ARCv2: entry: comments about hardware auto-save on taken interrupts (45869eb0) · Commits · jan.koester / Linux

arch/arc/include/asm/entry-arcv2.h

+62 −16

Original line number	Original line	Diff line number	Diff line
	@@ -7,15 +7,54 @@
	#include <asm/irqflags-arcv2.h>		#include <asm/irqflags-arcv2.h>
	#include <asm/thread_info.h> /* For THREAD_SIZE */		#include <asm/thread_info.h> /* For THREAD_SIZE */

			/*
			* Interrupt/Exception stack layout (pt_regs) for ARCv2
			* (End of struct aligned to end of page [unless nested])
			*
			* INTERRUPT EXCEPTION
			*
			* manual --------------------- manual
			* \| orig_r0 \|
			* \| event/ECR \|
			* \| bta \|
			* \| user_r25 \|
			* \| gp \|
			* \| fp \|
			* \| sp \|
			* \| r12 \|
			* \| r30 \|
			* \| r58 \|
			* \| r59 \|
			* hw autosave ---------------------
			* optional \| r0 \|
			* \| r1 \|
			* ~ ~
			* \| r9 \|
			* \| r10 \|
			* \| r11 \|
			* \| blink \|
			* \| lpe \|
			* \| lps \|
			* \| lpc \|
			* \| ei base \|
			* \| ldi base \|
			* \| jli base \|
			* ---------------------
			* hw autosave \| pc / eret \|
			* mandatory \| stat32 / erstatus \|
			* ---------------------
			*/

	/------------------------------------------------------------------------/		/------------------------------------------------------------------------/
	.macro INTERRUPT_PROLOGUE called_from		.macro INTERRUPT_PROLOGUE called_from
			; (A) Before jumping to Interrupt Vector, hardware micro-ops did following:
	; Before jumping to Interrupt Vector, hardware micro-ops did following:
	; 1. SP auto-switched to kernel mode stack		; 1. SP auto-switched to kernel mode stack
	; 2. STATUS32.Z flag set to U mode at time of interrupt (U:1, K:0)		; 2. STATUS32.Z flag set if in U mode at time of interrupt (U:1,K:0)
	; 3. Auto saved: r0-r11, blink, LPE,LPS,LPC, JLI,LDI,EI, PC, STAT32		; 3. Auto save: (mandatory) Push PC and STAT32 on stack
			; hardware does even if CONFIG_ARC_IRQ_NO_AUTOSAVE
			; 4. Auto save: (optional) r0-r11, blink, LPE,LPS,LPC, JLI,LDI,EI
	;		;
	; Now manually save: r12, sp, fp, gp, r25		; (B) Manually saved some regs: r12,r25,r30, sp,fp,gp, ACCL pair

	#ifdef CONFIG_ARC_IRQ_NO_AUTOSAVE		#ifdef CONFIG_ARC_IRQ_NO_AUTOSAVE
	.ifnc \called_from, exception		.ifnc \called_from, exception
	@@ -57,14 +96,17 @@
	; - U mode: retrieve it from AUX_USER_SP		; - U mode: retrieve it from AUX_USER_SP
	; - K mode: add the offset from current SP where H/w starts auto push		; - K mode: add the offset from current SP where H/w starts auto push
	;		;
	; Utilize the fact that Z bit is set if Intr taken in U mode		; 1. Utilize the fact that Z bit is set if Intr taken in U mode
			; 2. Upon entry SP is always saved (for any inspection, unwinding etc),
			; but on return, restored only if U mode

	mov.nz r9, sp		mov.nz r9, sp
	add.nz r9, r9, SZ_PT_REGS - PT_sp - 4		add.nz r9, r9, SZ_PT_REGS - PT_sp - 4 ; K mode SP
	bnz 1f		bnz 1f

	lr r9, [AUX_USER_SP]		lr r9, [AUX_USER_SP] ; U mode SP
	1:		1:
	PUSH r9 ; SP		PUSH r9 ; SP (pt_regs->sp)

	PUSH fp		PUSH fp
	PUSH gp		PUSH gp
	@@ -85,6 +127,8 @@
	/------------------------------------------------------------------------/		/------------------------------------------------------------------------/
	.macro INTERRUPT_EPILOGUE called_from		.macro INTERRUPT_EPILOGUE called_from

			; INPUT: r0 has STAT32 of calling context
			; INPUT: Z flag set if returning to K mode
	.ifnc \called_from, exception		.ifnc \called_from, exception
	add sp, sp, 12 ; skip BTA/ECR/orig_r0 placeholderss		add sp, sp, 12 ; skip BTA/ECR/orig_r0 placeholderss
	.endif		.endif
	@@ -98,9 +142,10 @@
	POP gp		POP gp
	POP fp		POP fp

	; Don't touch AUX_USER_SP if returning to K mode (Z bit set)		; Restore SP (into AUX_USER_SP) only if returning to U mode
	; (Z bit set on K mode is inverse of INTERRUPT_PROLOGUE)		; - for K mode, it will be implicitly restored as stack is unwound
	add.z sp, sp, 4		; - Z flag set on K is inverse of what hardware does on interrupt entry
			; but that doesn't really matter
	bz 1f		bz 1f

	POPAX AUX_USER_SP		POPAX AUX_USER_SP
	@@ -145,11 +190,11 @@
	/------------------------------------------------------------------------/		/------------------------------------------------------------------------/
	.macro EXCEPTION_PROLOGUE		.macro EXCEPTION_PROLOGUE

	; Before jumping to Exception Vector, hardware micro-ops did following:		; (A) Before jumping to Exception Vector, hardware micro-ops did following:
	; 1. SP auto-switched to kernel mode stack		; 1. SP auto-switched to kernel mode stack
	; 2. STATUS32.Z flag set to U mode at time of interrupt (U:1,K:0)		; 2. STATUS32.Z flag set if in U mode at time of exception (U:1,K:0)
	;		;
	; Now manually save the complete reg file		; (B) Manually save the complete reg file below

	PUSH r9 ; freeup a register: slot of erstatus		PUSH r9 ; freeup a register: slot of erstatus

	@@ -195,12 +240,13 @@
	PUSHAX ecr ; r9 contains ECR, expected by EV_Trap		PUSHAX ecr ; r9 contains ECR, expected by EV_Trap

	PUSH r0 ; orig_r0		PUSH r0 ; orig_r0
			; OUTPUT: r9 has ECR
	.endm		.endm

	/------------------------------------------------------------------------/		/------------------------------------------------------------------------/
	.macro EXCEPTION_EPILOGUE		.macro EXCEPTION_EPILOGUE

	; Assumes r0 has PT_status32		; INPUT: r0 has STAT32 of calling context
	btst r0, STATUS_U_BIT ; Z flag set if K, used in INTERRUPT_EPILOGUE		btst r0, STATUS_U_BIT ; Z flag set if K, used in INTERRUPT_EPILOGUE

	add sp, sp, 8 ; orig_r0/ECR don't need restoring		add sp, sp, 8 ; orig_r0/ECR don't need restoring