From: Nathan Chancellor <nathan@kernel.org>
To: Borislav Petkov <bp@alien8.de>
Cc: Ard Biesheuvel <ardb@kernel.org>,
Arvind Sankar <nivedita@alum.mit.edu>,
Arnd Bergmann <arnd@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, X86 ML <x86@kernel.org>,
Nathan Chancellor <natechancellor@gmail.com>,
Nick Desaulniers <ndesaulniers@google.com>,
Arnd Bergmann <arnd@arndb.de>, Darren Hart <dvhart@infradead.org>,
Andy Shevchenko <andy@infradead.org>,
"H. Peter Anvin" <hpa@zytor.com>,
linux-efi <linux-efi@vger.kernel.org>,
platform-driver-x86@vger.kernel.org,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
clang-built-linux <clang-built-linux@googlegroups.com>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Subject: Re: [PATCH] x86: efi: avoid BUILD_BUG_ON() for non-constant p4d_index
Date: Thu, 4 Feb 2021 12:16:28 -0700 [thread overview]
Message-ID: <20210204191628.GC2991903@localhost> (raw)
In-Reply-To: <20210204105155.GA32255@zn.tnic>
On Thu, Feb 04, 2021 at 11:51:55AM +0100, Borislav Petkov wrote:
> On Wed, Feb 03, 2021 at 09:29:18PM +0100, Ard Biesheuvel wrote:
> > I think we have agreement on the approach but it is unclear who is
> > going to write the patch.
>
> How's that below?
>
> And frankly, I'd even vote for removing those assertions altogether. If
> somehow the EFI pgd lands somewhere else, the kernel will crash'n'burn
> spectacularly and quickly so it's not like we won't catch it...
>
> ---
This resolves the issue initially reported in this thread. Obviously
removing the assertions will do that as well. Feel free to carry
forward
Tested-by: Nathan Chancellor <nathan@kernel.org>
on a patch if you send it out.
> diff --git a/arch/x86/include/asm/pgtable_64_types.h b/arch/x86/include/asm/pgtable_64_types.h
> index 91ac10654570..b6be19c09841 100644
> --- a/arch/x86/include/asm/pgtable_64_types.h
> +++ b/arch/x86/include/asm/pgtable_64_types.h
> @@ -156,8 +156,8 @@ extern unsigned int ptrs_per_p4d;
> #define CPU_ENTRY_AREA_PGD _AC(-4, UL)
> #define CPU_ENTRY_AREA_BASE (CPU_ENTRY_AREA_PGD << P4D_SHIFT)
>
> -#define EFI_VA_START ( -4 * (_AC(1, UL) << 30))
> -#define EFI_VA_END (-68 * (_AC(1, UL) << 30))
> +#define EFI_VA_START ( -4UL * (_AC(1, UL) << 30))
> +#define EFI_VA_END (-68UL * (_AC(1, UL) << 30))
>
> #define EARLY_DYNAMIC_PAGE_TABLES 64
>
> diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
> index e1e8d4e3a213..56fdc0bbb554 100644
> --- a/arch/x86/platform/efi/efi_64.c
> +++ b/arch/x86/platform/efi/efi_64.c
> @@ -123,9 +123,7 @@ void efi_sync_low_kernel_mappings(void)
> * only span a single PGD entry and that the entry also maps
> * other important kernel regions.
> */
> - MAYBE_BUILD_BUG_ON(pgd_index(EFI_VA_END) != pgd_index(MODULES_END));
> - MAYBE_BUILD_BUG_ON((EFI_VA_START & PGDIR_MASK) !=
> - (EFI_VA_END & PGDIR_MASK));
> + MAYBE_BUILD_BUG_ON((EFI_VA_START & PGDIR_MASK) != PGDIR_MASK);
>
> pgd_efi = efi_pgd + pgd_index(PAGE_OFFSET);
> pgd_k = pgd_offset_k(PAGE_OFFSET);
> @@ -137,8 +135,7 @@ void efi_sync_low_kernel_mappings(void)
> * As with PGDs, we share all P4D entries apart from the one entry
> * that covers the EFI runtime mapping space.
> */
> - BUILD_BUG_ON(p4d_index(EFI_VA_END) != p4d_index(MODULES_END));
> - BUILD_BUG_ON((EFI_VA_START & P4D_MASK) != (EFI_VA_END & P4D_MASK));
> + BUILD_BUG_ON((EFI_VA_START & P4D_MASK) != P4D_MASK);
>
> pgd_efi = efi_pgd + pgd_index(EFI_VA_END);
> pgd_k = pgd_offset_k(EFI_VA_END);
>
>
> --
> Regards/Gruss,
> Boris.
>
> https://people.kernel.org/tglx/notes-about-netiquette
next prev parent reply other threads:[~2021-02-04 19:18 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-07 22:34 [PATCH] x86: efi: avoid BUILD_BUG_ON() for non-constant p4d_index Arnd Bergmann
2021-01-07 22:42 ` Nathan Chancellor
2021-01-13 17:51 ` Ard Biesheuvel
2021-01-15 18:23 ` Borislav Petkov
2021-01-15 18:32 ` Nathan Chancellor
2021-01-15 19:07 ` Borislav Petkov
2021-01-15 19:11 ` Arvind Sankar
2021-01-15 19:18 ` Borislav Petkov
2021-01-15 19:54 ` Arnd Bergmann
2021-01-15 20:12 ` Arvind Sankar
2021-01-15 20:32 ` Arvind Sankar
2021-01-15 19:07 ` Arvind Sankar
2021-01-15 20:27 ` Arvind Sankar
2021-01-16 16:34 ` Ard Biesheuvel
2021-01-18 20:24 ` Borislav Petkov
2021-01-18 21:42 ` Arvind Sankar
2021-01-20 9:33 ` Ard Biesheuvel
2021-01-20 11:44 ` Borislav Petkov
2021-02-03 18:51 ` Nathan Chancellor
2021-02-03 20:29 ` Ard Biesheuvel
2021-02-04 10:51 ` Borislav Petkov
2021-02-04 10:59 ` Ard Biesheuvel
2021-02-04 19:16 ` Nathan Chancellor [this message]
2021-02-04 21:43 ` Arvind Sankar
2021-02-04 22:13 ` Borislav Petkov
2021-02-05 0:08 ` Arvind Sankar
2021-02-05 11:39 ` [PATCH] x86/efi: Remove EFI PGD build time checks Borislav Petkov
2021-02-05 11:57 ` Ard Biesheuvel
2021-02-05 18:14 ` Nick Desaulniers
2021-02-05 18:56 ` Nathan Chancellor
2021-02-05 10:34 ` [PATCH] x86: efi: avoid BUILD_BUG_ON() for non-constant p4d_index Borislav Petkov
2021-02-05 18:27 ` Nick Desaulniers
2021-02-05 18:31 ` Nathan Chancellor
2021-01-20 11:26 ` Kirill A. Shutemov
2021-01-20 11:06 ` Kirill A. Shutemov
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