arm64: insn: Add aarch64_insn_decode_immediate

Patching an instruction sometimes requires extracting the immediate
field from this instruction. To facilitate this, and avoid
potential duplication of code, add aarch64_insn_decode_immediate
as the reciprocal to aarch64_insn_encode_immediate.

Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

diff --git a/arch/arm64/include/asm/insn.h b/arch/arm64/include/asm/insn.h
index d2f4942..f81b328 100644 (file)
--- a/arch/arm64/include/asm/insn.h
+++ b/arch/arm64/include/asm/insn.h
@@ -285,6 +285,7 @@ bool aarch64_insn_is_nop(u32 insn);
 int aarch64_insn_read(void *addr, u32 *insnp);
 int aarch64_insn_write(void *addr, u32 insn);
 enum aarch64_insn_encoding_class aarch64_get_insn_class(u32 insn);
+u64 aarch64_insn_decode_immediate(enum aarch64_insn_imm_type type, u32 insn);
 u32 aarch64_insn_encode_immediate(enum aarch64_insn_imm_type type,
                                  u32 insn, u64 imm);
 u32 aarch64_insn_gen_branch_imm(unsigned long pc, unsigned long addr,

diff --git a/arch/arm64/kernel/insn.c b/arch/arm64/kernel/insn.c
index c8eca88..9249020 100644 (file)
--- a/arch/arm64/kernel/insn.c
+++ b/arch/arm64/kernel/insn.c
@@ -265,23 +265,13 @@ int __kprobes aarch64_insn_patch_text(void *addrs[], u32 insns[], int cnt)
        return aarch64_insn_patch_text_sync(addrs, insns, cnt);
 }
 
-u32 __kprobes aarch64_insn_encode_immediate(enum aarch64_insn_imm_type type,
-                                 u32 insn, u64 imm)
+static int __kprobes aarch64_get_imm_shift_mask(enum aarch64_insn_imm_type type,
+                                               u32 *maskp, int *shiftp)
 {
-       u32 immlo, immhi, lomask, himask, mask;
+       u32 mask;
        int shift;
 
        switch (type) {
-       case AARCH64_INSN_IMM_ADR:
-               lomask = 0x3;
-               himask = 0x7ffff;
-               immlo = imm & lomask;
-               imm >>= 2;
-               immhi = imm & himask;
-               imm = (immlo << 24) | (immhi);
-               mask = (lomask << 24) | (himask);
-               shift = 5;
-               break;
        case AARCH64_INSN_IMM_26:
                mask = BIT(26) - 1;
                shift = 0;
@@ -320,9 +310,68 @@ u32 __kprobes aarch64_insn_encode_immediate(enum aarch64_insn_imm_type type,
                shift = 16;
                break;
        default:
-               pr_err("aarch64_insn_encode_immediate: unknown immediate encoding %d\n",
-                       type);
-               return 0;
+               return -EINVAL;
+       }
+
+       *maskp = mask;
+       *shiftp = shift;
+
+       return 0;
+}
+
+#define ADR_IMM_HILOSPLIT      2
+#define ADR_IMM_SIZE           SZ_2M
+#define ADR_IMM_LOMASK         ((1 << ADR_IMM_HILOSPLIT) - 1)
+#define ADR_IMM_HIMASK         ((ADR_IMM_SIZE >> ADR_IMM_HILOSPLIT) - 1)
+#define ADR_IMM_LOSHIFT                29
+#define ADR_IMM_HISHIFT                5
+
+u64 aarch64_insn_decode_immediate(enum aarch64_insn_imm_type type, u32 insn)
+{
+       u32 immlo, immhi, mask;
+       int shift;
+
+       switch (type) {
+       case AARCH64_INSN_IMM_ADR:
+               shift = 0;
+               immlo = (insn >> ADR_IMM_LOSHIFT) & ADR_IMM_LOMASK;
+               immhi = (insn >> ADR_IMM_HISHIFT) & ADR_IMM_HIMASK;
+               insn = (immhi << ADR_IMM_HILOSPLIT) | immlo;
+               mask = ADR_IMM_SIZE - 1;
+               break;
+       default:
+               if (aarch64_get_imm_shift_mask(type, &mask, &shift) < 0) {
+                       pr_err("aarch64_insn_decode_immediate: unknown immediate encoding %d\n",
+                              type);
+                       return 0;
+               }
+       }
+
+       return (insn >> shift) & mask;
+}
+
+u32 __kprobes aarch64_insn_encode_immediate(enum aarch64_insn_imm_type type,
+                                 u32 insn, u64 imm)
+{
+       u32 immlo, immhi, mask;
+       int shift;
+
+       switch (type) {
+       case AARCH64_INSN_IMM_ADR:
+               shift = 0;
+               immlo = (imm & ADR_IMM_LOMASK) << ADR_IMM_LOSHIFT;
+               imm >>= ADR_IMM_HILOSPLIT;
+               immhi = (imm & ADR_IMM_HIMASK) << ADR_IMM_HISHIFT;
+               imm = immlo | immhi;
+               mask = ((ADR_IMM_LOMASK << ADR_IMM_LOSHIFT) |
+                       (ADR_IMM_HIMASK << ADR_IMM_HISHIFT));
+               break;
+       default:
+               if (aarch64_get_imm_shift_mask(type, &mask, &shift) < 0) {
+                       pr_err("aarch64_insn_encode_immediate: unknown immediate encoding %d\n",
+                              type);
+                       return 0;
+               }
        }
 
        /* Update the immediate field. */