diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c index ba7ca62f9605..65a2de82ecd2 100644 --- a/arch/x86/kernel/uprobes.c +++ b/arch/x86/kernel/uprobes.c @@ -276,15 +276,9 @@ static bool is_prefix_bad(struct insn *insn) return false; } -static int uprobe_init_insn(struct arch_uprobe *auprobe, struct insn *insn, bool x86_64) +static int uprobe_init_insn(struct arch_uprobe *auprobe, struct insn *insn) { - enum insn_mode m = x86_64 ? INSN_MODE_64 : INSN_MODE_32; u32 volatile *good_insns; - int ret; - - ret = insn_decode(insn, auprobe->insn, sizeof(auprobe->insn), m); - if (ret < 0) - return -ENOEXEC; if (is_prefix_bad(insn)) return -ENOTSUPP; @@ -293,7 +287,7 @@ static int uprobe_init_insn(struct arch_uprobe *auprobe, struct insn *insn, bool if (insn_masking_exception(insn)) return -ENOTSUPP; - if (x86_64) + if (insn->x86_64) good_insns = good_insns_64; else good_insns = good_insns_32; @@ -631,9 +625,29 @@ static struct vm_special_mapping tramp_mapping = { .pages = tramp_mapping_pages, }; + +#define LEA_INSN_SIZE 5 +#define OPT_INSN_SIZE (LEA_INSN_SIZE + CALL_INSN_SIZE) +#define REDZONE_SIZE 0x80 + +static const u8 lea_rsp[] = { 0x48, 0x8d, 0x64, 0x24, 0x80 }; + +static bool is_opt_insns(const uprobe_opcode_t *insn) +{ + return !memcmp(insn, lea_rsp, LEA_INSN_SIZE) && + insn[LEA_INSN_SIZE] == CALL_INSN_OPCODE; +} + +static bool is_swbp_opt_insns(uprobe_opcode_t *insn) +{ + return is_swbp_insn(&insn[0]) && + !memcmp(&insn[1], &lea_rsp[1], LEA_INSN_SIZE - 1) && + insn[LEA_INSN_SIZE] == CALL_INSN_OPCODE; +} + static bool is_reachable_by_call(unsigned long vtramp, unsigned long vaddr) { - long delta = (long)(vaddr + 5 - vtramp); + long delta = (long)(vaddr + OPT_INSN_SIZE - vtramp); return delta >= INT_MIN && delta <= INT_MAX; } @@ -646,7 +660,7 @@ static unsigned long find_nearest_trampoline(unsigned long vaddr) }; unsigned long low_limit, high_limit; unsigned long low_tramp, high_tramp; - unsigned long call_end = vaddr + 5; + unsigned long call_end = vaddr + OPT_INSN_SIZE; if (check_add_overflow(call_end, INT_MIN, &low_limit)) low_limit = PAGE_SIZE; @@ -754,7 +768,7 @@ SYSCALL_DEFINE0(uprobe) /* Allow execution only from uprobe trampolines. */ if (!in_uprobe_trampoline(regs->ip)) - return -ENXIO; + return -EPROTO; err = copy_from_user(&args, (void __user *)regs->sp, sizeof(args)); if (err) @@ -770,8 +784,8 @@ SYSCALL_DEFINE0(uprobe) regs->ax = args.ax; regs->r11 = args.r11; regs->cx = args.cx; - regs->ip = args.retaddr - 5; - regs->sp += sizeof(args); + regs->ip = args.retaddr - OPT_INSN_SIZE; + regs->sp += sizeof(args) + REDZONE_SIZE; regs->orig_ax = -1; sp = regs->sp; @@ -788,12 +802,12 @@ SYSCALL_DEFINE0(uprobe) */ if (regs->sp != sp) { /* skip the trampoline call */ - if (args.retaddr - 5 == regs->ip) - regs->ip += 5; + if (args.retaddr - OPT_INSN_SIZE == regs->ip) + regs->ip += OPT_INSN_SIZE; return regs->ax; } - regs->sp -= sizeof(args); + regs->sp -= sizeof(args) + REDZONE_SIZE; /* for the case uprobe_consumer has changed ax/r11/cx */ args.ax = regs->ax; @@ -801,7 +815,7 @@ SYSCALL_DEFINE0(uprobe) args.cx = regs->cx; /* keep return address unless we are instructed otherwise */ - if (args.retaddr - 5 != regs->ip) + if (args.retaddr - OPT_INSN_SIZE != regs->ip) args.retaddr = regs->ip; if (shstk_push(args.retaddr) == -EFAULT) @@ -835,7 +849,7 @@ asm ( "pop %rax\n" "pop %r11\n" "pop %rcx\n" - "ret\n" + "ret $" __stringify(REDZONE_SIZE) "\n" "int3\n" ".balign " __stringify(PAGE_SIZE) "\n" ".popsection\n" @@ -853,7 +867,8 @@ late_initcall(arch_uprobes_init); enum { EXPECT_SWBP, - EXPECT_CALL, + EXPECT_OPTIMIZED, + EXPECT_SWBP_OPTIMIZED, }; struct write_opcode_ctx { @@ -861,30 +876,29 @@ struct write_opcode_ctx { int expect; }; -static int is_call_insn(uprobe_opcode_t *insn) -{ - return *insn == CALL_INSN_OPCODE; -} - /* - * Verification callback used by int3_update uprobe_write calls to make sure - * the underlying instruction is as expected - either int3 or call. + * Verification callback used by uprobe_write calls to make sure the underlying + * instruction is in the expected stage of the INT3 update sequence. */ static int verify_insn(struct page *page, unsigned long vaddr, uprobe_opcode_t *new_opcode, int nbytes, void *data) { struct write_opcode_ctx *ctx = data; - uprobe_opcode_t old_opcode[5]; + uprobe_opcode_t old_opcode[OPT_INSN_SIZE]; - uprobe_copy_from_page(page, ctx->base, (uprobe_opcode_t *) &old_opcode, 5); + uprobe_copy_from_page(page, ctx->base, old_opcode, OPT_INSN_SIZE); switch (ctx->expect) { case EXPECT_SWBP: if (is_swbp_insn(&old_opcode[0])) return 1; break; - case EXPECT_CALL: - if (is_call_insn(&old_opcode[0])) + case EXPECT_OPTIMIZED: + if (is_opt_insns(&old_opcode[0])) + return 1; + break; + case EXPECT_SWBP_OPTIMIZED: + if (is_swbp_opt_insns(&old_opcode[0])) return 1; break; } @@ -893,48 +907,55 @@ static int verify_insn(struct page *page, unsigned long vaddr, uprobe_opcode_t * } /* - * Modify multi-byte instructions by using INT3 breakpoints on SMP. + * Modify the optimized instruction by using INT3 breakpoints on SMP. * We completely avoid using stop_machine() here, and achieve the * synchronization using INT3 breakpoints and SMP cross-calls. * (borrowed comment from smp_text_poke_batch_finish) * - * The way it is done: - * - Add an INT3 trap to the address that will be patched - * - SMP sync all CPUs - * - Update all but the first byte of the patched range - * - SMP sync all CPUs - * - Replace the first byte (INT3) by the first byte of the replacing opcode - * - SMP sync all CPUs + * For optimization (int3_update_optimize): + * 1) Start with the uprobe INT3 trap already installed + * 2) Update everything but the first byte + * 3) Replace the first INT3 by the first byte of the LEA instruction + * + * For unoptimization (int3_update_unoptimize): + * 1) Start with the optimized uprobe lea/call instructions + * 2) Add an INT3 trap to the address that will be patched + * 3) Restore the NOP bytes before the call opcode + * 4) Replace the first INT3 by the first byte of the NOP instruction + * + * Note that unoptimization deliberately keeps the call opcode and displacement + * in bytes 5..9. Those bytes become operands of the restored 10-byte NOP. + * + * Since there is only a single target uprobe-trampoline for the given nop10 + * instruction address, the CALL instruction will not be changed across + * unoptimization/optimization cycles. + * Therefore, any task that is preempted at the CALL instruction is guaranteed + * to observe that CALL and not anything else. */ -static int int3_update(struct arch_uprobe *auprobe, struct vm_area_struct *vma, - unsigned long vaddr, char *insn, bool optimize) +static int int3_update_optimize(struct arch_uprobe *auprobe, struct vm_area_struct *vma, + unsigned long vaddr, uprobe_opcode_t *insn) { - uprobe_opcode_t int3 = UPROBE_SWBP_INSN; struct write_opcode_ctx ctx = { .base = vaddr, }; int err; /* - * Write int3 trap. + * 1) Initial state after set_swbp() installed the uprobe: + * cc 2e 0f 1f 84 00 00 00 00 00 * - * The swbp_optimize path comes with breakpoint already installed, - * so we can skip this step for optimize == true. + * After a previous unoptimization bytes 5..9 may still contain the + * old call instruction, which remains valid for threads already there. */ - if (!optimize) { - ctx.expect = EXPECT_CALL; - err = uprobe_write(auprobe, vma, vaddr, &int3, 1, verify_insn, - true /* is_register */, false /* do_update_ref_ctr */, - &ctx); - if (err) - return err; - } - smp_text_poke_sync_each_cpu(); - /* Write all but the first byte of the patched range. */ + /* + * 2) Rewrite the LEA tail and call displacement: + * cc [8d 64 24 80 e8 d0 d1 d2 d3] + */ ctx.expect = EXPECT_SWBP; - err = uprobe_write(auprobe, vma, vaddr + 1, insn + 1, 4, verify_insn, + err = uprobe_write(auprobe, vma, vaddr + 1, insn + 1, + OPT_INSN_SIZE - 1, verify_insn, true /* is_register */, false /* do_update_ref_ctr */, &ctx); if (err) @@ -943,13 +964,98 @@ static int int3_update(struct arch_uprobe *auprobe, struct vm_area_struct *vma, smp_text_poke_sync_each_cpu(); /* - * Write first byte. + * 3) Publish the first LEA byte: + * [48] 8d 64 24 80 e8 d0 d1 d2 d3 * - * The swbp_unoptimize needs to finish uprobe removal together - * with ref_ctr update, using uprobe_write with proper flags. + * From offset 0 this is: + * lea -0x80(%rsp), %rsp + * call */ + ctx.expect = EXPECT_SWBP_OPTIMIZED; err = uprobe_write(auprobe, vma, vaddr, insn, 1, verify_insn, - optimize /* is_register */, !optimize /* do_update_ref_ctr */, + true /* is_register */, false /* do_update_ref_ctr */, + &ctx); + if (err) + goto error; + + smp_text_poke_sync_each_cpu(); + return 0; + +error: + /* + * In all intermediate states byte 0 is INT3, so EXPECT_SWBP covers every + * case. Restore NOP bytes 1..4, but keep the valid CALL at bytes 5..9 + * for a thread that had already executed the LEA before a previous + * unoptimization. + */ + ctx.expect = EXPECT_SWBP; + uprobe_write(auprobe, vma, vaddr + 1, auprobe->insn + 1, + LEA_INSN_SIZE - 1, verify_insn, true, false, &ctx); + smp_text_poke_sync_each_cpu(); + return err; +} + +static int int3_update_unoptimize(struct arch_uprobe *auprobe, struct vm_area_struct *vma, + unsigned long vaddr, uprobe_opcode_t *insn) +{ + uprobe_opcode_t int3 = UPROBE_SWBP_INSN; + struct write_opcode_ctx ctx = { + .base = vaddr, + .expect = EXPECT_OPTIMIZED, + }; + int err; + + /* + * Note the first two uprobe_write calls use is_register=true, because they + * are intermediate patching states while the probe is still active, so + * we force the exclusive anonymous page for the update. + * Also we use do_update_ref_ctr=false because refctr was already updated by + * the initial int3 install. + * + * The last uprobe_write to nop10 instruction is called with is_register=false + * and do_update_ref_ctr=true to trigger the refctr update and to instruct + * uprobe_write to zap the anonymous page if it now matches the file page. + * + * 1) Initial optimized state: + * 48 8d 64 24 80 e8 d0 d1 d2 d3 + * + * 2) Trap new entries before restoring the NOP bytes: + * [cc] 8d 64 24 80 e8 d0 d1 d2 d3 + */ + err = uprobe_write(auprobe, vma, vaddr, &int3, 1, verify_insn, + true /* is_register */, false /* do_update_ref_ctr */, + &ctx); + if (err) + return err; + + smp_text_poke_sync_each_cpu(); + + /* + * 3) Restore bytes 1..4 of the original NOP while keeping byte 0 trapped + * and byte 5 as CALL: + * cc [2e 0f 1f 84] e8 d0 d1 d2 d3 + */ + ctx.expect = EXPECT_SWBP_OPTIMIZED; + err = uprobe_write(auprobe, vma, vaddr + 1, insn + 1, + LEA_INSN_SIZE - 1, verify_insn, + true /* is_register */, false /* do_update_ref_ctr */, + &ctx); + if (err) + return err; + + smp_text_poke_sync_each_cpu(); + + /* + * 4) Publish the first byte of the original NOP: + * [66] 2e 0f 1f 84 e8 d0 d1 d2 d3 + * + * From offset 0 this is the restored 10-byte NOP; the CALL opcode and + * displacement are now only NOP operands. Offset 5 still decodes as + * CALL for a thread that was already there. + */ + ctx.expect = EXPECT_SWBP; + err = uprobe_write(auprobe, vma, vaddr, insn, 1, verify_insn, + false /* is_register */, true /* do_update_ref_ctr */, &ctx); if (err) return err; @@ -961,17 +1067,25 @@ static int int3_update(struct arch_uprobe *auprobe, struct vm_area_struct *vma, static int swbp_optimize(struct arch_uprobe *auprobe, struct vm_area_struct *vma, unsigned long vaddr, unsigned long tramp) { - u8 call[5]; + u8 insn[OPT_INSN_SIZE], *call = &insn[LEA_INSN_SIZE]; - __text_gen_insn(call, CALL_INSN_OPCODE, (const void *) vaddr, + /* + * We have nop10 instruction (with first byte overwritten to int3), + * changing it to: + * lea -0x80(%rsp), %rsp + * call tramp + */ + memcpy(insn, lea_rsp, LEA_INSN_SIZE); + __text_gen_insn(call, CALL_INSN_OPCODE, + (const void *) (vaddr + LEA_INSN_SIZE), (const void *) tramp, CALL_INSN_SIZE); - return int3_update(auprobe, vma, vaddr, call, true /* optimize */); + return int3_update_optimize(auprobe, vma, vaddr, insn); } static int swbp_unoptimize(struct arch_uprobe *auprobe, struct vm_area_struct *vma, unsigned long vaddr) { - return int3_update(auprobe, vma, vaddr, auprobe->insn, false /* optimize */); + return int3_update_unoptimize(auprobe, vma, vaddr, auprobe->insn); } static int copy_from_vaddr(struct mm_struct *mm, unsigned long vaddr, void *dst, int len) @@ -993,19 +1107,19 @@ static bool __is_optimized(struct mm_struct *mm, uprobe_opcode_t *insn, unsigned struct __packed __arch_relative_insn { u8 op; s32 raddr; - } *call = (struct __arch_relative_insn *) insn; + } *call = (struct __arch_relative_insn *)(insn + LEA_INSN_SIZE); - if (!is_call_insn(insn)) + if (!is_opt_insns(insn)) return false; - return __in_uprobe_trampoline(mm, vaddr + 5 + call->raddr); + return __in_uprobe_trampoline(mm, vaddr + OPT_INSN_SIZE + call->raddr); } static int is_optimized(struct mm_struct *mm, unsigned long vaddr) { - uprobe_opcode_t insn[5]; + uprobe_opcode_t insn[OPT_INSN_SIZE]; int err; - err = copy_from_vaddr(mm, vaddr, &insn, 5); + err = copy_from_vaddr(mm, vaddr, &insn, OPT_INSN_SIZE); if (err) return err; return __is_optimized(mm, (uprobe_opcode_t *)&insn, vaddr); @@ -1077,7 +1191,7 @@ static int __arch_uprobe_optimize(struct arch_uprobe *auprobe, struct mm_struct void arch_uprobe_optimize(struct arch_uprobe *auprobe, unsigned long vaddr) { struct mm_struct *mm = current->mm; - uprobe_opcode_t insn[5]; + uprobe_opcode_t insn[OPT_INSN_SIZE]; if (!should_optimize(auprobe)) return; @@ -1088,7 +1202,7 @@ void arch_uprobe_optimize(struct arch_uprobe *auprobe, unsigned long vaddr) * Check if some other thread already optimized the uprobe for us, * if it's the case just go away silently. */ - if (copy_from_vaddr(mm, vaddr, &insn, 5)) + if (copy_from_vaddr(mm, vaddr, &insn, OPT_INSN_SIZE)) goto unlock; if (!is_swbp_insn((uprobe_opcode_t*) &insn)) goto unlock; @@ -1104,16 +1218,32 @@ void arch_uprobe_optimize(struct arch_uprobe *auprobe, unsigned long vaddr) mmap_write_unlock(mm); } +static bool is_optimizable_nop10(struct insn *insn) +{ + static const u8 nop10_prefix[] = { + 0x66, 0x2e, 0x0f, 0x1f, 0x84 + }; + + /* + * Restrict this to the 10-byte NOP form whose last 5 bytes are + * SIB/displacement operands. Unoptimization keeps the call opcode and + * displacement in those bytes, so other NOP encodings are not safe. + */ + return insn->length == OPT_INSN_SIZE && + insn_is_nop(insn) && + !memcmp(insn->kaddr, nop10_prefix, ARRAY_SIZE(nop10_prefix)); +} + static bool can_optimize(struct insn *insn, unsigned long vaddr) { - if (!insn->x86_64 || insn->length != 5) + if (!insn->x86_64) return false; - if (!insn_is_nop(insn)) + if (!is_optimizable_nop10(insn)) return false; /* We can't do cross page atomic writes yet. */ - return PAGE_SIZE - (vaddr & ~PAGE_MASK) >= 5; + return PAGE_SIZE - (vaddr & ~PAGE_MASK) >= OPT_INSN_SIZE; } #else /* 32-bit: */ /* @@ -1495,16 +1625,26 @@ static int push_setup_xol_ops(struct arch_uprobe *auprobe, struct insn *insn) */ int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long addr) { + enum insn_mode m = is_64bit_mm(mm) ? INSN_MODE_64 : INSN_MODE_32; u8 fix_ip_or_call = UPROBE_FIX_IP; struct insn insn; int ret; - ret = uprobe_init_insn(auprobe, &insn, is_64bit_mm(mm)); - if (ret) - return ret; + ret = insn_decode(&insn, auprobe->insn, sizeof(auprobe->insn), m); + if (ret < 0) + return -ENOEXEC; - if (can_optimize(&insn, addr)) + /* + * No need to check instruction in uprobe_init_insn in case we + * are on top of optimizable nop10. + */ + if (can_optimize(&insn, addr)) { set_bit(ARCH_UPROBE_FLAG_CAN_OPTIMIZE, &auprobe->flags); + } else { + ret = uprobe_init_insn(auprobe, &insn); + if (ret) + return ret; + } ret = branch_setup_xol_ops(auprobe, &insn); if (ret != -ENOSYS)