svn commit: r261855 - head/sys/arm/arm

[Andrew Turner]

Author: andrew
Date: Thu Feb 13 21:30:54 2014
New Revision: 261855
URL: http://svnweb.freebsd.org/changeset/base/261855

Log:
  Allow the kernel to be loaded at any 1MiB address. This requirement is
  because we use the 1MiB section maps as they only need a single pagetable.
  
  To allow this we only use pc relative loads to ensure we only load from
  physical addresses until we are running from a known virtual address.
  
  As a side effect any data from before or 64MiB after the kernel needs to
  be mapped in to be used. This should not be an issue for kernels loaded
  with ubldr as it places this data just after the kernel. It will be a
  problem when loading directly from anything using the Linux ABI that
  places the ATAG data outside this range, for example U-Boot.

Modified:
  head/sys/arm/arm/locore.S

Modified: head/sys/arm/arm/locore.S
==============================================================================
--- head/sys/arm/arm/locore.S	Thu Feb 13 20:41:25 2014	(r261854)
+++ head/sys/arm/arm/locore.S	Thu Feb 13 21:30:54 2014	(r261855)
@@ -148,15 +148,31 @@ Lunmapped:
 	 * Build page table from scratch.
 	 */
 
-	/* Load the page tables physical address */
-	ldr	r1, Lstartup_pagetable
-	ldr	r2, =(KERNVIRTADDR - KERNPHYSADDR)
+	/* Find the delta between VA and PA */
+	adr	r0, Lpagetable
+	ldr	r1, [r0]
+	sub	r2, r1, r0
+	/* At this point: r2 = VA - PA */
+
+	/*
+	 * Find the physical address of the table. After these two
+	 * instructions:
+	 * r1 = va(pagetable)
+	 *
+	 * r0 = va(pagetable) - (VA - PA)
+	 *    = va(pagetable) - VA + PA
+	 *    = pa(pagetable)
+	 */
+	ldr	r1, [r0, #4]
 	sub	r0, r1, r2
 
 	/*
 	 * Map PA == VA
 	 */
-	ldr	r5, =(PHYSADDR)
+	/* Find the start kernels load address */
+	adr	r5, _start
+	ldr	r2, =(L1_S_OFFSET)
+	bic	r5, r2
 	mov	r1, r5
 	mov	r2, r5
 	/* Map 64MiB, preserved over calls to build_pagetables */
@@ -165,7 +181,7 @@ Lunmapped:
 
 	/* Create the kernel map to jump to */
 	mov	r1, r5
-	ldr	r2, =(KERNBASE)
+	ldr	r2, =(KERNVIRTADDR)
 	bl	build_pagetables
 	
 #if defined(SOCDEV_PA) && defined(SOCDEV_VA)
@@ -223,16 +239,16 @@ mmu_done:
 virt_done:
 	mov	r1, #28			/* loader info size is 28 bytes also second arg */
 	subs	sp, sp, r1		/* allocate arm_boot_params struct on stack */
-	bic	sp, sp, #7		/* align stack to 8 bytes */
 	mov	r0, sp			/* loader info pointer is first arg */
+	bic	sp, sp, #7		/* align stack to 8 bytes */
 	str	r1, [r0]		/* Store length of loader info */
 	str	r9, [r0, #4]		/* Store r0 from boot loader */
 	str	r8, [r0, #8]		/* Store r1 from boot loader */
 	str	ip, [r0, #12]		/* store r2 from boot loader */
 	str	fp, [r0, #16]		/* store r3 from boot loader */
-	ldr	r5, =KERNPHYSADDR	/* load KERNPHYSADDR as the physical address */
 	str	r5, [r0, #20]		/* store the physical address */
-	ldr	r5, Lstartup_pagetable
+	adr	r4, Lpagetable		/* load the pagetable address */
+	ldr	r5, [r4, #4]
 	str	r5, [r0, #24]		/* store the pagetable address */
 	mov	fp, #0			/* trace back starts here */
 	bl	_C_LABEL(initarm)	/* Off we go */
@@ -279,16 +295,19 @@ build_pagetables:
 
 	RET
 
+Lpagetable:
+	.word	.
+	.word	pagetable
+
 Lvirtaddr:
 	.word	KERNVIRTADDR
 Lphysaddr:
 	.word	KERNPHYSADDR
 Lreal_start:
 	.word	_start
-Lend:	
+Lend:
 	.word	_edata
-Lstartup_pagetable:
-	.word	pagetable
+
 #ifdef SMP
 Lstartup_pagetable_secondary:
 	.word	temp_pagetable