From nobody Wed Dec 17 10:46:07 2025 Received: from mail-wm1-f74.google.com (mail-wm1-f74.google.com [209.85.128.74]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C74F917C7BD for ; Fri, 12 Jul 2024 17:01:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.74 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720803705; cv=none; b=nHL9ywXcWBaEbzH/gsyKoLEWugKa0LjrMzZvRCDyt4K9s5dgeTQu2nJduE+gygTMdFgCpIc8JEBIF55WQhpbGAFf7r76cZD1jxpKrEEol3C55cOLDBP9cKqOs0HU24WKt2Uar+XHU36ZYM3L4KzKgywUs+AH6PyFoA6HiC8Y420= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720803705; c=relaxed/simple; bh=OoDGhAtZINf/eC54ISE3Likkp4nTLCyVsj6xWH4/LYU=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=lnBw4bvv/MAyJ80c5Y/GJgtLXo9Q8c9dDvNG8Pj2jNomL4NU1O4CEfkmTv9H28WsLF/3I+7pn2OSFOC354FJ7bivJ9OsIJ2vZCMaejTgjfsZV0A8toAciv9ndTJMNFuiIqZy3RcCuF9YrerrUsvwlJIsBmsBYDcQmn5qBM/m8VA= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--jackmanb.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=apyLtnmc; arc=none smtp.client-ip=209.85.128.74 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--jackmanb.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="apyLtnmc" Received: by mail-wm1-f74.google.com with SMTP id 5b1f17b1804b1-42668857c38so15411705e9.1 for ; Fri, 12 Jul 2024 10:01:42 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1720803701; x=1721408501; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=mWHMoCzbupyPLn4HJqmbJTZdF2QBYUbInE64x2NA2rE=; b=apyLtnmcUPymzIKsAD/MUoC0Z6tI0gArThPFKcpmi+m1mUp1Fen3vbEop1n6yCY5ov CgDn/IXU7zCeOjFteTKfL/NX0bF0H9cdN1uQM0Up4eVTSj+7sZSuCG9QxZiNo0iTNbeK zmLZY/fziBqYJjwKvj0Oc88kej3hIaYvoDIRursDi8NipPmWPqrHNjtYr5NgaWCMdp+l PCqJF8NiZwmiyqhhh1Fu0Tqrrolg+3zjF9tdMnXpV0rBNgaHhCWgOLXzOU25FRaMXb/3 MLExLGtSZ2iEMxJlqlEeo1fNQMwVT7L21TA3DxZPLfWGIBGdQamIaVU9nwAq6kGWL8i0 rm2Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1720803701; x=1721408501; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=mWHMoCzbupyPLn4HJqmbJTZdF2QBYUbInE64x2NA2rE=; b=deZtac08C8Xa3QKHcOAvCo9RVL6qHRrkTT6y4SybICr4DzfbtD07bAYN8irk6XLcHJ tZmN+JH23gKNC25IsjL91ilflHWGs+jqotj1Sk52cfns1FAvpweDIi+z4eetjp4nXXwr 38DyMY209ZwM5r+PDGhr1ULOsmhC+XoIPECVJTonAefdWNbpzvg2+S9chpg2B7gF9F9b t47nzZnhZoTBoMI3IMxkptiBSi0EZujAa3x+aeyD6ujeP5FiALXwXffTseFJduPynFqI Pzdnf4Jjw5EhYaYcrklt1r0Vu/OAFqYhRJKQTsbAbH+JBlt5hf/aTRO7sIsLD88Mq5Gj sPxg== X-Forwarded-Encrypted: i=1; AJvYcCVSVv7l2v6K4EdlH7PRBrRLLKqMHDwZZYQk09qc04WA01L2ILjTjbpVKV2HcE86AmQ0N6qSCfbAnwQU9KN3KK6V4db15L5L1/hSCFQB X-Gm-Message-State: AOJu0Yzxwmi6oi2n1UM9NylBcry5OjukWOeaEr4rFdhChxjvngpi1KzS TU6KpOLvRHlMX7PM1DTgpzSP+CAYg61zh9JB6x5GmIPOIIdNXIUZEmFVKaF2No4MGDJvboXSCIN DovGpTSCReA== X-Google-Smtp-Source: AGHT+IH7bbw/Dn5jSbbHkSsXS63XrNwSXZ9nYhS09PC8vYQaS4DPRI1dYsfdXRcOP1EzG0hCXTQisDlHIVSzOg== X-Received: from beeg.c.googlers.com ([fda3:e722:ac3:cc00:28:9cb1:c0a8:11db]) (user=jackmanb job=sendgmr) by 2002:a05:600c:4f0e:b0:426:6a73:fb5f with SMTP id 5b1f17b1804b1-426708f9ab5mr1905165e9.7.1720803701319; Fri, 12 Jul 2024 10:01:41 -0700 (PDT) Date: Fri, 12 Jul 2024 17:00:35 +0000 In-Reply-To: <20240712-asi-rfc-24-v1-0-144b319a40d8@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240712-asi-rfc-24-v1-0-144b319a40d8@google.com> X-Mailer: b4 0.14-dev Message-ID: <20240712-asi-rfc-24-v1-17-144b319a40d8@google.com> Subject: [PATCH 17/26] mm: asi: Map kernel text and static data as nonsensitive From: Brendan Jackman To: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Andy Lutomirski , Peter Zijlstra , Sean Christopherson , Paolo Bonzini , Alexandre Chartre , Liran Alon , Jan Setje-Eilers , Catalin Marinas , Will Deacon , Mark Rutland , Andrew Morton , Mel Gorman , Lorenzo Stoakes , David Hildenbrand , Vlastimil Babka , Michal Hocko , Khalid Aziz , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Valentin Schneider , Paul Turner , Reiji Watanabe , Junaid Shahid , Ofir Weisse , Yosry Ahmed , Patrick Bellasi , KP Singh , Alexandra Sandulescu , Matteo Rizzo , Jann Horn Cc: x86@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, kvm@vger.kernel.org, Brendan Jackman Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Basically we need to map the kernel code and all its static variables. Per-CPU variables need to be treated specially as described in the comments. The cpu_entry_area is similar - this needs to be nonsensitive so that the CPU can access the GDT etc when handling a page fault. Under 5-level paging, most of the kernel memory comes under a single PGD entry (see Documentation/x86/x86_64/mm.rst. Basically, the mapping is for this big region is the same as under 4-level, just wrapped in an outer PGD entry). For that region, the "clone" logic is moved down one step of the paging hierarchy. Note that the p4d_alloc in asi_clone_p4d won't actually be used in practice; the relevant PGD entry will always have been populated by prior asi_map calls so this code would "work" if we just wrote p4d_offset (but asi_clone_p4d would be broken if viewed in isolation). The vmemmap area is not under this single PGD, it has its own 2-PGD area, so we still use asi_clone_pgd for that one. Signed-off-by: Brendan Jackman --- arch/x86/mm/asi.c | 106 ++++++++++++++++++++++++++++++++++= +++- include/asm-generic/vmlinux.lds.h | 11 ++++ 2 files changed, 116 insertions(+), 1 deletion(-) diff --git a/arch/x86/mm/asi.c b/arch/x86/mm/asi.c index 6e106f25abbb..891b8d351df8 100644 --- a/arch/x86/mm/asi.c +++ b/arch/x86/mm/asi.c @@ -7,8 +7,8 @@ #include #include =20 -#include #include +#include #include #include #include @@ -184,8 +184,68 @@ void __init asi_check_boottime_disable(void) pr_info("ASI enablement ignored due to incomplete implementation.\n"); } =20 +/* + * Map data by sharing sub-PGD pagetables with the unrestricted mapping. T= his is + * more efficient than asi_map, but only works when you know the whole top= -level + * page needs to be mapped in the restricted tables. Note that the size of= the + * mappings this creates differs between 4 and 5-level paging. + */ +static void asi_clone_pgd(pgd_t *dst_table, pgd_t *src_table, size_t addr) +{ + pgd_t *src =3D pgd_offset_pgd(src_table, addr); + pgd_t *dst =3D pgd_offset_pgd(dst_table, addr); + + if (!pgd_val(*dst)) + set_pgd(dst, *src); + else + WARN_ON_ONCE(pgd_val(*dst) !=3D pgd_val(*src)); +} + +/* + * For 4-level paging this is exactly the same as asi_clone_pgd. For 5-lev= el + * paging it clones one level lower. So this always creates a mapping of t= he + * same size. + */ +static void asi_clone_p4d(pgd_t *dst_table, pgd_t *src_table, size_t addr) +{ + pgd_t *src_pgd =3D pgd_offset_pgd(src_table, addr); + pgd_t *dst_pgd =3D pgd_offset_pgd(dst_table, addr); + p4d_t *src_p4d =3D p4d_alloc(&init_mm, src_pgd, addr); + p4d_t *dst_p4d =3D p4d_alloc(&init_mm, dst_pgd, addr); + + if (!p4d_val(*dst_p4d)) + set_p4d(dst_p4d, *src_p4d); + else + WARN_ON_ONCE(p4d_val(*dst_p4d) !=3D p4d_val(*src_p4d)); +} + +/* + * percpu_addr is where the linker put the percpu variable. asi_map_percpu= finds + * the place where the percpu allocator copied the data during boot. + * + * This is necessary even when the page allocator defaults to + * global-nonsensitive, because the percpu allocator uses the memblock all= ocator + * for early allocations. + */ +static int asi_map_percpu(struct asi *asi, void *percpu_addr, size_t len) +{ + int cpu, err; + void *ptr; + + for_each_possible_cpu(cpu) { + ptr =3D per_cpu_ptr(percpu_addr, cpu); + err =3D asi_map(asi, ptr, len); + if (err) + return err; + } + + return 0; +} + static int __init asi_global_init(void) { + int err; + if (!boot_cpu_has(X86_FEATURE_ASI)) return 0; =20 @@ -205,6 +265,46 @@ static int __init asi_global_init(void) VMALLOC_START, VMALLOC_END, "ASI Global Non-sensitive vmalloc"); =20 + /* Map all kernel text and static data */ + err =3D asi_map(ASI_GLOBAL_NONSENSITIVE, (void *)__START_KERNEL, + (size_t)_end - __START_KERNEL); + if (WARN_ON(err)) + return err; + err =3D asi_map(ASI_GLOBAL_NONSENSITIVE, (void *)FIXADDR_START, + FIXADDR_SIZE); + if (WARN_ON(err)) + return err; + /* Map all static percpu data */ + err =3D asi_map_percpu( + ASI_GLOBAL_NONSENSITIVE, + __per_cpu_start, __per_cpu_end - __per_cpu_start); + if (WARN_ON(err)) + return err; + + /* + * The next areas are mapped using shared sub-P4D paging structures + * (asi_clone_p4d instead of asi_map), since we know the whole P4D will + * be mapped. + */ + asi_clone_p4d(asi_global_nonsensitive_pgd, init_mm.pgd, + CPU_ENTRY_AREA_BASE); +#ifdef CONFIG_X86_ESPFIX64 + asi_clone_p4d(asi_global_nonsensitive_pgd, init_mm.pgd, + ESPFIX_BASE_ADDR); +#endif + /* + * The vmemmap area actually _must_ be cloned via shared paging + * structures, since mappings can potentially change dynamically when + * hugetlbfs pages are created or broken down. + * + * We always clone 2 PGDs, this is a corrolary of the sizes of struct + * page, a page, and the physical address space. + */ + WARN_ON(sizeof(struct page) * MAXMEM / PAGE_SIZE !=3D 2 * (1UL << PGDIR_S= HIFT)); + asi_clone_pgd(asi_global_nonsensitive_pgd, init_mm.pgd, VMEMMAP_START); + asi_clone_pgd(asi_global_nonsensitive_pgd, init_mm.pgd, + VMEMMAP_START + (1UL << PGDIR_SHIFT)); + return 0; } subsys_initcall(asi_global_init) @@ -482,6 +582,10 @@ static bool follow_physaddr( * Map the given range into the ASI page tables. The source of the mapping= is * the regular unrestricted page tables. Can be used to map any kernel mem= ory. * + * In contrast to some internal ASI logic (asi_clone_pgd and asi_clone_p4d= ) this + * never shares pagetables between restricted and unrestricted address spa= ces, + * instead it creates wholly new equivalent mappings. + * * The caller MUST ensure that the source mapping will not change during t= his * function. For dynamic kernel memory, this is generally ensured by mappi= ng the * memory within the allocator. diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinu= x.lds.h index f7749d0f2562..4eca33d62950 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -1021,6 +1021,16 @@ COMMON_DISCARDS \ } =20 +/* + * ASI maps certain sections with certain sensitivity levels, so they need= to + * have a page-aligned size. + */ +#ifdef CONFIG_MITIGATION_ADDRESS_SPACE_ISOLATION +#define ASI_ALIGN() ALIGN(PAGE_SIZE) +#else +#define ASI_ALIGN() . +#endif + /** * PERCPU_INPUT - the percpu input sections * @cacheline: cacheline size @@ -1042,6 +1052,7 @@ *(.data..percpu) \ *(.data..percpu..shared_aligned) \ PERCPU_DECRYPTED_SECTION \ + . =3D ASI_ALIGN(); \ __per_cpu_end =3D .; =20 /** --=20 2.45.2.993.g49e7a77208-goog