ARC: [optim] Cache "current" in Register r25 (080c3747) · Commits · github.com / kvm-riscv / linux

arch/arc/Kconfig

+7 −0

Original line number	Diff line number	Diff line
		@@ -264,6 +264,13 @@ config LINUX_LINK_BASE

		endmenu # "Platform Board Configuration"

		config ARC_CURR_IN_REG
		bool "Dedicate Register r25 for current_task pointer"
		default y
		help
		This reserved Register R25 to point to Current Task in
		kernel mode. This saves memory access for each such access

		config ARC_STACK_NONEXEC
		bool "Make stack non-executable"
		default n

arch/arc/Makefile

+9 −0

Original line number	Diff line number	Diff line
		@@ -20,6 +20,15 @@ export PLATFORM
		cflags-y += -Iarch/arc/plat-$(PLATFORM)/include
		cflags-y += -mA7 -fno-common -pipe -fno-builtin -D__linux__

		ifdef CONFIG_ARC_CURR_IN_REG
		# For a global register defintion, make sure it gets passed to every file
		# We had a customer reported bug where some code built in kernel was NOT using
		# any kernel headers, and missing the r25 global register
		# Can't do unconditionally (like above) because of recursive include issues
		# due to <linux/thread_info.h>
		LINUXINCLUDE += -include ${src}/arch/arc/include/asm/current.h
		endif

		atleast_gcc44 := $(call cc-ifversion, -gt, 0402, y)
		cflags-$(atleast_gcc44) += -fsection-anchors

arch/arc/include/asm/Kbuild

+0 −1

Original line number	Diff line number	Diff line
		@@ -11,7 +11,6 @@ generic-y += bugs.h
		generic-y += bitsperlong.h
		generic-y += clkdev.h
		generic-y += cputime.h
		generic-y += current.h
		generic-y += device.h
		generic-y += div64.h
		generic-y += emergency-restart.h

arch/arc/include/asm/current.h

0 → 100644

+32 −0

Original line number	Diff line number	Diff line
		/*
		* Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
		*
		* This program is free software; you can redistribute it and/or modify
		* it under the terms of the GNU General Public License version 2 as
		* published by the Free Software Foundation.
		*
		* Vineetg: May 16th, 2008
		* - Current macro is now implemented as "global register" r25
		*/

		#ifndef _ASM_ARC_CURRENT_H
		#define _ASM_ARC_CURRENT_H

		#ifdef __KERNEL__

		#ifndef __ASSEMBLY__

		#ifdef CONFIG_ARC_CURR_IN_REG

		register struct task_struct *curr_arc asm("r25");
		#define current (curr_arc)

		#else
		#include <asm-generic/current.h>
		#endif /* ! CONFIG_ARC_CURR_IN_REG */

		#endif /* ! __ASSEMBLY__ */

		#endif /* __KERNEL__ */

		#endif /* _ASM_ARC_CURRENT_H */

arch/arc/include/asm/entry.h

+45 −0

Original line number	Diff line number	Diff line
		@@ -13,6 +13,8 @@
		* was being "CLEARED" rather then "SET". Actually "SET" clears ZOL context
		*
		* Vineetg: May 5th 2008
		* -Modified CALLEE_REG save/restore macros to handle the fact that
		* r25 contains the kernel current task ptr
		* - Defined Stack Switching Macro to be reused in all intr/excp hdlrs
		* - Shaved off 11 instructions from RESTORE_ALL_INT1 by using the
		* address Write back load ld.ab instead of seperate ld/add instn
		@@ -28,6 +30,7 @@
		#include <asm/asm-offsets.h>
		#include <asm/arcregs.h>
		#include <asm/ptrace.h>
		#include <asm/processor.h> /* For VMALLOC_START */
		#include <asm/thread_info.h> /* For THREAD_SIZE */

		/* Note on the LD/ST addr modes with addr reg wback
		@@ -106,7 +109,14 @@
		st.a r22, [sp, -4]
		st.a r23, [sp, -4]
		st.a r24, [sp, -4]

		#ifdef CONFIG_ARC_CURR_IN_REG
		; Retrieve orig r25 and save it on stack
		ld r12, [r25, TASK_THREAD + THREAD_USER_R25]
		st.a r12, [sp, -4]
		#else
		st.a r25, [sp, -4]
		#endif

		/* move up by 1 word to "create" callee_regs->"stack_place_holder" */
		sub sp, sp, 4
		@@ -131,8 +141,12 @@
		st.a r22, [sp, -4]
		st.a r23, [sp, -4]
		st.a r24, [sp, -4]
		#ifdef CONFIG_ARC_CURR_IN_REG
		sub sp, sp, 8
		#else
		st.a r25, [sp, -4]
		sub sp, sp, 4
		#endif
		.endm

		/*--------------------------------------------------------------
		@@ -148,8 +162,14 @@
		-------------------------------------------------------------/
		.macro RESTORE_CALLEE_SAVED_KERNEL


		#ifdef CONFIG_ARC_CURR_IN_REG
		add sp, sp, 8 /* skip callee_reg gutter and user r25 placeholder */
		#else
		add sp, sp, 4 /* skip "callee_regs->stack_place_holder" */
		ld.ab r25, [sp, 4]
		#endif

		ld.ab r24, [sp, 4]
		ld.ab r23, [sp, 4]
		ld.ab r22, [sp, 4]
		@@ -235,6 +255,7 @@
		*
		* Entry : r9 contains pre-IRQ/exception/trap status32
		* Exit : SP is set to kernel mode stack pointer
		* If CURR_IN_REG, r25 set to "current" task pointer
		* Clobbers: r9
		-------------------------------------------------------------/

		@@ -259,6 +280,16 @@

		GET_CURR_TASK_ON_CPU r9

		#ifdef CONFIG_ARC_CURR_IN_REG

		/* If current task pointer cached in r25, time to
		* -safekeep USER r25 in task->thread_struct->user_r25
		* -load r25 with current task ptr
		*/
		st.as r25, [r9, (TASK_THREAD + THREAD_USER_R25)/4]
		mov r25, r9
		#endif

		/* With current tsk in r9, get it's kernel mode stack base */
		GET_TSK_STACK_BASE r9, r9

		@@ -519,17 +550,31 @@

		.macro SET_CURR_TASK_ON_CPU tsk, tmp
		st \tsk, [@_current_task]
		#ifdef CONFIG_ARC_CURR_IN_REG
		mov r25, \tsk
		#endif
		.endm

		/* ------------------------------------------------------------------
		* Get the ptr to some field of Current Task at @off in task struct
		* -Uses r25 for Current task ptr if that is enabled
		*/

		#ifdef CONFIG_ARC_CURR_IN_REG

		.macro GET_CURR_TASK_FIELD_PTR off, reg
		add \reg, r25, \off
		.endm

		#else

		.macro GET_CURR_TASK_FIELD_PTR off, reg
		GET_CURR_TASK_ON_CPU \reg
		add \reg, \reg, \off
		.endm

		#endif /* CONFIG_ARC_CURR_IN_REG */

		#endif /* __ASSEMBLY__ */

		#endif /* __ASM_ARC_ENTRY_H */