[PATCHv2,11/19] arm64: don't reload GPRs after apply_ssbd

Message ID	20180601112441.37810-12-mark.rutland@arm.com
State	Superseded
Headers	show Delivered-To: patch@linaro.org Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; From: Mark Rutland <mark.rutland@arm.com> To: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, will.deacon@arm.com, catalin.marinas@arm.com Cc: Mark Rutland <mark.rutland@arm.com>, Marc Zyngier <marc.zyngier@arm.com> Subject: [PATCHv2 11/19] arm64: don't reload GPRs after apply_ssbd Date: Fri, 1 Jun 2018 12:24:33 +0100 Message-Id: <20180601112441.37810-12-mark.rutland@arm.com> In-Reply-To: <20180601112441.37810-1-mark.rutland@arm.com> References: <20180601112441.37810-1-mark.rutland@arm.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk
Series	arm64: invoke syscalls with pt_regs \| expand [PATCHv2,00/19] arm64: invoke syscalls with pt_regs [PATCHv2,01/19] arm64: consistently use unsigned long for thread flags [PATCHv2,02/19] arm64: move SCTLR_EL{1,2} assertions to <asm/sysreg.h> [PATCHv2,03/19] arm64: introduce sysreg_clear_set() [PATCHv2,04/19] arm64: kill config_sctlr_el1() [PATCHv2,05/19] arm64: kill change_cpacr() [PATCHv2,06/19] arm64: move sve_user_{enable,disable} to <asm/fpsimd.h> [PATCHv2,07/19] arm64: remove sigreturn wrappers [PATCHv2,08/19] arm64: convert raw syscall invocation to C [PATCHv2,09/19] arm64: convert syscall trace logic to C [PATCHv2,10/19] arm64: convert native/compat syscall entry to C [PATCHv2,11/19] arm64: don't reload GPRs after apply_ssbd [PATCHv2,12/19] arm64: zero GPRs upon entry from EL0 [PATCHv2,13/19] kernel: add ksys_personality() [PATCHv2,14/19] kernel: add kcompat_sys_{f,}statfs64() [PATCHv2,15/19] arm64: remove in-kernel call to sys_personality() [PATCHv2,16/19] arm64: use {COMPAT,}SYSCALL_DEFINE0 for sigreturn [PATCHv2,17/19] arm64: use SYSCALL_DEFINE6() for mmap [PATCHv2,18/19] arm64: convert compat wrappers to C [PATCHv2,19/19] arm64: implement syscall wrappers

Message ID

20180601112441.37810-12-mark.rutland@arm.com

State

Superseded

Headers

Received-SPF: pass (google.com: best guess record for domain of
	linux-kernel-owner@vger.kernel.org designates 209.132.180.67
	as permitted sender) client-ip=209.132.180.67; 
From: Mark Rutland <mark.rutland@arm.com>
To: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
	will.deacon@arm.com, catalin.marinas@arm.com
Cc: Mark Rutland <mark.rutland@arm.com>, Marc Zyngier <marc.zyngier@arm.com>
Subject: [PATCHv2 11/19] arm64: don't reload GPRs after apply_ssbd
Date: Fri,  1 Jun 2018 12:24:33 +0100
Message-Id: <20180601112441.37810-12-mark.rutland@arm.com>
In-Reply-To: <20180601112441.37810-1-mark.rutland@arm.com>
References: <20180601112441.37810-1-mark.rutland@arm.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Series

arm64: invoke syscalls with pt_regs | expand

Commit Message

Mark Rutland June 1, 2018, 11:24 a.m. UTC

Now that all of the syscall logic works on the saved pt_regs, apply_ssbd
can safely corrupt x0-x3 in the entry paths, and we no longer need to
restore them. So let's remotve the logic doing so.

With that logic gone, we can fold the branch target into the macro, so
that callers need not deal with this. GAS provides \@, which provides a
unique value per macro invocation, which we can use to create a unique
label.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
---
 arch/arm64/kernel/entry.S | 20 +++++++-------------
 1 file changed, 7 insertions(+), 13 deletions(-)

-- 
2.11.0

Comments

Marc Zyngier June 1, 2018, 2:41 p.m. UTC | #1

On 01/06/18 12:24, Mark Rutland wrote:
> Now that all of the syscall logic works on the saved pt_regs, apply_ssbd

> can safely corrupt x0-x3 in the entry paths, and we no longer need to

> restore them. So let's remotve the logic doing so.


remove*

> 

> With that logic gone, we can fold the branch target into the macro, so

> that callers need not deal with this. GAS provides \@, which provides a

> unique value per macro invocation, which we can use to create a unique

> label.

> 

> Signed-off-by: Mark Rutland <mark.rutland@arm.com>

> Cc: Catalin Marinas <catalin.marinas@arm.com>

> Cc: Marc Zyngier <marc.zyngier@arm.com>

> Cc: Will Deacon <will.deacon@arm.com>


Acked-by: Marc Zyngier <marc.zyngier@arm.com>


	M.
-- 
Jazz is not dead. It just smells funny...

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 156c4e3fd1a4..22c58e7dfc0f 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -140,20 +140,21 @@  alternative_else_nop_endif
 
 	// This macro corrupts x0-x3. It is the caller's duty
 	// to save/restore them if required.
-	.macro	apply_ssbd, state, targ, tmp1, tmp2
+	.macro	apply_ssbd, state, tmp1, tmp2
 #ifdef CONFIG_ARM64_SSBD
 alternative_cb	arm64_enable_wa2_handling
-	b	\targ
+	b	skip_apply_ssbd\@
 alternative_cb_end
 	ldr_this_cpu	\tmp2, arm64_ssbd_callback_required, \tmp1
-	cbz	\tmp2, \targ
+	cbz	\tmp2, skip_apply_ssbd\@
 	ldr	\tmp2, [tsk, #TSK_TI_FLAGS]
-	tbnz	\tmp2, #TIF_SSBD, \targ
+	tbnz	\tmp2, #TIF_SSBD, skip_apply_ssbd\@
 	mov	w0, #ARM_SMCCC_ARCH_WORKAROUND_2
 	mov	w1, #\state
 alternative_cb	arm64_update_smccc_conduit
 	nop					// Patched to SMC/HVC #0
 alternative_cb_end
+skip_apply_ssbd\@:
 #endif
 	.endm
 
@@ -183,13 +184,7 @@  alternative_cb_end
 	ldr	x19, [tsk, #TSK_TI_FLAGS]	// since we can unmask debug
 	disable_step_tsk x19, x20		// exceptions when scheduling.
 
-	apply_ssbd 1, 1f, x22, x23
-
-#ifdef CONFIG_ARM64_SSBD
-	ldp	x0, x1, [sp, #16 * 0]
-	ldp	x2, x3, [sp, #16 * 1]
-#endif
-1:
+	apply_ssbd 1, x22, x23
 
 	mov	x29, xzr			// fp pointed to user-space
 	.else
@@ -331,8 +326,7 @@  alternative_if ARM64_WORKAROUND_845719
 alternative_else_nop_endif
 #endif
 3:
-	apply_ssbd 0, 5f, x0, x1
-5:
+	apply_ssbd 0, x0, x1
 	.endif
 
 	msr	elr_el1, x21			// set up the return data