From: Justin Stitt <justinstitt@google.com>
To: Nathan Chancellor <nathan@kernel.org>
Cc: Ard Biesheuvel <ardb+git@google.com>,
linux-kernel@vger.kernel.org, x86@kernel.org,
Ard Biesheuvel <ardb@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
Eric Biederman <ebiederm@xmission.com>,
kexec@lists.infradead.org,
Nick Desaulniers <ndesaulniers@google.com>,
Kees Cook <keescook@chromium.org>,
Bill Wendling <morbo@google.com>,
Masahiro Yamada <masahiroy@kernel.org>
Subject: Re: [RFC PATCH 2/9] x86/purgatory: Simplify stack handling
Date: Fri, 26 Apr 2024 21:32:52 +0000 [thread overview]
Message-ID: <pgsqflimo7d2ozhpmdrmscx25mxs5lypcvwq6mgjs7uixsxvsl@5papnq46mwbs> (raw)
In-Reply-To: <20240424182659.GA2126602@dev-arch.thelio-3990X>
Hi,
On Wed, Apr 24, 2024 at 11:26:59AM -0700, Nathan Chancellor wrote:
> On Wed, Apr 24, 2024 at 05:53:12PM +0200, Ard Biesheuvel wrote:
> > From: Ard Biesheuvel <ardb@kernel.org>
> >
> > The x86 purgatory, which does little more than verify a SHA-256 hash of
> > the loaded segments, currently uses three different stacks:
> > - one in .bss that is used to call the purgatory C code
> > - one in .rodata that is only used to switch to an updated code segment
> > descriptor in the GDT
> > - one in .data, which allows it to be prepopulated from the kexec loader
> > in theory, but this is not actually being taken advantage of.
> >
> > Simplify this, by dropping the latter two stacks, as well as the loader
> > logic that programs RSP.
> >
> > Both the stacks in .bss and .data are 4k aligned, but 16 byte alignment
> > is more than sufficient.
> >
> > Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> > ---
> > arch/x86/include/asm/kexec.h | 1 -
> > arch/x86/kernel/kexec-bzimage64.c | 8 --------
> > arch/x86/purgatory/entry64.S | 8 --------
> > arch/x86/purgatory/setup-x86_64.S | 2 +-
> > arch/x86/purgatory/stack.S | 18 ------------------
>
> This needs a small fix up to build.
>
> make[6]: *** No rule to make target 'arch/x86/purgatory/stack.o', needed by 'arch/x86/purgatory/purgatory.ro'.
>
I was trying to reproduce this build failure, but to no avail. I am
curious what your build target / build command was.
It is clear that stack.S has been removed so your change makes sense, I
don't doubt that -- I just cannot get that specific error message you
encountered (what is a .ro file supposed to be, anyway?).
> diff --git a/arch/x86/purgatory/Makefile b/arch/x86/purgatory/Makefile
> index acc09799af2a..2b6b2fb033d6 100644
> --- a/arch/x86/purgatory/Makefile
> +++ b/arch/x86/purgatory/Makefile
> @@ -1,7 +1,7 @@
> # SPDX-License-Identifier: GPL-2.0
> OBJECT_FILES_NON_STANDARD := y
>
> -purgatory-y := purgatory.o stack.o setup-x86_$(BITS).o sha256.o entry64.o string.o
> +purgatory-y := purgatory.o setup-x86_$(BITS).o sha256.o entry64.o string.o
>
> targets += $(purgatory-y)
> PURGATORY_OBJS = $(addprefix $(obj)/,$(purgatory-y))
Thanks
Justin
next prev parent reply other threads:[~2024-04-26 21:32 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-24 15:53 [RFC PATCH 0/9] kexec x86 purgatory cleanup Ard Biesheuvel
2024-04-24 15:53 ` [RFC PATCH 1/9] x86/purgatory: Drop function entry padding from purgatory Ard Biesheuvel
2024-04-24 15:53 ` [RFC PATCH 2/9] x86/purgatory: Simplify stack handling Ard Biesheuvel
2024-04-24 18:26 ` Nathan Chancellor
2024-04-26 21:32 ` Justin Stitt [this message]
2024-04-26 21:53 ` Nathan Chancellor
2024-04-26 22:01 ` Justin Stitt
2024-04-24 15:53 ` [RFC PATCH 3/9] x86/purgatory: Drop pointless GDT switch Ard Biesheuvel
2024-04-24 15:53 ` [RFC PATCH 4/9] x86/purgatory: Avoid absolute reference to GDT Ard Biesheuvel
2024-04-24 17:38 ` Brian Gerst
2024-04-24 17:53 ` Ard Biesheuvel
2024-04-24 19:00 ` Brian Gerst
2024-04-24 15:53 ` [RFC PATCH 5/9] x86/purgatory: Simplify GDT and drop data segment Ard Biesheuvel
2024-04-24 15:53 ` [RFC PATCH 6/9] kexec: Add support for fully linked purgatory executables Ard Biesheuvel
2024-04-24 15:53 ` [RFC PATCH 7/9] x86/purgatory: Use fully linked PIE ELF executable Ard Biesheuvel
2024-04-24 15:53 ` [RFC PATCH 8/9] x86/purgatory: Simplify references to regs array Ard Biesheuvel
2024-04-24 15:53 ` [RFC PATCH 9/9] kexec: Drop support for partially linked purgatory executables Ard Biesheuvel
2024-04-24 20:04 ` [RFC PATCH 0/9] kexec x86 purgatory cleanup Eric W. Biederman
2024-04-24 20:52 ` Ard Biesheuvel
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