diff options
| -rw-r--r-- | arch/arm64/kernel/alternative.c | 55 |
1 files changed, 53 insertions, 2 deletions
diff --git a/arch/arm64/kernel/alternative.c b/arch/arm64/kernel/alternative.c index ad7821d64a1d..21033bba9390 100644 --- a/arch/arm64/kernel/alternative.c +++ b/arch/arm64/kernel/alternative.c @@ -24,6 +24,7 @@ #include <asm/cacheflush.h> #include <asm/alternative.h> #include <asm/cpufeature.h> +#include <asm/insn.h> #include <linux/stop_machine.h> extern struct alt_instr __alt_instructions[], __alt_instructions_end[]; @@ -33,6 +34,48 @@ struct alt_region { struct alt_instr *end; }; +/* + * Decode the imm field of a b/bl instruction, and return the byte + * offset as a signed value (so it can be used when computing a new + * branch target). + */ +static s32 get_branch_offset(u32 insn) +{ + s32 imm = aarch64_insn_decode_immediate(AARCH64_INSN_IMM_26, insn); + + /* sign-extend the immediate before turning it into a byte offset */ + return (imm << 6) >> 4; +} + +static u32 get_alt_insn(u8 *insnptr, u8 *altinsnptr) +{ + u32 insn; + + aarch64_insn_read(altinsnptr, &insn); + + /* Stop the world on instructions we don't support... */ + BUG_ON(aarch64_insn_is_cbz(insn)); + BUG_ON(aarch64_insn_is_cbnz(insn)); + BUG_ON(aarch64_insn_is_bcond(insn)); + /* ... and there is probably more. */ + + if (aarch64_insn_is_b(insn) || aarch64_insn_is_bl(insn)) { + enum aarch64_insn_branch_type type; + unsigned long target; + + if (aarch64_insn_is_b(insn)) + type = AARCH64_INSN_BRANCH_NOLINK; + else + type = AARCH64_INSN_BRANCH_LINK; + + target = (unsigned long)altinsnptr + get_branch_offset(insn); + insn = aarch64_insn_gen_branch_imm((unsigned long)insnptr, + target, type); + } + + return insn; +} + static int __apply_alternatives(void *alt_region) { struct alt_instr *alt; @@ -40,16 +83,24 @@ static int __apply_alternatives(void *alt_region) u8 *origptr, *replptr; for (alt = region->begin; alt < region->end; alt++) { + u32 insn; + int i; + if (!cpus_have_cap(alt->cpufeature)) continue; - BUG_ON(alt->alt_len > alt->orig_len); + BUG_ON(alt->alt_len != alt->orig_len); pr_info_once("patching kernel code\n"); origptr = (u8 *)&alt->orig_offset + alt->orig_offset; replptr = (u8 *)&alt->alt_offset + alt->alt_offset; - memcpy(origptr, replptr, alt->alt_len); + + for (i = 0; i < alt->alt_len; i += sizeof(insn)) { + insn = get_alt_insn(origptr + i, replptr + i); + aarch64_insn_write(origptr + i, insn); + } + flush_icache_range((uintptr_t)origptr, (uintptr_t)(origptr + alt->alt_len)); } |