From: Alexei Starovoitov <ast@xxxxxxxxxx>
Clarify two bpf_arena comments, use existing SZ_4G #define,
improve page_cnt check.
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
---
kernel/bpf/arena.c | 25 ++++++++++++++++++-------
1 file changed, 18 insertions(+), 7 deletions(-)
diff --git a/kernel/bpf/arena.c b/kernel/bpf/arena.c
index 86571e760dd6..343c3456c8dd 100644
--- a/kernel/bpf/arena.c
+++ b/kernel/bpf/arena.c
@@ -38,7 +38,7 @@
/* number of bytes addressable by LDX/STX insn with 16-bit 'off' field */
#define GUARD_SZ (1ull << sizeof(((struct bpf_insn *)0)->off) * 8)
-#define KERN_VM_SZ ((1ull << 32) + GUARD_SZ)
+#define KERN_VM_SZ (SZ_4G + GUARD_SZ)
struct bpf_arena {
struct bpf_map map;
@@ -110,7 +110,7 @@ static struct bpf_map *arena_map_alloc(union bpf_attr *attr)
return ERR_PTR(-EINVAL);
vm_range = (u64)attr->max_entries * PAGE_SIZE;
- if (vm_range > (1ull << 32))
+ if (vm_range > SZ_4G)
return ERR_PTR(-E2BIG);
if ((attr->map_extra >> 32) != ((attr->map_extra + vm_range - 1) >> 32))
@@ -301,7 +301,7 @@ static unsigned long arena_get_unmapped_area(struct file *filp, unsigned long ad
if (pgoff)
return -EINVAL;
- if (len > (1ull << 32))
+ if (len > SZ_4G)
return -E2BIG;
/* if user_vm_start was specified at arena creation time */
@@ -322,7 +322,7 @@ static unsigned long arena_get_unmapped_area(struct file *filp, unsigned long ad
if (WARN_ON_ONCE(arena->user_vm_start))
/* checks at map creation time should prevent this */
return -EFAULT;
- return round_up(ret, 1ull << 32);
+ return round_up(ret, SZ_4G);
}
static int arena_map_mmap(struct bpf_map *map, struct vm_area_struct *vma)
@@ -346,7 +346,7 @@ static int arena_map_mmap(struct bpf_map *map, struct vm_area_struct *vma)
return -EBUSY;
/* Earlier checks should prevent this */
- if (WARN_ON_ONCE(vma->vm_end - vma->vm_start > (1ull << 32) || vma->vm_pgoff))
+ if (WARN_ON_ONCE(vma->vm_end - vma->vm_start > SZ_4G || vma->vm_pgoff))
return -EFAULT;
if (remember_vma(arena, vma))
@@ -420,7 +420,7 @@ static long arena_alloc_pages(struct bpf_arena *arena, long uaddr, long page_cnt
if (uaddr & ~PAGE_MASK)
return 0;
pgoff = compute_pgoff(arena, uaddr);
- if (pgoff + page_cnt > page_cnt_max)
+ if (pgoff > page_cnt_max - page_cnt)
/* requested address will be outside of user VMA */
return 0;
}
@@ -447,7 +447,13 @@ static long arena_alloc_pages(struct bpf_arena *arena, long uaddr, long page_cnt
goto out;
uaddr32 = (u32)(arena->user_vm_start + pgoff * PAGE_SIZE);
- /* Earlier checks make sure that uaddr32 + page_cnt * PAGE_SIZE will not overflow 32-bit */
+ /* Earlier checks made sure that uaddr32 + page_cnt * PAGE_SIZE - 1
+ * will not overflow 32-bit. Lower 32-bit need to represent
+ * contiguous user address range.
+ * Map these pages at kern_vm_start base.
+ * kern_vm_start + uaddr32 + page_cnt * PAGE_SIZE - 1 can overflow
+ * lower 32-bit and it's ok.
+ */
ret = vm_area_map_pages(arena->kern_vm, kern_vm_start + uaddr32,
kern_vm_start + uaddr32 + page_cnt * PAGE_SIZE, pages);
if (ret) {
@@ -510,6 +516,11 @@ static void arena_free_pages(struct bpf_arena *arena, long uaddr, long page_cnt)
if (!page)
continue;
if (page_cnt == 1 && page_mapped(page)) /* mapped by some user process */
+ /* Optimization for the common case of page_cnt==1:
+ * If page wasn't mapped into some user vma there
+ * is no need to call zap_pages which is slow. When
+ * page_cnt is big it's faster to do the batched zap.
+ */
zap_pages(arena, full_uaddr, 1);
vm_area_unmap_pages(arena->kern_vm, kaddr, kaddr + PAGE_SIZE);
__free_page(page);
--
2.43.0
