forked from Minki/linux
7e6b9db27d
Instead of defaulting to patching NOP opcodes at init time, and leaving it to the architectures to override this if this is not needed, switch to a model where doing nothing is the default. This is the common case by far, as only MIPS requires NOP patching at init time. On all other architectures, the correct encodings are emitted by the compiler and so no initial patching is needed. Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Mark Rutland <mark.rutland@arm.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lore.kernel.org/r/20220615154142.1574619-4-ardb@kernel.org
45 lines
1.1 KiB
C
45 lines
1.1 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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