From: Alexei Starovoitov <ast@xxxxxxxxxx>
vmap/vmalloc APIs are used to map a set of pages into contiguous kernel virtual space.
get_vm_area() with appropriate flag is used to request an area of kernel address range.
It'se used for vmalloc, vmap, ioremap, xen use cases.
- vmalloc use case dominates the usage. Such vm areas have VM_ALLOC flag.
- the areas created by vmap() function should be tagged with VM_MAP.
- ioremap areas are tagged with VM_IOREMAP.
- xen use cases are VM_XEN.
BPF would like to extend the vmap API to implement a lazily-populated
sparse, yet contiguous kernel virtual space.
Introduce VM_SPARSE vm_area flag and
vm_area_map_pages(area, start_addr, count, pages) API to map a set
of pages within a given area.
It has the same sanity checks as vmap() does.
It also checks that get_vm_area() was created with VM_SPARSE flag
which identifies such areas in /proc/vmallocinfo
and returns zero pages on read through /proc/kcore.
The next commits will introduce bpf_arena which is a sparsely populated shared
memory region between bpf program and user space process. It will map
privately-managed pages into a sparse vm area with the following steps:
area = get_vm_area(area_size, VM_SPARSE); // at bpf prog verification time
vm_area_map_pages(area, kaddr, 1, page); // on demand
// it will return an error if kaddr is out of range
vm_area_unmap_pages(area, kaddr, 1);
free_vm_area(area); // after bpf prog is unloaded
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
---
include/linux/vmalloc.h | 4 +++
mm/vmalloc.c | 55 +++++++++++++++++++++++++++++++++++++++--
2 files changed, 57 insertions(+), 2 deletions(-)
diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
index 223e51c243bc..416bc7b0b4db 100644
--- a/include/linux/vmalloc.h
+++ b/include/linux/vmalloc.h
@@ -29,6 +29,7 @@ struct iov_iter; /* in uio.h */
#define VM_MAP_PUT_PAGES 0x00000200 /* put pages and free array in vfree */
#define VM_ALLOW_HUGE_VMAP 0x00000400 /* Allow for huge pages on archs with HAVE_ARCH_HUGE_VMALLOC */
#define VM_XEN 0x00000800 /* xen use cases */
+#define VM_SPARSE 0x00001000 /* sparse vm_area. not all pages are present. */
#if (defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)) && \
!defined(CONFIG_KASAN_VMALLOC)
@@ -233,6 +234,9 @@ static inline bool is_vm_area_hugepages(const void *addr)
}
#ifdef CONFIG_MMU
+int vm_area_map_pages(struct vm_struct *area, unsigned long addr, unsigned int count,
+ struct page **pages);
+int vm_area_unmap_pages(struct vm_struct *area, unsigned long addr, unsigned int count);
void vunmap_range(unsigned long addr, unsigned long end);
static inline void set_vm_flush_reset_perms(void *addr)
{
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index d769a65bddad..a05dfbbacb78 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -648,6 +648,54 @@ static int vmap_pages_range(unsigned long addr, unsigned long end,
return err;
}
+/**
+ * vm_area_map_pages - map pages inside given vm_area
+ * @area: vm_area
+ * @addr: start address inside vm_area
+ * @count: number of pages
+ * @pages: pages to map (always PAGE_SIZE pages)
+ */
+int vm_area_map_pages(struct vm_struct *area, unsigned long addr, unsigned int count,
+ struct page **pages)
+{
+ unsigned long size = ((unsigned long)count) * PAGE_SIZE;
+ unsigned long end = addr + size;
+
+ might_sleep();
+ if (WARN_ON_ONCE(area->flags & VM_FLUSH_RESET_PERMS))
+ return -EINVAL;
+ if (WARN_ON_ONCE(area->flags & VM_NO_GUARD))
+ return -EINVAL;
+ if (WARN_ON_ONCE(!(area->flags & VM_SPARSE)))
+ return -EINVAL;
+ if (count > totalram_pages())
+ return -E2BIG;
+ if (addr < (unsigned long)area->addr || (void *)end > area->addr + area->size)
+ return -ERANGE;
+
+ return vmap_pages_range(addr, end, PAGE_KERNEL, pages, PAGE_SHIFT);
+}
+
+/**
+ * vm_area_unmap_pages - unmap pages inside given vm_area
+ * @area: vm_area
+ * @addr: start address inside vm_area
+ * @count: number of pages to unmap
+ */
+int vm_area_unmap_pages(struct vm_struct *area, unsigned long addr, unsigned int count)
+{
+ unsigned long size = ((unsigned long)count) * PAGE_SIZE;
+ unsigned long end = addr + size;
+
+ if (WARN_ON_ONCE(!(area->flags & VM_SPARSE)))
+ return -EINVAL;
+ if (addr < (unsigned long)area->addr || (void *)end > area->addr + area->size)
+ return -ERANGE;
+
+ vunmap_range(addr, end);
+ return 0;
+}
+
int is_vmalloc_or_module_addr(const void *x)
{
/*
@@ -3822,9 +3870,9 @@ long vread_iter(struct iov_iter *iter, const char *addr, size_t count)
if (flags & VMAP_RAM)
copied = vmap_ram_vread_iter(iter, addr, n, flags);
- else if (!(vm && (vm->flags & (VM_IOREMAP | VM_XEN))))
+ else if (!(vm && (vm->flags & (VM_IOREMAP | VM_XEN | VM_SPARSE))))
copied = aligned_vread_iter(iter, addr, n);
- else /* IOREMAP|XEN area is treated as memory hole */
+ else /* IOREMAP|XEN|SPARSE area is treated as memory hole */
copied = zero_iter(iter, n);
addr += copied;
@@ -4418,6 +4466,9 @@ static int s_show(struct seq_file *m, void *p)
if (v->flags & VM_XEN)
seq_puts(m, " xen");
+ if (v->flags & VM_SPARSE)
+ seq_puts(m, " sparse");
+
if (v->flags & VM_ALLOC)
seq_puts(m, " vmalloc");
--
2.34.1
