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55 lines
1.5 KiB
55 lines
1.5 KiB
// SPDX-License-Identifier: GPL-2.0+ |
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/* |
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* Copyright (C) 2019 Helge Deller <[email protected]> |
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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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