[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <CAJcbSZEJBYOME2JqFdUxTVnb7F8uSY7PSaTDMEHf7vbEscUnbg@mail.gmail.com>
Date: Mon, 20 May 2019 16:23:58 -0700
From: Thomas Garnier <thgarnie@...gle.com>
To: Kernel Hardening <kernel-hardening@...ts.openwall.com>
Cc: Kristen Carlson Accardi <kristen@...ux.intel.com>, Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, "H. Peter Anvin" <hpa@...or.com>,
"the arch/x86 maintainers" <x86@...nel.org>, "Peter Zijlstra (Intel)" <peterz@...radead.org>, Nadav Amit <namit@...are.com>,
Michael Ellerman <mpe@...erman.id.au>, Masahiro Yamada <yamada.masahiro@...ionext.com>,
Ard Biesheuvel <ard.biesheuvel@...aro.org>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7 02/12] x86: Use symbol name in jump table for PIE support
On Mon, May 20, 2019 at 4:20 PM Thomas Garnier <thgarnie@...omium.org> wrote:
>
> From: Thomas Garnier <thgarnie@...gle.com>
>
> Replace the %c constraint with %P. The %c is incompatible with PIE
> because it implies an immediate value whereas %P reference a symbol.
> Change the _ASM_PTR reference to .long for expected relocation size and
> add a long padding to ensure entry alignment.
>
> Position Independent Executable (PIE) support will allow to extend the
> KASLR randomization range below 0xffffffff80000000.
>
> Signed-off-by: Thomas Garnier <thgarnie@...gle.com>
> ---
> arch/x86/include/asm/jump_label.h | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/include/asm/jump_label.h b/arch/x86/include/asm/jump_label.h
> index 65191ce8e1cf..e47fad8ee632 100644
> --- a/arch/x86/include/asm/jump_label.h
> +++ b/arch/x86/include/asm/jump_label.h
> @@ -25,9 +25,9 @@ static __always_inline bool arch_static_branch(struct static_key *key, bool bran
> ".pushsection __jump_table, \"aw\" \n\t"
> _ASM_ALIGN "\n\t"
> ".long 1b - ., %l[l_yes] - . \n\t"
> - _ASM_PTR "%c0 + %c1 - .\n\t"
> + _ASM_PTR "%P0 - .\n\t"
> ".popsection \n\t"
> - : : "i" (key), "i" (branch) : : l_yes);
> + : : "X" (&((char *)key)[branch]) : : l_yes);
>
> return false;
> l_yes:
> @@ -42,9 +42,9 @@ static __always_inline bool arch_static_branch_jump(struct static_key *key, bool
> ".pushsection __jump_table, \"aw\" \n\t"
> _ASM_ALIGN "\n\t"
> ".long 1b - ., %l[l_yes] - . \n\t"
> - _ASM_PTR "%c0 + %c1 - .\n\t"
> + _ASM_PTR "%P0 - .\n\t"
> ".popsection \n\t"
> - : : "i" (key), "i" (branch) : : l_yes);
> + : : "X" (&((char *)key)[branch]) : : l_yes);
>
> return false;
> l_yes:
> --
> 2.21.0.1020.gf2820cf01a-goog
>
Realized I forgot to address a feedback from the previous iteration on
this specific patch. Ignore it I will work to check if it can be
remove on the next iteration.
--
Thomas
Powered by blists - more mailing lists
Confused about mailing lists and their use?
Read about mailing lists on Wikipedia
and check out these
guidelines on proper formatting of your messages.
