From: Benjamin LaHaise <bcrl@kvack.org>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>,
Russell King <rmk@arm.linux.org.uk>,
Thomas Gleixner <tglx@linutronix.de>,
x86@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] x86_32: add support for 64 bit __get_user() v3
Date: Mon, 14 Mar 2016 11:37:47 -0400 [thread overview]
Message-ID: <20160314153747.GH17923@kvack.org> (raw)
In-Reply-To: <20160309200556.GT12913@kvack.org>
Any more comments/feedback on this? Can this be merged for 4.6?
-ben
On Wed, Mar 09, 2016 at 03:05:56PM -0500, Benjamin LaHaise wrote:
> The existing __get_user() implementation does not support fetching
> 64 bit values on 32 bit x86. Implement this in a way that does not
> generate any incorrect warnings as cautioned by Russell King. Test
> code available at http://www.kvack.org/~bcrl/x86_32-get_user.tar .
>
> v2: use __inttype() as suggested by H. Peter Anvin, which cleans the
> code up nicely, and fix things to work on x86_64 as well.
>
> v3: fix undefined behaviour on 32 bit x86 caused by multiple expansion
> of ptr in the 64 bit case.
>
> Signed-off-by: Benjamin LaHaise <bcrl@kvack.org>
>
> diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
> index a4a30e4..8743552 100644
> --- a/arch/x86/include/asm/uaccess.h
> +++ b/arch/x86/include/asm/uaccess.h
> @@ -333,7 +333,26 @@ do { \
> } while (0)
>
> #ifdef CONFIG_X86_32
> -#define __get_user_asm_u64(x, ptr, retval, errret) (x) = __get_user_bad()
> +#define __get_user_asm_u64(x, ptr, retval, errret) \
> +({ \
> + __typeof__(ptr) __ptr = (ptr); \
> + asm volatile(ASM_STAC "\n" \
> + "1: movl %2,%%eax\n" \
> + "2: movl %3,%%edx\n" \
> + "3: " ASM_CLAC "\n" \
> + ".section .fixup,\"ax\"\n" \
> + "4: mov %4,%0\n" \
> + " xorl %%eax,%%eax\n" \
> + " xorl %%edx,%%edx\n" \
> + " jmp 3b\n" \
> + ".previous\n" \
> + _ASM_EXTABLE(1b, 4b) \
> + _ASM_EXTABLE(2b, 4b) \
> + : "=r" (retval), "=A"(x) \
> + : "m" (__m(__ptr)), "m" __m(((u32 *)(__ptr)) + 1), \
> + "i" (errret), "0" (retval)); \
> +})
> +
> #define __get_user_asm_ex_u64(x, ptr) (x) = __get_user_bad()
> #else
> #define __get_user_asm_u64(x, ptr, retval, errret) \
> @@ -420,7 +439,7 @@ do { \
> #define __get_user_nocheck(x, ptr, size) \
> ({ \
> int __gu_err; \
> - unsigned long __gu_val; \
> + __inttype(*(ptr)) __gu_val; \
> __uaccess_begin(); \
> __get_user_size(__gu_val, (ptr), (size), __gu_err, -EFAULT); \
> __uaccess_end(); \
>
> --
> "Thought is the essence of where you are now."
--
"Thought is the essence of where you are now."
next prev parent reply other threads:[~2016-03-14 15:37 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-09 17:22 [PATCH] x86_32: add support for 64 bit __get_user() Benjamin LaHaise
2016-03-09 17:36 ` H. Peter Anvin
2016-03-09 17:50 ` Benjamin LaHaise
2016-03-09 18:22 ` H. Peter Anvin
2016-03-09 18:27 ` Benjamin LaHaise
2016-03-09 19:30 ` [PATCH] x86_32: add support for 64 bit __get_user() v2 Benjamin LaHaise
2016-03-09 19:41 ` kbuild test robot
2016-03-09 20:05 ` [PATCH] x86_32: add support for 64 bit __get_user() v3 Benjamin LaHaise
2016-03-14 15:37 ` Benjamin LaHaise [this message]
2016-03-14 16:39 ` Ingo Molnar
2016-03-09 20:24 ` [PATCH] x86_32: add support for 64 bit __get_user() v2 kbuild test robot
2016-03-09 18:17 ` [PATCH] x86_32: add support for 64 bit __get_user() kbuild test robot
2016-03-09 18:22 ` kbuild test robot
2016-03-09 18:23 ` kbuild test robot
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20160314153747.GH17923@kvack.org \
--to=bcrl@kvack.org \
--cc=hpa@zytor.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=rmk@arm.linux.org.uk \
--cc=tglx@linutronix.de \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).