"aw\" \n\t"
> - " .align " RISCV_LGPTR " \n\t"
> - " .long 1b - ., %l[label] - . \n\t"
> - " " RISCV_PTR " %0 - . \n\t"
> - " .popsection \n\t"
> + ARCH_STATIC_BRANCH_ASM("%0", "%l[label]")
> : : "i"(&((char *)key)[branch]) : : label);
>
> return false;
> @@ -38,21 +45,20 @@ static __always_inline bool arch_static_branch(struct static_key * const key,
> return true;
> }
>
> +#define ARCH_STATIC_BRANCH_JUMP_ASM(key, label) \
> + " .align 2 \n\t" \
> + " .option push \n\t" \
> + " .option norelax \n\t" \
> + " .option norvc \n\t" \
> + "1: j " label " \n\t" \
> + " .option pop \n\t" \
> + JUMP_TABLE_ENTRY(key, label)
> +
> static __always_inline bool arch_static_branch_jump(struct static_key * const key,
> const bool branch)
> {
> asm goto(
> - " .align 2 \n\t"
> - " .option push \n\t"
> - " .option norelax \n\t"
> - " .option norvc \n\t"
> - "1: j %l[label] \n\t"
> - " .option pop \n\t"
> - " .pushsection __jump_table, \"aw\" \n\t"
> - " .align " RISCV_LGPTR " \n\t"
> - " .long 1b - ., %l[label] - . \n\t"
> - " " RISCV_PTR " %0 - . \n\t"
> - " .popsection \n\t"
> + ARCH_STATIC_BRANCH_JUMP_ASM("%0", "%l[label]")
> : : "i"(&((char *)key)[branch]) : : label);
>
> return false;
> diff --git a/arch/x86/include/asm/jump_label.h b/arch/x86/include/asm/jump_label.h
> index cbbef32517f0..fb79fa1cf70a 100644
> --- a/arch/x86/include/asm/jump_label.h
> +++ b/arch/x86/include/asm/jump_label.h
> @@ -12,49 +12,41 @@
> #include <linux/stringify.h>
> #include <linux/types.h>
>
> -#define JUMP_TABLE_ENTRY \
> +#define JUMP_TABLE_ENTRY(key, label) \
> ".pushsection __jump_table, \"aw\" \n\t" \
> _ASM_ALIGN "\n\t" \
> ".long 1b - . \n\t" \
> - ".long %l[l_yes] - . \n\t" \
> - _ASM_PTR "%c0 + %c1 - .\n\t" \
> + ".long " label " - . \n\t" \
> + _ASM_PTR " " key " - . \n\t" \
> ".popsection \n\t"
>
> +/* This macro is also expanded on the Rust side. */
> #ifdef CONFIG_HAVE_JUMP_LABEL_HACK
> -
> -static __always_inline bool arch_static_branch(struct static_key *key, bool branch)
> -{
> - asm goto("1:"
> - "jmp %l[l_yes] # objtool NOPs this \n\t"
> - JUMP_TABLE_ENTRY
> - : : "i" (key), "i" (2 | branch) : : l_yes);
> -
> - return false;
> -l_yes:
> - return true;
> -}
> -
> +#define ARCH_STATIC_BRANCH_ASM(key, label) \
> + "1: jmp " label " # objtool NOPs this \n\t" \
> + JUMP_TABLE_ENTRY(key, label)
> #else /* !CONFIG_HAVE_JUMP_LABEL_HACK */
> +#define ARCH_STATIC_BRANCH_ASM(key, label) \
> + "1: .byte " __stringify(BYTES_NOP5) "\n\t" \
> + JUMP_TABLE_ENTRY(key, label)
> +#endif /* CONFIG_HAVE_JUMP_LABEL_HACK */
>
> static __always_inline bool arch_static_branch(struct static_key * const key, const bool branch)
> {
> - asm goto("1:"
> - ".byte " __stringify(BYTES_NOP5) "\n\t"
> - JUMP_TABLE_ENTRY
> - : : "i" (key), "i" (branch) : : l_yes);
> + 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);
>
> return false;
> l_yes:
> return true;
> }
>
> -#endif /* CONFIG_HAVE_JUMP_LABEL_HACK */
> -
> static __always_inline bool arch_static_branch_jump(struct static_key * const key, const bool branch)
> {
> asm goto("1:"
> "jmp %l[l_yes]\n\t"
> - JUMP_TABLE_ENTRY
> + JUMP_TABLE_ENTRY("%c0 + %c1", "%l[l_yes]")
> : : "i" (key), "i" (branch) : : l_yes);
>
> return false;
>