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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>
This commit is contained in:
Marc Zyngier 2015-03-27 13:09:21 +00:00 committed by Will Deacon
parent 849176c96d
commit 0978fb25f8
2 changed files with 66 additions and 16 deletions
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1
arch/arm64/include/asm/insn.h
View File

@ -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,

81
arch/arm64/kernel/insn.c
View File

@ -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. */