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xen/arm: arm64: Add helpers to decode and encode branch instructions
We may need to update branch instruction when patching Xen. The code has been imported from the files arch/arm64/kernel/insn.c and arch/arm64/include/asm/insn.h in Linux v4.6. Note that only the necessary helpers have been imported. Signed-off-by: Julien Grall <julien.grall@arm.com> Acked-by: Stefano Stabellini <sstabellini@kernel.org>
This commit is contained in:
Julien Grall authored and Stefano Stabellini committed
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@@ -5,6 +5,7 @@ obj-$(EARLY_PRINTK) += debug.o
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obj-y += domctl.o
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obj-y += domain.o
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obj-y += entry.o
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obj-y += insn.o
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obj-y += smpboot.o
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obj-y += traps.o
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obj-y += vfp.o
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@@ -0,0 +1,219 @@
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/*
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* Based on Linux v4.6 arch/arm64/kernel.ins.c
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*
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* Copyright (C) 2013 Huawei Ltd.
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* Author: Jiang Liu <liuj97@gmail.com>
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*
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* Copyright (C) 2014-2016 Zi Shen Lim <zlim.lnx@gmail.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <xen/config.h>
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#include <xen/types.h>
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#include <xen/lib.h>
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#include <xen/errno.h>
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#include <xen/sizes.h>
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#include <xen/bitops.h>
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#include <asm/insn.h>
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#include <asm/arm64/insn.h>
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#define __kprobes
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#define pr_err(fmt, ...) printk(XENLOG_ERR fmt, ## __VA_ARGS__)
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bool aarch64_insn_is_branch_imm(u32 insn)
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{
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return (aarch64_insn_is_b(insn) || aarch64_insn_is_bl(insn) ||
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aarch64_insn_is_tbz(insn) || aarch64_insn_is_tbnz(insn) ||
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aarch64_insn_is_cbz(insn) || aarch64_insn_is_cbnz(insn) ||
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aarch64_insn_is_bcond(insn));
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}
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static int __kprobes aarch64_get_imm_shift_mask(enum aarch64_insn_imm_type type,
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u32 *maskp, int *shiftp)
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{
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u32 mask;
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int shift;
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switch (type) {
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case AARCH64_INSN_IMM_26:
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mask = BIT(26) - 1;
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shift = 0;
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break;
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case AARCH64_INSN_IMM_19:
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mask = BIT(19) - 1;
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shift = 5;
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break;
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case AARCH64_INSN_IMM_16:
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mask = BIT(16) - 1;
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shift = 5;
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break;
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case AARCH64_INSN_IMM_14:
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mask = BIT(14) - 1;
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shift = 5;
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break;
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case AARCH64_INSN_IMM_12:
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mask = BIT(12) - 1;
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shift = 10;
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break;
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case AARCH64_INSN_IMM_9:
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mask = BIT(9) - 1;
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shift = 12;
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break;
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case AARCH64_INSN_IMM_7:
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mask = BIT(7) - 1;
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shift = 15;
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break;
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case AARCH64_INSN_IMM_6:
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case AARCH64_INSN_IMM_S:
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mask = BIT(6) - 1;
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shift = 10;
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break;
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case AARCH64_INSN_IMM_R:
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mask = BIT(6) - 1;
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shift = 16;
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break;
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default:
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return -EINVAL;
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}
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*maskp = mask;
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*shiftp = shift;
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return 0;
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}
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#define ADR_IMM_HILOSPLIT 2
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#define ADR_IMM_SIZE SZ_2M
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#define ADR_IMM_LOMASK ((1 << ADR_IMM_HILOSPLIT) - 1)
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#define ADR_IMM_HIMASK ((ADR_IMM_SIZE >> ADR_IMM_HILOSPLIT) - 1)
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#define ADR_IMM_LOSHIFT 29
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#define ADR_IMM_HISHIFT 5
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u64 aarch64_insn_decode_immediate(enum aarch64_insn_imm_type type, u32 insn)
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{
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u32 immlo, immhi, mask;
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int shift;
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switch (type) {
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case AARCH64_INSN_IMM_ADR:
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shift = 0;
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immlo = (insn >> ADR_IMM_LOSHIFT) & ADR_IMM_LOMASK;
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immhi = (insn >> ADR_IMM_HISHIFT) & ADR_IMM_HIMASK;
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insn = (immhi << ADR_IMM_HILOSPLIT) | immlo;
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mask = ADR_IMM_SIZE - 1;
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break;
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default:
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if (aarch64_get_imm_shift_mask(type, &mask, &shift) < 0) {
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pr_err("aarch64_insn_decode_immediate: unknown immediate encoding %d\n",
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type);
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return 0;
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}
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}
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return (insn >> shift) & mask;
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}
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u32 __kprobes aarch64_insn_encode_immediate(enum aarch64_insn_imm_type type,
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u32 insn, u64 imm)
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{
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u32 immlo, immhi, mask;
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int shift;
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if (insn == AARCH64_BREAK_FAULT)
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return AARCH64_BREAK_FAULT;
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switch (type) {
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case AARCH64_INSN_IMM_ADR:
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shift = 0;
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immlo = (imm & ADR_IMM_LOMASK) << ADR_IMM_LOSHIFT;
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imm >>= ADR_IMM_HILOSPLIT;
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immhi = (imm & ADR_IMM_HIMASK) << ADR_IMM_HISHIFT;
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imm = immlo | immhi;
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mask = ((ADR_IMM_LOMASK << ADR_IMM_LOSHIFT) |
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(ADR_IMM_HIMASK << ADR_IMM_HISHIFT));
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break;
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default:
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if (aarch64_get_imm_shift_mask(type, &mask, &shift) < 0) {
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pr_err("aarch64_insn_encode_immediate: unknown immediate encoding %d\n",
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type);
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return AARCH64_BREAK_FAULT;
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}
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}
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/* Update the immediate field. */
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insn &= ~(mask << shift);
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insn |= (imm & mask) << shift;
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return insn;
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}
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/*
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* Decode the imm field of a branch, and return the byte offset as a
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* signed value (so it can be used when computing a new branch
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* target).
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*/
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s32 aarch64_get_branch_offset(u32 insn)
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{
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s32 imm;
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if (aarch64_insn_is_b(insn) || aarch64_insn_is_bl(insn)) {
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imm = aarch64_insn_decode_immediate(AARCH64_INSN_IMM_26, insn);
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return (imm << 6) >> 4;
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}
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if (aarch64_insn_is_cbz(insn) || aarch64_insn_is_cbnz(insn) ||
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aarch64_insn_is_bcond(insn)) {
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imm = aarch64_insn_decode_immediate(AARCH64_INSN_IMM_19, insn);
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return (imm << 13) >> 11;
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}
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if (aarch64_insn_is_tbz(insn) || aarch64_insn_is_tbnz(insn)) {
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imm = aarch64_insn_decode_immediate(AARCH64_INSN_IMM_14, insn);
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return (imm << 18) >> 16;
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}
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/* Unhandled instruction */
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BUG();
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}
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/*
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* Encode the displacement of a branch in the imm field and return the
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* updated instruction.
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*/
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u32 aarch64_set_branch_offset(u32 insn, s32 offset)
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{
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if (aarch64_insn_is_b(insn) || aarch64_insn_is_bl(insn))
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return aarch64_insn_encode_immediate(AARCH64_INSN_IMM_26, insn,
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offset >> 2);
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if (aarch64_insn_is_cbz(insn) || aarch64_insn_is_cbnz(insn) ||
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aarch64_insn_is_bcond(insn))
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return aarch64_insn_encode_immediate(AARCH64_INSN_IMM_19, insn,
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offset >> 2);
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if (aarch64_insn_is_tbz(insn) || aarch64_insn_is_tbnz(insn))
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return aarch64_insn_encode_immediate(AARCH64_INSN_IMM_14, insn,
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offset >> 2);
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/* Unhandled instruction */
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BUG();
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}
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/*
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* Local variables:
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* mode: C
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* c-file-style: "BSD"
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* c-basic-offset: 8
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* indent-tabs-mode: t
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* End:
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*/
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@@ -0,0 +1,72 @@
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/*
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* Copyright (C) 2013 Huawei Ltd.
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* Author: Jiang Liu <liuj97@gmail.com>
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*
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* Copyright (C) 2014 Zi Shen Lim <zlim.lnx@gmail.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef __ARCH_ARM_ARM64_INSN
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#define __ARCH_ARM_ARM64_INSN
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#include <xen/config.h>
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#include <xen/types.h>
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#include <xen/stdbool.h>
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enum aarch64_insn_imm_type {
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AARCH64_INSN_IMM_ADR,
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AARCH64_INSN_IMM_26,
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AARCH64_INSN_IMM_19,
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AARCH64_INSN_IMM_16,
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AARCH64_INSN_IMM_14,
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AARCH64_INSN_IMM_12,
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AARCH64_INSN_IMM_9,
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AARCH64_INSN_IMM_7,
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AARCH64_INSN_IMM_6,
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AARCH64_INSN_IMM_S,
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AARCH64_INSN_IMM_R,
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AARCH64_INSN_IMM_MAX
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};
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#define __AARCH64_INSN_FUNCS(abbr, mask, val) \
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static always_inline bool_t aarch64_insn_is_##abbr(u32 code) \
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{ return (code & (mask)) == (val); } \
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static always_inline u32 aarch64_insn_get_##abbr##_value(void) \
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{ return (val); }
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__AARCH64_INSN_FUNCS(b, 0xFC000000, 0x14000000)
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__AARCH64_INSN_FUNCS(bl, 0xFC000000, 0x94000000)
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__AARCH64_INSN_FUNCS(cbz, 0x7F000000, 0x34000000)
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__AARCH64_INSN_FUNCS(cbnz, 0x7F000000, 0x35000000)
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__AARCH64_INSN_FUNCS(tbz, 0x7F000000, 0x36000000)
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__AARCH64_INSN_FUNCS(tbnz, 0x7F000000, 0x37000000)
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__AARCH64_INSN_FUNCS(bcond, 0xFF000010, 0x54000000)
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bool aarch64_insn_is_branch_imm(u32 insn);
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u64 aarch64_insn_decode_immediate(enum aarch64_insn_imm_type type, u32 insn);
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u32 aarch64_insn_encode_immediate(enum aarch64_insn_imm_type type,
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u32 insn, u64 imm);
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s32 aarch64_get_branch_offset(u32 insn);
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u32 aarch64_set_branch_offset(u32 insn, s32 offset);
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#endif /* !__ARCH_ARM_ARM64_INSN */
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/*
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* Local variables:
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* mode: C
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* c-file-style: "BSD"
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* c-basic-offset: 8
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* indent-tabs-mode: t
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* End:
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*/
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@@ -0,0 +1,20 @@
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#ifndef __ARCH_ARM_INSN
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#define __ARCH_ARM_INSN
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#include <xen/types.h>
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#if defined(CONFIG_ARM_64)
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# include <asm/arm64/insn.h>
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#else
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# error "unknown ARM variant"
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#endif
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#endif /* !__ARCH_ARM_INSN */
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/*
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* Local variables:
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* mode: C
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* c-file-style: "BSD"
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* c-basic-offset: 8
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* indent-tabs-mode: t
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* End:
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*/
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