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From: Catalin Marinas <catalin.marinas@arm.com>
To: Guenter Roeck <linux@roeck-us.net>
Cc: Mark Rutland <mark.rutland@arm.com>,
	elver@google.com, paulmck@kernel.org, peterz@infradead.org,
	james.morse@arm.com, dvyukov@google.com, will@kernel.org,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCHv2 05/11] arm64: entry: prepare ret_to_user for function call
Date: Thu, 17 Dec 2020 18:38:11 +0000	[thread overview]
Message-ID: <20201217183810.GD20278@gaia> (raw)
In-Reply-To: <20201217175740.GA90220@roeck-us.net>

On Thu, Dec 17, 2020 at 09:57:40AM -0800, Guenter Roeck wrote:
> Hi,
> 
> On Mon, Nov 30, 2020 at 11:59:44AM +0000, Mark Rutland wrote:
> > In a subsequent patch ret_to_user will need to make a C function call
> > (in some configurations) which may clobber x0-x18 at the start of the
> > finish_ret_to_user block, before enable_step_tsk consumes the flags
> > loaded into x1.
> > 
> > In preparation for this, let's load the flags into x19, which is
> > preserved across C function calls. This avoids a redundant reload of the
> > flags and ensures we operate on a consistent shapshot regardless.
> > 
> > There should be no functional change as a result of this patch. At this
> > point of the entry/exit paths we only need to preserve x28 (tsk) and the
> > sp, and x19 is free for this use.
> > 
> > Signed-off-by: Mark Rutland <mark.rutland@arm.com>
> > Cc: Catalin Marinas <catalin.marinas@arm.com>
> > Cc: James Morse <james.morse@arm.com>
> > Cc: Will Deacon <will@kernel.org>
> 
> This patch results in:
> 
> arch/arm64/kernel/entry.S: Assembler messages:
> arch/arm64/kernel/entry.S:774: Error: immediate out of range at operand 3 -- `and x2,x19,#((1<<1)|(1<<0)|(1<<2)|(1<<3)|(1<<4)|(1<<5)|(1<<7))'
> 
> This is with gcc 9.3.0 and binutils 2.34. Do I need a special compiler
> and/or binutils version to make it compile ?

It has been fixed in Linus' tree last night. It's a limitation of the
instruction rather than toolchain.

-- 
Catalin

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  reply	other threads:[~2020-12-17 18:39 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-30 11:59 [PATCHv2 00/11] arm64: entry lockdep/rcu/tracing fixes Mark Rutland
2020-11-30 11:59 ` [PATCHv2 01/11] arm64: syscall: exit userspace before unmasking exceptions Mark Rutland
2020-11-30 11:59 ` [PATCHv2 02/11] arm64: mark idle code as noinstr Mark Rutland
2020-11-30 11:59 ` [PATCHv2 03/11] arm64: entry: mark entry " Mark Rutland
2020-11-30 11:59 ` [PATCHv2 04/11] arm64: entry: move enter_from_user_mode to entry-common.c Mark Rutland
2020-11-30 11:59 ` [PATCHv2 05/11] arm64: entry: prepare ret_to_user for function call Mark Rutland
2020-12-17 17:57   ` Guenter Roeck
2020-12-17 18:38     ` Catalin Marinas [this message]
2020-11-30 11:59 ` [PATCHv2 06/11] arm64: entry: move el1 irq/nmi logic to C Mark Rutland
2021-05-06  8:28   ` He Ying
2021-05-06  9:16     ` Mark Rutland
     [not found]       ` <e3843e03-173e-10a6-5b14-0d8c14219e09@huawei.com>
2021-05-06 10:58         ` Mark Rutland
2021-05-07  3:25           ` He Ying
2021-05-07  9:41             ` Mark Rutland
2021-05-07 10:02               ` He Ying
2020-11-30 11:59 ` [PATCHv2 07/11] arm64: entry: fix non-NMI user<->kernel transitions Mark Rutland
2020-11-30 11:59 ` [PATCHv2 08/11] arm64: ptrace: prepare for EL1 irq/rcu tracking Mark Rutland
2020-11-30 11:59 ` [PATCHv2 09/11] arm64: entry: fix non-NMI kernel<->kernel transitions Mark Rutland
2021-04-25  5:29   ` Zenghui Yu
2021-04-26  9:21     ` Mark Rutland
2021-04-26 13:39       ` Zenghui Yu
2021-04-27  7:15         ` Zenghui Yu
2021-04-27 14:43           ` Mark Rutland
2020-11-30 11:59 ` [PATCHv2 10/11] arm64: entry: fix NMI {user, kernel}->kernel transitions Mark Rutland
2020-11-30 11:59 ` [PATCHv2 11/11] arm64: entry: fix EL1 debug transitions Mark Rutland
2020-11-30 13:52 ` [PATCHv2 00/11] arm64: entry lockdep/rcu/tracing fixes Will Deacon

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