From nobody Sat Dec 21 18:07:38 2024 Received: from mail-yb1-f202.google.com (mail-yb1-f202.google.com [209.85.219.202]) (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 35FD2192580 for ; Wed, 25 Sep 2024 15:02:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.219.202 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727276560; cv=none; b=RxoobmmXM+39K9H8LfrmhgA7jc4ziiBDfTFiK8zSTNogVkUQanCRlL5HmbnXwzG9DgSiMpKSoht8FMCbeI/Af3ZMqRru+GoGdGHUZkn/bKNxS98Q3UhSiGLUq1kWJGGeOpcNs3A+sroocAsF1FRq9gRy+vzDZgVFXH1Ope3kIx8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727276560; c=relaxed/simple; bh=i/QYg4imAjIe1bwTsD55fhiHAflGFWUqPqRf587cmXw=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=IgzoE777BNWqdW7LPPolRJtmsZ0uanPUnrWUOEGXp4or/E1HjhwjcdE7fWon5gVgnMH4SR+qDKNSaqeWzn77ds6U3fybSmtbNz4xgEjZfCslSF5r3xl2eKuYJ7G9Nbyqtnmbcu+2Qc4XWEI2Xady1IGDbYLrOCKg85RVxBWz10o= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--ardb.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=t4Rppe0o; arc=none smtp.client-ip=209.85.219.202 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--ardb.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="t4Rppe0o" Received: by mail-yb1-f202.google.com with SMTP id 3f1490d57ef6-e1d46cee0b0so10267739276.2 for ; Wed, 25 Sep 2024 08:02:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1727276556; x=1727881356; 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=yDR79FvO/p7pnSynPl14YMv6NBkHhQBDE9t/OHYGGd4=; b=t4Rppe0oOZrM8rrVvSNlggls1ZRJPpECq26qFnMncuOtFgzJr46mGusEymy3qWdvjG OkmwarU5hNsJqz/Wh5t61KCFoWUz+AuEgMqrOJ1TazD5+6aIFjevSDXJbKGmDSqTX7Ew CCDANtXnw+qfm76PgKJlBQWSB6BVvF38zmAyKZeZifaZ3dAQZc/naSXMoWSrWh54iiZu 19+JCAkmeYxbqwZHm1oMglO4xPvB/zNYVQddPlc5M9ZsGsOYzlPE3GC8tDYY4nhgyeBS TJ5ONJAIqyf9vEuBbIouLLhXZfht7FqE/E141vxkUC/oXnxa2811TyADIndgQmoWmG7P kKUg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1727276556; x=1727881356; 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=yDR79FvO/p7pnSynPl14YMv6NBkHhQBDE9t/OHYGGd4=; b=pH9tfNHkdz+0f1fm3x37yXNOPM86LUWFVO59rXb5tiZqljy2RzDrvgH6jo7Xs8PEXf ZZYOs2sY081J7H5MUzi5oDGlb17HvNK3NenBMhWXk7yaPpx0t6KsWMqC1lYtWcsvIA5O aTU0TSxYfaPFkiT+vkOWD/+SXAGwU/KTlXcG2q6gp6DmVxfHcEFhqvDszvCzPHLX3lxB bDWrjErT4CS9WLIqjkpb03YzuKaxXzDqOIJ6k9QpH5ZvkeYnNralqAHixmuiiIYLnP2t CDZBaqDFI5r+6DRP4QRTC1JnEwdIlgQh1g73Rdoz0im43NlEhz80JjhQevoAIh9jAVqc Hibw== X-Gm-Message-State: AOJu0Yz6bPd8tldSMqEfKCo5QTkEp3ofjSdwkd32URFc2Xj9OwxJzCuG m664FFK0QU00p+j74GgPQ3StM85lVm1IDKSxnI2P0EsObX4jN9ArIAoLHaQqKCQi0yb/BV1SEBU cq2Eng8z2IWpemoSsoP0WeEzVD6t13tq6V8obZVh0bMt9EY8vqhp2vnto3Ubp3wD82Gqx2EsXHf 1uv+NVF70hBHGc248SOfNVEgv4X+Uzrg== X-Google-Smtp-Source: AGHT+IHZ4KYfHMEhV3OEcung24V1cc8XfcFAbHD7O3r+Hgg2lidAI5AomtBdq038iHk4HR3+YtV8+eXL X-Received: from palermo.c.googlers.com ([fda3:e722:ac3:cc00:7b:198d:ac11:8138]) (user=ardb job=sendgmr) by 2002:a5b:ec8:0:b0:e0b:f93:fe8c with SMTP id 3f1490d57ef6-e24d47abf13mr23895276.0.1727276555668; Wed, 25 Sep 2024 08:02:35 -0700 (PDT) Date: Wed, 25 Sep 2024 17:01:18 +0200 In-Reply-To: <20240925150059.3955569-30-ardb+git@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240925150059.3955569-30-ardb+git@google.com> X-Developer-Key: i=ardb@kernel.org; a=openpgp; fpr=F43D03328115A198C90016883D200E9CA6329909 X-Developer-Signature: v=1; a=openpgp-sha256; l=4435; i=ardb@kernel.org; h=from:subject; bh=GHJcalcWc5Qb+zlhfpCjetJZ0xMQ4h6Eadch5mSu/kI=; b=owGbwMvMwCFmkMcZplerG8N4Wi2JIe2L6tGDolHZO8I/hR3x3e/2aucUz1XW9pJNyVMcgt6LK d6perupo5SFQYyDQVZMkUVg9t93O09PlKp1niULM4eVCWQIAxenAExkjgkjw6k/n413NQiwSlie DnVk14nq3/xeMf2gfMyRHcx1Ja3nuRj+h2Vr7vj9abJ2U31nzqv2/TMymqLWPwla++d7/1o/hhv mDAA= X-Mailer: git-send-email 2.46.0.792.g87dc391469-goog Message-ID: <20240925150059.3955569-48-ardb+git@google.com> Subject: [RFC PATCH 18/28] x86/boot/64: Determine VA/PA offset before entering C code From: Ard Biesheuvel To: linux-kernel@vger.kernel.org Cc: Ard Biesheuvel , x86@kernel.org, "H. Peter Anvin" , Andy Lutomirski , Peter Zijlstra , Uros Bizjak , Dennis Zhou , Tejun Heo , Christoph Lameter , Mathieu Desnoyers , Paolo Bonzini , Vitaly Kuznetsov , Juergen Gross , Boris Ostrovsky , Greg Kroah-Hartman , Arnd Bergmann , Masahiro Yamada , Kees Cook , Nathan Chancellor , Keith Packard , Justin Stitt , Josh Poimboeuf , Arnaldo Carvalho de Melo , Namhyung Kim , Jiri Olsa , Ian Rogers , Adrian Hunter , Kan Liang , linux-doc@vger.kernel.org, linux-pm@vger.kernel.org, kvm@vger.kernel.org, xen-devel@lists.xenproject.org, linux-efi@vger.kernel.org, linux-arch@vger.kernel.org, linux-sparse@vger.kernel.org, linux-kbuild@vger.kernel.org, linux-perf-users@vger.kernel.org, rust-for-linux@vger.kernel.org, llvm@lists.linux.dev Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Ard Biesheuvel Implicit absolute symbol references (e.g., taking the address of a global variable) must be avoided in the C code that runs from the early 1:1 mapping of the kernel, given that this is a practice that violates assumptions on the part of the toolchain. I.e., RIP-relative and absolute references are expected to produce the same values, and so the compiler is free to choose either. However, the code currently assumes that RIP-relative references are never emitted here. So an explicit virtual-to-physical offset needs to be used instead to derive the kernel virtual addresses of _text and _end, instead of simply taking the addresses and assuming that the compiler will not choose to use a RIP-relative references in this particular case. Currently, phys_base is already used to perform such calculations, but it is derived from the kernel virtual address of _text, which is taken using an implicit absolute symbol reference. So instead, derive this VA-to-PA offset in asm code, using the kernel VA of common_startup_64 (which we already keep in a global variable for other reasons), and pass it to the C startup code. Signed-off-by: Ard Biesheuvel --- arch/x86/include/asm/setup.h | 2 +- arch/x86/kernel/head64.c | 8 +++++--- arch/x86/kernel/head_64.S | 9 ++++++++- 3 files changed, 14 insertions(+), 5 deletions(-) diff --git a/arch/x86/include/asm/setup.h b/arch/x86/include/asm/setup.h index 0667b2a88614..85f4fde3515c 100644 --- a/arch/x86/include/asm/setup.h +++ b/arch/x86/include/asm/setup.h @@ -49,7 +49,7 @@ extern unsigned long saved_video_mode; =20 extern void reserve_standard_io_resources(void); extern void i386_reserve_resources(void); -extern unsigned long __startup_64(unsigned long physaddr, struct boot_para= ms *bp); +extern unsigned long __startup_64(unsigned long p2v_offset, struct boot_pa= rams *bp); extern void startup_64_setup_gdt_idt(void); extern void early_setup_idt(void); extern void __init do_early_exception(struct pt_regs *regs, int trapnr); diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c index d4398261ad81..de33ac34773c 100644 --- a/arch/x86/kernel/head64.c +++ b/arch/x86/kernel/head64.c @@ -138,12 +138,14 @@ static unsigned long __head sme_postprocess_startup(s= truct boot_params *bp, pmdv * doesn't have to generate PC-relative relocations when accessing globals= from * that function. Clang actually does not generate them, which leads to * boot-time crashes. To work around this problem, every global pointer mu= st - * be accessed using RIP_REL_REF(). + * be accessed using RIP_REL_REF(). Kernel virtual addresses can be determ= ined + * by subtracting p2v_offset from the RIP-relative address. */ -unsigned long __head __startup_64(unsigned long physaddr, +unsigned long __head __startup_64(unsigned long p2v_offset, struct boot_params *bp) { pmd_t (*early_pgts)[PTRS_PER_PMD] =3D RIP_REL_REF(early_dynamic_pgts); + unsigned long physaddr =3D (unsigned long)&RIP_REL_REF(_text); unsigned long pgtable_flags; unsigned long load_delta; pgdval_t *pgd; @@ -163,7 +165,7 @@ unsigned long __head __startup_64(unsigned long physadd= r, * Compute the delta between the address I am compiled to run at * and the address I am actually running at. */ - load_delta =3D physaddr - (unsigned long)(_text - __START_KERNEL_map); + load_delta =3D __START_KERNEL_map + p2v_offset; RIP_REL_REF(phys_base) =3D load_delta; =20 /* Is the address not 2M aligned? */ diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S index ab6ccee81493..db71cf64204b 100644 --- a/arch/x86/kernel/head_64.S +++ b/arch/x86/kernel/head_64.S @@ -99,13 +99,20 @@ SYM_CODE_START_NOALIGN(startup_64) /* Sanitize CPU configuration */ call verify_cpu =20 + /* + * Use the 1:1 physical and kernel virtual addresses of + * common_startup_64 to determine the physical-to-virtual offset, and + * pass it as the first argument to __startup_64(). + */ + leaq common_startup_64(%rip), %rdi + subq 0f(%rip), %rdi + /* * Perform pagetable fixups. Additionally, if SME is active, encrypt * the kernel and retrieve the modifier (SME encryption mask if SME * is active) to be added to the initial pgdir entry that will be * programmed into CR3. */ - leaq _text(%rip), %rdi movq %r15, %rsi call __startup_64 =20 --=20 2.46.0.792.g87dc391469-goog