The following commit has been merged into the locking/core branch of tip: Commit-ID: 0c3b61e00a0d0872c521586494ec23f6016c317a Gitweb: https://git.kernel.org/tip/0c3b61e00a0d0872c521586494ec23f6016c317a Author: Ard Biesheuvel <ardb@xxxxxxxxxx> AuthorDate: Wed, 15 Jun 2022 17:41:40 +02:00 Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx> CommitterDate: Fri, 24 Jun 2022 09:48:54 +02:00 jump_label: s390: avoid pointless initial NOP patching 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> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20220615154142.1574619-2-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 916cfcb..895f774 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" ".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 6bec000..d764f0d 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(); }
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