[PATCH v3 05/60] arm64: mm: Move fixmap region above vmemmap region

Ard Biesheuvel
2023-03-07T14:07:22Z

Move the fixmap region above the vmemmap region, so that the start of
the vmemmap delineates the end of the region available for vmalloc and
vmap allocations and the randomized placement of the kernel and modules.

In a subsequent patch, we will take advantage of this to reclaim most of
the vmemmap area when running a 52-bit VA capable build with 52-bit
virtual addressing disabled at runtime.

Note that the existing guard region of 256 MiB covers the fixmap and PCI
I/O regions as well, so we can reduce it 8 MiB, which is what we use in
other places too.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
arch/arm64/include/asm/memory.h | 2 +-
arch/arm64/include/asm/pgtable.h | 2 +-
arch/arm64/mm/ptdump.c | 4 ++--
3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index 6e321cc06a3c30f0..9b9e52d823beccc6 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -51,7 +51,7 @@
#define VMEMMAP_END (VMEMMAP_START + VMEMMAP_SIZE)
#define PCI_IO_START (VMEMMAP_END + SZ_8M)
#define PCI_IO_END (PCI_IO_START + PCI_IO_SIZE)
-#define FIXADDR_TOP (VMEMMAP_START - SZ_32M)
+#define FIXADDR_TOP (ULONG_MAX - SZ_8M + 1)

#if VA_BITS > 48
#define VA_BITS_MIN (48)
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index b6ba466e2e8a3fc7..3eff06c5d0eb73c7 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -22,7 +22,7 @@
* and fixed mappings
*/
#define VMALLOC_START (MODULES_END)
-#define VMALLOC_END (VMEMMAP_START - SZ_256M)
+#define VMALLOC_END (VMEMMAP_START - SZ_8M)

#define vmemmap ((struct page *)VMEMMAP_START - (memstart_addr >> PAGE_SHIFT))

diff --git a/arch/arm64/mm/ptdump.c b/arch/arm64/mm/ptdump.c
index 9d1f4cdc6672ed5f..76d28056bd14920a 100644
--- a/arch/arm64/mm/ptdump.c
+++ b/arch/arm64/mm/ptdump.c
@@ -45,12 +45,12 @@ static struct addr_marker address_markers[] = {
{ MODULES_END, "Modules end" },
{ VMALLOC_START, "vmalloc() area" },
{ VMALLOC_END, "vmalloc() end" },
- { FIXADDR_START, "Fixmap start" },
- { FIXADDR_TOP, "Fixmap end" },
{ VMEMMAP_START, "vmemmap start" },
{ VMEMMAP_START + VMEMMAP_SIZE, "vmemmap end" },
{ PCI_IO_START, "PCI I/O start" },
{ PCI_IO_END, "PCI I/O end" },
+ { FIXADDR_START, "Fixmap start" },
+ { FIXADDR_TOP, "Fixmap end" },
{ -1, NULL },
};

--
2.39.2