The encoder for ADD/SUB (immediate) can only cope with 12bit
immediates, while there is an encoding for a 12bit immediate shifted
by 12 bits to the left.
Let's fix this small oversight by allowing the LSL_12 bit to be set.
Reviewed-by: Christoffer Dall <christoffer.dall@xxxxxxxxxx>
Acked-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
---
arch/arm64/kernel/insn.c | 18 ++++++++++++++++--
1 file changed, 16 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/kernel/insn.c b/arch/arm64/kernel/insn.c
index 2929adaad587..816d03c4c913 100644
--- a/arch/arm64/kernel/insn.c
+++ b/arch/arm64/kernel/insn.c
@@ -35,6 +35,7 @@
#define AARCH64_INSN_SF_BIT BIT(31)
#define AARCH64_INSN_N_BIT BIT(22)
+#define AARCH64_INSN_LSL_12 BIT(22)
static int aarch64_insn_encoding_class[] = {
AARCH64_INSN_CLS_UNKNOWN,
@@ -903,9 +904,18 @@ u32 aarch64_insn_gen_add_sub_imm(enum aarch64_insn_register dst,
return AARCH64_BREAK_FAULT;
}
+ /* We can't encode more than a 24bit value (12bit + 12bit shift) */
+ if (imm & ~(BIT(24) - 1))
+ goto out;
+
+ /* If we have something in the top 12 bits... */
if (imm & ~(SZ_4K - 1)) {
- pr_err("%s: invalid immediate encoding %d\n", __func__, imm);
- return AARCH64_BREAK_FAULT;
+ /* ... and in the low 12 bits -> error */
+ if (imm & (SZ_4K - 1))
+ goto out;
+
+ imm >>= 12;
+ insn |= AARCH64_INSN_LSL_12;
}
insn = aarch64_insn_encode_register(AARCH64_INSN_REGTYPE_RD, insn, dst);
@@ -913,6 +923,10 @@ u32 aarch64_insn_gen_add_sub_imm(enum aarch64_insn_register dst,
insn = aarch64_insn_encode_register(AARCH64_INSN_REGTYPE_RN, insn, src);
return aarch64_insn_encode_immediate(AARCH64_INSN_IMM_12, insn, imm);
+
+out:
+ pr_err("%s: invalid immediate encoding %d\n", __func__, imm);
+ return AARCH64_BREAK_FAULT;
}
u32 aarch64_insn_gen_bitfield(enum aarch64_insn_register dst,
--
2.14.2
