[PATCH v4 10/13] arm64: move kernel mapping out of linear region
Ard Biesheuvel
ard.biesheuvel at linaro.org
Wed Apr 15 08:34:21 PDT 2015
This moves the primary mapping of the kernel Image out of
the linear region. This is a preparatory step towards allowing
the kernel Image to reside anywhere in physical memory without
affecting the ability to map all of it efficiently.
Signed-off-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
---
arch/arm64/include/asm/boot.h | 7 +++++++
arch/arm64/include/asm/memory.h | 28 ++++++++++++++++++++++++----
arch/arm64/kernel/head.S | 8 ++++----
arch/arm64/kernel/vmlinux.lds.S | 11 +++++++++--
arch/arm64/mm/mmu.c | 11 ++++++++++-
5 files changed, 54 insertions(+), 11 deletions(-)
diff --git a/arch/arm64/include/asm/boot.h b/arch/arm64/include/asm/boot.h
index 81151b67b26b..092d1096ce9a 100644
--- a/arch/arm64/include/asm/boot.h
+++ b/arch/arm64/include/asm/boot.h
@@ -11,4 +11,11 @@
#define MIN_FDT_ALIGN 8
#define MAX_FDT_SIZE SZ_2M
+/*
+ * arm64 requires the kernel image to be 2 MB aligned and
+ * not exceed 64 MB in size.
+ */
+#define MIN_KIMG_ALIGN SZ_2M
+#define MAX_KIMG_SIZE SZ_64M
+
#endif
diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index f800d45ea226..801331793bd3 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -24,6 +24,7 @@
#include <linux/compiler.h>
#include <linux/const.h>
#include <linux/types.h>
+#include <asm/boot.h>
#include <asm/sizes.h>
/*
@@ -39,7 +40,12 @@
#define PCI_IO_SIZE SZ_16M
/*
- * PAGE_OFFSET - the virtual address of the start of the kernel image (top
+ * Offset below PAGE_OFFSET where to map the kernel Image.
+ */
+#define KIMAGE_OFFSET MAX_KIMG_SIZE
+
+/*
+ * PAGE_OFFSET - the virtual address of the base of the linear mapping (top
* (VA_BITS - 1))
* VA_BITS - the maximum number of bits for virtual addresses.
* TASK_SIZE - the maximum size of a user space task.
@@ -49,7 +55,8 @@
*/
#define VA_BITS (CONFIG_ARM64_VA_BITS)
#define PAGE_OFFSET (UL(0xffffffffffffffff) << (VA_BITS - 1))
-#define MODULES_END (PAGE_OFFSET)
+#define KIMAGE_VADDR (PAGE_OFFSET - KIMAGE_OFFSET)
+#define MODULES_END KIMAGE_VADDR
#define MODULES_VADDR (MODULES_END - SZ_64M)
#define PCI_IO_END (MODULES_VADDR - SZ_2M)
#define PCI_IO_START (PCI_IO_END - PCI_IO_SIZE)
@@ -77,7 +84,11 @@
* private definitions which should NOT be used outside memory.h
* files. Use virt_to_phys/phys_to_virt/__pa/__va instead.
*/
-#define __virt_to_phys(x) (((phys_addr_t)(x) - PAGE_OFFSET + PHYS_OFFSET))
+#define __virt_to_phys(x) ({ \
+ long __x = (long)(x) - PAGE_OFFSET; \
+ __x >= 0 ? (phys_addr_t)(__x + PHYS_OFFSET) : \
+ (phys_addr_t)(__x + PHYS_OFFSET + kernel_va_offset); })
+
#define __phys_to_virt(x) ((unsigned long)((x) - PHYS_OFFSET + PAGE_OFFSET))
/*
@@ -111,7 +122,16 @@
extern phys_addr_t memstart_addr;
/* PHYS_OFFSET - the physical address of the start of memory. */
-#define PHYS_OFFSET ({ memstart_addr; })
+#define PHYS_OFFSET ({ memstart_addr + phys_offset_bias; })
+
+/*
+ * Before the linear mapping has been set up, __va() translations will
+ * not produce usable virtual addresses unless we tweak PHYS_OFFSET to
+ * compensate for the offset between the kernel mapping and the base of
+ * the linear mapping. We will undo this in map_mem().
+ */
+extern u64 phys_offset_bias;
+extern u64 kernel_va_offset;
/*
* PFNs are used to describe any physical page; this means
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index c0ff3ce4299e..3bf1d339dd8d 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -36,8 +36,6 @@
#include <asm/page.h>
#include <asm/virt.h>
-#define __PHYS_OFFSET (KERNEL_START - TEXT_OFFSET)
-
#if (TEXT_OFFSET & 0xfff) != 0
#error TEXT_OFFSET must be at least 4KB aligned
#elif (PAGE_OFFSET & 0x1fffff) != 0
@@ -58,6 +56,8 @@
#define KERNEL_START _text
#define KERNEL_END _end
+#define KERNEL_BASE (KERNEL_START - TEXT_OFFSET)
+
/*
* Initial memory map attributes.
@@ -235,7 +235,7 @@ section_table:
ENTRY(stext)
bl preserve_boot_args
bl el2_setup // Drop to EL1, w20=cpu_boot_mode
- adrp x24, __PHYS_OFFSET
+ adrp x24, KERNEL_BASE
bl set_cpu_boot_mode_flag
bl __create_page_tables // x25=TTBR0, x26=TTBR1
/*
@@ -411,7 +411,7 @@ __create_page_tables:
* Map the kernel image (starting with PHYS_OFFSET).
*/
mov x0, x26 // swapper_pg_dir
- mov x5, #PAGE_OFFSET
+ ldr x5, =KERNEL_BASE
create_pgd_entry x0, x5, x3, x6
ldr x6, =KERNEL_END // __va(KERNEL_END)
mov x3, x24 // phys offset
diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
index 338eaa7bcbfd..8dbb816c0338 100644
--- a/arch/arm64/kernel/vmlinux.lds.S
+++ b/arch/arm64/kernel/vmlinux.lds.S
@@ -6,6 +6,7 @@
#include <asm-generic/vmlinux.lds.h>
#include <asm/thread_info.h>
+#include <asm/boot.h>
#include <asm/memory.h>
#include <asm/page.h>
#include <asm/pgtable.h>
@@ -95,7 +96,7 @@ SECTIONS
*(.discard.*)
}
- . = PAGE_OFFSET + TEXT_OFFSET;
+ . = KIMAGE_VADDR + TEXT_OFFSET;
.head.text : {
_text = .;
@@ -203,4 +204,10 @@ ASSERT(SIZEOF(.pgdir) < ALIGNOF(.pgdir), ".pgdir size exceeds its alignment")
/*
* If padding is applied before .head.text, virt<->phys conversions will fail.
*/
-ASSERT(_text == (PAGE_OFFSET + TEXT_OFFSET), "HEAD is misaligned")
+ASSERT(_text == (KIMAGE_VADDR + TEXT_OFFSET), "HEAD is misaligned")
+
+/*
+ * Make sure the memory footprint of the kernel Image does not exceed the limit.
+ */
+ASSERT(_end - _text + TEXT_OFFSET <= MAX_KIMG_SIZE,
+ "Kernel Image memory footprint exceeds MAX_KIMG_SIZE")
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 93e5a2497f01..b457b7e425cc 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -50,6 +50,9 @@ u64 idmap_t0sz = TCR_T0SZ(VA_BITS);
struct page *empty_zero_page;
EXPORT_SYMBOL(empty_zero_page);
+u64 phys_offset_bias __read_mostly = KIMAGE_OFFSET;
+u64 kernel_va_offset __read_mostly;
+
pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
unsigned long size, pgprot_t vma_prot)
{
@@ -386,6 +389,9 @@ static void __init bootstrap_linear_mapping(unsigned long va_offset)
* Bootstrap the linear range that covers swapper_pg_dir so that the
* statically allocated page tables as well as newly allocated ones
* are accessible via the linear mapping.
+ * Since at this point, PHYS_OFFSET is still biased to redirect __va()
+ * translations into the kernel text mapping, we need to apply an
+ * explicit va_offset to calculate virtual linear addresses.
*/
static struct bootstrap_pgtables linear_bs_pgtables __pgdir;
const phys_addr_t swapper_phys = __pa(swapper_pg_dir);
@@ -441,7 +447,10 @@ static void __init map_mem(void)
{
struct memblock_region *reg;
- bootstrap_linear_mapping(0);
+ bootstrap_linear_mapping(KIMAGE_OFFSET);
+
+ kernel_va_offset = KIMAGE_OFFSET;
+ phys_offset_bias = 0;
/* map all the memory banks */
for_each_memblock(memory, reg) {
--
1.8.3.2
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