* [PATCH v4 1/3] arm64: mm: BUG on unsupported manipulations of live kernel mappings
2016-10-21 11:22 [PATCH v4 0/3] arm64/mm: use the contiguous attribute for kernel mappings Ard Biesheuvel
@ 2016-10-21 11:22 ` Ard Biesheuvel
2016-10-21 11:22 ` [PATCH v4 2/3] arm64: mm: replace 'block_mappings_allowed' with 'page_mappings_only' Ard Biesheuvel
` (2 subsequent siblings)
3 siblings, 0 replies; 5+ messages in thread
From: Ard Biesheuvel @ 2016-10-21 11:22 UTC (permalink / raw)
To: linux-arm-kernel
Now that we take care not manipulate the live kernel page tables in a
way that may lead to TLB conflicts, the case where a table mapping is
replaced by a block mapping can no longer occur. So remove the handling
of this at the PUD and PMD levels, and instead, BUG() on any occurrence
of live kernel page table manipulations that modify anything other than
the permission bits.
Since mark_rodata_ro() is the only caller where the kernel mappings that
are being manipulated are actually live, drop the various conditional
flush_tlb_all() invocations, and add a single call to mark_rodata_ro()
instead.
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
arch/arm64/mm/mmu.c | 70 ++++++++++++--------
1 file changed, 43 insertions(+), 27 deletions(-)
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 05615a3fdc6f..27dc0e5012a8 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -28,8 +28,6 @@
#include <linux/memblock.h>
#include <linux/fs.h>
#include <linux/io.h>
-#include <linux/slab.h>
-#include <linux/stop_machine.h>
#include <asm/barrier.h>
#include <asm/cputype.h>
@@ -95,6 +93,17 @@ static phys_addr_t __init early_pgtable_alloc(void)
return phys;
}
+static bool pgattr_change_is_safe(u64 old, u64 new)
+{
+ /*
+ * The following mapping attributes may be updated in live
+ * kernel mappings without the need for break-before-make.
+ */
+ static const pteval_t mask = PTE_PXN | PTE_RDONLY | PTE_WRITE;
+
+ return old == 0 || new == 0 || ((old ^ new) & ~mask) == 0;
+}
+
static void alloc_init_pte(pmd_t *pmd, unsigned long addr,
unsigned long end, unsigned long pfn,
pgprot_t prot,
@@ -115,8 +124,17 @@ static void alloc_init_pte(pmd_t *pmd, unsigned long addr,
pte = pte_set_fixmap_offset(pmd, addr);
do {
+ pte_t old_pte = *pte;
+
set_pte(pte, pfn_pte(pfn, prot));
pfn++;
+
+ /*
+ * After the PTE entry has been populated once, we
+ * only allow updates to the permission attributes.
+ */
+ BUG_ON(!pgattr_change_is_safe(pte_val(old_pte), pte_val(*pte)));
+
} while (pte++, addr += PAGE_SIZE, addr != end);
pte_clear_fixmap();
@@ -146,27 +164,27 @@ static void alloc_init_pmd(pud_t *pud, unsigned long addr, unsigned long end,
pmd = pmd_set_fixmap_offset(pud, addr);
do {
+ pmd_t old_pmd = *pmd;
+
next = pmd_addr_end(addr, end);
+
/* try section mapping first */
if (((addr | next | phys) & ~SECTION_MASK) == 0 &&
allow_block_mappings) {
- pmd_t old_pmd =*pmd;
pmd_set_huge(pmd, phys, prot);
+
/*
- * Check for previous table entries created during
- * boot (__create_page_tables) and flush them.
+ * After the PMD entry has been populated once, we
+ * only allow updates to the permission attributes.
*/
- if (!pmd_none(old_pmd)) {
- flush_tlb_all();
- if (pmd_table(old_pmd)) {
- phys_addr_t table = pmd_page_paddr(old_pmd);
- if (!WARN_ON_ONCE(slab_is_available()))
- memblock_free(table, PAGE_SIZE);
- }
- }
+ BUG_ON(!pgattr_change_is_safe(pmd_val(old_pmd),
+ pmd_val(*pmd)));
} else {
alloc_init_pte(pmd, addr, next, __phys_to_pfn(phys),
prot, pgtable_alloc);
+
+ BUG_ON(pmd_val(old_pmd) != 0 &&
+ pmd_val(old_pmd) != pmd_val(*pmd));
}
phys += next - addr;
} while (pmd++, addr = next, addr != end);
@@ -204,33 +222,28 @@ static void alloc_init_pud(pgd_t *pgd, unsigned long addr, unsigned long end,
pud = pud_set_fixmap_offset(pgd, addr);
do {
+ pud_t old_pud = *pud;
+
next = pud_addr_end(addr, end);
/*
* For 4K granule only, attempt to put down a 1GB block
*/
if (use_1G_block(addr, next, phys) && allow_block_mappings) {
- pud_t old_pud = *pud;
pud_set_huge(pud, phys, prot);
/*
- * If we have an old value for a pud, it will
- * be pointing to a pmd table that we no longer
- * need (from swapper_pg_dir).
- *
- * Look up the old pmd table and free it.
+ * After the PUD entry has been populated once, we
+ * only allow updates to the permission attributes.
*/
- if (!pud_none(old_pud)) {
- flush_tlb_all();
- if (pud_table(old_pud)) {
- phys_addr_t table = pud_page_paddr(old_pud);
- if (!WARN_ON_ONCE(slab_is_available()))
- memblock_free(table, PAGE_SIZE);
- }
- }
+ BUG_ON(!pgattr_change_is_safe(pud_val(old_pud),
+ pud_val(*pud)));
} else {
alloc_init_pmd(pud, addr, next, phys, prot,
pgtable_alloc, allow_block_mappings);
+
+ BUG_ON(pud_val(old_pud) != 0 &&
+ pud_val(old_pud) != pud_val(*pud));
}
phys += next - addr;
} while (pud++, addr = next, addr != end);
@@ -396,6 +409,9 @@ void mark_rodata_ro(void)
section_size = (unsigned long)__init_begin - (unsigned long)__start_rodata;
create_mapping_late(__pa(__start_rodata), (unsigned long)__start_rodata,
section_size, PAGE_KERNEL_RO);
+
+ /* flush the TLBs after updating live kernel mappings */
+ flush_tlb_all();
}
static void __init map_kernel_segment(pgd_t *pgd, void *va_start, void *va_end,
--
2.7.4
^ permalink raw reply related [flat|nested] 5+ messages in thread* [PATCH v4 2/3] arm64: mm: replace 'block_mappings_allowed' with 'page_mappings_only'
2016-10-21 11:22 [PATCH v4 0/3] arm64/mm: use the contiguous attribute for kernel mappings Ard Biesheuvel
2016-10-21 11:22 ` [PATCH v4 1/3] arm64: mm: BUG on unsupported manipulations of live " Ard Biesheuvel
@ 2016-10-21 11:22 ` Ard Biesheuvel
2016-10-21 11:22 ` [PATCH v4 3/3] arm64: mm: set the contiguous bit for kernel mappings where appropriate Ard Biesheuvel
2016-10-30 14:47 ` [PATCH v4 0/3] arm64/mm: use the contiguous attribute for kernel mappings Catalin Marinas
3 siblings, 0 replies; 5+ messages in thread
From: Ard Biesheuvel @ 2016-10-21 11:22 UTC (permalink / raw)
To: linux-arm-kernel
In preparation of adding support for contiguous PTE and PMD mappings,
let's replace 'block_mappings_allowed' with 'page_mappings_only', which
will be a more accurate description of the nature of the setting once we
add such contiguous mappings into the mix.
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
arch/arm64/include/asm/mmu.h | 2 +-
arch/arm64/kernel/efi.c | 8 ++---
arch/arm64/mm/mmu.c | 32 ++++++++++----------
3 files changed, 21 insertions(+), 21 deletions(-)
diff --git a/arch/arm64/include/asm/mmu.h b/arch/arm64/include/asm/mmu.h
index 8d9fce037b2f..a81454ad5455 100644
--- a/arch/arm64/include/asm/mmu.h
+++ b/arch/arm64/include/asm/mmu.h
@@ -34,7 +34,7 @@ extern void __iomem *early_io_map(phys_addr_t phys, unsigned long virt);
extern void init_mem_pgprot(void);
extern void create_pgd_mapping(struct mm_struct *mm, phys_addr_t phys,
unsigned long virt, phys_addr_t size,
- pgprot_t prot, bool allow_block_mappings);
+ pgprot_t prot, bool page_mappings_only);
extern void *fixmap_remap_fdt(phys_addr_t dt_phys);
#endif
diff --git a/arch/arm64/kernel/efi.c b/arch/arm64/kernel/efi.c
index ba9bee389fd5..5d17f377d905 100644
--- a/arch/arm64/kernel/efi.c
+++ b/arch/arm64/kernel/efi.c
@@ -62,8 +62,8 @@ struct screen_info screen_info __section(.data);
int __init efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md)
{
pteval_t prot_val = create_mapping_protection(md);
- bool allow_block_mappings = (md->type != EFI_RUNTIME_SERVICES_CODE &&
- md->type != EFI_RUNTIME_SERVICES_DATA);
+ bool page_mappings_only = (md->type == EFI_RUNTIME_SERVICES_CODE ||
+ md->type == EFI_RUNTIME_SERVICES_DATA);
if (!PAGE_ALIGNED(md->phys_addr) ||
!PAGE_ALIGNED(md->num_pages << EFI_PAGE_SHIFT)) {
@@ -76,12 +76,12 @@ int __init efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md)
* from the MMU routines. So avoid block mappings altogether in
* that case.
*/
- allow_block_mappings = false;
+ page_mappings_only = true;
}
create_pgd_mapping(mm, md->phys_addr, md->virt_addr,
md->num_pages << EFI_PAGE_SHIFT,
- __pgprot(prot_val | PTE_NG), allow_block_mappings);
+ __pgprot(prot_val | PTE_NG), page_mappings_only);
return 0;
}
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 27dc0e5012a8..7b0dd07212ae 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -143,7 +143,7 @@ static void alloc_init_pte(pmd_t *pmd, unsigned long addr,
static void alloc_init_pmd(pud_t *pud, unsigned long addr, unsigned long end,
phys_addr_t phys, pgprot_t prot,
phys_addr_t (*pgtable_alloc)(void),
- bool allow_block_mappings)
+ bool page_mappings_only)
{
pmd_t *pmd;
unsigned long next;
@@ -170,7 +170,7 @@ static void alloc_init_pmd(pud_t *pud, unsigned long addr, unsigned long end,
/* try section mapping first */
if (((addr | next | phys) & ~SECTION_MASK) == 0 &&
- allow_block_mappings) {
+ !page_mappings_only) {
pmd_set_huge(pmd, phys, prot);
/*
@@ -207,7 +207,7 @@ static inline bool use_1G_block(unsigned long addr, unsigned long next,
static void alloc_init_pud(pgd_t *pgd, unsigned long addr, unsigned long end,
phys_addr_t phys, pgprot_t prot,
phys_addr_t (*pgtable_alloc)(void),
- bool allow_block_mappings)
+ bool page_mappings_only)
{
pud_t *pud;
unsigned long next;
@@ -229,7 +229,7 @@ static void alloc_init_pud(pgd_t *pgd, unsigned long addr, unsigned long end,
/*
* For 4K granule only, attempt to put down a 1GB block
*/
- if (use_1G_block(addr, next, phys) && allow_block_mappings) {
+ if (use_1G_block(addr, next, phys) && !page_mappings_only) {
pud_set_huge(pud, phys, prot);
/*
@@ -240,7 +240,7 @@ static void alloc_init_pud(pgd_t *pgd, unsigned long addr, unsigned long end,
pud_val(*pud)));
} else {
alloc_init_pmd(pud, addr, next, phys, prot,
- pgtable_alloc, allow_block_mappings);
+ pgtable_alloc, page_mappings_only);
BUG_ON(pud_val(old_pud) != 0 &&
pud_val(old_pud) != pud_val(*pud));
@@ -255,7 +255,7 @@ static void __create_pgd_mapping(pgd_t *pgdir, phys_addr_t phys,
unsigned long virt, phys_addr_t size,
pgprot_t prot,
phys_addr_t (*pgtable_alloc)(void),
- bool allow_block_mappings)
+ bool page_mappings_only)
{
unsigned long addr, length, end, next;
pgd_t *pgd = pgd_offset_raw(pgdir, virt);
@@ -275,7 +275,7 @@ static void __create_pgd_mapping(pgd_t *pgdir, phys_addr_t phys,
do {
next = pgd_addr_end(addr, end);
alloc_init_pud(pgd, addr, next, phys, prot, pgtable_alloc,
- allow_block_mappings);
+ page_mappings_only);
phys += next - addr;
} while (pgd++, addr = next, addr != end);
}
@@ -304,17 +304,17 @@ static void __init create_mapping_noalloc(phys_addr_t phys, unsigned long virt,
&phys, virt);
return;
}
- __create_pgd_mapping(init_mm.pgd, phys, virt, size, prot, NULL, true);
+ __create_pgd_mapping(init_mm.pgd, phys, virt, size, prot, NULL, false);
}
void __init create_pgd_mapping(struct mm_struct *mm, phys_addr_t phys,
unsigned long virt, phys_addr_t size,
- pgprot_t prot, bool allow_block_mappings)
+ pgprot_t prot, bool page_mappings_only)
{
BUG_ON(mm == &init_mm);
__create_pgd_mapping(mm->pgd, phys, virt, size, prot,
- pgd_pgtable_alloc, allow_block_mappings);
+ pgd_pgtable_alloc, page_mappings_only);
}
static void create_mapping_late(phys_addr_t phys, unsigned long virt,
@@ -327,7 +327,7 @@ static void create_mapping_late(phys_addr_t phys, unsigned long virt,
}
__create_pgd_mapping(init_mm.pgd, phys, virt, size, prot,
- NULL, !debug_pagealloc_enabled());
+ NULL, debug_pagealloc_enabled());
}
static void __init __map_memblock(pgd_t *pgd, phys_addr_t start, phys_addr_t end)
@@ -345,7 +345,7 @@ static void __init __map_memblock(pgd_t *pgd, phys_addr_t start, phys_addr_t end
__create_pgd_mapping(pgd, start, __phys_to_virt(start),
end - start, PAGE_KERNEL,
early_pgtable_alloc,
- !debug_pagealloc_enabled());
+ debug_pagealloc_enabled());
return;
}
@@ -358,13 +358,13 @@ static void __init __map_memblock(pgd_t *pgd, phys_addr_t start, phys_addr_t end
__phys_to_virt(start),
kernel_start - start, PAGE_KERNEL,
early_pgtable_alloc,
- !debug_pagealloc_enabled());
+ debug_pagealloc_enabled());
if (kernel_end < end)
__create_pgd_mapping(pgd, kernel_end,
__phys_to_virt(kernel_end),
end - kernel_end, PAGE_KERNEL,
early_pgtable_alloc,
- !debug_pagealloc_enabled());
+ debug_pagealloc_enabled());
/*
* Map the linear alias of the [_text, __init_begin) interval as
@@ -374,7 +374,7 @@ static void __init __map_memblock(pgd_t *pgd, phys_addr_t start, phys_addr_t end
*/
__create_pgd_mapping(pgd, kernel_start, __phys_to_virt(kernel_start),
kernel_end - kernel_start, PAGE_KERNEL_RO,
- early_pgtable_alloc, !debug_pagealloc_enabled());
+ early_pgtable_alloc, debug_pagealloc_enabled());
}
static void __init map_mem(pgd_t *pgd)
@@ -424,7 +424,7 @@ static void __init map_kernel_segment(pgd_t *pgd, void *va_start, void *va_end,
BUG_ON(!PAGE_ALIGNED(size));
__create_pgd_mapping(pgd, pa_start, (unsigned long)va_start, size, prot,
- early_pgtable_alloc, !debug_pagealloc_enabled());
+ early_pgtable_alloc, debug_pagealloc_enabled());
vma->addr = va_start;
vma->phys_addr = pa_start;
--
2.7.4
^ permalink raw reply related [flat|nested] 5+ messages in thread* [PATCH v4 3/3] arm64: mm: set the contiguous bit for kernel mappings where appropriate
2016-10-21 11:22 [PATCH v4 0/3] arm64/mm: use the contiguous attribute for kernel mappings Ard Biesheuvel
2016-10-21 11:22 ` [PATCH v4 1/3] arm64: mm: BUG on unsupported manipulations of live " Ard Biesheuvel
2016-10-21 11:22 ` [PATCH v4 2/3] arm64: mm: replace 'block_mappings_allowed' with 'page_mappings_only' Ard Biesheuvel
@ 2016-10-21 11:22 ` Ard Biesheuvel
2016-10-30 14:47 ` [PATCH v4 0/3] arm64/mm: use the contiguous attribute for kernel mappings Catalin Marinas
3 siblings, 0 replies; 5+ messages in thread
From: Ard Biesheuvel @ 2016-10-21 11:22 UTC (permalink / raw)
To: linux-arm-kernel
Now that we no longer allow live kernel PMDs to be split, it is safe to
start using the contiguous bit for kernel mappings. So set the contiguous
bit in the kernel page mappings for regions whose size and alignment are
suitable for this.
This enables the following contiguous range sizes for the virtual mapping
of the kernel image, and for the linear mapping:
granule size | cont PTE | cont PMD |
-------------+------------+------------+
4 KB | 64 KB | 32 MB |
16 KB | 2 MB | 1 GB* |
64 KB | 2 MB | 16 GB* |
* Only when built for 3 or more levels of translation. This is due to the
fact that a 2 level configuration only consists of PGDs and PTEs, and the
added complexity of dealing with folded PMDs is not justified considering
that 16 GB contiguous ranges are likely to be ignored by the hardware (and
16k/2 levels is a niche configuration)
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
arch/arm64/mm/mmu.c | 34 +++++++++++++++++---
1 file changed, 30 insertions(+), 4 deletions(-)
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 7b0dd07212ae..dd5f12d0959e 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -107,8 +107,10 @@ static bool pgattr_change_is_safe(u64 old, u64 new)
static void alloc_init_pte(pmd_t *pmd, unsigned long addr,
unsigned long end, unsigned long pfn,
pgprot_t prot,
- phys_addr_t (*pgtable_alloc)(void))
+ phys_addr_t (*pgtable_alloc)(void),
+ bool page_mappings_only)
{
+ pgprot_t __prot = prot;
pte_t *pte;
BUG_ON(pmd_sect(*pmd));
@@ -126,7 +128,18 @@ static void alloc_init_pte(pmd_t *pmd, unsigned long addr,
do {
pte_t old_pte = *pte;
- set_pte(pte, pfn_pte(pfn, prot));
+ /*
+ * Set the contiguous bit for the subsequent group of PTEs if
+ * its size and alignment are appropriate.
+ */
+ if (((addr | PFN_PHYS(pfn)) & ~CONT_PTE_MASK) == 0) {
+ if (end - addr >= CONT_PTE_SIZE && !page_mappings_only)
+ __prot = __pgprot(pgprot_val(prot) | PTE_CONT);
+ else
+ __prot = prot;
+ }
+
+ set_pte(pte, pfn_pte(pfn, __prot));
pfn++;
/*
@@ -145,6 +158,7 @@ static void alloc_init_pmd(pud_t *pud, unsigned long addr, unsigned long end,
phys_addr_t (*pgtable_alloc)(void),
bool page_mappings_only)
{
+ pgprot_t __prot = prot;
pmd_t *pmd;
unsigned long next;
@@ -171,7 +185,18 @@ static void alloc_init_pmd(pud_t *pud, unsigned long addr, unsigned long end,
/* try section mapping first */
if (((addr | next | phys) & ~SECTION_MASK) == 0 &&
!page_mappings_only) {
- pmd_set_huge(pmd, phys, prot);
+ /*
+ * Set the contiguous bit for the subsequent group of
+ * PMDs if its size and alignment are appropriate.
+ */
+ if (((addr | phys) & ~CONT_PMD_MASK) == 0) {
+ if (end - addr >= CONT_PMD_SIZE)
+ __prot = __pgprot(pgprot_val(prot) |
+ PTE_CONT);
+ else
+ __prot = prot;
+ }
+ pmd_set_huge(pmd, phys, __prot);
/*
* After the PMD entry has been populated once, we
@@ -181,7 +206,8 @@ static void alloc_init_pmd(pud_t *pud, unsigned long addr, unsigned long end,
pmd_val(*pmd)));
} else {
alloc_init_pte(pmd, addr, next, __phys_to_pfn(phys),
- prot, pgtable_alloc);
+ prot, pgtable_alloc,
+ page_mappings_only);
BUG_ON(pmd_val(old_pmd) != 0 &&
pmd_val(old_pmd) != pmd_val(*pmd));
--
2.7.4
^ permalink raw reply related [flat|nested] 5+ messages in thread