From patchwork Fri Jan 10 18:40:42 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Brendan Jackman X-Patchwork-Id: 13935360 Received: from mail-wm1-f73.google.com (mail-wm1-f73.google.com [209.85.128.73]) (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 E85D021D585 for ; Fri, 10 Jan 2025 18:41:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.73 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736534511; cv=none; b=GJVFBQwfJxY0wBnb+Jpls9MVyxF7jMgOOdIcUTx+QFxKrM77yMAka4vpelOmFnh7wmAZgE07vMcn4yFZjxHuCqJ2OQrawJ22ODOmmAwoRSrKGKMacn303FXy4VcGnkrX/LJJcYSNlYCuCAn9G1Gxupbv7O0EyxtuI65Gn5Yiw9U= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736534511; c=relaxed/simple; bh=zBI1psGUx2ZMyNcPIssPW/XtqnOnCklYQm4H2tEY0xY=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=jo58AKkHg2qihKub4Li5DL7PAJhp4r8kmdG6lFyQsYnrSUACGH9w/vUDjVbJ/pn+SFpvWmlEdpCagteB9K/NJi2o1Px3yXqAyGjsZMItHRzcEzWR74sRJuJE2CaZyAB9lbcHrFVpIV6hW/WIY1oOF3eKw23wPkkxwDuP5TDIyx0= 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=IVYgJPPT; arc=none smtp.client-ip=209.85.128.73 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="IVYgJPPT" Received: by mail-wm1-f73.google.com with SMTP id 5b1f17b1804b1-436379713baso11447055e9.2 for ; Fri, 10 Jan 2025 10:41:27 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1736534482; x=1737139282; 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=KV+yP+i7I0yJqjdnPuT5zohhg/S0Da4STnyrBal2kA0=; b=IVYgJPPTrtRli0vpqhVNbeeT+Wtki78MpyrxdsfTUAul5RUoh9tKdaocA1JBZy5XYm qnIRLYbMwBTXAjE/OiF1IS9LQaRurSfV6LZ1VGzPIRJ6z3XepytSCZpYRN3tl03HnEwI wyzg3uN9h0kc3W8EwPAKzpAPVvT2UsokBgf2kRI3SPPJcJiMEGlFu4Yq3A1/Pt6bq8VH FxPstcSDQUcq/f3Xri7Xqbcb666DUmFSOgABYoSjzbbkwQ253tTEc99jl0hBJ+WQRb1V jQDamZaqeFQDrH8AQI5pWapSdHVU98lSuVcLigMst4O1Fz4S7Cd3y4IbVDLMeQo0X8lh obCQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1736534482; x=1737139282; 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=KV+yP+i7I0yJqjdnPuT5zohhg/S0Da4STnyrBal2kA0=; b=Ue3gRBC0txGQrE3rh6AiqklD1Xp+5JQoOkTXFgO3L6OGEe6CpuyshQ1UG3FaSqJIfK NMAT+ko2wyvRoMM9rV+NqRM5N0CG9EfZlv0+FWsJWPSGPq+LvXOKQ/SS9GM53bcK8MDq luMua2Ts4oHl+wStXPbQgbyThdaWKtVTU5V3/23YI6xaXDNzJKU1HJ3x+jAL/IXgwTuC brkkDT/SzxHZQ0M/Aosyb7DFro77nqo9gILLj/joQBZ2bQmeSlO1GMHPsk9+4j0otLZE QQzHU/y+D5WBDdoixMRIGyrvw1VpEdxALmNRHgg008SxaF0rhZy+OmQECL8jeSUPe9gG Pqww== X-Forwarded-Encrypted: i=1; AJvYcCWmb+Tsy9mXv7PzfkcPq/sd4iGYHdAAyv5lOjrlccibR1ORmTwTWXBYNgqucpcAE69lvok=@vger.kernel.org X-Gm-Message-State: AOJu0Yw3KaHz0fVb2W6ciITAVj7CH1YHlNXCXpxL1fu53dCVNCmwrf/y IRhrpRyUi5EbvrchtBiBAw/9HuCBqy3hbL3ElRC18yJuW/XdUleF1Wayc0czSz8M911rBgmjr/O Vh3VtRcOyAg== X-Google-Smtp-Source: AGHT+IGysxF4lj+Pa3edYCQyxcx2uUdgDB4x/aH3it4KUk62HUjYx0xS9V+RTFKPnAfHJUfpiQOrJBNcPZbgiA== X-Received: from wmbfl22.prod.google.com ([2002:a05:600c:b96:b0:436:6fa7:621]) (user=jackmanb job=prod-delivery.src-stubby-dispatcher) by 2002:a05:600c:5117:b0:431:60ec:7a96 with SMTP id 5b1f17b1804b1-436e26ddc53mr94187935e9.25.1736534481726; Fri, 10 Jan 2025 10:41:21 -0800 (PST) Date: Fri, 10 Jan 2025 18:40:42 +0000 In-Reply-To: <20250110-asi-rfc-v2-v2-0-8419288bc805@google.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250110-asi-rfc-v2-v2-0-8419288bc805@google.com> X-Mailer: b4 0.15-dev Message-ID: <20250110-asi-rfc-v2-v2-16-8419288bc805@google.com> Subject: [PATCH RFC v2 16/29] 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 , Richard Henderson , Matt Turner , Vineet Gupta , Russell King , Catalin Marinas , Will Deacon , Guo Ren , Brian Cain , Huacai Chen , WANG Xuerui , Geert Uytterhoeven , Michal Simek , Thomas Bogendoerfer , Dinh Nguyen , Jonas Bonn , Stefan Kristiansson , Stafford Horne , "James E.J. Bottomley" , Helge Deller , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Naveen N Rao , Madhavan Srinivasan , Paul Walmsley , Palmer Dabbelt , Albert Ou , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , Yoshinori Sato , Rich Felker , John Paul Adrian Glaubitz , "David S. Miller" , Andreas Larsson , Richard Weinberger , Anton Ivanov , Johannes Berg , Chris Zankel , Max Filippov , Arnd Bergmann , Andrew Morton , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Uladzislau Rezki , Christoph Hellwig , Masami Hiramatsu , Mathieu Desnoyers , Mike Rapoport , Arnaldo Carvalho de Melo , Namhyung Kim , Mark Rutland , Alexander Shishkin , Jiri Olsa , Ian Rogers , Adrian Hunter , Dennis Zhou , Tejun Heo , Christoph Lameter , Sean Christopherson , Paolo Bonzini , Ard Biesheuvel , Josh Poimboeuf , Pawan Gupta Cc: x86@kernel.org, linux-kernel@vger.kernel.org, linux-alpha@vger.kernel.org, linux-snps-arc@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-csky@vger.kernel.org, linux-hexagon@vger.kernel.org, loongarch@lists.linux.dev, linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org, linux-openrisc@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-um@lists.infradead.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, kvm@vger.kernel.org, linux-efi@vger.kernel.org, Brendan Jackman 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 | 105 +++++++++++++++++++++++++++++++++++++- include/asm-generic/vmlinux.lds.h | 11 ++++ 2 files changed, 115 insertions(+), 1 deletion(-) diff --git a/arch/x86/mm/asi.c b/arch/x86/mm/asi.c index b951f2100b8bdea5738ded16166255deb29faf57..bc2cf0475a0e7344a66d81453f55034b2fc77eef 100644 --- a/arch/x86/mm/asi.c +++ b/arch/x86/mm/asi.c @@ -7,7 +7,6 @@ #include #include -#include #include #include #include @@ -186,8 +185,68 @@ void __init asi_check_boottime_disable(void) pr_info("ASI enablement ignored due to incomplete implementation.\n"); } +/* + * Map data by sharing sub-PGD pagetables with the unrestricted mapping. This 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 = pgd_offset_pgd(src_table, addr); + pgd_t *dst = pgd_offset_pgd(dst_table, addr); + + if (!pgd_val(*dst)) + set_pgd(dst, *src); + else + WARN_ON_ONCE(pgd_val(*dst) != pgd_val(*src)); +} + +/* + * For 4-level paging this is exactly the same as asi_clone_pgd. For 5-level + * paging it clones one level lower. So this always creates a mapping of the + * same size. + */ +static void asi_clone_p4d(pgd_t *dst_table, pgd_t *src_table, size_t addr) +{ + pgd_t *src_pgd = pgd_offset_pgd(src_table, addr); + pgd_t *dst_pgd = pgd_offset_pgd(dst_table, addr); + p4d_t *src_p4d = p4d_alloc(&init_mm, src_pgd, addr); + p4d_t *dst_p4d = 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) != 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 allocator + * 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 = per_cpu_ptr(percpu_addr, cpu); + err = 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; @@ -207,6 +266,46 @@ static int __init asi_global_init(void) VMALLOC_START, VMALLOC_END, "ASI Global Non-sensitive vmalloc"); + /* Map all kernel text and static data */ + err = asi_map(ASI_GLOBAL_NONSENSITIVE, (void *)__START_KERNEL, + (size_t)_end - __START_KERNEL); + if (WARN_ON(err)) + return err; + err = asi_map(ASI_GLOBAL_NONSENSITIVE, (void *)FIXADDR_START, + FIXADDR_SIZE); + if (WARN_ON(err)) + return err; + /* Map all static percpu data */ + err = 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 != 2 * (1UL << PGDIR_SHIFT)); + 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) @@ -599,6 +698,10 @@ 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 memory. * + * In contrast to some internal ASI logic (asi_clone_pgd and asi_clone_p4d) this + * never shares pagetables between restricted and unrestricted address spaces, + * instead it creates wholly new equivalent mappings. + * * The caller MUST ensure that the source mapping will not change during this * function. For dynamic kernel memory, this is generally ensured by mapping the * memory within the allocator. diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index eeadbaeccf88b73af40efe5221760a7cb37058d2..18f6c0448baf5dfbd0721ba9a6d89000fa86f061 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -1022,6 +1022,16 @@ COMMON_DISCARDS \ } +/* + * 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 @@ -1043,6 +1053,7 @@ *(.data..percpu) \ *(.data..percpu..shared_aligned) \ PERCPU_DECRYPTED_SECTION \ + . = ASI_ALIGN(); \ __per_cpu_end = .; /**