On Wed, Jun 15, 2022 at 05:41:40PM +0200, Ard Biesheuvel wrote:
> Patching NOPs into other NOPs at boot time serves no purpose, so let's
> use the same NOP encodings at compile time and runtime.
>
> Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
> ---
> arch/s390/include/asm/jump_label.h | 5 ++---
> arch/s390/kernel/jump_label.c | 23 +++++---------------
> 2 files changed, 7 insertions(+), 21 deletions(-)
>
> diff --git a/arch/s390/include/asm/jump_label.h b/arch/s390/include/asm/jump_label.h
> index 916cfcb36d8a..895f774bbcc5 100644
> --- a/arch/s390/include/asm/jump_label.h
> +++ b/arch/s390/include/asm/jump_label.h
> @@ -10,7 +10,6 @@
> #include <linux/stringify.h>
>
> #define JUMP_LABEL_NOP_SIZE 6
> -#define JUMP_LABEL_NOP_OFFSET 2
>
> #ifdef CONFIG_CC_IS_CLANG
> #define JUMP_LABEL_STATIC_KEY_CONSTRAINT "i"
> @@ -21,12 +20,12 @@
> #endif
>
> /*
> - * We use a brcl 0,2 instruction for jump labels at compile time so it
> + * We use a brcl 0,<offset> instruction for jump labels so it
> * can be easily distinguished from a hotpatch generated instruction.
> */
> static __always_inline bool arch_static_branch(struct static_key *key, bool branch)
> {
> - asm_volatile_goto("0: brcl 0,"__stringify(JUMP_LABEL_NOP_OFFSET)"\n"
> + asm_volatile_goto("0: brcl 0,%l[label]\n"
Please, use tab after brcl, not space.
> ".pushsection __jump_table,\"aw\"\n"
> ".balign 8\n"
> ".long 0b-.,%l[label]-.\n"
> diff --git a/arch/s390/kernel/jump_label.c b/arch/s390/kernel/jump_label.c
> index 6bec000c6c1c..d764f0d229ab 100644
> --- a/arch/s390/kernel/jump_label.c
> +++ b/arch/s390/kernel/jump_label.c
> @@ -44,14 +44,8 @@ static void jump_label_bug(struct jump_entry *entry, struct insn *expected,
> panic("Corrupted kernel text");
> }
>
> -static struct insn orignop = {
> - .opcode = 0xc004,
> - .offset = JUMP_LABEL_NOP_OFFSET >> 1,
> -};
> -
> static void jump_label_transform(struct jump_entry *entry,
> - enum jump_label_type type,
> - int init)
> + enum jump_label_type type)
> {
> void *code = (void *)jump_entry_code(entry);
> struct insn old, new;
> @@ -63,27 +57,22 @@ static void jump_label_transform(struct jump_entry *entry,
> jump_label_make_branch(entry, &old);
> jump_label_make_nop(entry, &new);
> }
> - if (init) {
> - if (memcmp(code, &orignop, sizeof(orignop)))
> - jump_label_bug(entry, &orignop, &new);
> - } else {
> - if (memcmp(code, &old, sizeof(old)))
> - jump_label_bug(entry, &old, &new);
> - }
> + if (memcmp(code, &old, sizeof(old)))
> + jump_label_bug(entry, &old, &new);
> s390_kernel_write(code, &new, sizeof(new));
> }
>
> void arch_jump_label_transform(struct jump_entry *entry,
> enum jump_label_type type)
> {
> - jump_label_transform(entry, type, 0);
> + jump_label_transform(entry, type);
> text_poke_sync();
> }
>
> bool arch_jump_label_transform_queue(struct jump_entry *entry,
> enum jump_label_type type)
> {
> - jump_label_transform(entry, type, 0);
> + jump_label_transform(entry, type);
> return true;
> }
>
> @@ -95,6 +84,4 @@ void arch_jump_label_transform_apply(void)
> void __init_or_module arch_jump_label_transform_static(struct jump_entry *entry,
> enum jump_label_type type)
> {
> - jump_label_transform(entry, type, 1);
> - text_poke_sync();
> }
With the comment above:
Acked-by: Alexander Gordeev <agordeev@xxxxxxxxxxxxx>
Thanks!
> --
> 2.35.1
>
