From patchwork Mon Apr 25 20:39:46 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Song Liu X-Patchwork-Id: 12826214 X-Patchwork-Delegate: bpf@iogearbox.net Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A503FC433EF for ; Mon, 25 Apr 2022 20:43:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240968AbiDYUqW convert rfc822-to-8bit (ORCPT ); Mon, 25 Apr 2022 16:46:22 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45644 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235364AbiDYUqW (ORCPT ); Mon, 25 Apr 2022 16:46:22 -0400 Received: from mx0a-00082601.pphosted.com (mx0a-00082601.pphosted.com [67.231.145.42]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 274F0762B5 for ; Mon, 25 Apr 2022 13:43:17 -0700 (PDT) Received: from pps.filterd (m0148461.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.17.1.5/8.17.1.5) with ESMTP id 23PHP4lT011178 for ; Mon, 25 Apr 2022 13:43:17 -0700 Received: from mail.thefacebook.com ([163.114.132.120]) by mx0a-00082601.pphosted.com (PPS) with ESMTPS id 3fmejp58rk-2 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Mon, 25 Apr 2022 13:43:16 -0700 Received: from twshared29473.14.frc2.facebook.com (2620:10d:c085:108::4) by mail.thefacebook.com (2620:10d:c085:11d::5) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Mon, 25 Apr 2022 13:43:16 -0700 Received: by devbig932.frc1.facebook.com (Postfix, from userid 4523) id 19BB8652E7A4; Mon, 25 Apr 2022 13:40:37 -0700 (PDT) From: Song Liu To: , , CC: , , , , , , , Song Liu Subject: [PATCH v2 bpf 2/3] x86/alternative: introduce text_poke_set Date: Mon, 25 Apr 2022 13:39:46 -0700 Message-ID: <20220425203947.3311308-3-song@kernel.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20220425203947.3311308-1-song@kernel.org> References: <20220425203947.3311308-1-song@kernel.org> MIME-Version: 1.0 X-FB-Internal: Safe X-Proofpoint-GUID: P5dze0BTEMZjG9h1URNzi8uRpPn8TCo3 X-Proofpoint-ORIG-GUID: P5dze0BTEMZjG9h1URNzi8uRpPn8TCo3 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.858,Hydra:6.0.486,FMLib:17.11.64.514 definitions=2022-04-25_10,2022-04-25_03,2022-02-23_01 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net Introduce a memset like API for text_poke. This will be used to fill the unused RX memory with illegal instructions. Suggested-by: Peter Zijlstra Signed-off-by: Song Liu --- arch/x86/include/asm/text-patching.h | 1 + arch/x86/kernel/alternative.c | 70 ++++++++++++++++++++++++---- 2 files changed, 61 insertions(+), 10 deletions(-) diff --git a/arch/x86/include/asm/text-patching.h b/arch/x86/include/asm/text-patching.h index d20ab0921480..1cc15528ce29 100644 --- a/arch/x86/include/asm/text-patching.h +++ b/arch/x86/include/asm/text-patching.h @@ -45,6 +45,7 @@ extern void *text_poke(void *addr, const void *opcode, size_t len); extern void text_poke_sync(void); extern void *text_poke_kgdb(void *addr, const void *opcode, size_t len); extern void *text_poke_copy(void *addr, const void *opcode, size_t len); +extern void *text_poke_set(void *addr, int c, size_t len); extern int poke_int3_handler(struct pt_regs *regs); extern void text_poke_bp(void *addr, const void *opcode, size_t len, const void *emulate); diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index d374cb3cf024..732814065389 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -994,7 +994,21 @@ static inline void unuse_temporary_mm(temp_mm_state_t prev_state) __ro_after_init struct mm_struct *poking_mm; __ro_after_init unsigned long poking_addr; -static void *__text_poke(void *addr, const void *opcode, size_t len) +static void text_poke_memcpy(void *dst, const void *src, size_t len) +{ + memcpy(dst, src, len); +} + +static void text_poke_memset(void *dst, const void *src, size_t len) +{ + int c = *(int *)src; + + memset(dst, c, len); +} + +typedef void text_poke_f(void *dst, const void *src, size_t len); + +static void *__text_poke(text_poke_f func, void *addr, const void *src, size_t len) { bool cross_page_boundary = offset_in_page(addr) + len > PAGE_SIZE; struct page *pages[2] = {NULL}; @@ -1059,7 +1073,7 @@ static void *__text_poke(void *addr, const void *opcode, size_t len) prev = use_temporary_mm(poking_mm); kasan_disable_current(); - memcpy((u8 *)poking_addr + offset_in_page(addr), opcode, len); + func((u8 *)poking_addr + offset_in_page(addr), src, len); kasan_enable_current(); /* @@ -1087,11 +1101,13 @@ static void *__text_poke(void *addr, const void *opcode, size_t len) (cross_page_boundary ? 2 : 1) * PAGE_SIZE, PAGE_SHIFT, false); - /* - * If the text does not match what we just wrote then something is - * fundamentally screwy; there's nothing we can really do about that. - */ - BUG_ON(memcmp(addr, opcode, len)); + if (func == text_poke_memcpy) { + /* + * If the text does not match what we just wrote then something is + * fundamentally screwy; there's nothing we can really do about that. + */ + BUG_ON(memcmp(addr, src, len)); + } local_irq_restore(flags); pte_unmap_unlock(ptep, ptl); @@ -1118,7 +1134,7 @@ void *text_poke(void *addr, const void *opcode, size_t len) { lockdep_assert_held(&text_mutex); - return __text_poke(addr, opcode, len); + return __text_poke(text_poke_memcpy, addr, opcode, len); } /** @@ -1137,7 +1153,7 @@ void *text_poke(void *addr, const void *opcode, size_t len) */ void *text_poke_kgdb(void *addr, const void *opcode, size_t len) { - return __text_poke(addr, opcode, len); + return __text_poke(text_poke_memcpy, addr, opcode, len); } /** @@ -1167,7 +1183,41 @@ void *text_poke_copy(void *addr, const void *opcode, size_t len) s = min_t(size_t, PAGE_SIZE * 2 - offset_in_page(ptr), len - patched); - __text_poke((void *)ptr, opcode + patched, s); + __text_poke(text_poke_memcpy, (void *)ptr, opcode + patched, s); + patched += s; + } + mutex_unlock(&text_mutex); + return addr; +} + +/** + * text_poke_set - memset into (an unused part of) RX memory + * @addr: address to modify + * @c: the byte to fill the area with + * @len: length to copy, could be more than 2x PAGE_SIZE + * + * Not safe against concurrent execution; useful for JITs to dump + * new code blocks into unused regions of RX memory. Can be used in + * conjunction with synchronize_rcu_tasks() to wait for existing + * execution to quiesce after having made sure no existing functions + * pointers are live. + */ +void *text_poke_set(void *addr, int c, size_t len) +{ + unsigned long start = (unsigned long)addr; + size_t patched = 0; + + if (WARN_ON_ONCE(core_kernel_text(start))) + return NULL; + + mutex_lock(&text_mutex); + while (patched < len) { + unsigned long ptr = start + patched; + size_t s; + + s = min_t(size_t, PAGE_SIZE * 2 - offset_in_page(ptr), len - patched); + + __text_poke(text_poke_memset, (void *)ptr, (void *)&c, s); patched += s; } mutex_unlock(&text_mutex);