svn commit: r365296 - in head/sys/arm64: arm64 include

[Andrew Turner]

Author: andrew
Date: Thu Sep  3 10:11:12 2020
New Revision: 365296
URL: https://svnweb.freebsd.org/changeset/base/365296

Log:
  Switch to an empty ttbr0 pagetable when the MMU is enabled
  
  We don't need these pagetables after the early boot. Remove the chance we
  write to memory we didn't expect to and remove architectural undefined
  behaviour.
  
  Reviewed by:	alc (earlier version), mmel
  Sponsored by:	Innovate UK
  Differential Revision:	https://reviews.freebsd.org/D22606

Modified:
  head/sys/arm64/arm64/locore.S
  head/sys/arm64/arm64/machdep.c
  head/sys/arm64/include/machdep.h

Modified: head/sys/arm64/arm64/locore.S
==============================================================================
--- head/sys/arm64/arm64/locore.S	Thu Sep  3 09:09:44 2020	(r365295)
+++ head/sys/arm64/arm64/locore.S	Thu Sep  3 10:11:12 2020	(r365296)
@@ -128,6 +128,9 @@ _start:
 	/* Enable the mmu */
 	bl	start_mmu
 
+	/* Load the new ttbr0 pagetable */
+	adr	x27, pagetable_l0_ttbr0
+
 	/* Jump to the virtual address space */
 	ldr	x15, .Lvirtdone
 	br	x15
@@ -166,6 +169,7 @@ virtdone:
 	str	x25, [x0, #BP_KERN_STACK]
 	str	x24, [x0, #BP_KERN_L0PT]
 	str	x23, [x0, #BP_BOOT_EL]
+	str	x27, [x0, 40]	/* kern_ttbr0 */
 
 	/* trace back starts here */
 	mov	fp, #0
@@ -204,11 +208,14 @@ ENTRY(mpentry)
 	/* Load the kernel page table */
 	adr	x24, pagetable_l0_ttbr1
 	/* Load the identity page table */
-	adr	x27, pagetable_l0_ttbr0
+	adr	x27, pagetable_l0_ttbr0_boostrap
 
 	/* Enable the mmu */
 	bl	start_mmu
 
+	/* Load the new ttbr0 pagetable */
+	adr	x27, pagetable_l0_ttbr0
+
 	/* Jump to the virtual address space */
 	ldr	x15, =mp_virtdone
 	br	x15
@@ -218,6 +225,16 @@ mp_virtdone:
 	ldr	x4, =bootstack
 	ldr	x4, [x4]
 	mov	sp, x4
+
+	/* Load the kernel ttbr0 pagetable */
+	msr	ttbr0_el1, x27
+	isb
+
+	/* Invalidate the TLB */
+	tlbi	vmalle1
+	dsb	sy
+	isb
+
 	b	init_secondary
 END(mpentry)
 #endif
@@ -760,10 +777,13 @@ abort:
 	//.section .init_pagetable
 	.align 12 /* 4KiB aligned */
 	/*
-	 * 3 initial tables (in the following order):
+	 * 6 initial tables (in the following order):
 	 *           L2 for kernel (High addresses)
 	 *           L1 for kernel
-	 *           L1 for user   (Low addresses)
+	 *           L0 for kernel
+	 *           L1 bootstrap for user   (Low addresses)
+	 *           L0 bootstrap for user
+	 *           L0 for user
 	 */
 pagetable:
 	.space	PAGE_SIZE
@@ -771,7 +791,9 @@ pagetable_l1_ttbr1:
 	.space	PAGE_SIZE
 pagetable_l0_ttbr1:
 	.space	PAGE_SIZE
-pagetable_l1_ttbr0:
+pagetable_l1_ttbr0_bootstrap:
+	.space	PAGE_SIZE
+pagetable_l0_ttbr0_boostrap:
 	.space	PAGE_SIZE
 pagetable_l0_ttbr0:
 	.space	PAGE_SIZE

Modified: head/sys/arm64/arm64/machdep.c
==============================================================================
--- head/sys/arm64/arm64/machdep.c	Thu Sep  3 09:09:44 2020	(r365295)
+++ head/sys/arm64/arm64/machdep.c	Thu Sep  3 10:11:12 2020	(r365296)
@@ -1235,6 +1235,8 @@ initarm(struct arm64_bootparams *abp)
 	valid = bus_probe();
 
 	cninit();
+	set_ttbr0(abp->kern_ttbr0);
+	cpu_tlb_flushID();
 
 	if (!valid)
 		panic("Invalid bus configuration: %s",

Modified: head/sys/arm64/include/machdep.h
==============================================================================
--- head/sys/arm64/include/machdep.h	Thu Sep  3 09:09:44 2020	(r365295)
+++ head/sys/arm64/include/machdep.h	Thu Sep  3 10:11:12 2020	(r365296)
@@ -37,6 +37,7 @@ struct arm64_bootparams {
 	uint64_t	kern_delta;
 	vm_offset_t	kern_stack;
 	vm_offset_t	kern_l0pt;	/* L1 page table for the kernel */
+	vm_paddr_t	kern_ttbr0;
 	int		boot_el;	/* EL the kernel booted from */
 	int		pad;
 };