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