ARM: 9012/1: move device tree mapping out of linear region

On ARM, setting up the linear region is tricky, given the constraints
around placement and alignment of the memblocks, and how the kernel
itself as well as the DT are placed in physical memory.

Let's simplify matters a bit, by moving the device tree mapping to the
top of the address space, right between the end of the vmalloc region
and the start of the the fixmap region, and create a read-only mapping
for it that is independent of the size of the linear region, and how it
is organized.

Since this region was formerly used as a guard region, which will now be
populated fully on LPAE builds by this read-only mapping (which will
still be able to function as a guard region for stray writes), bump the
start of the [underutilized] fixmap region by 512 KB as well, to ensure
that there is always a proper guard region here. Doing so still leaves
ample room for the fixmap space, even with NR_CPUS set to its maximum
value of 32.

Tested-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Nicolas Pitre <nico@fluxnic.net>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

diff --git a/Documentation/arm/memory.rst b/Documentation/arm/memory.rst
index 0521b4c..34bb23c 100644 (file)
--- a/Documentation/arm/memory.rst
+++ b/Documentation/arm/memory.rst
@@ -45,9 +45,14 @@ fffe8000     fffeffff        DTCM mapping area for platforms with
 fffe0000       fffe7fff        ITCM mapping area for platforms with
                                ITCM mounted inside the CPU.
 
-ffc00000       ffefffff        Fixmap mapping region.  Addresses provided
+ffc80000       ffefffff        Fixmap mapping region.  Addresses provided
                                by fix_to_virt() will be located here.
 
+ffc00000       ffc7ffff        Guard region
+
+ff800000       ffbfffff        Permanent, fixed read-only mapping of the
+                               firmware provided DT blob
+
 fee00000       feffffff        Mapping of PCI I/O space. This is a static
                                mapping within the vmalloc space.
 

diff --git a/arch/arm/include/asm/fixmap.h b/arch/arm/include/asm/fixmap.h
index fc56fc3..9575b40 100644 (file)
--- a/arch/arm/include/asm/fixmap.h
+++ b/arch/arm/include/asm/fixmap.h
@@ -2,7 +2,7 @@
 #ifndef _ASM_FIXMAP_H
 #define _ASM_FIXMAP_H
 
-#define FIXADDR_START          0xffc00000UL
+#define FIXADDR_START          0xffc80000UL
 #define FIXADDR_END            0xfff00000UL
 #define FIXADDR_TOP            (FIXADDR_END - PAGE_SIZE)
 

diff --git a/arch/arm/include/asm/memory.h b/arch/arm/include/asm/memory.h
index 99035b5..bb79e52 100644 (file)
--- a/arch/arm/include/asm/memory.h
+++ b/arch/arm/include/asm/memory.h
@@ -67,6 +67,10 @@
  */
 #define XIP_VIRT_ADDR(physaddr)  (MODULES_VADDR + ((physaddr) & 0x000fffff))
 
+#define FDT_FIXED_BASE         UL(0xff800000)
+#define FDT_FIXED_SIZE         (2 * PMD_SIZE)
+#define FDT_VIRT_ADDR(physaddr)        ((void *)(FDT_FIXED_BASE | (physaddr) % PMD_SIZE))
+
 #if !defined(CONFIG_SMP) && !defined(CONFIG_ARM_LPAE)
 /*
  * Allow 16MB-aligned ioremap pages
@@ -107,6 +111,7 @@ extern unsigned long vectors_base;
 #define MODULES_VADDR          PAGE_OFFSET
 
 #define XIP_VIRT_ADDR(physaddr)  (physaddr)
+#define FDT_VIRT_ADDR(physaddr)  ((void *)(physaddr))
 
 #endif /* !CONFIG_MMU */
 

diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S
index f890422..9b18d8c 100644 (file)
--- a/arch/arm/kernel/head.S
+++ b/arch/arm/kernel/head.S
@@ -275,9 +275,8 @@ __create_page_tables:
         */
        mov     r0, r2, lsr #SECTION_SHIFT
        movs    r0, r0, lsl #SECTION_SHIFT
-       subne   r3, r0, r8
-       addne   r3, r3, #PAGE_OFFSET
-       addne   r3, r4, r3, lsr #(SECTION_SHIFT - PMD_ORDER)
+       ldrne   r3, =FDT_FIXED_BASE >> (SECTION_SHIFT - PMD_ORDER)
+       addne   r3, r3, r4
        orrne   r6, r7, r0
        strne   r6, [r3], #1 << PMD_ORDER
        addne   r6, r6, #1 << SECTION_SHIFT

diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
index 306bcd9..694aa6b 100644 (file)
--- a/arch/arm/kernel/setup.c
+++ b/arch/arm/kernel/setup.c
@@ -18,6 +18,7 @@
 #include <linux/of_platform.h>
 #include <linux/init.h>
 #include <linux/kexec.h>
+#include <linux/libfdt.h>
 #include <linux/of_fdt.h>
 #include <linux/cpu.h>
 #include <linux/interrupt.h>
@@ -89,7 +90,6 @@ unsigned int cacheid __read_mostly;
 EXPORT_SYMBOL(cacheid);
 
 unsigned int __atags_pointer __initdata;
-void *atags_vaddr __initdata;
 
 unsigned int system_rev;
 EXPORT_SYMBOL(system_rev);
@@ -1083,13 +1083,18 @@ void __init hyp_mode_check(void)
 void __init setup_arch(char **cmdline_p)
 {
        const struct machine_desc *mdesc = NULL;
+       void *atags_vaddr = NULL;
 
        if (__atags_pointer)
-               atags_vaddr = phys_to_virt(__atags_pointer);
+               atags_vaddr = FDT_VIRT_ADDR(__atags_pointer);
 
        setup_processor();
-       if (atags_vaddr)
+       if (atags_vaddr) {
                mdesc = setup_machine_fdt(atags_vaddr);
+               if (mdesc)
+                       memblock_reserve(__atags_pointer,
+                                        fdt_totalsize(atags_vaddr));
+       }
        if (!mdesc)
                mdesc = setup_machine_tags(atags_vaddr, __machine_arch_type);
        if (!mdesc) {

diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
index d57112a..a391804 100644 (file)
--- a/arch/arm/mm/init.c
+++ b/arch/arm/mm/init.c
@@ -223,7 +223,6 @@ void __init arm_memblock_init(const struct machine_desc *mdesc)
        if (mdesc->reserve)
                mdesc->reserve();
 
-       early_init_fdt_reserve_self();
        early_init_fdt_scan_reserved_mem();
 
        /* reserve memory for DMA contiguous allocations */

diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index 55991fe..fa25982 100644 (file)
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -39,6 +39,8 @@
 #include "mm.h"
 #include "tcm.h"
 
+extern unsigned long __atags_pointer;
+
 /*
  * empty_zero_page is a special page that is used for
  * zero-initialized data and COW.
@@ -946,7 +948,7 @@ static void __init create_mapping(struct map_desc *md)
                return;
        }
 
-       if ((md->type == MT_DEVICE || md->type == MT_ROM) &&
+       if (md->type == MT_DEVICE &&
            md->virtual >= PAGE_OFFSET && md->virtual < FIXADDR_START &&
            (md->virtual < VMALLOC_START || md->virtual >= VMALLOC_END)) {
                pr_warn("BUG: mapping for 0x%08llx at 0x%08lx out of vmalloc space\n",
@@ -1333,6 +1335,15 @@ static void __init devicemaps_init(const struct machine_desc *mdesc)
        for (addr = VMALLOC_START; addr < (FIXADDR_TOP & PMD_MASK); addr += PMD_SIZE)
                pmd_clear(pmd_off_k(addr));
 
+       if (__atags_pointer) {
+               /* create a read-only mapping of the device tree */
+               map.pfn = __phys_to_pfn(__atags_pointer & SECTION_MASK);
+               map.virtual = FDT_FIXED_BASE;
+               map.length = FDT_FIXED_SIZE;
+               map.type = MT_ROM;
+               create_mapping(&map);
+       }
+
        /*
         * Map the kernel if it is XIP.
         * It is always first in the modulearea.
@@ -1489,8 +1500,7 @@ static void __init map_lowmem(void)
 }
 
 #ifdef CONFIG_ARM_PV_FIXUP
-extern void *atags_vaddr;
-typedef void pgtables_remap(long long offset, unsigned long pgd, void *bdata);
+typedef void pgtables_remap(long long offset, unsigned long pgd);
 pgtables_remap lpae_pgtables_remap_asm;
 
 /*
@@ -1503,7 +1513,6 @@ static void __init early_paging_init(const struct machine_desc *mdesc)
        unsigned long pa_pgd;
        unsigned int cr, ttbcr;
        long long offset;
-       void *boot_data;
 
        if (!mdesc->pv_fixup)
                return;
@@ -1520,7 +1529,6 @@ static void __init early_paging_init(const struct machine_desc *mdesc)
         */
        lpae_pgtables_remap = (pgtables_remap *)(unsigned long)__pa(lpae_pgtables_remap_asm);
        pa_pgd = __pa(swapper_pg_dir);
-       boot_data = atags_vaddr;
        barrier();
 
        pr_info("Switching physical address space to 0x%08llx\n",
@@ -1556,7 +1564,7 @@ static void __init early_paging_init(const struct machine_desc *mdesc)
         * needs to be assembly.  It's fairly simple, as we're using the
         * temporary tables setup by the initial assembly code.
         */
-       lpae_pgtables_remap(offset, pa_pgd, boot_data);
+       lpae_pgtables_remap(offset, pa_pgd);
 
        /* Re-enable the caches and cacheable TLB walks */
        asm volatile("mcr p15, 0, %0, c2, c0, 2" : : "r" (ttbcr));

diff --git a/arch/arm/mm/pv-fixup-asm.S b/arch/arm/mm/pv-fixup-asm.S
index 8eade04..5c5e195 100644 (file)
--- a/arch/arm/mm/pv-fixup-asm.S
+++ b/arch/arm/mm/pv-fixup-asm.S
@@ -39,8 +39,8 @@ ENTRY(lpae_pgtables_remap_asm)
 
        /* Update level 2 entries for the boot data */
        add     r7, r2, #0x1000
-       add     r7, r7, r3, lsr #SECTION_SHIFT - L2_ORDER
-       bic     r7, r7, #(1 << L2_ORDER) - 1
+       movw    r3, #FDT_FIXED_BASE >> (SECTION_SHIFT - L2_ORDER)
+       add     r7, r7, r3
        ldrd    r4, r5, [r7]
        adds    r4, r4, r0
        adc     r5, r5, r1