Rewrite the armv7 context switch code. The new code is much closer to the

arm64 version and fixes some (but not all) remaining issues with SMP support
on armv7.

ok visa@, patrick@

1 files changed, 36 insertions, 131 deletions

diff --git a/sys/arch/arm/arm/cpuswitch7.S b/sys/arch/arm/arm/cpuswitch7.S
index 2f025aac324..cd5997330c4 100644
--- a/sys/arch/arm/arm/cpuswitch7.S
+++ b/sys/arch/arm/arm/cpuswitch7.S
@@ -1,4 +1,4 @@
-/*	$OpenBSD: cpuswitch7.S,v 1.14 2018/08/06 18:39:13 kettenis Exp $	*/
+/*	$OpenBSD: cpuswitch7.S,v 1.15 2020/01/06 15:53:00 kettenis Exp $	*/
 /*	$NetBSD: cpuswitch.S,v 1.41 2003/11/15 08:44:18 scw Exp $	*/
 
 /*
@@ -148,156 +148,60 @@ ENTRY(cpu_idle_leave)
  */
 
 ENTRY(cpu_switchto)
+	/* check if old context needs to be saved */
+	teq	r0, #0
+	beq	1f
+
+	/* create switchframe */
 	stmfd	sp!, {r4-r7, lr}
 	sub	sp, sp, #4
 
-	/* Get curcpu from TPIDRPRW. */
-	mrc	CP15_TPIDRPRW(r3)
-#ifdef MULTIPROCESSOR
-	str	r3, [r1, #(P_CPU)]
-#else
-	/* p->p_cpu initialized in fork1() for single-processor */
-#endif
-
-	/* Process is now on a processor. */
-	mov	r2, #SONPROC			/* p->p_stat = SONPROC */
-	strb	r2, [r1, #(P_STAT)]
-
-	/* We have a new curproc now so make a note it */
-	str	r1, [r3, #(CI_CURPROC)]
-
-	/* Hook in a new pcb */
-	ldr	r6, [r3, #(CI_CURPCB)]		/* Remember the old PCB */
-	ldr	r2, [r1, #(P_ADDR)]
-	str	r2, [r3, #(CI_CURPCB)]
-
-	/*
-	 * If the old proc on entry to cpu_switch was zero then the
-	 * process that called it was exiting. This means that we do
-	 * not need to save the current context (we nevertheless need
-	 * to clear the cache and TLB).
-	 */
-	teq	r0, #0x00000000
-	beq	.Lswitch_exited
-
-	/* Stage two: Save old context */
-
-	/* Save all the registers in the old proc's pcb */
-	add	r7, r6, #(PCB_R8)
-	stmia	r7, {r8-r13}
-
-.Lswitch_exited:
-	/*
-	 * NOTE: We can now use r8-r13 until it is time to restore
-	 * them for the new process.
-	 */
-
-	/* Remember the old PCB. */
-	mov	r8, r6
-
-	/* Save new proc in r6 now. */
-	mov	r6, r1
-
-	/* Get the user structure for the new process in r9 */
-	ldr	r9, [r6, #(P_ADDR)]
+	mrc	CP15_TPIDRPRW(r2)		/* load curcpu */
+	ldr	r5, [r2, #(CI_CURPCB)]
 
+	/* save old stack pointer */
 	mrs	r3, cpsr
 	cpsid	i, #(PSR_UND32_MODE)
+	str	sp, [r5, #(PCB_UND_SP)]
+	msr	cpsr_c, r3
 
-#ifdef notworthit
-	teq	r0, #0x00000000
-	strne	sp, [r8, #(PCB_UND_SP)]
-#else
-	str	sp, [r8, #(PCB_UND_SP)]
-#endif
-
-	msr	cpsr_c, r3		/* Restore the old mode */
-
-	/* rem: r0 = old proc */
-	/* rem: r1 = r6 = new process */
-	/* rem: r8 = old PCB */
-	/* rem: r9 = new PCB */
-
-	/* What else needs to be saved  Only FPA stuff when that is supported */
-
-	/* Third phase: restore saved context */
-
-	/*
-	 * Get the new L1 table pointer into r11.  If we're switching to
-	 * an LWP with the same address space as the outgoing one, we can
-	 * skip the cache purge and the TTB load.
-	 *
-	 * To avoid data dep stalls that would happen anyway, we try
-	 * and get some useful work done in the mean time.
-	 */
-	ldr	r10, [r8, #(PCB_PAGEDIR)]	/* r10 = old L1 */
-	ldr	r11, [r9, #(PCB_PAGEDIR)]	/* r11 = new L1 */
-
-	/* rem: r6 = new proc */
-	/* rem: r9 = new PCB */
-	/* rem: r10 = old L1 */
-	/* rem: r11 = new L1 */
-
-	/*
-	 * At this point we need to kill IRQ's again.
-	 *
-	 * XXXSCW: Don't need to block FIQs if vectors have been relocated
-	 */
-	IRQdisableALL
-
-	cmp	r10, r11		/* Switching to the same L1? */
-	ldr	r10, .Lcpufuncs
-	beq	.Lcs_context_switched	/* Yup. */
-
-	/*
-	 * Do a full context switch, including full TLB flush.
-	 */
-	mov	r0, r11
-	mov	lr, pc
-	ldr	pc, [r10, #CF_CONTEXT_SWITCH]
-
-.Lcs_context_switched:
+	add	r6, r5, #(PCB_R8)
+	stmia	r6, {r8-r13}
 
-	/* XXXSCW: Safe to re-enable FIQs here */
+1:
+	mrc	CP15_TPIDRPRW(r2)		/* load curcpu */
+	mov	r5, #SONPROC
+	strb	r5, [r1, #(P_STAT)]		/* mark new on cpu */
+	str	r2, [r1, #(P_CPU)]
+	ldr	r5, [r1, #(P_ADDR)]		/* load new pcb */
+	str	r5, [r2, #(CI_CURPCB)]
+	str	r1, [r2, #(CI_CURPROC)]
 
-	/* rem: r6 = new proc */
-	/* rem: r9 = new PCB */
+	ldr	r4, [r5, #(PCB_TCB)]
+	mcr	CP15_TPIDRURO(r4)		/* load user tls */
 
-	/* stick tcb into user visable register */
-	ldr	r3, [r9, #(PCB_TCB)]
-	mcr	CP15_TPIDRURO(r3)
+	add	r6, r5, #PCB_R8
+	ldmia	r6, {r8-r13}
 
+	/* load new stack pointer */
 	mrs	r3, cpsr
 	cps	#(PSR_UND32_MODE)
+	ldr	sp, [r5, #(PCB_UND_SP)]
+	msr	cpsr_c, r3
 
-	ldr	sp, [r9, #(PCB_UND_SP)]
-
-	msr	cpsr_c, r3		/* Restore the old mode */
-
-	/* Restore all the save registers */
-	add	r7, r9, #PCB_R8
-	ldmia	r7, {r8-r13}
-
-	sub	r7, r7, #PCB_R8		/* restore PCB pointer */
+	IRQdisableALL
 
-	/* rem: r6 = new proc */
-	/* rem: r7 = new pcb */
+	ldr	r0, [r5, #(PCB_PAGEDIR)]
+	ldr	r3, .Lcpufuncs
+	mov	lr, pc
+	ldr	pc, [r3, #CF_CONTEXT_SWITCH]
 
-	/* We can enable interrupts again */
 	IRQenableALL
-
-	/* rem: r6 = new proc */
-	/* rem: r7 = new PCB */
-
-.Lswitch_return:
-	/*
-	 * Pull the registers that got pushed when either savectx() or
-	 * cpu_switch() was called and return.
-	 */
+	
 	add	sp, sp, #4
 	ldmfd	sp!, {r4-r7, pc}
 
-/* LINTSTUB: Func: void savectx(struct pcb *pcb) */
+
 ENTRY(savectx)
 	/*
 	 * r0 = pcb
@@ -315,6 +219,7 @@ ENTRY(savectx)
 	add	sp, sp, #4
 	ldmfd	sp!, {r4-r7, pc}
 
+
 ENTRY(proc_trampoline)
 #ifdef MULTIPROCESSOR
 	bl	_C_LABEL(proc_trampoline_mp)