Merge tag 'arc-5.3-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/vgupta/arc

Pull ARC updates from Vineet Gupta:

 - long due rewrite of do_page_fault

 - refactoring of entry/exit code to utilize the double load/store
   instructions

 - hsdk platform updates

* tag 'arc-5.3-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/vgupta/arc:
  ARC: [plat-hsdk]: Enable AXI DW DMAC in defconfig
  ARC: [plat-hsdk]: enable DW SPI controller
  ARC: hide unused function unw_hdr_alloc
  ARC: [haps] Add Virtio support
  ARCv2: entry: simplify return to Delay Slot via interrupt
  ARC: entry: EV_Trap expects r10 (vs. r9) to have exception cause
  ARCv2: entry: rewrite to enable use of double load/stores LDD/STD
  ARCv2: entry: avoid a branch
  ARCv2: entry: push out the Z flag unclobber from common EXCEPTION_PROLOGUE
  ARCv2: entry: comments about hardware auto-save on taken interrupts
  ARC: mm: do_page_fault refactor #8: release mmap_sem sooner
  ARC: mm: do_page_fault refactor #7: fold the various error handling
  ARC: mm: do_page_fault refactor #6: error handlers to use same pattern
  ARC: mm: do_page_fault refactor #5: scoot no_context to end
  ARC: mm: do_page_fault refactor #4: consolidate retry related logic
  ARC: mm: do_page_fault refactor #3: tidyup vma access permission code
  ARC: mm: do_page_fault refactor #2: remove short lived variable
  ARC: mm: do_page_fault refactor #1: remove label @good_area

arch/arc/boot/dts/haps_hs.dts

@@ -62,5 +62,35 @@ arcpct0: pct {
 			#interrupt-cells = <1>;
 			interrupts = <20>;
 		};
+
+		virtio0: virtio@f0100000 {
+			compatible = "virtio,mmio";
+			reg = <0xf0100000 0x2000>;
+			interrupts = <31>;
+		};
+
+		virtio1: virtio@f0102000 {
+			compatible = "virtio,mmio";
+			reg = <0xf0102000 0x2000>;
+			interrupts = <32>;
+		};
+
+		virtio2: virtio@f0104000 {
+			compatible = "virtio,mmio";
+			reg = <0xf0104000 0x2000>;
+			interrupts = <33>;
+		};
+
+		virtio3: virtio@f0106000 {
+			compatible = "virtio,mmio";
+			reg = <0xf0106000 0x2000>;
+			interrupts = <34>;
+		};
+
+		virtio4: virtio@f0108000 {
+			compatible = "virtio,mmio";
+			reg = <0xf0108000 0x2000>;
+			interrupts = <35>;
+		};
 	};
 };

arch/arc/boot/dts/hsdk.dts

@@ -8,6 +8,7 @@
  */
 /dts-v1/;
 
+#include <dt-bindings/gpio/gpio.h>
 #include <dt-bindings/reset/snps,hsdk-reset.h>
 
 / {
@@ -252,6 +253,19 @@ mmc@a000 {
 			dma-coherent;
 		};
 
+		spi0: spi@20000 {
+			compatible = "snps,dw-apb-ssi";
+			reg = <0x20000 0x100>;
+			#address-cells = <1>;
+			#size-cells = <0>;
+			interrupts = <16>;
+			num-cs = <2>;
+			reg-io-width = <4>;
+			clocks = <&input_clk>;
+			cs-gpios = <&creg_gpio 0 GPIO_ACTIVE_LOW>,
+				   <&creg_gpio 1 GPIO_ACTIVE_LOW>;
+		};
+
 		creg_gpio: gpio@14b0 {
 			compatible = "snps,creg-gpio-hsdk";
 			reg = <0x14b0 0x4>;

arch/arc/configs/haps_hs_defconfig

@@ -35,10 +35,12 @@ CONFIG_INET=y
 # CONFIG_IPV6 is not set
 # CONFIG_WIRELESS is not set
 CONFIG_DEVTMPFS=y
+CONFIG_DEVTMPFS_MOUNT=y
 # CONFIG_STANDALONE is not set
 # CONFIG_PREVENT_FIRMWARE_BUILD is not set
-# CONFIG_BLK_DEV is not set
+CONFIG_VIRTIO_BLK=y
 CONFIG_NETDEVICES=y
+CONFIG_VIRTIO_NET=y
 # CONFIG_NET_VENDOR_ARC is not set
 # CONFIG_NET_VENDOR_BROADCOM is not set
 # CONFIG_NET_VENDOR_INTEL is not set
@@ -68,6 +70,7 @@ CONFIG_FRAMEBUFFER_CONSOLE=y
 CONFIG_LOGO=y
 # CONFIG_HID is not set
 # CONFIG_USB_SUPPORT is not set
+CONFIG_VIRTIO_MMIO=y
 # CONFIG_IOMMU_SUPPORT is not set
 CONFIG_EXT2_FS=y
 CONFIG_EXT2_FS_XATTR=y

arch/arc/configs/hsdk_defconfig

@@ -46,6 +46,9 @@ CONFIG_SERIAL_8250_CONSOLE=y
 CONFIG_SERIAL_8250_DW=y
 CONFIG_SERIAL_OF_PLATFORM=y
 # CONFIG_HW_RANDOM is not set
+CONFIG_SPI=y
+CONFIG_SPI_DESIGNWARE=y
+CONFIG_SPI_DW_MMIO=y
 CONFIG_GPIOLIB=y
 CONFIG_GPIO_SYSFS=y
 CONFIG_GPIO_DWAPB=y
@@ -66,6 +69,8 @@ CONFIG_MMC=y
 CONFIG_MMC_SDHCI=y
 CONFIG_MMC_SDHCI_PLTFM=y
 CONFIG_MMC_DW=y
+CONFIG_DMADEVICES=y
+CONFIG_DW_AXI_DMAC=y
 CONFIG_EXT3_FS=y
 CONFIG_VFAT_FS=y
 CONFIG_TMPFS=y

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

@@ -7,232 +7,251 @@
 #include <asm/irqflags-arcv2.h>
 #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
 
-	; Before jumping to Interrupt Vector, hardware micro-ops did following:
+	; (A) Before jumping to Interrupt Vector, hardware micro-ops did following:
 	;   1. SP auto-switched to kernel mode stack
-	;   2. STATUS32.Z flag set to U mode at time of interrupt (U:1, K:0)
-	;   3. Auto saved: r0-r11, blink, LPE,LPS,LPC, JLI,LDI,EI, PC, STAT32
+	;   2. STATUS32.Z flag set if in U mode at time of interrupt (U:1,K:0)
+	;   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
-.ifnc \called_from, exception
-	st.as	r9, [sp, -10]	; save r9 in it's final stack slot
-	sub	sp, sp, 12	; skip JLI, LDI, EI
-
-	PUSH	lp_count
-	PUSHAX	lp_start
-	PUSHAX	lp_end
-	PUSH	blink
-
-	PUSH	r11
-	PUSH	r10
-
-	sub	sp, sp, 4	; skip r9
-
-	PUSH	r8
-	PUSH	r7
-	PUSH	r6
-	PUSH	r5
-	PUSH	r4
-	PUSH	r3
-	PUSH	r2
-	PUSH	r1
-	PUSH	r0
-.endif
-#endif
+	; carve pt_regs on stack (case #3), PC/STAT32 already on stack
+	sub	sp, sp, SZ_PT_REGS - 8
 
-#ifdef CONFIG_ARC_HAS_ACCL_REGS
-	PUSH	r59
-	PUSH	r58
+	__SAVE_REGFILE_HARD
+#else
+	; carve pt_regs on stack (case #4), which grew partially already
+	sub	sp, sp, PT_r0
 #endif
 
-	PUSH	r30
-	PUSH	r12
+	__SAVE_REGFILE_SOFT
+.endm
+
+/*------------------------------------------------------------------------*/
+.macro EXCEPTION_PROLOGUE
+
+	; (A) Before jumping to Exception Vector, hardware micro-ops did following:
+	;   1. SP auto-switched to kernel mode stack
+	;   2. STATUS32.Z flag set if in U mode at time of exception (U:1,K:0)
+	;
+	; (B) Manually save the complete reg file below
+
+	sub	sp, sp, SZ_PT_REGS	; carve pt_regs
+
+	; _HARD saves r10 clobbered by _SOFT as scratch hence comes first
+
+	__SAVE_REGFILE_HARD
+	__SAVE_REGFILE_SOFT
+
+	st	r0, [sp]	; orig_r0
+
+	lr	r10, [eret]
+	lr	r11, [erstatus]
+	ST2	r10, r11, PT_ret
+
+	lr	r10, [ecr]
+	lr	r11, [erbta]
+	ST2	r10, r11, PT_event
+
+	; OUTPUT: r10 has ECR expected by EV_Trap
+.endm
+
+/*------------------------------------------------------------------------
+ * This macro saves the registers manually which would normally be autosaved
+ * by hardware on taken interrupts. It is used by
+ *   - exception handlers (which don't have autosave)
+ *   - interrupt autosave disabled due to CONFIG_ARC_IRQ_NO_AUTOSAVE
+ */
+.macro __SAVE_REGFILE_HARD
+
+	ST2	r0,  r1,  PT_r0
+	ST2	r2,  r3,  PT_r2
+	ST2	r4,  r5,  PT_r4
+	ST2	r6,  r7,  PT_r6
+	ST2	r8,  r9,  PT_r8
+	ST2	r10, r11, PT_r10
+
+	st	blink, [sp, PT_blink]
+
+	lr	r10, [lp_end]
+	lr	r11, [lp_start]
+	ST2	r10, r11, PT_lpe
+
+	st	lp_count, [sp, PT_lpc]
+
+	; skip JLI, LDI, EI for now
+.endm
+
+/*------------------------------------------------------------------------
+ * This macros saves a bunch of other registers which can't be autosaved for
+ * various reasons:
+ *   - r12: the last caller saved scratch reg since hardware saves in pairs so r0-r11
+ *   - r30: free reg, used by gcc as scratch
+ *   - ACCL/ACCH pair when they exist
+ */
+.macro __SAVE_REGFILE_SOFT
+
+	ST2	gp, fp, PT_r26		; gp (r26), fp (r27)
+
+	st	r12, [sp, PT_sp + 4]
+	st	r30, [sp, PT_sp + 8]
 
 	; Saving pt_regs->sp correctly requires some extra work due to the way
 	; Auto stack switch works
 	;  - U mode: retrieve it from AUX_USER_SP
 	;  - 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
-	mov.nz	r9, sp
-	add.nz	r9, r9, SZ_PT_REGS - PT_sp - 4
-	bnz	1f
+	; 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
 
-	lr	r9, [AUX_USER_SP]
-1:
-	PUSH	r9	; SP
+	lr	r10, [AUX_USER_SP]	; U mode SP
+
+	; ISA requires ADD.nz to have same dest and src reg operands
+	mov.nz	r10, sp
+	add.nz	r10, r10, SZ_PT_REGS	; K mode SP
 
-	PUSH	fp
-	PUSH	gp
+	st	r10, [sp, PT_sp]	; SP (pt_regs->sp)
 
 #ifdef CONFIG_ARC_CURR_IN_REG
-	PUSH	r25			; user_r25
+	st	r25, [sp, PT_user_r25]
 	GET_CURR_TASK_ON_CPU	r25
-#else
-	sub	sp, sp, 4
 #endif
 
-.ifnc \called_from, exception
-	sub	sp, sp, 12	; BTA/ECR/orig_r0 placeholder per pt_regs
-.endif
+#ifdef CONFIG_ARC_HAS_ACCL_REGS
+	ST2	r58, r59, PT_sp + 12
+#endif
 
 .endm
 
 /*------------------------------------------------------------------------*/
-.macro INTERRUPT_EPILOGUE	called_from
+.macro __RESTORE_REGFILE_SOFT
 
-.ifnc \called_from, exception
-	add	sp, sp, 12	; skip BTA/ECR/orig_r0 placeholderss
-.endif
+	LD2	gp, fp, PT_r26		; gp (r26), fp (r27)
 
-#ifdef CONFIG_ARC_CURR_IN_REG
-	POP	r25
-#else
-	add	sp, sp, 4
-#endif
+	ld	r12, [sp, PT_sp + 4]
+	ld	r30, [sp, PT_sp + 8]
 
-	POP	gp
-	POP	fp
-
-	; Don't touch AUX_USER_SP if returning to K mode (Z bit set)
-	; (Z bit set on K mode is inverse of INTERRUPT_PROLOGUE)
-	add.z	sp, sp, 4
+	; Restore SP (into AUX_USER_SP) only if returning to U mode
+	;  - for K mode, it will be implicitly restored as stack is unwound
+	;  - Z flag set on K is inverse of what hardware does on interrupt entry
+	;    but that doesn't really matter
 	bz	1f
 
-	POPAX	AUX_USER_SP
+	ld	r10, [sp, PT_sp]	; SP (pt_regs->sp)
+	sr	r10, [AUX_USER_SP]
 1:
-	POP	r12
-	POP	r30
 
-#ifdef CONFIG_ARC_HAS_ACCL_REGS
-	POP	r58
-	POP	r59
+#ifdef CONFIG_ARC_CURR_IN_REG
+	ld	r25, [sp, PT_user_r25]
 #endif
 
-#ifdef CONFIG_ARC_IRQ_NO_AUTOSAVE
-.ifnc \called_from, exception
-	POP	r0
-	POP	r1
-	POP	r2
-	POP	r3
-	POP	r4
-	POP	r5
-	POP	r6
-	POP	r7
-	POP	r8
-	POP	r9
-	POP	r10
-	POP	r11
-
-	POP	blink
-	POPAX	lp_end
-	POPAX	lp_start
-
-	POP	r9
-	mov	lp_count, r9
-
-	add	sp, sp, 12	; skip JLI, LDI, EI
-	ld.as	r9, [sp, -10]	; reload r9 which got clobbered
-.endif
+#ifdef CONFIG_ARC_HAS_ACCL_REGS
+	LD2	r58, r59, PT_sp + 12
 #endif
+.endm
 
+/*------------------------------------------------------------------------*/
+.macro __RESTORE_REGFILE_HARD
+
+	ld	blink, [sp, PT_blink]
+
+	LD2	r10, r11, PT_lpe
+	sr	r10, [lp_end]
+	sr	r11, [lp_start]
+
+	ld	r10, [sp, PT_lpc]	; lp_count can't be target of LD
+	mov	lp_count, r10
+
+	LD2	r0,  r1,  PT_r0
+	LD2	r2,  r3,  PT_r2
+	LD2	r4,  r5,  PT_r4
+	LD2	r6,  r7,  PT_r6
+	LD2	r8,  r9,  PT_r8
+	LD2	r10, r11, PT_r10
 .endm
 
+
 /*------------------------------------------------------------------------*/
-.macro EXCEPTION_PROLOGUE
+.macro INTERRUPT_EPILOGUE
 
-	; Before jumping to Exception Vector, hardware micro-ops did following:
-	;   1. SP auto-switched to kernel mode stack
-	;   2. STATUS32.Z flag set to U mode at time of interrupt (U:1,K:0)
-	;
-	; Now manually save the complete reg file
-
-	PUSH	r9		; freeup a register: slot of erstatus
-
-	PUSHAX	eret
-	sub	sp, sp, 12	; skip JLI, LDI, EI
-	PUSH	lp_count
-	PUSHAX	lp_start
-	PUSHAX	lp_end
-	PUSH	blink
-
-	PUSH	r11
-	PUSH	r10
-
-	ld.as	r9,  [sp, 10]	; load stashed r9 (status32 stack slot)
-	lr	r10, [erstatus]
-	st.as	r10, [sp, 10]	; save status32 at it's right stack slot
-
-	PUSH	r9
-	PUSH	r8
-	PUSH	r7
-	PUSH	r6
-	PUSH	r5
-	PUSH	r4
-	PUSH	r3
-	PUSH	r2
-	PUSH	r1
-	PUSH	r0
-
-	; -- for interrupts, regs above are auto-saved by h/w in that order --
-	; Now do what ISR prologue does (manually save r12, sp, fp, gp, r25)
-	;
-	; Set Z flag if this was from U mode (expected by INTERRUPT_PROLOGUE)
-	; Although H/w exception micro-ops do set Z flag for U mode (just like
-	; for interrupts), it could get clobbered in case we soft land here from
-	; a TLB Miss exception handler (tlbex.S)
+	; INPUT: r0 has STAT32 of calling context
+	; INPUT: Z flag set if returning to K mode
 
-	and	r10, r10, STATUS_U_MASK
-	xor.f	0, r10, STATUS_U_MASK
+	; _SOFT clobbers r10 restored by _HARD hence the order
 
-	INTERRUPT_PROLOGUE  exception
+	__RESTORE_REGFILE_SOFT
 
-	PUSHAX	erbta
-	PUSHAX	ecr		; r9 contains ECR, expected by EV_Trap
+#ifdef CONFIG_ARC_IRQ_NO_AUTOSAVE
+	__RESTORE_REGFILE_HARD
+	add	sp, sp, SZ_PT_REGS - 8
+#else
+	add	sp, sp, PT_r0
+#endif
 
-	PUSH	r0		; orig_r0
 .endm
 
 /*------------------------------------------------------------------------*/
 .macro EXCEPTION_EPILOGUE
 
-	; Assumes r0 has PT_status32
-	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
-	POPAX	erbta
-
-	INTERRUPT_EPILOGUE  exception
+	; INPUT: r0 has STAT32 of calling context
 
-	POP	r0
-	POP	r1
-	POP	r2
-	POP	r3
-	POP	r4
-	POP	r5
-	POP	r6
-	POP	r7
-	POP	r8
-	POP	r9
-	POP	r10
-	POP	r11
+	btst	r0, STATUS_U_BIT	; Z flag set if K, used in restoring SP
 
-	POP	blink
-	POPAX	lp_end
-	POPAX	lp_start
+	ld	r10, [sp, PT_event + 4]
+	sr	r10, [erbta]
 
-	POP	r9
-	mov	lp_count, r9
+	LD2	r10, r11, PT_ret
+	sr	r10, [eret]
+	sr	r11, [erstatus]
 
-	add	sp, sp, 12	; skip JLI, LDI, EI
-	POPAX	eret
-	POPAX	erstatus
+	__RESTORE_REGFILE_SOFT
+	__RESTORE_REGFILE_HARD
 
-	ld.as	r9, [sp, -12]	; reload r9 which got clobbered
+	add	sp, sp, SZ_PT_REGS
 .endm
 
 .macro FAKE_RET_FROM_EXCPN

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

@@ -195,8 +195,8 @@
 	PUSHAX  CTOP_AUX_EFLAGS
 #endif
 
-	lr	r9, [ecr]
-	st      r9, [sp, PT_event]    /* EV_Trap expects r9 to have ECR */
+	lr	r10, [ecr]
+	st      r10, [sp, PT_event]    /* EV_Trap expects r10 to have ECR */
 .endm
 
 /*--------------------------------------------------------------

arch/arc/include/asm/linkage.h

@@ -10,6 +10,24 @@
 
 #ifdef __ASSEMBLY__
 
+.macro ST2 e, o, off
+#ifdef CONFIG_ARC_HAS_LL64
+	std	\e, [sp, \off]
+#else
+	st	\e, [sp, \off]
+	st	\o, [sp, \off+4]
+#endif
+.endm
+
+.macro LD2 e, o, off
+#ifdef CONFIG_ARC_HAS_LL64
+	ldd	\e, [sp, \off]
+#else
+	ld	\e, [sp, \off]
+	ld	\o, [sp, \off+4]
+#endif
+.endm
+
 #define ASM_NL		 `	/* use '`' to mark new line in macro */
 
 /* annotation for data we want in DCCM - if enabled in .config */

arch/arc/kernel/asm-offsets.c

@@ -55,7 +55,14 @@ int main(void)
 	DEFINE(PT_r5, offsetof(struct pt_regs, r5));
 	DEFINE(PT_r6, offsetof(struct pt_regs, r6));
 	DEFINE(PT_r7, offsetof(struct pt_regs, r7));
+	DEFINE(PT_r8, offsetof(struct pt_regs, r8));
+	DEFINE(PT_r10, offsetof(struct pt_regs, r10));
+	DEFINE(PT_r26, offsetof(struct pt_regs, r26));
 	DEFINE(PT_ret, offsetof(struct pt_regs, ret));
+	DEFINE(PT_blink, offsetof(struct pt_regs, blink));
+	DEFINE(PT_lpe, offsetof(struct pt_regs, lp_end));
+	DEFINE(PT_lpc, offsetof(struct pt_regs, lp_count));
+	DEFINE(PT_user_r25, offsetof(struct pt_regs, user_r25));
 
 	DEFINE(SZ_CALLEE_REGS, sizeof(struct callee_regs));
 	DEFINE(SZ_PT_REGS, sizeof(struct pt_regs));

arch/arc/kernel/entry-arcv2.S

@@ -67,7 +67,7 @@ reserved:
 
 ENTRY(handle_interrupt)
 
-	INTERRUPT_PROLOGUE  irq
+	INTERRUPT_PROLOGUE
 
 	# irq control APIs local_irq_save/restore/disable/enable fiddle with
 	# global interrupt enable bits in STATUS32 (.IE for 1 prio, .E[] for 2 prio)
@@ -79,7 +79,7 @@ ENTRY(handle_interrupt)
 	#
 	# Note this disable is only for consistent book-keeping as further interrupts
 	# will be disabled anyways even w/o this. Hardware tracks active interrupts
-	# seperately in AUX_IRQ_ACTIVE.active and will not take new interrupts
+	# seperately in AUX_IRQ_ACT.active and will not take new interrupts
 	# unless this one returns (or higher prio becomes pending in 2-prio scheme)
 
 	IRQ_DISABLE
@@ -200,17 +200,18 @@ restore_regs:
 	ld	r0, [sp, PT_status32]	; U/K mode at time of entry
 	lr	r10, [AUX_IRQ_ACT]
 
-	bmsk	r11, r10, 15	; AUX_IRQ_ACT.ACTIVE
+	bmsk	r11, r10, 15		; extract AUX_IRQ_ACT.active
 	breq	r11, 0, .Lexcept_ret	; No intr active, ret from Exception
 
 ;####### Return from Intr #######
 
+.Lisr_ret:
+
 debug_marker_l1:
 	; bbit1.nt r0, STATUS_DE_BIT, .Lintr_ret_to_delay_slot
 	btst	r0, STATUS_DE_BIT		; Z flag set if bit clear
 	bnz	.Lintr_ret_to_delay_slot	; branch if STATUS_DE_BIT set
 
-.Lisr_ret_fast_path:
 	; Handle special case #1: (Entry via Exception, Return via IRQ)
 	;
 	; Exception in U mode, preempted in kernel, Intr taken (K mode), orig
@@ -223,7 +224,7 @@ debug_marker_l1:
 	bset.nz	r11, r11, AUX_IRQ_ACT_BIT_U	; NZ means U
 	sr	r11, [AUX_IRQ_ACT]
 
-	INTERRUPT_EPILOGUE  irq
+	INTERRUPT_EPILOGUE
 	rtie
 
 ;####### Return from Exception / pure kernel mode #######
@@ -244,8 +245,8 @@ debug_marker_syscall:
 ;
 ; IRQ RTIE won't reliably restore DE bit and/or BTA, needs workaround
 ;
-; Solution is return from Intr w/o any delay slot quirks into a kernel trampoline
-; and from pure kernel mode return to delay slot which handles DS bit/BTA correctly
+; Solution is to drop out of interrupt context into pure kernel mode
+; and return from pure kernel mode which does right things for delay slot
 
 .Lintr_ret_to_delay_slot:
 debug_marker_ds:
@@ -254,48 +255,9 @@ debug_marker_ds:
 	add	r2, r2, 1
 	st	r2, [@intr_to_DE_cnt]
 
-	ld	r2, [sp, PT_ret]
-	ld	r3, [sp, PT_status32]
-
-	; STAT32 for Int return created from scratch
-	; (No delay dlot, disable Further intr in trampoline)
-
-	bic  	r0, r3, STATUS_U_MASK|STATUS_DE_MASK|STATUS_IE_MASK|STATUS_L_MASK
-	st	r0, [sp, PT_status32]
-
-	mov	r1, .Lintr_ret_to_delay_slot_2
-	st	r1, [sp, PT_ret]
-
-	; Orig exception PC/STAT32 safekept @orig_r0 and @event stack slots
-	st	r2, [sp, 0]
-	st	r3, [sp, 4]
-
-	b	.Lisr_ret_fast_path
-
-.Lintr_ret_to_delay_slot_2:
-	; Trampoline to restore orig exception PC/STAT32/BTA/AUX_USER_SP
-	sub	sp, sp, SZ_PT_REGS
-	st	r9, [sp, -4]
-
-	ld	r9, [sp, 0]
-	sr	r9, [eret]
-
-	ld	r9, [sp, 4]
-	sr	r9, [erstatus]
-
-	; restore AUX_USER_SP if returning to U mode
-	bbit0	r9, STATUS_U_BIT, 1f
-	ld	r9, [sp, PT_sp]
-	sr	r9, [AUX_USER_SP]
-
-1:
-	ld	r9, [sp, 8]
-	sr	r9, [erbta]
-
-	ld	r9, [sp, -4]
-	add	sp, sp, SZ_PT_REGS
-
-	; return from pure kernel mode to delay slot
-	rtie
+	; drop out of interrupt context (clear AUX_IRQ_ACT.active)
+	bmskn	r11, r10, 15
+	sr	r11, [AUX_IRQ_ACT]
+	b	.Lexcept_ret
 
 END(ret_from_exception)

arch/arc/kernel/entry-compact.S

@@ -256,7 +256,7 @@ ENTRY(EV_TLBProtV)
 
 	EXCEPTION_PROLOGUE
 
-	mov r2, r9	; ECR set into r9 already
+	mov r2, r10	; ECR set into r10 already
 	lr  r0, [efa]	; Faulting Data address (not part of pt_regs saved above)
 
 	; Exception auto-disables further Intr/exceptions.

arch/arc/kernel/entry.S

@@ -232,8 +232,8 @@ ENTRY(EV_Trap)
 	EXCEPTION_PROLOGUE
 
 	;============ TRAP 1   :breakpoints
-	; Check ECR for trap with arg (PROLOGUE ensures r9 has ECR)
-	bmsk.f 0, r9, 7
+	; Check ECR for trap with arg (PROLOGUE ensures r10 has ECR)
+	bmsk.f 0, r10, 7
 	bnz    trap_with_param
 
 	;============ TRAP  (no param): syscall top level

arch/arc/kernel/unwind.c

@@ -181,11 +181,6 @@ static void *__init unw_hdr_alloc_early(unsigned long sz)
 	return memblock_alloc_from(sz, sizeof(unsigned int), MAX_DMA_ADDRESS);
 }
 
-static void *unw_hdr_alloc(unsigned long sz)
-{
-	return kmalloc(sz, GFP_KERNEL);
-}
-
 static void init_unwind_table(struct unwind_table *table, const char *name,
 			      const void *core_start, unsigned long core_size,
 			      const void *init_start, unsigned long init_size,
@@ -366,6 +361,10 @@ static void init_unwind_hdr(struct unwind_table *table,
 }
 
 #ifdef CONFIG_MODULES
+static void *unw_hdr_alloc(unsigned long sz)
+{
+	return kmalloc(sz, GFP_KERNEL);
+}
 
 static struct unwind_table *last_table;
 

arch/arc/mm/fault.c

@@ -63,24 +63,19 @@ void do_page_fault(unsigned long address, struct pt_regs *regs)
 	struct vm_area_struct *vma = NULL;
 	struct task_struct *tsk = current;
 	struct mm_struct *mm = tsk->mm;
-	int si_code = SEGV_MAPERR;
-	int ret;
-	vm_fault_t fault;
-	int write = regs->ecr_cause & ECR_C_PROTV_STORE;  /* ST/EX */
-	unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
+	int sig, si_code = SEGV_MAPERR;
+	unsigned int write = 0, exec = 0, mask;
+	vm_fault_t fault = VM_FAULT_SIGSEGV;	/* handle_mm_fault() output */
+	unsigned int flags;			/* handle_mm_fault() input */
 
 	/*
-	 * We fault-in kernel-space virtual memory on-demand. The
-	 * 'reference' page table is init_mm.pgd.
-	 *
 	 * NOTE! We MUST NOT take any locks for this case. We may
 	 * be in an interrupt or a critical region, and should
 	 * only copy the information from the master page table,
 	 * nothing more.
 	 */
 	if (address >= VMALLOC_START && !user_mode(regs)) {
-		ret = handle_kernel_vaddr_fault(address);
-		if (unlikely(ret))
+		if (unlikely(handle_kernel_vaddr_fault(address)))
 			goto no_context;
 		else
 			return;
@@ -93,67 +88,80 @@ void do_page_fault(unsigned long address, struct pt_regs *regs)
 	if (faulthandler_disabled() || !mm)
 		goto no_context;
 
+	if (regs->ecr_cause & ECR_C_PROTV_STORE)	/* ST/EX */
+		write = 1;
+	else if ((regs->ecr_vec == ECR_V_PROTV) &&
+	         (regs->ecr_cause == ECR_C_PROTV_INST_FETCH))
+		exec = 1;
+
+	flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
 	if (user_mode(regs))
 		flags |= FAULT_FLAG_USER;
+	if (write)
+		flags |= FAULT_FLAG_WRITE;
+
 retry:
 	down_read(&mm->mmap_sem);
+
 	vma = find_vma(mm, address);
 	if (!vma)
 		goto bad_area;
-	if (vma->vm_start <= address)
-		goto good_area;
-	if (!(vma->vm_flags & VM_GROWSDOWN))
-		goto bad_area;
-	if (expand_stack(vma, address))
+	if (unlikely(address < vma->vm_start)) {
+		if (!(vma->vm_flags & VM_GROWSDOWN) || expand_stack(vma, address))
 			goto bad_area;
+	}
 
 	/*
-	 * Ok, we have a good vm_area for this memory access, so
-	 * we can handle it..
+	 * vm_area is good, now check permissions for this memory access
 	 */
-good_area:
-	si_code = SEGV_ACCERR;
-
-	/* Handle protection violation, execute on heap or stack */
+	mask = VM_READ;
+	if (write)
+		mask = VM_WRITE;
+	if (exec)
+		mask = VM_EXEC;
 
-	if ((regs->ecr_vec == ECR_V_PROTV) &&
-	    (regs->ecr_cause == ECR_C_PROTV_INST_FETCH))
-		goto bad_area;
-
-	if (write) {
-		if (!(vma->vm_flags & VM_WRITE))
-			goto bad_area;
-		flags |= FAULT_FLAG_WRITE;
-	} else {
-		if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
+	if (!(vma->vm_flags & mask)) {
+		si_code = SEGV_ACCERR;
 		goto bad_area;
 	}
 
-	/*
-	 * If for any reason at all we couldn't handle the fault,
-	 * make sure we exit gracefully rather than endlessly redo
-	 * the fault.
-	 */
 	fault = handle_mm_fault(vma, address, flags);
 
-	if (fatal_signal_pending(current)) {
+	/*
+	 * Fault retry nuances
+	 */
+	if (unlikely(fault & VM_FAULT_RETRY)) {
 
 		/*
-		 * if fault retry, mmap_sem already relinquished by core mm
-		 * so OK to return to user mode (with signal handled first)
+		 * If fault needs to be retried, handle any pending signals
+		 * first (by returning to user mode).
+		 * mmap_sem already relinquished by core mm for RETRY case
 		 */
-		if (fault & VM_FAULT_RETRY) {
+		if (fatal_signal_pending(current)) {
 			if (!user_mode(regs))
 				goto no_context;
 			return;
 		}
+		/*
+		 * retry state machine
+		 */
+		if (flags & FAULT_FLAG_ALLOW_RETRY) {
+			flags &= ~FAULT_FLAG_ALLOW_RETRY;
+			flags |= FAULT_FLAG_TRIED;
+			goto retry;
+		}
 	}
 
+bad_area:
+	up_read(&mm->mmap_sem);
+
+	/*
+	 * Major/minor page fault accounting
+	 * (in case of retry we only land here once)
+	 */
 	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 
 	if (likely(!(fault & VM_FAULT_ERROR))) {
-		if (flags & FAULT_FLAG_ALLOW_RETRY) {
-			/* To avoid updating stats twice for retry case */
 		if (fault & VM_FAULT_MAJOR) {
 			tsk->maj_flt++;
 			perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
@@ -164,72 +172,33 @@ void do_page_fault(unsigned long address, struct pt_regs *regs)
 				      regs, address);
 		}
 
-			if (fault & VM_FAULT_RETRY) {
-				flags &= ~FAULT_FLAG_ALLOW_RETRY;
-				flags |= FAULT_FLAG_TRIED;
-				goto retry;
-			}
-		}
-
-		/* Fault Handled Gracefully */
-		up_read(&mm->mmap_sem);
+		/* Normal return path: fault Handled Gracefully */
 		return;
 	}
 
-	if (fault & VM_FAULT_OOM)
-		goto out_of_memory;
-	else if (fault & VM_FAULT_SIGSEGV)
-		goto bad_area;
-	else if (fault & VM_FAULT_SIGBUS)
-		goto do_sigbus;
+	if (!user_mode(regs))
+		goto no_context;
 
-	/* no man's land */
-	BUG();
+	if (fault & VM_FAULT_OOM) {
+		pagefault_out_of_memory();
+		return;
+	}
 
-	/*
-	 * Something tried to access memory that isn't in our memory map..
-	 * Fix it, but check if it's kernel or user first..
-	 */
-bad_area:
-	up_read(&mm->mmap_sem);
+	if (fault & VM_FAULT_SIGBUS) {
+		sig = SIGBUS;
+		si_code = BUS_ADRERR;
+	}
+	else {
+		sig = SIGSEGV;
+	}
 
-	/* User mode accesses just cause a SIGSEGV */
-	if (user_mode(regs)) {
 	tsk->thread.fault_address = address;
-		force_sig_fault(SIGSEGV, si_code, (void __user *)address);
+	force_sig_fault(sig, si_code, (void __user *)address);
 	return;
-	}
 
 no_context:
-	/* Are we prepared to handle this kernel fault?
-	 *
-	 * (The kernel has valid exception-points in the source
-	 *  when it accesses user-memory. When it fails in one
-	 *  of those points, we find it in a table and do a jump
-	 *  to some fixup code that loads an appropriate error
-	 *  code)
-	 */
 	if (fixup_exception(regs))
 		return;
 
 	die("Oops", regs, address);
-
-out_of_memory:
-	up_read(&mm->mmap_sem);
-
-	if (user_mode(regs)) {
-		pagefault_out_of_memory();
-		return;
-	}
-
-	goto no_context;
-
-do_sigbus:
-	up_read(&mm->mmap_sem);
-
-	if (!user_mode(regs))
-		goto no_context;
-
-	tsk->thread.fault_address = address;
-	force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address);
 }

arch/arc/mm/tlbex.S

@@ -393,6 +393,17 @@ EV_TLBMissD_fast_ret:	; additional label for VDK OS-kit instrumentation
 ;-------- Common routine to call Linux Page Fault Handler -----------
 do_slow_path_pf:
 
+#ifdef CONFIG_ISA_ARCV2
+	; Set Z flag if exception in U mode. Hardware micro-ops do this on any
+	; taken interrupt/exception, and thus is already the case at the entry
+	; above, but ensuing code would have already clobbered.
+	; EXCEPTION_PROLOGUE called in slow path, relies on correct Z flag set
+
+	lr	r2, [erstatus]
+	and	r2, r2, STATUS_U_MASK
+	bxor.f	0, r2, STATUS_U_BIT
+#endif
+
 	; Restore the 4-scratch regs saved by fast path miss handler
 	TLBMISS_RESTORE_REGS