[PATCH v2 05/17] vdso: Avoid call to memset() by getrandom

Christophe Leroy
2024-08-22T07:13:56Z

With the current implementation, __cvdso_getrandom_data() calls
memset(), which is unexpected in the VDSO.

Rewrite opaque data initialisation to avoid memset().

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
lib/vdso/getrandom.c | 15 ++++++++++-----
1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/lib/vdso/getrandom.c b/lib/vdso/getrandom.c
index cab153c5f9be..4a56f45141b4 100644
--- a/lib/vdso/getrandom.c
+++ b/lib/vdso/getrandom.c
@@ -4,6 +4,7 @@
*/

#include <linux/minmax.h>
+#include <linux/array_size.h>
#include <vdso/datapage.h>
#include <vdso/getrandom.h>
#include <vdso/unaligned.h>
@@ -74,11 +75,15 @@ __cvdso_getrandom_data(const struct vdso_rng_data *rng_info, void *buffer, size_
u32 counter[2] = { 0 };

if (unlikely(opaque_len == ~0UL && !buffer && !len && !flags)) {
- *(struct vgetrandom_opaque_params *)opaque_state = (struct vgetrandom_opaque_params) {
- .size_of_opaque_state = sizeof(*state),
- .mmap_prot = PROT_READ | PROT_WRITE,
- .mmap_flags = MAP_DROPPABLE | MAP_ANONYMOUS
- };
+ struct vgetrandom_opaque_params *params = opaque_state;
+ int i;
+
+ params->size_of_opaque_state = sizeof(*state);
+ params->mmap_prot = PROT_READ | PROT_WRITE;
+ params->mmap_flags = MAP_DROPPABLE | MAP_ANONYMOUS;
+ for (i = 0; i < ARRAY_SIZE(params->reserved); i++)
+ params->reserved[i] = 0;
+
return 0;
}

--
2.44.0