// SPDX-License-Identifier: GPL-2.0+ /* * Copyright (C) 2019 Helge Deller <deller@gmx.de> * * Based on arch/arm64/kernel/jump_label.c */ #include <linux/kernel.h> #include <linux/jump_label.h> #include <linux/bug.h> #include <asm/alternative.h> #include <asm/patch.h> static inline int reassemble_17(int as17) { return (((as17 & 0x10000) >> 16) | ((as17 & 0x0f800) << 5) | ((as17 & 0x00400) >> 8) | ((as17 & 0x003ff) << 3)); } void arch_jump_label_transform(struct jump_entry *entry, enum jump_label_type type) { void *addr = (void *)jump_entry_code(entry); u32 insn; if (type == JUMP_LABEL_JMP) { void *target = (void *)jump_entry_target(entry); int distance = target - addr; /* * Encode the PA1.1 "b,n" instruction with a 17-bit * displacement. In case we hit the BUG(), we could use * another branch instruction with a 22-bit displacement on * 64-bit CPUs instead. But this seems sufficient for now. */ distance -= 8; BUG_ON(distance > 262143 || distance < -262144); insn = 0xe8000002 | reassemble_17(distance >> 2); } else { insn = INSN_NOP; } patch_text(addr, insn); } void arch_jump_label_transform_static(struct jump_entry *entry, enum jump_label_type type) { /* * We use the architected NOP in arch_static_branch, so there's no * need to patch an identical NOP over the top of it here. The core * will call arch_jump_label_transform from a module notifier if the * NOP needs to be replaced by a branch. */ }