[PATCH] random: vDSO: add a __vdso_getrandom prototype for all architectures

[Xi Ruoyao]

Without a prototype, we'll have to add a prototype for each architecture
implementing vDSO getrandom. As most architectures will likely have the
vDSO getrandom implemented in a near future, and we'd like to keep the
declarations compatible everywhere (to ease the libc implementor work),
we should really just have one copy of the prototype.

This also is what's already done inside of include/vdso/gettime.h for
those vDSO functions, so this continues that convention.

Suggested-by: Huacai Chen <chenhuacai@xxxxxxxxxx>
Signed-off-by: Xi Ruoyao <xry111@xxxxxxxxxxx>
Acked-by: Huacai Chen <chenhuacai@xxxxxxxxxx>
[Jason: rewrite docbook comment for prototype.]
Signed-off-by: Jason A. Donenfeld <Jason@xxxxxxxxx>
---
 arch/x86/entry/vdso/vgetrandom.c |  2 --
 include/vdso/getrandom.h         | 16 ++++++++++++++++
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/arch/x86/entry/vdso/vgetrandom.c b/arch/x86/entry/vdso/vgetrandom.c
index 52d3c7faae2e..430862b8977c 100644
--- a/arch/x86/entry/vdso/vgetrandom.c
+++ b/arch/x86/entry/vdso/vgetrandom.c
@@ -6,8 +6,6 @@

 #include "../../../../lib/vdso/getrandom.c"

-ssize_t __vdso_getrandom(void *buffer, size_t len, unsigned int flags, void *opaque_state, size_t opaque_len);
-
 ssize_t __vdso_getrandom(void *buffer, size_t len, unsigned int flags, void *opaque_state, size_t opaque_len)
 {
 	return __cvdso_getrandom(buffer, len, flags, opaque_state, opaque_len);
diff --git a/include/vdso/getrandom.h b/include/vdso/getrandom.h
index 4cf02e678f5e..0d3849145a89 100644
--- a/include/vdso/getrandom.h
+++ b/include/vdso/getrandom.h
@@ -56,4 +56,20 @@ struct vgetrandom_state {
  */
 extern void __arch_chacha20_blocks_nostack(u8 *dst_bytes, const u32 *key, u32 *counter, size_t nblocks);

+/**
+ * __vdso_getrandom - Architecture-specific vDSO implementation of getrandom() syscall.
+ * @buffer:		Passed to __cvdso_getrandom_data().
+ * @len:		Passed to __cvdso_getrandom_data().
+ * @flags:		Passed to __cvdso_getrandom_data().
+ * @opaque_state:	Passed to __cvdso_getrandom_data().
+ * @opaque_len:		Passed to __cvdso_getrandom_data();
+ *
+ * This function acquires a pointer to the architecture-specific shared vDSO RNG datapage, and
+ * passes it, along with all of its arguments, to __cvdso_getrandom_data(), whose documentation may
+ * be consulted for more information.
+ *
+ * Returns:	The value of __cvdso_getrandom_data().
+ */
+extern ssize_t __vdso_getrandom(void *buffer, size_t len, unsigned int flags, void *opaque_state, size_t opaque_len);
+
 #endif /* _VDSO_GETRANDOM_H */
--
2.46.0