diff options
Diffstat (limited to 'arch/arm64/kernel/alternative.c')
-rw-r--r-- | arch/arm64/kernel/alternative.c | 119 |
1 files changed, 110 insertions, 9 deletions
diff --git a/arch/arm64/kernel/alternative.c b/arch/arm64/kernel/alternative.c index 1a3badab800a..392c9193da54 100644 --- a/arch/arm64/kernel/alternative.c +++ b/arch/arm64/kernel/alternative.c @@ -24,16 +24,77 @@ #include <asm/cacheflush.h> #include <asm/alternative.h> #include <asm/cpufeature.h> +#include <asm/insn.h> #include <linux/stop_machine.h> +#define __ALT_PTR(a,f) (u32 *)((void *)&(a)->f + (a)->f) +#define ALT_ORIG_PTR(a) __ALT_PTR(a, orig_offset) +#define ALT_REPL_PTR(a) __ALT_PTR(a, alt_offset) + extern struct alt_instr __alt_instructions[], __alt_instructions_end[]; -static int __apply_alternatives(void *dummy) +struct alt_region { + struct alt_instr *begin; + struct alt_instr *end; +}; + +/* + * Check if the target PC is within an alternative block. + */ +static bool branch_insn_requires_update(struct alt_instr *alt, unsigned long pc) +{ + unsigned long replptr; + + if (kernel_text_address(pc)) + return 1; + + replptr = (unsigned long)ALT_REPL_PTR(alt); + if (pc >= replptr && pc <= (replptr + alt->alt_len)) + return 0; + + /* + * Branching into *another* alternate sequence is doomed, and + * we're not even trying to fix it up. + */ + BUG(); +} + +static u32 get_alt_insn(struct alt_instr *alt, u32 *insnptr, u32 *altinsnptr) +{ + u32 insn; + + insn = le32_to_cpu(*altinsnptr); + + if (aarch64_insn_is_branch_imm(insn)) { + s32 offset = aarch64_get_branch_offset(insn); + unsigned long target; + + target = (unsigned long)altinsnptr + offset; + + /* + * If we're branching inside the alternate sequence, + * do not rewrite the instruction, as it is already + * correct. Otherwise, generate the new instruction. + */ + if (branch_insn_requires_update(alt, target)) { + offset = target - (unsigned long)insnptr; + insn = aarch64_set_branch_offset(insn, offset); + } + } + + return insn; +} + +static void __apply_alternatives(void *alt_region) { struct alt_instr *alt; - u8 *origptr, *replptr; + struct alt_region *region = alt_region; + u32 *origptr, *replptr; + + for (alt = region->begin; alt < region->end; alt++) { + u32 insn; + int i, nr_inst; - for (alt = __alt_instructions; alt < __alt_instructions_end; alt++) { if (!cpus_have_cap(alt->cpufeature)) continue; @@ -41,20 +102,60 @@ static int __apply_alternatives(void *dummy) 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); + origptr = ALT_ORIG_PTR(alt); + replptr = ALT_REPL_PTR(alt); + nr_inst = alt->alt_len / sizeof(insn); + + for (i = 0; i < nr_inst; i++) { + insn = get_alt_insn(alt, origptr + i, replptr + i); + *(origptr + i) = cpu_to_le32(insn); + } + flush_icache_range((uintptr_t)origptr, - (uintptr_t)(origptr + alt->alt_len)); + (uintptr_t)(origptr + nr_inst)); + } +} + +/* + * We might be patching the stop_machine state machine, so implement a + * really simple polling protocol here. + */ +static int __apply_alternatives_multi_stop(void *unused) +{ + static int patched = 0; + struct alt_region region = { + .begin = __alt_instructions, + .end = __alt_instructions_end, + }; + + /* We always have a CPU 0 at this point (__init) */ + if (smp_processor_id()) { + while (!READ_ONCE(patched)) + cpu_relax(); + } else { + BUG_ON(patched); + __apply_alternatives(®ion); + /* Barriers provided by the cache flushing */ + WRITE_ONCE(patched, 1); } return 0; } -void apply_alternatives(void) +void __init apply_alternatives_all(void) { /* better not try code patching on a live SMP system */ - stop_machine(__apply_alternatives, NULL, NULL); + stop_machine(__apply_alternatives_multi_stop, NULL, cpu_online_mask); +} + +void apply_alternatives(void *start, size_t length) +{ + struct alt_region region = { + .begin = start, + .end = start + length, + }; + + __apply_alternatives(®ion); } void free_alternatives_memory(void) |