From: Ard Biesheuvel <ardb@kernel.org>
To: Arvind Sankar <nivedita@alum.mit.edu>
Cc: Brian Gerst <brgerst@gmail.com>,
linux-efi <linux-efi@vger.kernel.org>,
Ingo Molnar <mingo@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Arnd Bergmann <arnd@arndb.de>, Borislav Petkov <bp@suse.de>,
Colin Ian King <colin.king@canonical.com>,
Gary Lin <glin@suse.com>, Jiri Slaby <jslaby@suse.cz>,
Sergey Shatunov <me@prok.pw>, Takashi Iwai <tiwai@suse.de>
Subject: Re: [PATCH 3/9] efi/x86: Move efi stub globals from .bss to .data
Date: Fri, 10 Apr 2020 18:03:38 +0200 [thread overview]
Message-ID: <CAMj1kXGMNMdgjinYNgrN2wGRFG4rKE2YHo-=3s4Ofv2KPUMqKQ@mail.gmail.com> (raw)
In-Reply-To: <20200410151612.GA970420@rani.riverdale.lan>
On Fri, 10 Apr 2020 at 17:16, Arvind Sankar <nivedita@alum.mit.edu> wrote:
>
> On Fri, Apr 10, 2020 at 10:20:42AM +0200, Ard Biesheuvel wrote:
> > On Thu, 9 Apr 2020 at 23:08, Arvind Sankar <nivedita@alum.mit.edu> wrote:
> > >
> > > On Thu, Apr 09, 2020 at 04:53:07PM -0400, Brian Gerst wrote:
> > > > > Can we use the -fno-zero-initialized-in-bss compiler flag instead of
> > > > > explicitly marking global variables?
> > > >
> > > > Scratch that. Apparently it only works when a variable is explicitly
> > > > initialized to zero.
> > > >
> > > > --
> > > > Brian Gerst
> > >
> > > Right, there doesn't seem to be a compiler option to turn off the use of
> > > .bss altogether.
> >
> > Yeah. I'll try to come up with a way to consolidate this a bit across
> > architectures (which is a bit easier now that all of the EFI stub C
> > code lives in the same place). It is probably easiest to use a section
> > renaming trick similar to the one I added for ARM (as Arvind suggested
> > as well, IIRC), and get rid of the per-symbol annotations altogether.
>
> Does that work for 32-bit ARM, or does it need to be .data to tell the
> compiler to avoid generating GOT references? If that's fine, we don't
> actually need to rename sections -- linker script magic is enough. For
> eg, the below pulls the EFI stub bss into .data for x86 without the need
> for the annotations.
>
> diff --git a/arch/x86/boot/compressed/vmlinux.lds.S b/arch/x86/boot/compressed/vmlinux.lds.S
> index 508cfa6828c5..e324819c95bc 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.*)
> + drivers/firmware/efi/libstub/lib.a:(.bss .bss.*)
> _edata = . ;
> }
> . = ALIGN(L1_CACHE_BYTES);
No, we can add this to ARM as well, and get rid of the
__efistub_global annotations entirely.
We'll still need .data.efistub for the .data pieces, but that is a
separate issue.
next prev parent reply other threads:[~2020-04-10 16:03 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-09 13:04 [GIT PULL 0/9] EFI fixes for v5.7-rc Ard Biesheuvel
2020-04-09 13:04 ` [PATCH 1/9] efi/cper: Use scnprintf() for avoiding potential buffer overflow Ard Biesheuvel
2020-04-09 13:04 ` [PATCH 2/9] efi/libstub/x86: remove redundant assignment to pointer hdr Ard Biesheuvel
2020-04-09 13:04 ` [PATCH 3/9] efi/x86: Move efi stub globals from .bss to .data Ard Biesheuvel
2020-04-09 20:05 ` Brian Gerst
2020-04-09 20:53 ` Brian Gerst
2020-04-09 21:08 ` Arvind Sankar
2020-04-10 8:20 ` Ard Biesheuvel
2020-04-10 15:16 ` Arvind Sankar
2020-04-10 16:03 ` Ard Biesheuvel [this message]
2020-04-10 18:01 ` Arvind Sankar
2020-04-10 18:03 ` Ard Biesheuvel
2020-04-10 19:03 ` Arvind Sankar
2020-04-11 1:03 ` Arvind Sankar
2020-04-09 13:04 ` [PATCH 4/9] efi/x86: Always relocate the kernel for EFI handover entry Ard Biesheuvel
2020-04-09 13:04 ` [PATCH 5/9] efi/arm: Deal with ADR going out of range in efi_enter_kernel() Ard Biesheuvel
2020-04-14 8:20 ` [tip: efi/urgent] " tip-bot2 for Ard Biesheuvel
2020-04-09 13:04 ` [PATCH 6/9] Documentation: efi/x86: clarify EFI handover protocol and its requirements Ard Biesheuvel
2020-04-14 8:20 ` [tip: efi/urgent] Documentation/x86, efi/x86: Clarify " tip-bot2 for Ard Biesheuvel
2020-04-09 13:04 ` [PATCH 7/9] efi/libstub/file: merge filename buffers to reduce stack usage Ard Biesheuvel
2020-04-14 8:20 ` [tip: efi/urgent] efi/libstub/file: Merge file name " tip-bot2 for Ard Biesheuvel
2020-04-09 13:04 ` [PATCH 8/9] efi/x86: Fix the deletion of variables in mixed mode Ard Biesheuvel
2020-04-09 13:04 ` [PATCH 9/9] efi/x86: Don't remap text<->rodata gap read-only for " Ard Biesheuvel
2020-04-14 8:20 ` [tip: efi/urgent] " tip-bot2 for Ard Biesheuvel
2020-04-09 19:01 ` [GIT PULL 0/9] EFI fixes for v5.7-rc Theodore Y. Ts'o
2020-04-09 19:04 ` Ard Biesheuvel
2020-04-09 20:16 ` Theodore Y. Ts'o
2020-04-09 21:29 ` Ard Biesheuvel
2020-04-09 23:57 ` Theodore Y. Ts'o
2020-04-10 7:08 ` Ard Biesheuvel
2020-04-10 13:54 ` Dave Young
2020-04-11 19:43 ` Theodore Y. Ts'o
2020-04-12 3:51 ` Dave Young
2020-04-13 14:07 ` David Howells
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