[PATCH v2 1/2] arm64/mm: Introduce init_pg_dir
From: Jun Yao
Date: Mon Jun 25 2018 - 07:39:54 EST
We setup initial page tables in init_pg_dir, which is a reserved
area of the __initdata section. And in paging_init(), we no
longer need a temporary top-level and we can setup final page
tables in swapper_pg_dir directly.
Signed-off-by: Jun Yao <yaojun8558363@xxxxxxxxx>
---
arch/arm64/include/asm/fixmap.h | 1 -
arch/arm64/include/asm/pgtable.h | 5 ++--
arch/arm64/kernel/head.S | 46 +++++++++++++++++++++++--------
arch/arm64/kernel/vmlinux.lds.S | 3 +-
arch/arm64/mm/mmu.c | 30 ++++----------------
include/asm-generic/vmlinux.lds.h | 5 ++++
mm/init-mm.c | 2 +-
7 files changed, 49 insertions(+), 43 deletions(-)
diff --git a/arch/arm64/include/asm/fixmap.h b/arch/arm64/include/asm/fixmap.h
index ec1e6d6fa14c..62908eeedcdc 100644
--- a/arch/arm64/include/asm/fixmap.h
+++ b/arch/arm64/include/asm/fixmap.h
@@ -83,7 +83,6 @@ enum fixed_addresses {
FIX_PTE,
FIX_PMD,
FIX_PUD,
- FIX_PGD,
__end_of_fixed_addresses
};
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 7c4c8f318ba9..b2435e8b975b 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -592,9 +592,6 @@ static inline phys_addr_t pgd_page_paddr(pgd_t pgd)
/* to find an entry in a kernel page-table-directory */
#define pgd_offset_k(addr) pgd_offset(&init_mm, addr)
-#define pgd_set_fixmap(addr) ((pgd_t *)set_fixmap_offset(FIX_PGD, addr))
-#define pgd_clear_fixmap() clear_fixmap(FIX_PGD)
-
static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
{
const pteval_t mask = PTE_USER | PTE_PXN | PTE_UXN | PTE_RDONLY |
@@ -718,6 +715,8 @@ static inline pmd_t pmdp_establish(struct vm_area_struct *vma,
}
#endif
+extern pgd_t init_pg_dir[PTRS_PER_PGD];
+extern pgd_t init_pg_end[];
extern pgd_t swapper_pg_dir[PTRS_PER_PGD];
extern pgd_t swapper_pg_end[];
extern pgd_t idmap_pg_dir[PTRS_PER_PGD];
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index b0853069702f..9677deb7b6c7 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -276,6 +276,15 @@ ENDPROC(preserve_boot_args)
populate_entries \tbl, \count, \istart, \iend, \flags, #SWAPPER_BLOCK_SIZE, \tmp
.endm
+ .macro clear_pages, start, size
+1: stp xzr, xzr, [\start], #16
+ stp xzr, xzr, [\start], #16
+ stp xzr, xzr, [\start], #16
+ stp xzr, xzr, [\start], #16
+ subs \size, \size, #64
+ b.ne 1b
+ .endm
+
/*
* Setup the initial page tables. We only setup the barest amount which is
* required to get the kernel running. The following sections are required:
@@ -287,7 +296,7 @@ __create_page_tables:
mov x28, lr
/*
- * Invalidate the idmap and swapper page tables to avoid potential
+ * Invalidate the idmap and init page tables to avoid potential
* dirty cache lines being evicted.
*/
adrp x0, idmap_pg_dir
@@ -295,18 +304,23 @@ __create_page_tables:
sub x1, x1, x0
bl __inval_dcache_area
+ adrp x0, init_pg_dir
+ adrp x1, init_pg_end
+ sub x1, x1, x0
+ bl __inval_dcache_area
+
/*
- * Clear the idmap and swapper page tables.
+ * Clear the idmap and init page tables.
*/
adrp x0, idmap_pg_dir
adrp x1, swapper_pg_end
sub x1, x1, x0
-1: stp xzr, xzr, [x0], #16
- stp xzr, xzr, [x0], #16
- stp xzr, xzr, [x0], #16
- stp xzr, xzr, [x0], #16
- subs x1, x1, #64
- b.ne 1b
+ clear_pages x0, x1
+
+ adrp x0, init_pg_dir
+ adrp x1, init_pg_end
+ sub x1, x1, x0
+ clear_pages x0, x1
mov x7, SWAPPER_MM_MMUFLAGS
@@ -373,7 +387,7 @@ __create_page_tables:
/*
* Map the kernel image (starting with PHYS_OFFSET).
*/
- adrp x0, swapper_pg_dir
+ adrp x0, init_pg_dir
mov_q x5, KIMAGE_VADDR + TEXT_OFFSET // compile time __va(_text)
add x5, x5, x23 // add KASLR displacement
mov x4, PTRS_PER_PGD
@@ -386,7 +400,7 @@ __create_page_tables:
/*
* Since the page tables have been populated with non-cacheable
- * accesses (MMU disabled), invalidate the idmap and swapper page
+ * accesses (MMU disabled), invalidate the idmap and init page
* tables again to remove any speculatively loaded cache lines.
*/
adrp x0, idmap_pg_dir
@@ -395,6 +409,12 @@ __create_page_tables:
dmb sy
bl __inval_dcache_area
+ adrp x0, init_pg_dir
+ adrp x1, init_pg_end
+ sub x1, x1, x0
+ dmb sy
+ bl __inval_dcache_area
+
ret x28
ENDPROC(__create_page_tables)
.ltorg
@@ -706,6 +726,7 @@ secondary_startup:
* Common entry point for secondary CPUs.
*/
bl __cpu_setup // initialise processor
+ adr_l x26, swapper_pg_dir
bl __enable_mmu
ldr x8, =__secondary_switched
br x8
@@ -748,6 +769,7 @@ ENDPROC(__secondary_switched)
* Enable the MMU.
*
* x0 = SCTLR_EL1 value for turning on the MMU.
+ * x26 = TTBR1_EL1 value for turning on the MMU.
*
* Returns to the caller via x30/lr. This requires the caller to be covered
* by the .idmap.text section.
@@ -762,7 +784,7 @@ ENTRY(__enable_mmu)
b.ne __no_granule_support
update_early_cpu_boot_status 0, x1, x2
adrp x1, idmap_pg_dir
- adrp x2, swapper_pg_dir
+ mov x2, x26
phys_to_ttbr x3, x1
phys_to_ttbr x4, x2
msr ttbr0_el1, x3 // load TTBR0
@@ -822,7 +844,7 @@ __primary_switch:
mov x19, x0 // preserve new SCTLR_EL1 value
mrs x20, sctlr_el1 // preserve old SCTLR_EL1 value
#endif
-
+ adrp x26, init_pg_dir
bl __enable_mmu
#ifdef CONFIG_RELOCATABLE
bl __relocate_kernel
diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
index 605d1b60469c..b0e4255fcba4 100644
--- a/arch/arm64/kernel/vmlinux.lds.S
+++ b/arch/arm64/kernel/vmlinux.lds.S
@@ -168,6 +168,7 @@ SECTIONS
CON_INITCALL
SECURITY_INITCALL
INIT_RAM_FS
+ INIT_DIR
*(.init.rodata.* .init.bss) /* from the EFI stub */
}
.exit.data : {
@@ -229,7 +230,7 @@ SECTIONS
. += RESERVED_TTBR0_SIZE;
#endif
swapper_pg_dir = .;
- . += SWAPPER_DIR_SIZE;
+ . += PAGE_SIZE;
swapper_pg_end = .;
__pecoff_data_size = ABSOLUTE(. - __initdata_begin);
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 2dbb2c9f1ec1..a3b5f1dffb84 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -628,34 +628,14 @@ static void __init map_kernel(pgd_t *pgdp)
*/
void __init paging_init(void)
{
- phys_addr_t pgd_phys = early_pgtable_alloc();
- pgd_t *pgdp = pgd_set_fixmap(pgd_phys);
-
- map_kernel(pgdp);
- map_mem(pgdp);
-
/*
- * We want to reuse the original swapper_pg_dir so we don't have to
- * communicate the new address to non-coherent secondaries in
- * secondary_entry, and so cpu_switch_mm can generate the address with
- * adrp+add rather than a load from some global variable.
- *
- * To do this we need to go via a temporary pgd.
+ * Setup final page tables in swapper_pg_dir.
*/
- cpu_replace_ttbr1(__va(pgd_phys));
- memcpy(swapper_pg_dir, pgdp, PGD_SIZE);
- cpu_replace_ttbr1(lm_alias(swapper_pg_dir));
+ map_kernel(swapper_pg_dir);
+ map_mem(swapper_pg_dir);
- pgd_clear_fixmap();
- memblock_free(pgd_phys, PAGE_SIZE);
-
- /*
- * We only reuse the PGD from the swapper_pg_dir, not the pud + pmd
- * allocated with it.
- */
- memblock_free(__pa_symbol(swapper_pg_dir) + PAGE_SIZE,
- __pa_symbol(swapper_pg_end) - __pa_symbol(swapper_pg_dir)
- - PAGE_SIZE);
+ cpu_replace_ttbr1(lm_alias(swapper_pg_dir));
+ init_mm.pgd = swapper_pg_dir;
}
/*
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index af240573e482..a11e7117da4d 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -230,6 +230,11 @@
KEEP(*(.dtb.init.rodata)) \
VMLINUX_SYMBOL(__dtb_end) = .;
+#define INIT_DIR \
+ . = ALIGN(PAGE_SIZE); \
+ init_pg_dir = .; \
+ . += SWAPPER_DIR_SIZE; \
+ init_pg_end = .;
/*
* .data section
*/
diff --git a/mm/init-mm.c b/mm/init-mm.c
index f94d5d15ebc0..08a0eed00667 100644
--- a/mm/init-mm.c
+++ b/mm/init-mm.c
@@ -17,7 +17,7 @@
struct mm_struct init_mm = {
.mm_rb = RB_ROOT,
- .pgd = swapper_pg_dir,
+ .pgd = init_pg_dir,
.mm_users = ATOMIC_INIT(2),
.mm_count = ATOMIC_INIT(1),
.mmap_sem = __RWSEM_INITIALIZER(init_mm.mmap_sem),
--
2.17.1