This moves the vmemmap region right below PAGE_OFFSET, aka the start
of the linear region, and redefines its size to be a power of two.
Due to the placement of PAGE_OFFSET in the middle of the address space,
whose size is a power of two as well, this guarantees that virt to
page conversions and vice versa can be implemented efficiently, by
masking and shifting rather than ordinary arithmetic.
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
---
arch/arm64/include/asm/memory.h | 18 +++++++++++++++++-
arch/arm64/include/asm/pgtable.h | 11 +++--------
arch/arm64/mm/dump.c | 16 ++++++++--------
arch/arm64/mm/init.c | 14 ++++++++++----
4 files changed, 38 insertions(+), 21 deletions(-)
diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index 12f8a00fb3f1..8a2ab195ca77 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -40,6 +40,21 @@
#define PCI_IO_SIZE SZ_16M
/*
+ * Log2 of the upper bound of the size of a struct page. Used for sizing
+ * the vmemmap region only, does not affect actual memory footprint.
+ * We don't use sizeof(struct page) directly since taking its size here
+ * requires its definition to be available at this point in the inclusion
+ * chain, and it may not be a power of 2 in the first place.
+ */
+#define STRUCT_PAGE_MAX_SHIFT 6
+
+/*
+ * VMEMMAP_SIZE - allows the whole linear region to be covered by
+ * a struct page array
+ */
+#define VMEMMAP_SIZE (UL(1) << (VA_BITS - PAGE_SHIFT - 1 + STRUCT_PAGE_MAX_SHIFT))
+
+/*
* PAGE_OFFSET - the virtual address of the start of the kernel image (top
* (VA_BITS - 1))
* VA_BITS - the maximum number of bits for virtual addresses.
@@ -54,7 +69,8 @@
#define MODULES_END (MODULES_VADDR + MODULES_VSIZE)
#define MODULES_VADDR (VA_START + KASAN_SHADOW_SIZE)
#define MODULES_VSIZE (SZ_128M)
-#define PCI_IO_END (PAGE_OFFSET - SZ_2M)
+#define VMEMMAP_START (PAGE_OFFSET - VMEMMAP_SIZE)
+#define PCI_IO_END (VMEMMAP_START - SZ_2M)
#define PCI_IO_START (PCI_IO_END - PCI_IO_SIZE)
#define FIXADDR_TOP (PCI_IO_START - SZ_2M)
#define TASK_SIZE_64 (UL(1) << VA_BITS)
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 377257a8d393..2abfa4d09e65 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -24,20 +24,15 @@
#include <asm/pgtable-prot.h>
/*
- * VMALLOC and SPARSEMEM_VMEMMAP ranges.
+ * VMALLOC range.
*
- * VMEMAP_SIZE: allows the whole linear region to be covered by a struct page array
- * (rounded up to PUD_SIZE).
* VMALLOC_START: beginning of the kernel vmalloc space
- * VMALLOC_END: extends to the available space below vmmemmap, PCI I/O space,
- * fixed mappings and modules
+ * VMALLOC_END: extends to the available space below vmmemmap, PCI I/O space
+ * and fixed mappings
*/
-#define VMEMMAP_SIZE ALIGN((1UL << (VA_BITS - PAGE_SHIFT - 1)) * sizeof(struct page), PUD_SIZE)
-
#define VMALLOC_START (MODULES_END)
#define VMALLOC_END (PAGE_OFFSET - PUD_SIZE - VMEMMAP_SIZE - SZ_64K)
-#define VMEMMAP_START (VMALLOC_END + SZ_64K)
#define vmemmap ((struct page *)VMEMMAP_START - (memstart_addr >> PAGE_SHIFT))
#define FIRST_USER_ADDRESS 0UL
diff --git a/arch/arm64/mm/dump.c b/arch/arm64/mm/dump.c
index f9271cb2f5e3..a21f47421b0c 100644
--- a/arch/arm64/mm/dump.c
+++ b/arch/arm64/mm/dump.c
@@ -37,14 +37,14 @@ enum address_markers_idx {
MODULES_END_NR,
VMALLOC_START_NR,
VMALLOC_END_NR,
-#ifdef CONFIG_SPARSEMEM_VMEMMAP
- VMEMMAP_START_NR,
- VMEMMAP_END_NR,
-#endif
FIXADDR_START_NR,
FIXADDR_END_NR,
PCI_START_NR,
PCI_END_NR,
+#ifdef CONFIG_SPARSEMEM_VMEMMAP
+ VMEMMAP_START_NR,
+ VMEMMAP_END_NR,
+#endif
KERNEL_SPACE_NR,
};
@@ -53,14 +53,14 @@ static struct addr_marker address_markers[] = {
{ MODULES_END, "Modules end" },
{ VMALLOC_START, "vmalloc() Area" },
{ VMALLOC_END, "vmalloc() End" },
-#ifdef CONFIG_SPARSEMEM_VMEMMAP
- { 0, "vmemmap start" },
- { 0, "vmemmap end" },
-#endif
{ FIXADDR_START, "Fixmap start" },
{ FIXADDR_TOP, "Fixmap end" },
{ PCI_IO_START, "PCI I/O start" },
{ PCI_IO_END, "PCI I/O end" },
+#ifdef CONFIG_SPARSEMEM_VMEMMAP
+ { 0, "vmemmap start" },
+ { 0, "vmemmap end" },
+#endif
{ PAGE_OFFSET, "Linear Mapping" },
{ -1, NULL },
};
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 89376f3c65a3..d55d720dba79 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -412,6 +412,10 @@ void __init mem_init(void)
MLK_ROUNDUP(__start_rodata, _etext),
MLK_ROUNDUP(__init_begin, __init_end),
MLK_ROUNDUP(_sdata, _edata));
+ pr_cont(" fixed : 0x%16lx - 0x%16lx (%6ld KB)\n",
+ MLK(FIXADDR_START, FIXADDR_TOP));
+ pr_cont(" PCI I/O : 0x%16lx - 0x%16lx (%6ld MB)\n",
+ MLM(PCI_IO_START, PCI_IO_END));
#ifdef CONFIG_SPARSEMEM_VMEMMAP
pr_cont(" vmemmap : 0x%16lx - 0x%16lx (%6ld GB maximum)\n"
" 0x%16lx - 0x%16lx (%6ld MB actual)\n",
@@ -420,10 +424,6 @@ void __init mem_init(void)
MLM((unsigned long)phys_to_page(memblock_start_of_DRAM()),
(unsigned long)virt_to_page(high_memory)));
#endif
- pr_cont(" fixed : 0x%16lx - 0x%16lx (%6ld KB)\n",
- MLK(FIXADDR_START, FIXADDR_TOP));
- pr_cont(" PCI I/O : 0x%16lx - 0x%16lx (%6ld MB)\n",
- MLM(PCI_IO_START, PCI_IO_END));
pr_cont(" memory : 0x%16lx - 0x%16lx (%6ld MB)\n",
MLM(__phys_to_virt(memblock_start_of_DRAM()),
(unsigned long)high_memory));
@@ -440,6 +440,12 @@ void __init mem_init(void)
BUILD_BUG_ON(TASK_SIZE_32 > TASK_SIZE_64);
#endif
+ /*
+ * Make sure we chose the upper bound of sizeof(struct page)
+ * correctly.
+ */
+ BUILD_BUG_ON(sizeof(struct page) > (1 << STRUCT_PAGE_MAX_SHIFT));
+
if (PAGE_SIZE >= 16384 && get_num_physpages() <= 128) {
extern int sysctl_overcommit_memory;
/*
--
2.5.0
--
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