From: Kees Cook <keescook@chromium.org>
To: Arvind Sankar <nivedita@alum.mit.edu>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"H. Peter Anvin" <hpa@zytor.com>,
x86@kernel.org, Nick Desaulniers <ndesaulniers@google.com>,
Fangrui Song <maskray@google.com>,
Dmitry Golovin <dima@golovin.in>,
clang-built-linux@googlegroups.com,
Ard Biesheuvel <ardb@kernel.org>,
Masahiro Yamada <masahiroy@kernel.org>,
Daniel Kiper <daniel.kiper@oracle.com>,
Sedat Dilek <sedat.dilek@gmail.com>,
Nathan Chancellor <natechancellor@gmail.com>,
Arnd Bergmann <arnd@arndb.de>, "H . J . Lu" <hjl@sourceware.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 1/7] x86/boot/compressed: Move .got.plt entries out of the .got section
Date: Mon, 29 Jun 2020 08:48:05 -0700 [thread overview]
Message-ID: <202006290846.5A5C76A4D7@keescook> (raw)
In-Reply-To: <20200629140928.858507-2-nivedita@alum.mit.edu>
On Mon, Jun 29, 2020 at 10:09:22AM -0400, Arvind Sankar wrote:
> From: Ard Biesheuvel <ardb@kernel.org>
>
> The .got.plt section contains the part of the GOT which is used by PLT
> entries, and which gets updated lazily by the dynamic loader when
> function calls are dispatched through those PLT entries.
>
> On fully linked binaries such as the kernel proper or the decompressor,
> this never happens, and so in practice, the .got.plt section consists
> only of the first 3 magic entries that are meant to point at the _DYNAMIC
> section and at the fixup routine in the loader. However, since we don't
> use a dynamic loader, those entries are never populated or used.
>
> This means that treating those entries like ordinary GOT entries, and
> updating their values based on the actual placement of the executable in
> memory is completely pointless, and we can just ignore the .got.plt
> section entirely, provided that it has no additional entries beyond
> the first 3 ones.
>
> So add an assertion in the linker script to ensure that this assumption
> holds, and move the contents out of the [_got, _egot) memory range that
> is modified by the GOT fixup routines.
>
> While at it, drop the KEEP(), since it has no effect on the contents
> of output sections that are created by the linker itself.
>
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> Acked-by: Arvind Sankar <nivedita@alum.mit.edu>
> Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
> From: Ard Biesheuvel <ardb@kernel.org>
> Link: https://lore.kernel.org/r/20200523120021.34996-2-ardb@kernel.org
> ---
> arch/x86/boot/compressed/vmlinux.lds.S | 11 ++++++++++-
> 1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/boot/compressed/vmlinux.lds.S b/arch/x86/boot/compressed/vmlinux.lds.S
> index 8f1025d1f681..b17d218ccdf9 100644
> --- a/arch/x86/boot/compressed/vmlinux.lds.S
> +++ b/arch/x86/boot/compressed/vmlinux.lds.S
> @@ -44,10 +44,13 @@ SECTIONS
> }
> .got : {
> _got = .;
> - KEEP(*(.got.plt))
> KEEP(*(.got))
> _egot = .;
> }
> + .got.plt : {
> + *(.got.plt)
> + }
This is also being done on arm64, and the section was specified slightly
differently (with INFO) which maybe should be done here too?
.got.plt (INFO) : { *(.got.plt) }
ASSERT(SIZEOF(.got.plt) == 0 || SIZEOF(.got.plt) == 0x18, ".got.plt not empty")
Otherwise, yes, looks good.
Reviewed-by: Kees Cook <keescook@chromium.org>
> +
> .data : {
> _data = . ;
> *(.data)
> @@ -77,3 +80,9 @@ SECTIONS
>
> DISCARDS
> }
> +
> +#ifdef CONFIG_X86_64
> +ASSERT(SIZEOF(.got.plt) == 0 || SIZEOF(.got.plt) == 0x18, "Unexpected GOT/PLT entries detected!")
> +#else
> +ASSERT(SIZEOF(.got.plt) == 0 || SIZEOF(.got.plt) == 0xc, "Unexpected GOT/PLT entries detected!")
> +#endif
> --
> 2.26.2
>
--
Kees Cook
next prev parent reply other threads:[~2020-06-29 19:27 UTC|newest]
Thread overview: 113+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-29 14:09 [PATCH v3 0/7] x86/boot: Remove runtime relocations from compressed kernel Arvind Sankar
2020-06-29 14:09 ` [PATCH v3 1/7] x86/boot/compressed: Move .got.plt entries out of the .got section Arvind Sankar
2020-06-29 15:48 ` Kees Cook [this message]
2020-06-29 15:50 ` Arvind Sankar
2020-06-29 15:51 ` Ard Biesheuvel
2020-06-29 16:10 ` Kees Cook
2020-06-29 14:09 ` [PATCH v3 2/7] x86/boot/compressed: Force hidden visibility for all symbol references Arvind Sankar
2020-06-29 15:50 ` Kees Cook
2020-07-14 9:20 ` Sedat Dilek
2020-07-14 9:47 ` Ard Biesheuvel
2020-06-29 14:09 ` [PATCH v3 3/7] x86/boot/compressed: Get rid of GOT fixup code Arvind Sankar
2020-06-29 15:53 ` Kees Cook
2020-06-29 14:09 ` [PATCH v3 4/7] x86/boot: Add .text.* to setup.ld Arvind Sankar
2020-06-29 15:55 ` Kees Cook
2020-06-29 14:09 ` [PATCH v3 5/7] x86/boot: Remove run-time relocations from .head.text code Arvind Sankar
2020-06-29 16:04 ` Kees Cook
2020-06-29 17:01 ` Arvind Sankar
2020-07-14 13:20 ` Sedat Dilek
2020-06-29 14:09 ` [PATCH v3 6/7] x86/boot: Remove runtime relocations from head_{32,64}.S Arvind Sankar
2020-06-29 16:06 ` Kees Cook
2020-06-29 16:52 ` Arvind Sankar
2020-06-29 14:09 ` [PATCH v3 7/7] x86/boot: Check that there are no runtime relocations Arvind Sankar
2020-06-29 16:09 ` Kees Cook
2020-06-29 16:11 ` Ard Biesheuvel
2020-06-29 16:20 ` Kees Cook
2020-06-29 16:56 ` Arvind Sankar
2020-06-29 17:37 ` Fangrui Song
2020-06-29 18:11 ` Ard Biesheuvel
2020-06-29 23:34 ` Fangrui Song
2020-06-30 16:26 ` Ard Biesheuvel
2020-06-30 17:54 ` Arvind Sankar
2020-06-30 22:00 ` Fangrui Song
2020-06-30 23:27 ` Arvind Sankar
2020-07-01 6:44 ` Ard Biesheuvel
2020-07-01 14:42 ` Arvind Sankar
2020-06-29 18:43 ` Arvind Sankar
2020-07-14 2:38 ` [PATCH v4 0/7] x86/boot: Remove runtime relocations from compressed kernel Arvind Sankar
2020-07-14 13:15 ` Sedat Dilek
2020-07-14 14:15 ` Arvind Sankar
2020-07-14 18:13 ` Sedat Dilek
2020-07-14 18:30 ` Sedat Dilek
2020-07-14 18:33 ` Sedat Dilek
2020-07-14 19:21 ` Sedat Dilek
2020-07-14 19:29 ` Arvind Sankar
2020-07-14 19:53 ` Sedat Dilek
2020-07-14 20:07 ` Arvind Sankar
2020-07-14 20:10 ` Sedat Dilek
2020-07-14 20:14 ` Arvind Sankar
2020-07-14 20:17 ` Sedat Dilek
2020-07-14 20:08 ` Sedat Dilek
2020-07-14 20:21 ` Arvind Sankar
2020-07-14 20:24 ` Sedat Dilek
2020-07-14 20:27 ` Sedat Dilek
2020-07-14 20:35 ` Arvind Sankar
2020-07-14 20:43 ` Sedat Dilek
2020-07-14 21:07 ` Arvind Sankar
2020-07-14 20:33 ` Arvind Sankar
2020-07-15 0:41 ` [PATCH v5 0/7] x86/boot: Remove run-time " Arvind Sankar
2020-07-15 1:46 ` Sedat Dilek
2020-07-15 7:11 ` Sedat Dilek
2020-07-17 13:46 ` Arvind Sankar
2020-07-17 18:16 ` Nick Desaulniers
2020-07-17 18:21 ` Sedat Dilek
2020-07-17 20:17 ` [PATCH-next " Arvind Sankar
2020-07-17 23:46 ` Nick Desaulniers
2020-07-29 22:04 ` Kees Cook
2020-07-29 22:23 ` Arvind Sankar
2020-07-30 2:38 ` Kees Cook
2020-07-17 20:17 ` [PATCH-next v5 1/7] x86/boot/compressed: Move .got.plt entries out of the .got section Arvind Sankar
2020-07-17 20:17 ` [PATCH-next v5 2/7] x86/boot/compressed: Force hidden visibility for all symbol references Arvind Sankar
2020-07-17 20:17 ` [PATCH-next v5 3/7] x86/boot/compressed: Get rid of GOT fixup code Arvind Sankar
2020-07-17 20:17 ` [PATCH-next v5 4/7] x86/boot: Add .text.* to setup.ld Arvind Sankar
2020-07-17 20:17 ` [PATCH-next v5 5/7] x86/boot: Remove run-time relocations from .head.text code Arvind Sankar
2020-07-17 20:18 ` [PATCH-next v5 6/7] x86/boot: Remove run-time relocations from head_{32,64}.S Arvind Sankar
2020-07-17 20:18 ` [PATCH-next v5 7/7] x86/boot: Check that there are no run-time relocations Arvind Sankar
2020-07-18 5:44 ` [PATCH v5 0/7] x86/boot: Remove run-time relocations from compressed kernel Ard Biesheuvel
2020-07-18 7:01 ` Sedat Dilek
2020-07-24 23:25 ` Kees Cook
2020-07-31 14:53 ` Arvind Sankar
2020-07-31 14:58 ` Sedat Dilek
2020-07-31 20:27 ` [PATCH v6 " Arvind Sankar
2020-07-31 20:27 ` [PATCH v6 1/7] x86/boot/compressed: Move .got.plt entries out of the .got section Arvind Sankar
2020-07-31 20:27 ` [PATCH v6 2/7] x86/boot/compressed: Force hidden visibility for all symbol references Arvind Sankar
2020-07-31 20:27 ` [PATCH v6 3/7] x86/boot/compressed: Get rid of GOT fixup code Arvind Sankar
2020-07-31 20:27 ` [PATCH v6 4/7] x86/boot: Add .text.* to setup.ld Arvind Sankar
2020-07-31 20:27 ` [PATCH v6 5/7] x86/boot: Remove run-time relocations from .head.text code Arvind Sankar
2020-07-31 20:27 ` [PATCH v6 6/7] x86/boot: Remove run-time relocations from head_{32,64}.S Arvind Sankar
2020-07-31 20:27 ` [PATCH v6 7/7] x86/boot: Check that there are no run-time relocations Arvind Sankar
2020-07-31 23:15 ` [PATCH v6 0/7] x86/boot: Remove run-time relocations from compressed kernel Kees Cook
2020-07-15 0:41 ` [PATCH v5 1/7] x86/boot/compressed: Move .got.plt entries out of the .got section Arvind Sankar
2020-07-15 8:52 ` Sedat Dilek
2020-07-15 0:41 ` [PATCH v5 2/7] x86/boot/compressed: Force hidden visibility for all symbol references Arvind Sankar
2020-07-15 8:54 ` Sedat Dilek
2020-07-15 0:41 ` [PATCH v5 3/7] x86/boot/compressed: Get rid of GOT fixup code Arvind Sankar
2020-07-15 8:54 ` Sedat Dilek
2020-07-15 0:41 ` [PATCH v5 4/7] x86/boot: Add .text.* to setup.ld Arvind Sankar
2020-07-15 8:55 ` Sedat Dilek
2020-07-15 0:41 ` [PATCH v5 5/7] x86/boot: Remove run-time relocations from .head.text code Arvind Sankar
2020-07-15 8:56 ` Sedat Dilek
2020-07-15 0:41 ` [PATCH v5 6/7] x86/boot: Remove run-time relocations from head_{32,64}.S Arvind Sankar
2020-07-15 8:58 ` Sedat Dilek
2020-07-15 9:03 ` Ard Biesheuvel
2020-07-15 9:10 ` Sedat Dilek
2020-07-15 0:41 ` [PATCH v5 7/7] x86/boot: Check that there are no run-time relocations Arvind Sankar
2020-07-15 9:00 ` Sedat Dilek
2020-07-15 9:12 ` Sedat Dilek
2020-07-14 2:38 ` [PATCH v4 1/7] x86/boot/compressed: Move .got.plt entries out of the .got section Arvind Sankar
2020-07-14 2:38 ` [PATCH v4 2/7] x86/boot/compressed: Force hidden visibility for all symbol references Arvind Sankar
2020-07-14 2:38 ` [PATCH v4 3/7] x86/boot/compressed: Get rid of GOT fixup code Arvind Sankar
2020-07-14 2:38 ` [PATCH v4 4/7] x86/boot: Add .text.* to setup.ld Arvind Sankar
2020-07-14 2:38 ` [PATCH v4 5/7] x86/boot: Remove run-time relocations from .head.text code Arvind Sankar
2020-07-14 2:38 ` [PATCH v4 6/7] x86/boot: Remove runtime relocations from head_{32,64}.S Arvind Sankar
2020-07-14 2:38 ` [PATCH v4 7/7] x86/boot: Check that there are no runtime relocations Arvind Sankar
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