From: Mark Rutland <mark.rutland@arm.com>
To: linux-arm-kernel@lists.infradead.org, will@kernel.org
Cc: mark.rutland@arm.com, elver@google.com, paulmck@kernel.org,
peterz@infradead.org, catalin.marinas@arm.com,
james.morse@arm.com, dvyukov@google.com
Subject: [PATCHv2 05/11] arm64: entry: prepare ret_to_user for function call
Date: Mon, 30 Nov 2020 11:59:44 +0000 [thread overview]
Message-ID: <20201130115950.22492-6-mark.rutland@arm.com> (raw)
In-Reply-To: <20201130115950.22492-1-mark.rutland@arm.com>
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>
---
arch/arm64/kernel/entry.S | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index b295fb912b12..84aec600eeed 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -774,13 +774,13 @@ SYM_CODE_END(el0_error)
SYM_CODE_START_LOCAL(ret_to_user)
disable_daif
gic_prio_kentry_setup tmp=x3
- ldr x1, [tsk, #TSK_TI_FLAGS]
- and x2, x1, #_TIF_WORK_MASK
+ ldr x19, [tsk, #TSK_TI_FLAGS]
+ and x2, x19, #_TIF_WORK_MASK
cbnz x2, work_pending
finish_ret_to_user:
/* Ignore asynchronous tag check faults in the uaccess routines */
clear_mte_async_tcf
- enable_step_tsk x1, x2
+ enable_step_tsk x19, x2
#ifdef CONFIG_GCC_PLUGIN_STACKLEAK
bl stackleak_erase
#endif
@@ -791,11 +791,12 @@ finish_ret_to_user:
*/
work_pending:
mov x0, sp // 'regs'
+ mov x1, x19
bl do_notify_resume
#ifdef CONFIG_TRACE_IRQFLAGS
bl trace_hardirqs_on // enabled while in userspace
#endif
- ldr x1, [tsk, #TSK_TI_FLAGS] // re-check for single-step
+ ldr x19, [tsk, #TSK_TI_FLAGS] // re-check for single-step
b finish_ret_to_user
SYM_CODE_END(ret_to_user)
--
2.11.0
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next prev parent reply other threads:[~2020-11-30 12:02 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 ` Mark Rutland [this message]
2020-12-17 17:57 ` [PATCHv2 05/11] arm64: entry: prepare ret_to_user for function call Guenter Roeck
2020-12-17 18:38 ` Catalin Marinas
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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