We only support instruction decoding for valid reasonable MMIO operations
where trapping them do not provide sufficient information in the HSR (no
16-bit Thumb instructions provide register writeback that we care about).
The following instruciton types are NOT supported for MMIO operations
despite the HSR not containing decode info:
- any Load/Store multiple
- any load/store exclusive
- any load/store dual
- anything with the PC as the dest register
Signed-off-by: Christoffer Dall <c.dall@xxxxxxxxxxxxxxxxxxxxxx>
---
arch/arm/kvm/emulate.c | 154 +++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 153 insertions(+), 1 deletion(-)
diff --git a/arch/arm/kvm/emulate.c b/arch/arm/kvm/emulate.c
index 6044c02..5f43b65 100644
--- a/arch/arm/kvm/emulate.c
+++ b/arch/arm/kvm/emulate.c
@@ -396,9 +396,161 @@ static bool kvm_decode_arm_ls(struct kvm_vcpu *vcpu, unsigned long instr,
return true;
}
+struct thumb_instr {
+ bool is32;
+
+ union {
+ struct {
+ u8 opcode;
+ u8 mask;
+ } t16;
+
+ struct {
+ u8 op1;
+ u8 op2;
+ u8 op2_mask;
+ } t32;
+ };
+
+ bool (*decode)(struct kvm_vcpu *vcpu, struct kvm_exit_mmio *mmio,
+ unsigned long instr, const struct thumb_instr *ti);
+};
+
+static bool decode_thumb_wb(struct kvm_vcpu *vcpu, struct kvm_exit_mmio *mmio,
+ unsigned long instr)
+{
+ bool P = (instr >> 10) & 1;
+ bool U = (instr >> 9) & 1;
+ u8 imm8 = instr & 0xff;
+ u32 offset_addr = vcpu->arch.hdfar;
+ u8 Rn = (instr >> 16) & 0xf;
+
+ vcpu->arch.mmio.rd = (instr >> 12) & 0xf;
+
+ if (Rn == 15)
+ return false;
+
+ /* Handle Writeback */
+ if (!P && U)
+ *vcpu_reg(vcpu, Rn) = offset_addr + imm8;
+ else if (!P && U)
+ *vcpu_reg(vcpu, Rn) = offset_addr - imm8;
+ return true;
+}
+
+static bool decode_thumb_str(struct kvm_vcpu *vcpu, struct kvm_exit_mmio *mmio,
+ unsigned long instr, const struct thumb_instr *ti)
+{
+ u8 op1 = (instr >> (16 + 5)) & 0x7;
+ u8 op2 = (instr >> 6) & 0x3f;
+
+ mmio->is_write = true;
+ vcpu->arch.mmio.sign_extend = false;
+
+ switch (op1) {
+ case 0x0: mmio->len = 1; break;
+ case 0x1: mmio->len = 2; break;
+ case 0x2: mmio->len = 4; break;
+ default:
+ return false; /* Only register write-back versions! */
+ }
+
+ if ((op2 & 0x24) == 0x24) {
+ /* STRB (immediate, thumb, W=1) */
+ return decode_thumb_wb(vcpu, mmio, instr);
+ }
+
+ return false;
+}
+
+static bool decode_thumb_ldr(struct kvm_vcpu *vcpu, struct kvm_exit_mmio *mmio,
+ unsigned long instr, const struct thumb_instr *ti)
+{
+ u8 op1 = (instr >> (16 + 7)) & 0x3;
+ u8 op2 = (instr >> 6) & 0x3f;
+
+ mmio->is_write = false;
+
+ switch (ti->t32.op2 & 0x7) {
+ case 0x1: mmio->len = 1; break;
+ case 0x3: mmio->len = 2; break;
+ case 0x5: mmio->len = 4; break;
+ }
+
+ if (op1 == 0x0)
+ vcpu->arch.mmio.sign_extend = false;
+ else if (op1 == 0x2 && (ti->t32.op2 & 0x7) != 0x5)
+ vcpu->arch.mmio.sign_extend = true;
+ else
+ return false; /* Only register write-back versions! */
+
+ if ((op2 & 0x24) == 0x24) {
+ /* LDR{S}X (immediate, thumb, W=1) */
+ return decode_thumb_wb(vcpu, mmio, instr);
+ }
+
+ return false;
+}
+
+/*
+ * We only support instruction decoding for valid reasonable MMIO operations
+ * where trapping them do not provide sufficient information in the HSR (no
+ * 16-bit Thumb instructions provide register writeback that we care about).
+ *
+ * The following instruciton types are NOT supported for MMIO operations
+ * despite the HSR not containing decode info:
+ * - any Load/Store multiple
+ * - any load/store exclusive
+ * - any load/store dual
+ * - anything with the PC as the dest register
+ */
+static const struct thumb_instr thumb_instr[] = {
+ /**************** 32-bit Thumb instructions **********************/
+ /* Store single data item: Op1 == 11, Op2 == 000xxx0 */
+ { .is32 = true, .t32 = { 3, 0x00, 0x71}, decode_thumb_str },
+ /* Load byte: Op1 == 11, Op2 == 00xx001 */
+ { .is32 = true, .t32 = { 3, 0x67, 0x01}, decode_thumb_ldr },
+ /* Load halfword: Op1 == 11, Op2 == 00xx011 */
+ { .is32 = true, .t32 = { 3, 0x67, 0x03}, decode_thumb_ldr },
+ /* Load word: Op1 == 11, Op2 == 00xx101 */
+ { .is32 = true, .t32 = { 3, 0x67, 0x05}, decode_thumb_ldr },
+};
+
+
+
static bool kvm_decode_thumb_ls(struct kvm_vcpu *vcpu, unsigned long instr,
- struct kvm_exit_mmio *mmio)
+ struct kvm_exit_mmio *mmio)
{
+ bool is32 = is_wide_instruction(instr);
+ bool is16 = !is32;
+ struct thumb_instr tinstr; /* re-use to pass on already decoded info */
+ int i;
+
+ if (is16) {
+ tinstr.t16.opcode = (instr >> 10) & 0x3f;
+ } else {
+ tinstr.t32.op1 = (instr >> (16 + 11)) & 0x3;
+ tinstr.t32.op2 = (instr >> (16 + 4)) & 0x7f;
+ }
+
+ for (i = 0; i < ARRAY_SIZE(thumb_instr); i++) {
+ const struct thumb_instr *ti = &thumb_instr[i];
+ if (ti->is32 != is32)
+ continue;
+
+ if (is16) {
+ if ((tinstr.t16.opcode & ti->t16.mask) != ti->t16.opcode)
+ continue;
+ } else {
+ if (ti->t32.op1 != tinstr.t32.op1)
+ continue;
+ if ((ti->t32.op2_mask & tinstr.t32.op2) != ti->t32.op2)
+ continue;
+ }
+
+ return ti->decode(vcpu, mmio, instr, &tinstr);
+ }
+
return false;
}
--
1.7.9.5
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