From patchwork Mon Jan 23 20:59:16 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Peter Zijlstra X-Patchwork-Id: 47411 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:adf:eb09:0:0:0:0:0 with SMTP id s9csp1825110wrn; Mon, 23 Jan 2023 13:32:31 -0800 (PST) X-Google-Smtp-Source: AMrXdXv4fgjQ0U6NQk2JeJvi4RlDkxze8QWcgyrtT6CbqkS87vSy16gJpFXSkzrU3IU4UDgyipvB X-Received: by 2002:a17:902:9a4c:b0:192:4f32:3ba7 with SMTP id x12-20020a1709029a4c00b001924f323ba7mr26540307plv.18.1674509551027; Mon, 23 Jan 2023 13:32:31 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1674509551; cv=none; d=google.com; s=arc-20160816; b=W+VNyOdbRGmAxdKEOiOiaa8Q4/w5oCnRjnBdHHO7o53CBCIm2aUsRsaXSf7VYUJBiq lLNJ5nzH+/vMNgUt/hbotXmTs2dK80p8TTMXoNyhAWs/NAUEyXhVkGSEG67dtiA1GkWH uVbqX2KrlTGsW6Ueq1r5hg6cPL9MS+L0TkL5SP8/gHhNb6zIReBxzU0ioo81/mCAA7M4 y24kYe1ol0Qshvoo3oLkLbmwLdWgtNstjDqwU8SzkbFwXE1mEs/h2LUPaWrLC0y3LwqX 9/bxw82aQ6uEDr+uq+ZB1XPcGdFdnWZ/FxmZRgiyZCKD+LYNPQQbEqzljTr3CehY6tOb ezpg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:mime-version:references:subject:cc:to:from:date :user-agent:message-id:dkim-signature; bh=pkk66lDIJdbY60ClGNOpgyRAJcMk6omCEJ+djxw5JoA=; b=lwNjSNCY/j3yRqx7XRzZ3I5VSZztudsW2EAI1qqGRAI5jg2t36zA+GXFocRE+UZcGr 5o6jAyoQtsg3ga7Q7lqL2Gy4lS6/wLjrAbOOLIopW51Z2zUMn/Y0rll3gFnGqKCBzkhk UCtcY45LVEQEBI679jTcWmf4kQlYKN0yyW7DXS5prTwXuuEY2tt6LgRjyfRfW6noTYBx ba98FBLjIDNBhKtjD7zStce22dKd/15qeX9ixFXcu/LANbCmYxHSUJpL46JxCno5uQRg S7aS88zrtkNVA7vDfxxtoLjcpQH78csvn5l+qcKjOuSNxwK1TptBNEe5Vt16mlwIhDdJ zRDA== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@infradead.org header.s=casper.20170209 header.b=qVtHjS1I; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: from out1.vger.email (out1.vger.email. [2620:137:e000::1:20]) by mx.google.com with ESMTP id e10-20020a170902f1ca00b0018994e35cbfsi366710plc.364.2023.01.23.13.32.17; Mon, 23 Jan 2023 13:32:30 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@infradead.org header.s=casper.20170209 header.b=qVtHjS1I; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232884AbjAWVHF (ORCPT + 99 others); Mon, 23 Jan 2023 16:07:05 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40854 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232599AbjAWVHC (ORCPT ); Mon, 23 Jan 2023 16:07:02 -0500 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5E58530E95 for ; Mon, 23 Jan 2023 13:07:01 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=Content-Type:MIME-Version:References: Subject:Cc:To:From:Date:Message-ID:Sender:Reply-To:Content-Transfer-Encoding: Content-ID:Content-Description:In-Reply-To; bh=pkk66lDIJdbY60ClGNOpgyRAJcMk6omCEJ+djxw5JoA=; b=qVtHjS1IZwObvMJEhV0hetLUHa +rbrAxQlZcVwT0dQnAArr5cbptj8fQDv4vnpEv8YMg7FKIaPFOEGv4ZFCxmFm6OOVVLvHWjS5HAp4 5eYb5dZRMKkD5qNJQ9EGuyETZM/0AWHKgmJR0ByGfZXrTNgbfGCNKaVNPw4Qi9bZgZISVMqCLbanB VzMLHomINHP63+4/SN8BzPN4sCB03UgUZc5QTKjY5yCI53lGkKRb8U1okcSbVA8xG2DVqin3Bb21/ GeQhsgbCuPhEn2z0dbKFltN9hknYu27I5cnEIQtVt0IWbj4p2CwGmo/dTc9xyLZ2vYGtum7JYTDE8 +nNPnVLg==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1pK41f-004Wrc-CF; Mon, 23 Jan 2023 21:06:47 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 6217B300673; Mon, 23 Jan 2023 22:06:45 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 0) id 2930E2038B0D9; Mon, 23 Jan 2023 22:06:45 +0100 (CET) Message-ID: <20230123210607.057678245@infradead.org> User-Agent: quilt/0.66 Date: Mon, 23 Jan 2023 21:59:16 +0100 From: Peter Zijlstra To: mingo@kernel.org Cc: tglx@linutronix.de, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, peterz@infradead.org, jpoimboe@kernel.org, jbaron@akamai.com, rostedt@goodmis.org, ardb@kernel.org, linux-kernel@vger.kernel.org, erhard_f@mailbox.org, ndesaulniers@google.com, mhiramat@kernel.org, sandipan.das@amd.com Subject: [PATCH 1/3] x86/alternative: Introduce int3_emulate_jcc() References: <20230123205915.751729592@infradead.org> MIME-Version: 1.0 X-Spam-Status: No, score=-4.4 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_MED,SPF_HELO_NONE, SPF_NONE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1755850526943743941?= X-GMAIL-MSGID: =?utf-8?q?1755850526943743941?= Move the kprobe Jcc emulation into int3_emulate_jcc() so it can be used by more code -- specifically static_call() will need this. Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Masami Hiramatsu (Google) --- arch/x86/include/asm/text-patching.h | 31 ++++++++++++++++++++++++++++ arch/x86/kernel/kprobes/core.c | 38 +++++++---------------------------- 2 files changed, 39 insertions(+), 30 deletions(-) --- a/arch/x86/include/asm/text-patching.h +++ b/arch/x86/include/asm/text-patching.h @@ -184,6 +184,37 @@ void int3_emulate_ret(struct pt_regs *re unsigned long ip = int3_emulate_pop(regs); int3_emulate_jmp(regs, ip); } + +static __always_inline +void int3_emulate_jcc(struct pt_regs *regs, u8 cc, unsigned long ip, unsigned long disp) +{ + static const unsigned long jcc_mask[6] = { + [0] = X86_EFLAGS_OF, + [1] = X86_EFLAGS_CF, + [2] = X86_EFLAGS_ZF, + [3] = X86_EFLAGS_CF | X86_EFLAGS_ZF, + [4] = X86_EFLAGS_SF, + [5] = X86_EFLAGS_PF, + }; + + bool invert = cc & 1; + bool match; + + if (cc < 0xc) { + match = regs->flags & jcc_mask[cc >> 1]; + } else { + match = ((regs->flags & X86_EFLAGS_SF) >> X86_EFLAGS_SF_BIT) ^ + ((regs->flags & X86_EFLAGS_OF) >> X86_EFLAGS_OF_BIT); + if (cc >= 0xe) + match = match || (regs->flags & X86_EFLAGS_ZF); + } + + if ((match && !invert) || (!match && invert)) + ip += disp; + + int3_emulate_jmp(regs, ip); +} + #endif /* !CONFIG_UML_X86 */ #endif /* _ASM_X86_TEXT_PATCHING_H */ --- a/arch/x86/kernel/kprobes/core.c +++ b/arch/x86/kernel/kprobes/core.c @@ -464,50 +464,26 @@ static void kprobe_emulate_call(struct k } NOKPROBE_SYMBOL(kprobe_emulate_call); -static nokprobe_inline -void __kprobe_emulate_jmp(struct kprobe *p, struct pt_regs *regs, bool cond) +static void kprobe_emulate_jmp(struct kprobe *p, struct pt_regs *regs) { unsigned long ip = regs->ip - INT3_INSN_SIZE + p->ainsn.size; - if (cond) - ip += p->ainsn.rel32; + ip += p->ainsn.rel32; int3_emulate_jmp(regs, ip); } - -static void kprobe_emulate_jmp(struct kprobe *p, struct pt_regs *regs) -{ - __kprobe_emulate_jmp(p, regs, true); -} NOKPROBE_SYMBOL(kprobe_emulate_jmp); -static const unsigned long jcc_mask[6] = { - [0] = X86_EFLAGS_OF, - [1] = X86_EFLAGS_CF, - [2] = X86_EFLAGS_ZF, - [3] = X86_EFLAGS_CF | X86_EFLAGS_ZF, - [4] = X86_EFLAGS_SF, - [5] = X86_EFLAGS_PF, -}; - static void kprobe_emulate_jcc(struct kprobe *p, struct pt_regs *regs) { - bool invert = p->ainsn.jcc.type & 1; - bool match; + unsigned long ip = regs->ip - INT3_INSN_SIZE + p->ainsn.size; - if (p->ainsn.jcc.type < 0xc) { - match = regs->flags & jcc_mask[p->ainsn.jcc.type >> 1]; - } else { - match = ((regs->flags & X86_EFLAGS_SF) >> X86_EFLAGS_SF_BIT) ^ - ((regs->flags & X86_EFLAGS_OF) >> X86_EFLAGS_OF_BIT); - if (p->ainsn.jcc.type >= 0xe) - match = match || (regs->flags & X86_EFLAGS_ZF); - } - __kprobe_emulate_jmp(p, regs, (match && !invert) || (!match && invert)); + int3_emulate_jcc(regs, p->ainsn.jcc.type, ip, p->ainsn.rel32); } NOKPROBE_SYMBOL(kprobe_emulate_jcc); static void kprobe_emulate_loop(struct kprobe *p, struct pt_regs *regs) { + unsigned long ip = regs->ip - INT3_INSN_SIZE + p->ainsn.size; bool match; if (p->ainsn.loop.type != 3) { /* LOOP* */ @@ -535,7 +511,9 @@ static void kprobe_emulate_loop(struct k else if (p->ainsn.loop.type == 1) /* LOOPE */ match = match && (regs->flags & X86_EFLAGS_ZF); - __kprobe_emulate_jmp(p, regs, match); + if (match) + ip += p->ainsn.rel32; + int3_emulate_jmp(regs, ip); } NOKPROBE_SYMBOL(kprobe_emulate_loop); From patchwork Mon Jan 23 20:59:17 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Peter Zijlstra X-Patchwork-Id: 47408 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:adf:eb09:0:0:0:0:0 with SMTP id s9csp1822236wrn; Mon, 23 Jan 2023 13:24:09 -0800 (PST) X-Google-Smtp-Source: AMrXdXt8Z5nDLk72VIkcHUUBIhEXJiEEk/jBlRe+RPjKRnAcBWNGV7kAvL320PvGdiXoR9UwXGEy X-Received: by 2002:a17:90b:1bc6:b0:229:fa91:cc18 with SMTP id oa6-20020a17090b1bc600b00229fa91cc18mr16985239pjb.8.1674509049457; Mon, 23 Jan 2023 13:24:09 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1674509049; cv=none; d=google.com; s=arc-20160816; b=ksyuCWZF05quON3fQ0v4Hvp3CffMW6D/c1715dXmj8jed4VxUUxPafOQzf63FSbiVv IY3TDrPczqwCIMlvUWTr1w7dF160iEcz7ZTI6d96SbBOvY6TtE0O/x/J4PTKEmSzMPwo CvkB1EyvhjVbDiqEFnlpZ9YTpOBm5NgUWzp3LeU2yLfJAb5VXFctPARWG3c9NdZlmYQy +OSI3AiESYnRveZGrwICuvnEoOa1rtMWWQ6IM/6O1Q8Wx2sqG94Hi63perDZduQQpFfe L6528YEUn0lEV6bJTd8FT7gon987DZUJxaJ8vK/dHmM/LC51L+hdsVRQtuSEa8nzwH2F TPgw== ARC-Message-Signature: i=1; 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The biggest hurdle is that the whole machinery is currently made for 5 byte instructions and extending this would grow struct text_poke_loc which is currently a nice 16 bytes and used in an array. However, since text_poke_loc contains a full copy of the (s32) displacement, it is possible to map the Jcc.d32 2 byte opcodes to Jcc.d8 1 byte opcode for the int3 emulation. This then leaves the replacement bytes; fudge that by only storing the last 5 bytes and adding the rule that 'length == 6' instruction will be prefixed with a 0x0f byte. Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Masami Hiramatsu (Google) --- arch/x86/kernel/alternative.c | 62 +++++++++++++++++++++++++++++++----------- 1 file changed, 47 insertions(+), 15 deletions(-) --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -338,6 +338,12 @@ void __init_or_module noinline apply_alt } } +static inline bool is_jcc32(struct insn *insn) +{ + /* Jcc.d32 second opcode byte is in the range: 0x80-0x8f */ + return insn->opcode.bytes[0] == 0x0f && (insn->opcode.bytes[1] & 0xf0) == 0x80; +} + #if defined(CONFIG_RETPOLINE) && defined(CONFIG_OBJTOOL) /* @@ -376,12 +382,6 @@ static int emit_indirect(int op, int reg return i; } -static inline bool is_jcc32(struct insn *insn) -{ - /* Jcc.d32 second opcode byte is in the range: 0x80-0x8f */ - return insn->opcode.bytes[0] == 0x0f && (insn->opcode.bytes[1] & 0xf0) == 0x80; -} - static int emit_call_track_retpoline(void *addr, struct insn *insn, int reg, u8 *bytes) { u8 op = insn->opcode.bytes[0]; @@ -1770,6 +1770,11 @@ void text_poke_sync(void) on_each_cpu(do_sync_core, NULL, 1); } +/* + * NOTE: crazy scheme to allow patching Jcc.d32 but not increase the size of + * this thing. When len == 6 everything is prefixed with 0x0f and we map + * opcode to Jcc.d8, using len to distinguish. + */ struct text_poke_loc { /* addr := _stext + rel_addr */ s32 rel_addr; @@ -1891,6 +1896,10 @@ noinstr int poke_int3_handler(struct pt_ int3_emulate_jmp(regs, (long)ip + tp->disp); break; + case 0x70 ... 0x7f: /* Jcc */ + int3_emulate_jcc(regs, tp->opcode & 0xf, (long)ip, tp->disp); + break; + default: BUG(); } @@ -1964,16 +1973,26 @@ static void text_poke_bp_batch(struct te * Second step: update all but the first byte of the patched range. */ for (do_sync = 0, i = 0; i < nr_entries; i++) { - u8 old[POKE_MAX_OPCODE_SIZE] = { tp[i].old, }; + u8 old[POKE_MAX_OPCODE_SIZE+1] = { tp[i].old, }; + u8 _new[POKE_MAX_OPCODE_SIZE+1]; + const u8 *new = tp[i].text; int len = tp[i].len; if (len - INT3_INSN_SIZE > 0) { memcpy(old + INT3_INSN_SIZE, text_poke_addr(&tp[i]) + INT3_INSN_SIZE, len - INT3_INSN_SIZE); + + if (len == 6) { + _new[0] = 0x0f; + memcpy(_new + 1, new, 5); + new = _new; + } + text_poke(text_poke_addr(&tp[i]) + INT3_INSN_SIZE, - (const char *)tp[i].text + INT3_INSN_SIZE, + new + INT3_INSN_SIZE, len - INT3_INSN_SIZE); + do_sync++; } @@ -2001,8 +2020,7 @@ static void text_poke_bp_batch(struct te * The old instruction is recorded so that the event can be * processed forwards or backwards. */ - perf_event_text_poke(text_poke_addr(&tp[i]), old, len, - tp[i].text, len); + perf_event_text_poke(text_poke_addr(&tp[i]), old, len, new, len); } if (do_sync) { @@ -2019,10 +2037,15 @@ static void text_poke_bp_batch(struct te * replacing opcode. */ for (do_sync = 0, i = 0; i < nr_entries; i++) { - if (tp[i].text[0] == INT3_INSN_OPCODE) + u8 byte = tp[i].text[0]; + + if (tp[i].len == 6) + byte = 0x0f; + + if (byte == INT3_INSN_OPCODE) continue; - text_poke(text_poke_addr(&tp[i]), tp[i].text, INT3_INSN_SIZE); + text_poke(text_poke_addr(&tp[i]), &byte, INT3_INSN_SIZE); do_sync++; } @@ -2040,9 +2063,11 @@ static void text_poke_loc_init(struct te const void *opcode, size_t len, const void *emulate) { struct insn insn; - int ret, i; + int ret, i = 0; - memcpy((void *)tp->text, opcode, len); + if (len == 6) + i = 1; + memcpy((void *)tp->text, opcode+i, len-i); if (!emulate) emulate = opcode; @@ -2053,6 +2078,13 @@ static void text_poke_loc_init(struct te tp->len = len; tp->opcode = insn.opcode.bytes[0]; + if (is_jcc32(&insn)) { + /* + * Map Jcc.d32 onto Jcc.d8 and use len to distinguish. + */ + tp->opcode = insn.opcode.bytes[1] - 0x10; + } + switch (tp->opcode) { case RET_INSN_OPCODE: case JMP32_INSN_OPCODE: @@ -2069,7 +2101,6 @@ static void text_poke_loc_init(struct te BUG_ON(len != insn.length); } - switch (tp->opcode) { case INT3_INSN_OPCODE: case RET_INSN_OPCODE: @@ -2078,6 +2109,7 @@ static void text_poke_loc_init(struct te case CALL_INSN_OPCODE: case JMP32_INSN_OPCODE: case JMP8_INSN_OPCODE: + case 0x70 ... 0x7f: /* Jcc */ tp->disp = insn.immediate.value; break; From patchwork Mon Jan 23 20:59:18 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Peter Zijlstra X-Patchwork-Id: 47412 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:adf:eb09:0:0:0:0:0 with SMTP id s9csp1826170wrn; Mon, 23 Jan 2023 13:35:28 -0800 (PST) X-Google-Smtp-Source: AMrXdXuRU668BnJ5NFeVpAkOVb/9MKi/3NyK6fZq0KhI43m6cOI66HA8qy3OUrVX9vcSdnejK3QU X-Received: by 2002:a62:3007:0:b0:587:8d47:acdd with SMTP id w7-20020a623007000000b005878d47acddmr26841664pfw.34.1674509727628; Mon, 23 Jan 2023 13:35:27 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1674509727; cv=none; d=google.com; s=arc-20160816; b=DyHiGO7tbrIMjUHr78YySUUHNfs8th70Wyape4gES2FPfH0HYNyBWUHq14bvQFLfH7 GtbaT/FYgaf9l2JZ/TreNSpcYwY2NR9sSgpYK+a2qfFOvQ6NicUCdv7LATUJmWRV55Wy lFhA7EYJJMFlv0RCv1AVVEywwl2XX4fHbMuC5aSB4/akSOqy9vRNG8Dig0JbmeEPzGcf oft9Egh9bQnXYuv9D8uECFbwUGdetIvzisB7dxCkKBqhjGJqpdIwLeG9iMDYuja+WDIp QSfrol6VAra+2Wtv6szXLYWc61yYlO0tMazAs1TuGavEph0QLkioNnEwk8Y9y772jb// zP0Q== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:mime-version:references:subject:cc:to:from:date :user-agent:message-id:dkim-signature; bh=KKXDnmc2Es+6ZmW+DV2eYtRfLFf2Gu02YvShw/3lB4Y=; b=tkuTPXnRRwSaeuPaPWrEBD7yR4gNfbPlZcD4zKmq3okd1Rhgge6uAAmXqovfVEsj1r ptBxEAJ7lPQzTbcBRFpq6nf/ao0QHfUCy6E6a2RT/RGVFTpsknOdgUQo/YUAoCbxCc8X F7oiwYYYwbINcFxnbiOkJ/A1doL8ZBvIIN8BuDiwOmyxcwHyBWE4NOugiciPkDxliaXo u6bkCLoA/cvttVtWM1E34iu4s6MujCM5uMVj4tbK0CHrDax6j03NqxO/A/pZ6FwpjjId T9gik0dhALEmel8FGmavk3C/Fnk3DLTCX9pwRgpsHfksWZUPKNqqyfuxrBziahR/bBxK LRCA== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@infradead.org header.s=desiato.20200630 header.b=PT4Npcye; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: from out1.vger.email (out1.vger.email. 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Notably, since there is no conditional-ret, in that caes patch the Jcc to point at an empty stub function that does the ret -- or the return thunk when needed. Reported-by: "Erhard F." Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Masami Hiramatsu (Google) --- arch/x86/kernel/static_call.c | 50 +++++++++++++++++++++++++++++++++++++++--- 1 file changed, 47 insertions(+), 3 deletions(-) --- a/arch/x86/kernel/static_call.c +++ b/arch/x86/kernel/static_call.c @@ -9,6 +9,7 @@ enum insn_type { NOP = 1, /* site cond-call */ JMP = 2, /* tramp / site tail-call */ RET = 3, /* tramp / site cond-tail-call */ + JCC = 4, }; /* @@ -25,12 +26,40 @@ static const u8 xor5rax[] = { 0x2e, 0x2e static const u8 retinsn[] = { RET_INSN_OPCODE, 0xcc, 0xcc, 0xcc, 0xcc }; +static u8 __is_Jcc(u8 *insn) /* Jcc.d32 */ +{ + u8 ret = 0; + + if (insn[0] == 0x0f) { + u8 tmp = insn[1]; + if ((tmp & 0xf0) == 0x80) + ret = tmp; + } + + return ret; +} + +extern void __static_call_return(void); + +asm (".global __static_call_return\n\t" + ".type __static_call_return, @function\n\t" + ASM_FUNC_ALIGN "\n\t" + "__static_call_return:\n\t" + ANNOTATE_NOENDBR + ANNOTATE_RETPOLINE_SAFE + "ret; int3\n\t" + ".size __static_call_return, . - __static_call_return \n\t"); + static void __ref __static_call_transform(void *insn, enum insn_type type, void *func, bool modinit) { const void *emulate = NULL; int size = CALL_INSN_SIZE; const void *code; + u8 op, buf[6]; + + if ((type == JMP || type == RET) && (op = __is_Jcc(insn))) + type = JCC; switch (type) { case CALL: @@ -57,6 +86,20 @@ static void __ref __static_call_transfor else code = &retinsn; break; + + case JCC: + if (!func) { + func = __static_call_return; + if (cpu_feature_enabled(X86_FEATURE_RETHUNK)) + func = x86_return_thunk; + } + + buf[0] = 0x0f; + __text_gen_insn(buf+1, op, insn+1, func, 5); + code = buf; + size = 6; + + break; } if (memcmp(insn, code, size) == 0) @@ -68,9 +111,9 @@ static void __ref __static_call_transfor text_poke_bp(insn, code, size, emulate); } -static void __static_call_validate(void *insn, bool tail, bool tramp) +static void __static_call_validate(u8 *insn, bool tail, bool tramp) { - u8 opcode = *(u8 *)insn; + u8 opcode = insn[0]; if (tramp && memcmp(insn+5, tramp_ud, 3)) { pr_err("trampoline signature fail"); @@ -79,7 +122,8 @@ static void __static_call_validate(void if (tail) { if (opcode == JMP32_INSN_OPCODE || - opcode == RET_INSN_OPCODE) + opcode == RET_INSN_OPCODE || + __is_Jcc(insn)) return; } else { if (opcode == CALL_INSN_OPCODE ||