From: Robin Murphy <robin.murphy@arm.com>
To: Richard Henderson <richard.henderson@linaro.org>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 3/6] arm64: uaccess: Untie the input address in __range_ok
Date: Wed, 11 Mar 2020 19:08:55 +0000 [thread overview]
Message-ID: <f6cad657-f78d-b65b-76a8-073580e9ad4b@arm.com> (raw)
In-Reply-To: <20200311180416.6509-4-richard.henderson@linaro.org>
On 11/03/2020 6:04 pm, Richard Henderson wrote:
> There's no reason for the input address to match the output
> register. Give the register allocator a bit more freedom.
See commit 9085b34d0e83 - as originally written they *were* the same
operand, and this was just some impedance-matching for types. However, I
suppose this might save a mov to initialise "ret" in the
!CONFIG_ARM64_TAGGED_ADDR_ABI case where the original value of "addr" is
still live for subsequent use, so it's probably reasonable. On the other
hand, the naming only reinforces my previous complaint - now we have
"addr_in" corresponding to "addr", and "addr" bearing no relation to
either of those :(
Robin.
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
> arch/arm64/include/asm/uaccess.h | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
> index ceb1d79eab09..fe3dd70e901e 100644
> --- a/arch/arm64/include/asm/uaccess.h
> +++ b/arch/arm64/include/asm/uaccess.h
> @@ -75,7 +75,7 @@ static inline unsigned long __range_ok(const void __user *addr, unsigned long si
> asm volatile(
> // A + B <= C + 1 for all A,B,C, in four easy steps:
> // 1: X = A + B; X' = X % 2^64
> - " adds %[addr], %[addr], %[size]\n"
> + " adds %[addr], %[addr_in], %[size]\n"
> // 2: Set C = 0 if X > 2^64, to guarantee X' > C in step 4
> " csel %[limit], xzr, %[limit], hi\n"
> // 3: Set X' = ~0 if X >= 2^64. For X == 2^64, this decrements X'
> @@ -88,7 +88,7 @@ static inline unsigned long __range_ok(const void __user *addr, unsigned long si
> " sbcs xzr, %[addr], %[limit]\n"
> " cset %[addr], ls\n"
> : [addr] "=&r" (ret), [limit] "+r" (limit)
> - : [size] "Ir" (size), "0" (addr)
> + : [size] "Ir" (size), [addr_in] "r" (addr)
> : "cc");
>
> return ret;
>
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2020-03-11 19:09 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-11 18:04 [PATCH 0/6] arm64: gcc asm flag outputs Richard Henderson
2020-03-11 18:04 ` [PATCH 1/6] arm64: Add asm/ccset.h header Richard Henderson
2020-03-13 10:54 ` Mark Rutland
2020-03-13 16:29 ` Richard Henderson
2020-03-11 18:04 ` [PATCH 2/6] arm64: uaccess: Use named asm operands for __in_range Richard Henderson
2020-03-11 19:08 ` Robin Murphy
2020-03-11 21:48 ` Richard Henderson
2020-03-13 16:14 ` Robin Murphy
2020-03-11 18:04 ` [PATCH 3/6] arm64: uaccess: Untie the input address in __range_ok Richard Henderson
2020-03-11 19:08 ` Robin Murphy [this message]
2020-03-11 18:04 ` [PATCH 4/6] arm64: uaccess: Use asm/ccset.h macros " Richard Henderson
2020-03-12 11:48 ` Robin Murphy
2020-03-13 11:04 ` Mark Rutland
2020-03-13 16:51 ` Robin Murphy
2020-03-13 17:14 ` Mark Rutland
2020-03-11 18:04 ` [PATCH 5/6] arm64: archrandom: Use asm/ccset.h macros in __arm64_rndr Richard Henderson
2020-03-11 18:04 ` [PATCH 6/6] arm64: Hoist CONFIG option out of ALTERNATIVE in uaccess.h Richard Henderson
2020-03-13 10:46 ` Mark Rutland
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=f6cad657-f78d-b65b-76a8-073580e9ad4b@arm.com \
--to=robin.murphy@arm.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=richard.henderson@linaro.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).