From c778aa7608f6decb6a82507cca19ab8aa6d4fd05 Mon Sep 17 00:00:00 2001
From: ian <ian@FreeBSD.org>
Date: Tue, 26 Dec 2017 19:02:56 +0000
Subject: [PATCH] Add a new ARM kernel option, LOCORE_MAP_MB, to control the
 size of the kernel VA mapping in the temporary page tables set up by
 locore-v6.S.

The number used to be hard-coded to 64MB, which is still the default if
the kernel option is not specified.  However, 64MB is insufficient for
using a large mdroot filesystem.  The hard-coded number can't be safely
increased because too large a number may run into memory-mapped IO space
on some SoCs that must not be mapped as ordinary memory.
---
 sys/arm/arm/genassym.c  |  9 +++++++++
 sys/arm/arm/locore-v6.S | 12 +++++++++---
 sys/conf/options.arm    |  1 +
 3 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/sys/arm/arm/genassym.c b/sys/arm/arm/genassym.c
index 7132423686dc..ab7ec0f6636f 100644
--- a/sys/arm/arm/genassym.c
+++ b/sys/arm/arm/genassym.c
@@ -161,3 +161,12 @@ ASSYM(DCACHE_LINE_SIZE, offsetof(struct cpuinfo, dcache_line_size));
 ASSYM(DCACHE_LINE_MASK, offsetof(struct cpuinfo, dcache_line_mask));
 ASSYM(ICACHE_LINE_SIZE, offsetof(struct cpuinfo, icache_line_size));
 ASSYM(ICACHE_LINE_MASK, offsetof(struct cpuinfo, icache_line_mask));
+
+/*
+ * Emit the LOCORE_MAP_MB option as a #define only if the option was set.
+ */
+#include "opt_locore.h"
+
+#ifdef LOCORE_MAP_MB
+ASSYM(LOCORE_MAP_MB, LOCORE_MAP_MB);
+#endif
diff --git a/sys/arm/arm/locore-v6.S b/sys/arm/arm/locore-v6.S
index ef96c61a8fee..04858426ba34 100644
--- a/sys/arm/arm/locore-v6.S
+++ b/sys/arm/arm/locore-v6.S
@@ -38,6 +38,11 @@
 
 __FBSDID("$FreeBSD$");
 
+/* We map 64MB of kernel unless overridden in assym.s by the kernel option. */
+#ifndef LOCORE_MAP_MB
+#define	LOCORE_MAP_MB	64
+#endif
+
 #if __ARM_ARCH >= 7
 #if defined(__ARM_ARCH_7VE__) || defined(__clang__)
 /*
@@ -176,12 +181,13 @@ ASENTRY_NP(_start)
 	bl	build_pagetables
 
 	/* 
-	 * Next we do 64MiB starting at the physical load address, mapped to
-	 * the VA the kernel is linked for.
+	 * Next we map the kernel starting at the physical load address, mapped
+	 * to the VA the kernel is linked for.  The default size we map is 64MiB
+	 * but it can be overridden with a kernel option.
 	 */
 	mov	r1, r5
 	ldr	r2, =(KERNVIRTADDR)
-	mov	r3, #64
+	ldr	r3, =(LOCORE_MAP_MB)
 	bl	build_pagetables
 
 	/* Create a device mapping for early_printf if specified. */
diff --git a/sys/conf/options.arm b/sys/conf/options.arm
index 91ca74b8edbe..3f91b2896e52 100644
--- a/sys/conf/options.arm
+++ b/sys/conf/options.arm
@@ -35,6 +35,7 @@ KERNBASE		opt_global.h
 KERNVIRTADDR		opt_global.h
 LINUX_BOOT_ABI		opt_global.h
 LOADERRAMADDR		opt_global.h
+LOCORE_MAP_MB		opt_locore.h
 NKPT2PG			opt_pmap.h
 PHYSADDR		opt_global.h
 PLATFORM		opt_global.h