From: Andreas Schwab <schwab@suse.de>
To: Jisheng Zhang <jszhang@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>,
Paul Walmsley <paul.walmsley@sifive.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Albert Ou <aou@eecs.berkeley.edu>,
linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/4] riscv: uaccess: use input constraints for ptr of __put_user
Date: Wed, 26 Jun 2024 15:35:54 +0200 [thread overview]
Message-ID: <mvma5j7omh1.fsf@suse.de> (raw)
In-Reply-To: <ZnwObmA70Bfx9yCn@xhacker> (Jisheng Zhang's message of "Wed, 26 Jun 2024 20:49:50 +0800")
On Jun 26 2024, Jisheng Zhang wrote:
> no output constraints either. It just uses "r" input constraints to tell
> gcc to read the store address into one proper GP reg.
Again, this is backwards. Being an input operand means the asm is using
this operand as an input to the instructions. The compiler needs to
arrange to put the value in the allocated operand location according to
the constraint.
--
Andreas Schwab, SUSE Labs, schwab@suse.de
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE 1748 E4D4 88E3 0EEA B9D7
"And now for something completely different."
next prev parent reply other threads:[~2024-06-26 13:35 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-06-25 4:04 [PATCH 0/4] riscv: uaccess: optimizations Jisheng Zhang
2024-06-25 4:04 ` [PATCH 1/4] riscv: implement user_access_begin and families Jisheng Zhang
2024-06-26 23:38 ` Cyril Bur
2024-06-25 4:04 ` [PATCH 2/4] riscv: uaccess: use input constraints for ptr of __put_user Jisheng Zhang
2024-06-25 5:54 ` Arnd Bergmann
2024-06-26 12:32 ` Jisheng Zhang
2024-06-26 12:49 ` Jisheng Zhang
2024-06-26 13:18 ` Jisheng Zhang
2024-06-26 13:35 ` Andreas Schwab [this message]
2024-06-26 13:54 ` Jisheng Zhang
2024-06-26 13:12 ` Andreas Schwab
2024-06-26 13:12 ` Jisheng Zhang
2024-06-26 14:25 ` Arnd Bergmann
2024-06-26 16:02 ` Jisheng Zhang
2024-06-27 6:46 ` Arnd Bergmann
2024-06-28 15:36 ` David Laight
2024-06-25 4:04 ` [PATCH 3/4] riscv: uaccess: use 'asm goto' for put_user() Jisheng Zhang
2024-07-05 2:22 ` kernel test robot
2024-07-06 0:02 ` kernel test robot
2024-06-25 4:05 ` [PATCH 4/4] riscv: uaccess: use 'asm goto output' for get_user Jisheng Zhang
2024-07-05 4:13 ` kernel test robot
2024-06-25 7:21 ` [PATCH 0/4] riscv: uaccess: optimizations Arnd Bergmann
2024-06-25 18:12 ` Linus Torvalds
2024-06-26 13:04 ` Jisheng Zhang
2024-06-30 16:59 ` Linus Torvalds
2024-07-05 11:25 ` Will Deacon
2024-07-05 17:58 ` Linus Torvalds
2024-07-08 13:52 ` Will Deacon
2024-07-08 15:30 ` Mark Rutland
2024-07-23 14:16 ` Will Deacon
2024-07-08 15:21 ` Mark Rutland
2024-07-24 22:57 ` Palmer Dabbelt
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