From: Alexei Starovoitov <ast@xxxxxxxxxx>
vmap() API is used to map a set of pages into contiguous kernel virtual space.
BPF would like to extend the vmap API to implement a lazily-populated
contiguous kernel virtual space which size and start address is fixed early.
The vmap API has functions to request and release areas of kernel address space:
get_vm_area() and free_vm_area().
Introduce vm_area_map_pages(area, start_addr, count, pages)
to map a set of pages within a given area.
It has the same sanity checks as vmap() does.
In addition it also checks that get_vm_area() was created with VM_MAP flag
(as all users of vmap() should be doing).
Also add vm_area_unmap_pages() that is a safer alternative to
existing vunmap_range() api.
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 an existing vm area with the following steps:
area = get_vm_area(area_size, VM_MAP | VM_USERMAP); // at bpf prog verification time
vm_area_map_pages(area, kaddr, 1, page); // on demand
vm_area_unmap_pages(area, kaddr, 1);
free_vm_area(area); // after bpf prog is unloaded
For BPF use case the area_size will be 4Gbyte plus 64Kbyte of guard pages and
area->addr known and fixed at the program verification time.
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
---
include/linux/vmalloc.h | 3 +++
mm/vmalloc.c | 46 +++++++++++++++++++++++++++++++++++++++++
2 files changed, 49 insertions(+)
diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
index c720be70c8dd..7d112cc5f2a3 100644
--- a/include/linux/vmalloc.h
+++ b/include/linux/vmalloc.h
@@ -232,6 +232,9 @@ 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 d12a17fc0c17..d6337d46f1d8 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -635,6 +635,52 @@ 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_MAP)))
+ 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 (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)
{
/*
--
2.34.1
