From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-17.0 required=3.0 tests=BAYES_00,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 68CF4C4167B for ; Sun, 6 Dec 2020 14:12:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 385AD2313B for ; Sun, 6 Dec 2020 14:12:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728440AbgLFOMZ (ORCPT ); Sun, 6 Dec 2020 09:12:25 -0500 Received: from mail.kernel.org ([198.145.29.99]:38078 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726757AbgLFOMY (ORCPT ); Sun, 6 Dec 2020 09:12:24 -0500 From: Masami Hiramatsu Authentication-Results: mail.kernel.org; dkim=permerror (bad message/signature format) To: Ingo Molnar , Steven Rostedt Cc: mhiramat@kernel.org, linux-kernel@vger.kernel.org, "Naveen N . Rao" , Anil S Keshavamurthy , David Miller , Borislav Petkov , x86@kernel.org Subject: [PATCH 1/1] x86/kprobes: Do not decode opcode in resume_execution() Date: Sun, 6 Dec 2020 23:11:38 +0900 Message-Id: <160726389867.3413805.17190350990123597258.stgit@devnote2> X-Mailer: git-send-email 2.25.1 In-Reply-To: <160726388853.3413805.4854581312983421622.stgit@devnote2> References: <160726388853.3413805.4854581312983421622.stgit@devnote2> User-Agent: StGit/0.19 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Currently kprobes x86 decodes opcode right after single stepping in resume_execution(). But it already decoded the opcode while preparing arch_specific_insn in arch_copy_kprobe(). This decodes opcode in arch_copy_kprobe() instead of resume_execution() and sets some flags which classifies the opcode for resuming process. Signed-off-by: Masami Hiramatsu --- arch/x86/include/asm/kprobes.h | 11 ++- arch/x86/kernel/kprobes/core.c | 166 ++++++++++++++++++---------------------- 2 files changed, 80 insertions(+), 97 deletions(-) diff --git a/arch/x86/include/asm/kprobes.h b/arch/x86/include/asm/kprobes.h index 991a7ad540c7..d20a3d6be36e 100644 --- a/arch/x86/include/asm/kprobes.h +++ b/arch/x86/include/asm/kprobes.h @@ -58,14 +58,17 @@ struct arch_specific_insn { /* copy of the original instruction */ kprobe_opcode_t *insn; /* - * boostable = false: This instruction type is not boostable. - * boostable = true: This instruction has been boosted: we have + * boostable = 0: This instruction type is not boostable. + * boostable = 1: This instruction has been boosted: we have * added a relative jump after the instruction copy in insn, * so no single-step and fixup are needed (unless there's * a post_handler). */ - bool boostable; - bool if_modifier; + unsigned boostable:1; + unsigned if_modifier:1; + unsigned is_call:1; + unsigned is_pushf:1; + unsigned is_abs_ip:1; /* Number of bytes of text poked */ int tp_len; }; diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c index 547c7abb39f5..9d95f43363f1 100644 --- a/arch/x86/kernel/kprobes/core.c +++ b/arch/x86/kernel/kprobes/core.c @@ -132,26 +132,6 @@ void synthesize_relcall(void *dest, void *from, void *to) } NOKPROBE_SYMBOL(synthesize_relcall); -/* - * Skip the prefixes of the instruction. - */ -static kprobe_opcode_t *skip_prefixes(kprobe_opcode_t *insn) -{ - insn_attr_t attr; - - attr = inat_get_opcode_attribute((insn_byte_t)*insn); - while (inat_is_legacy_prefix(attr)) { - insn++; - attr = inat_get_opcode_attribute((insn_byte_t)*insn); - } -#ifdef CONFIG_X86_64 - if (inat_is_rex_prefix(attr)) - insn++; -#endif - return insn; -} -NOKPROBE_SYMBOL(skip_prefixes); - /* * Returns non-zero if INSN is boostable. * RIP relative instructions are adjusted at copying time in 64 bits mode @@ -311,25 +291,6 @@ static int can_probe(unsigned long paddr) return (addr == paddr); } -/* - * Returns non-zero if opcode modifies the interrupt flag. - */ -static int is_IF_modifier(kprobe_opcode_t *insn) -{ - /* Skip prefixes */ - insn = skip_prefixes(insn); - - switch (*insn) { - case 0xfa: /* cli */ - case 0xfb: /* sti */ - case 0xcf: /* iret/iretd */ - case 0x9d: /* popf/popfd */ - return 1; - } - - return 0; -} - /* * Copy an instruction with recovering modified instruction by kprobes * and adjust the displacement if the instruction uses the %rip-relative @@ -411,9 +372,9 @@ static int prepare_boost(kprobe_opcode_t *buf, struct kprobe *p, synthesize_reljump(buf + len, p->ainsn.insn + len, p->addr + insn->length); len += JMP32_INSN_SIZE; - p->ainsn.boostable = true; + p->ainsn.boostable = 1; } else { - p->ainsn.boostable = false; + p->ainsn.boostable = 0; } return len; @@ -450,12 +411,75 @@ void free_insn_page(void *page) module_memfree(page); } +static void set_resume_flags(struct kprobe *p, struct insn *insn) +{ + insn_byte_t opcode = insn->opcode.bytes[0]; + + switch (opcode) { + case 0xfa: /* cli */ + case 0xfb: /* sti */ + case 0x9d: /* popf/popfd */ + /* Check whether the instruction modifies Interrupt Flag or not */ + p->ainsn.if_modifier = 1; + break; + case 0x9c: /* pushfl */ + p->ainsn.is_pushf = 1; + break; + case 0xcf: /* iret */ + p->ainsn.if_modifier = 1; + fallthrough; + case 0xc2: /* ret/lret */ + case 0xc3: + case 0xca: + case 0xcb: + case 0xea: /* jmp absolute -- ip is correct */ + /* ip is already adjusted, no more changes required */ + p->ainsn.is_abs_ip = 1; + /* Without resume jump, this is boostable */ + p->ainsn.boostable = 1; + break; + case 0xe8: /* call relative - Fix return addr */ + p->ainsn.is_call = 1; + break; +#ifdef CONFIG_X86_32 + case 0x9a: /* call absolute -- same as call absolute, indirect */ + p->ainsn.is_call = 1; + p->ainsn.is_abs_ip = 1; + break; +#endif + case 0xff: + opcode = insn->opcode.bytes[1]; + if ((opcode & 0x30) == 0x10) { + /* + * call absolute, indirect + * Fix return addr; ip is correct. + * But this is not boostable + */ + p->ainsn.is_call = 1; + p->ainsn.is_abs_ip = 1; + break; + } else if (((opcode & 0x31) == 0x20) || + ((opcode & 0x31) == 0x21)) { + /* + * jmp near and far, absolute indirect + * ip is correct. + */ + p->ainsn.is_abs_ip = 1; + /* Without resume jump, this is boostable */ + p->ainsn.boostable = 1; + } + break; + } +} + static int arch_copy_kprobe(struct kprobe *p) { struct insn insn; kprobe_opcode_t buf[MAX_INSN_SIZE]; int len; + memset(&p->ainsn, 0, sizeof(p->ainsn)); + /* Copy an instruction with recovering if other optprobe modifies it.*/ len = __copy_instruction(buf, p->addr, p->ainsn.insn, &insn); if (!len) @@ -467,8 +491,8 @@ static int arch_copy_kprobe(struct kprobe *p) */ len = prepare_boost(buf, p, &insn); - /* Check whether the instruction modifies Interrupt Flag or not */ - p->ainsn.if_modifier = is_IF_modifier(buf); + /* Analyze the opcode and set resume flags */ + set_resume_flags(p, &insn); /* Also, displacement change doesn't affect the first byte */ p->opcode = buf[0]; @@ -806,11 +830,6 @@ NOKPROBE_SYMBOL(trampoline_handler); * 2) If the single-stepped instruction was a call, the return address * that is atop the stack is the address following the copied instruction. * We need to make it the address following the original instruction. - * - * If this is the first time we've single-stepped the instruction at - * this probepoint, and the instruction is boostable, boost it: add a - * jump instruction after the copied instruction, that jumps to the next - * instruction after the probepoint. */ static void resume_execution(struct kprobe *p, struct pt_regs *regs, struct kprobe_ctlblk *kcb) @@ -818,59 +837,20 @@ static void resume_execution(struct kprobe *p, struct pt_regs *regs, unsigned long *tos = stack_addr(regs); unsigned long copy_ip = (unsigned long)p->ainsn.insn; unsigned long orig_ip = (unsigned long)p->addr; - kprobe_opcode_t *insn = p->ainsn.insn; - - /* Skip prefixes */ - insn = skip_prefixes(insn); regs->flags &= ~X86_EFLAGS_TF; - switch (*insn) { - case 0x9c: /* pushfl */ + + /* Fixup the contents of top of stack */ + if (p->ainsn.is_pushf) { *tos &= ~(X86_EFLAGS_TF | X86_EFLAGS_IF); *tos |= kcb->kprobe_old_flags; - break; - case 0xc2: /* iret/ret/lret */ - case 0xc3: - case 0xca: - case 0xcb: - case 0xcf: - case 0xea: /* jmp absolute -- ip is correct */ - /* ip is already adjusted, no more changes required */ - p->ainsn.boostable = true; - goto no_change; - case 0xe8: /* call relative - Fix return addr */ + } else if (p->ainsn.is_call) { *tos = orig_ip + (*tos - copy_ip); - break; -#ifdef CONFIG_X86_32 - case 0x9a: /* call absolute -- same as call absolute, indirect */ - *tos = orig_ip + (*tos - copy_ip); - goto no_change; -#endif - case 0xff: - if ((insn[1] & 0x30) == 0x10) { - /* - * call absolute, indirect - * Fix return addr; ip is correct. - * But this is not boostable - */ - *tos = orig_ip + (*tos - copy_ip); - goto no_change; - } else if (((insn[1] & 0x31) == 0x20) || - ((insn[1] & 0x31) == 0x21)) { - /* - * jmp near and far, absolute indirect - * ip is correct. And this is boostable - */ - p->ainsn.boostable = true; - goto no_change; - } - default: - break; } - regs->ip += orig_ip - copy_ip; + if (!p->ainsn.is_abs_ip) + regs->ip += orig_ip - copy_ip; -no_change: restore_btf(); } NOKPROBE_SYMBOL(resume_execution);