From: Ard Biesheuvel <ardb@kernel.org>
To: Evgeniy Baskov <baskov@ispras.ru>
Cc: Borislav Petkov <bp@alien8.de>, Andy Lutomirski <luto@kernel.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Alexey Khoroshilov <khoroshilov@ispras.ru>,
lvc-project@linuxtesting.org, x86@kernel.org,
linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-hardening@vger.kernel.org
Subject: Re: [PATCH 08/16] x86/boot: Remove mapping from page fault handler
Date: Wed, 19 Oct 2022 09:20:34 +0200 [thread overview]
Message-ID: <CAMj1kXEr9qgSjWmXboXXp9_+EBvnzodwegAC9XXNUyt1o6=2cA@mail.gmail.com> (raw)
In-Reply-To: <fae59721001d43db9a0ad2c9c09947284f1ecaa1.1662459668.git.baskov@ispras.ru>
On Tue, 6 Sept 2022 at 12:41, Evgeniy Baskov <baskov@ispras.ru> wrote:
>
> After every implicit mapping is removed, this code is no longer needed.
>
> Remove memory mapping from page fault handler to ensure that there are
> no hidden invalid memory accesses.
>
> Signed-off-by: Evgeniy Baskov <baskov@ispras.ru>
I don't grok this 100% but to me, it seems not having to rely on a
page fault handler to ensure that the 1:1 mapping has sufficient
coverage is a win so
Acked-by: Ard Biesheuvel <ardb@kernel.org>
> ---
> arch/x86/boot/compressed/ident_map_64.c | 26 ++++++++++---------------
> 1 file changed, 10 insertions(+), 16 deletions(-)
>
> diff --git a/arch/x86/boot/compressed/ident_map_64.c b/arch/x86/boot/compressed/ident_map_64.c
> index 880e08293023..c20cd31e665f 100644
> --- a/arch/x86/boot/compressed/ident_map_64.c
> +++ b/arch/x86/boot/compressed/ident_map_64.c
> @@ -385,27 +385,21 @@ void do_boot_page_fault(struct pt_regs *regs, unsigned long error_code)
> {
> unsigned long address = native_read_cr2();
> unsigned long end;
> - bool ghcb_fault;
> + char *msg;
>
> - ghcb_fault = sev_es_check_ghcb_fault(address);
> + if (sev_es_check_ghcb_fault(address))
> + msg = "Page-fault on GHCB page:";
> + else
> + msg = "Unexpected page-fault:";
>
> address &= PMD_MASK;
> end = address + PMD_SIZE;
>
> /*
> - * Check for unexpected error codes. Unexpected are:
> - * - Faults on present pages
> - * - User faults
> - * - Reserved bits set
> - */
> - if (error_code & (X86_PF_PROT | X86_PF_USER | X86_PF_RSVD))
> - do_pf_error("Unexpected page-fault:", error_code, address, regs->ip);
> - else if (ghcb_fault)
> - do_pf_error("Page-fault on GHCB page:", error_code, address, regs->ip);
> -
> - /*
> - * Error code is sane - now identity map the 2M region around
> - * the faulting address.
> + * Since all memory allocations are made explicit
> + * now, every page fault at this stage is an
> + * error and the error handler is there only
> + * for debug purposes.
> */
> - kernel_add_identity_map(address, end, MAP_WRITE);
> + do_pf_error(msg, error_code, address, regs->ip);
> }
> --
> 2.35.1
>
next prev parent reply other threads:[~2022-10-19 7:21 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-06 10:41 [PATCH 00/16] x86_64: Improvements at compressed kernel stage Evgeniy Baskov
2022-09-06 10:41 ` [PATCH 01/16] x86/boot: Align vmlinuz sections on page size Evgeniy Baskov
2022-10-19 7:01 ` Ard Biesheuvel
2022-10-20 11:13 ` Evgeniy Baskov
2022-09-06 10:41 ` [PATCH 02/16] x86/build: Remove RWX sections and align on 4KB Evgeniy Baskov
2022-10-19 7:04 ` Ard Biesheuvel
2022-10-20 11:15 ` Evgeniy Baskov
2022-09-06 10:41 ` [PATCH 03/16] x86/boot: Set cr0 to known state in trampoline Evgeniy Baskov
2022-10-19 7:06 ` Ard Biesheuvel
2022-10-20 11:23 ` Evgeniy Baskov
2022-10-19 7:44 ` Andrew Cooper
2022-10-20 13:25 ` Evgeniy Baskov
2022-09-06 10:41 ` [PATCH 04/16] x86/boot: Increase boot page table size Evgeniy Baskov
2022-10-19 7:08 ` Ard Biesheuvel
2022-10-20 11:29 ` Evgeniy Baskov
2022-09-06 10:41 ` [PATCH 05/16] x86/boot: Support 4KB pages for identity mapping Evgeniy Baskov
2022-10-19 7:11 ` Ard Biesheuvel
2022-10-20 11:30 ` Evgeniy Baskov
2022-09-06 10:41 ` [PATCH 06/16] x86/boot: Setup memory protection for bzImage code Evgeniy Baskov
2022-10-19 7:17 ` Ard Biesheuvel
2022-10-20 12:07 ` Evgeniy Baskov
2022-10-19 7:57 ` Andrew Cooper
2022-10-20 13:30 ` Evgeniy Baskov
2022-10-20 16:51 ` Andrew Cooper
2022-09-06 10:41 ` [PATCH 07/16] x86/boot: Map memory explicitly Evgeniy Baskov
2022-09-06 10:41 ` [PATCH 08/16] x86/boot: Remove mapping from page fault handler Evgeniy Baskov
2022-10-19 7:20 ` Ard Biesheuvel [this message]
2022-09-06 10:41 ` [PATCH 09/16] efi/libstub: Move helper function to related file Evgeniy Baskov
2022-10-19 7:21 ` Ard Biesheuvel
2022-09-06 10:41 ` [PATCH 10/16] x86/boot: Make console interface more abstract Evgeniy Baskov
2022-10-19 7:23 ` Ard Biesheuvel
2022-10-20 12:10 ` Evgeniy Baskov
2022-09-06 10:41 ` [PATCH 11/16] x86/boot: Split trampoline and pt init code Evgeniy Baskov
2022-09-06 10:41 ` [PATCH 12/16] x86/boot: Add EFI kernel extraction interface Evgeniy Baskov
2022-10-19 7:27 ` Ard Biesheuvel
2022-10-20 12:14 ` Evgeniy Baskov
2022-09-06 10:41 ` [PATCH 13/16] efi/x86: Support extracting kernel from libstub Evgeniy Baskov
2022-10-19 7:35 ` Ard Biesheuvel
2022-10-20 12:36 ` Evgeniy Baskov
2022-09-06 10:41 ` [PATCH 14/16] x86/build: Make generated PE more spec compliant Evgeniy Baskov
2022-10-19 7:39 ` Ard Biesheuvel
2022-10-20 13:07 ` Evgeniy Baskov
2022-09-06 10:41 ` [PATCH 15/16] efi/libstub: Add memory attribute protocol definitions Evgeniy Baskov
2022-10-19 7:39 ` Ard Biesheuvel
2022-09-06 10:41 ` [PATCH 16/16] efi/libstub: Use memory attribute protocol Evgeniy Baskov
2022-10-18 20:51 ` [PATCH] efi/libstub: make memory protection warnings include newlines Peter Jones
2022-10-19 7:44 ` Ard Biesheuvel
2022-10-19 7:42 ` [PATCH 16/16] efi/libstub: Use memory attribute protocol Ard Biesheuvel
2022-10-20 13:13 ` Evgeniy Baskov
2022-10-18 21:04 ` [PATCH 00/16] x86_64: Improvements at compressed kernel stage Peter Jones
2022-10-20 11:05 ` Evgeniy Baskov
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