From: Ard Biesheuvel <ardb@kernel.org>
To: Arvind Sankar <nivedita@alum.mit.edu>
Cc: linux-efi <linux-efi@vger.kernel.org>, X86 ML <x86@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Thomas Gleixner <tglx@linutronix.de>,
Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH 3/5] efi/x86: Remove __efistub_global annotation
Date: Thu, 16 Apr 2020 09:51:30 +0200 [thread overview]
Message-ID: <CAMj1kXFMgrj8POtc0UQ6D-dbDKU+RmuHjUH-bAkMBAqjL_p+mg@mail.gmail.com> (raw)
In-Reply-To: <20200415221520.2692512-4-nivedita@alum.mit.edu>
On Thu, 16 Apr 2020 at 00:15, Arvind Sankar <nivedita@alum.mit.edu> wrote:
>
> Instead of using __efistub_global to force variables into the .data
> section, leave them in the .bss but pull the EFI stub's .bss section
> into .data in the linker script for the compressed kernel.
>
> Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
With the R_386_32/R_X86_64_64 check folded in:
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
> ---
> arch/x86/boot/compressed/vmlinux.lds.S | 1 +
> drivers/firmware/efi/libstub/Makefile | 12 ++++++++++--
> drivers/firmware/efi/libstub/efistub.h | 4 ----
> 3 files changed, 11 insertions(+), 6 deletions(-)
>
> diff --git a/arch/x86/boot/compressed/vmlinux.lds.S b/arch/x86/boot/compressed/vmlinux.lds.S
> index 508cfa6828c5..0dc5c2b9614b 100644
> --- a/arch/x86/boot/compressed/vmlinux.lds.S
> +++ b/arch/x86/boot/compressed/vmlinux.lds.S
> @@ -52,6 +52,7 @@ SECTIONS
> _data = . ;
> *(.data)
> *(.data.*)
> + *(.bss.efistub)
> _edata = . ;
> }
> . = ALIGN(L1_CACHE_BYTES);
> diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
> index e5e76677f2da..0bb2916eb12b 100644
> --- a/drivers/firmware/efi/libstub/Makefile
> +++ b/drivers/firmware/efi/libstub/Makefile
> @@ -73,8 +73,8 @@ CFLAGS_arm64-stub.o := -DTEXT_OFFSET=$(TEXT_OFFSET)
> # a verification pass to see if any absolute relocations exist in any of the
> # object files.
> #
> -extra-$(CONFIG_EFI_ARMSTUB) := $(lib-y)
> -lib-$(CONFIG_EFI_ARMSTUB) := $(patsubst %.o,%.stub.o,$(lib-y))
> +extra-y := $(lib-y)
> +lib-y := $(patsubst %.o,%.stub.o,$(lib-y))
>
> STUBCOPY_FLAGS-$(CONFIG_ARM64) += --prefix-alloc-sections=.init \
> --prefix-symbols=__efistub_
> @@ -89,6 +89,14 @@ STUBCOPY_FLAGS-$(CONFIG_ARM) += --rename-section .data=.data.efistub \
> --rename-section .bss=.bss.efistub,load,alloc
> STUBCOPY_RELOC-$(CONFIG_ARM) := R_ARM_ABS
>
> +#
> +# For x86, bootloaders like systemd-boot or grub-efi do not zero-initialize the
> +# .bss section, so the .bss section of the EFI stub needs to be included in the
> +# .data section of the compressed kernel to ensure initialization. Rename the
> +# .bss section here so it's easy to pick out in the linker script.
> +#
> +STUBCOPY_FLAGS-$(CONFIG_X86) += --rename-section .bss=.bss.efistub,load,alloc
> +
> $(obj)/%.stub.o: $(obj)/%.o FORCE
> $(call if_changed,stubcopy)
>
> diff --git a/drivers/firmware/efi/libstub/efistub.h b/drivers/firmware/efi/libstub/efistub.h
> index a92d42ffd9f7..49651e20bb9f 100644
> --- a/drivers/firmware/efi/libstub/efistub.h
> +++ b/drivers/firmware/efi/libstub/efistub.h
> @@ -25,11 +25,7 @@
> #define EFI_ALLOC_ALIGN EFI_PAGE_SIZE
> #endif
>
> -#if defined(CONFIG_X86)
> -#define __efistub_global __section(.data)
> -#else
> #define __efistub_global
> -#endif
>
> extern bool __pure nochunk(void);
> extern bool __pure nokaslr(void);
> --
> 2.24.1
>
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next prev parent reply other threads:[~2020-04-16 7:51 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-15 22:15 [PATCH 0/5] efi: Remove __efistub_global annotation Arvind Sankar
2020-04-15 22:15 ` [PATCH 1/5] efi/arm: " Arvind Sankar
2020-04-16 7:50 ` Ard Biesheuvel
2020-04-15 22:15 ` [PATCH 2/5] efi/libstub: Factor out relocation checking Arvind Sankar
2020-04-15 22:15 ` [PATCH 3/5] efi/x86: Remove __efistub_global annotation Arvind Sankar
2020-04-16 7:51 ` Ard Biesheuvel [this message]
2020-04-15 22:15 ` [PATCH 4/5] efi: Kill __efistub_global Arvind Sankar
2020-04-16 7:51 ` Ard Biesheuvel
2020-04-15 22:15 ` [PATCH 5/5] efi/x86: Check for bad relocations Arvind Sankar
2020-04-16 7:38 ` Ard Biesheuvel
2020-04-16 14:48 ` Arvind Sankar
2020-04-16 15:12 ` [PATCH v2 0/3] efi: Remove __efistub_global annotation Arvind Sankar
2020-04-16 16:01 ` Ard Biesheuvel
2020-04-16 15:12 ` [PATCH v2 1/3] efi/arm: " Arvind Sankar
2020-04-16 15:12 ` [PATCH v2 2/3] efi/x86: Remove __efistub_global and add relocation check Arvind Sankar
2020-04-16 15:12 ` [PATCH v2 3/3] efi: Kill __efistub_global Arvind Sankar
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