[PATCH 2/4] random: vDSO: Don't use PAGE_SIZE and PAGE_MASK

[Christophe Leroy]

Using PAGE_SIZE and PAGE_MASK in VDSO requires inclusion of
page.h and it creates several problems, see
commit 8b3843ae3634 ("vdso/datapage: Quick fix - use asm/page-def.h
for ARM64") and commit cffaefd15a8f ("vdso: Use CONFIG_PAGE_SHIFT in
vdso/datapage.h").

An easy solution would be to define PAGE_SIZE and PAGE_MASK in vDSO
when they do not exist already, but this can be misleading.

So follow the same approach as commit cffaefd15a8f ("vdso: Use
CONFIG_PAGE_SHIFT in vdso/datapage.h") and exclusively use
CONFIG_PAGE_SHIFT. To avoid too much ugliness, define local consts
that constains the calculated page size and page mask.

Signed-off-by: Christophe Leroy <christophe.le...@csgroup.eu>
---
v3: Use local consts instead of _PAGE_SIZE and _PAGE_MASK macros that are 
already defined by some architectures.
---
 lib/vdso/getrandom.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/lib/vdso/getrandom.c b/lib/vdso/getrandom.c
index f1643656d0b0..5874e3072bfe 100644
--- a/lib/vdso/getrandom.c
+++ b/lib/vdso/getrandom.c
@@ -65,7 +65,9 @@ static __always_inline ssize_t
 __cvdso_getrandom_data(const struct vdso_rng_data *rng_info, void *buffer, 
size_t len,
                       unsigned int flags, void *opaque_state, size_t 
opaque_len)
 {
-       ssize_t ret = min_t(size_t, INT_MAX & PAGE_MASK /* = MAX_RW_COUNT */, 
len);
+       const unsigned long page_size = 1UL << CONFIG_PAGE_SHIFT;
+       const unsigned long page_mask = ~(page_size - 1);
+       ssize_t ret = min_t(size_t, INT_MAX & page_mask /* = MAX_RW_COUNT */, 
len);
        struct vgetrandom_state *state = opaque_state;
        size_t batch_len, nblocks, orig_len = len;
        bool in_use, have_retried = false;
@@ -84,7 +86,7 @@ __cvdso_getrandom_data(const struct vdso_rng_data *rng_info, 
void *buffer, size_
        }
 
        /* The state must not straddle a page, since pages can be zeroed at any 
time. */
-       if (unlikely(((unsigned long)opaque_state & ~PAGE_MASK) + 
sizeof(*state) > PAGE_SIZE))
+       if (unlikely(((unsigned long)opaque_state & ~page_mask) + 
sizeof(*state) > page_size))
                return -EFAULT;
 
        /* Handle unexpected flags by falling back to the kernel. */
-- 
2.44.0