random: vDSO: minimize and simplify header includes

Depending on the architecture, building a 32-bit vDSO on a 64-bit kernel
is problematic when some system headers are included.

Minimise the amount of headers by moving needed items, such as
__{get,put}_unaligned_t, into dedicated common headers and in general
use more specific headers, similar to what was done in commit
8165b57b ("linux/const.h: Extract common header for vDSO") and
commit 8c59ab83 ("lib/vdso: Enable common headers").

On some architectures this results in missing PAGE_SIZE, as was
described by commit 8b3843ae ("vdso/datapage: Quick fix - use
asm/page-def.h for ARM64"), so define this if necessary, in the same way
as done prior by commit cffaefd1 ("vdso: Use CONFIG_PAGE_SHIFT in
vdso/datapage.h").

Removing linux/time64.h leads to missing 'struct timespec64' in
x86's asm/pvclock.h. Add a forward declaration of that struct in
that file.
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

arch/x86/include/asm/pvclock.h

@@ -5,6 +5,7 @@
 #include <asm/clocksource.h>
 #include <asm/pvclock-abi.h>
 
+struct timespec64;
 /* some helper functions for xen and kvm pv clock sources */
 u64 pvclock_clocksource_read(struct pvclock_vcpu_time_info *src);
 u64 pvclock_clocksource_read_nowd(struct pvclock_vcpu_time_info *src);

include/asm-generic/unaligned.h

@@ -8,16 +8,7 @@
  */
 #include <linux/unaligned/packed_struct.h>
 #include <asm/byteorder.h>
-
-#define __get_unaligned_t(type, ptr) ({						\
-	const struct { type x; } __packed *__pptr = (typeof(__pptr))(ptr);	\
-	__pptr->x;								\
-})
-
-#define __put_unaligned_t(type, val, ptr) do {					\
-	struct { type x; } __packed *__pptr = (typeof(__pptr))(ptr);		\
-	__pptr->x = (val);							\
-} while (0)
+#include <vdso/unaligned.h>
 
 #define get_unaligned(ptr)	__get_unaligned_t(typeof(*(ptr)), (ptr))
 #define put_unaligned(val, ptr) __put_unaligned_t(typeof(*(ptr)), (val), (ptr))

include/vdso/helpers.h

@@ -4,6 +4,7 @@
 
 #ifndef __ASSEMBLY__
 
+#include <asm/barrier.h>
 #include <vdso/datapage.h>
 
 static __always_inline u32 vdso_read_begin(const struct vdso_data *vd)

include/vdso/unaligned.h

+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __VDSO_UNALIGNED_H
+#define __VDSO_UNALIGNED_H
+
+#define __get_unaligned_t(type, ptr) ({						\
+	const struct { type x; } __packed *__pptr = (typeof(__pptr))(ptr);	\
+	__pptr->x;								\
+})
+
+#define __put_unaligned_t(type, val, ptr) do {					\
+	struct { type x; } __packed *__pptr = (typeof(__pptr))(ptr);		\
+	__pptr->x = (val);							\
+} while (0)
+
+#endif /* __VDSO_UNALIGNED_H */

lib/vdso/getrandom.c

@@ -4,15 +4,18 @@
  */
 
 #include <linux/array_size.h>
-#include <linux/cache.h>
-#include <linux/kernel.h>
-#include <linux/time64.h>
+#include <linux/minmax.h>
 #include <vdso/datapage.h>
 #include <vdso/getrandom.h>
+#include <vdso/unaligned.h>
 #include <asm/vdso/getrandom.h>
-#include <asm/vdso/vsyscall.h>
-#include <asm/unaligned.h>
 #include <uapi/linux/mman.h>
+#include <uapi/linux/random.h>
+
+#undef PAGE_SIZE
+#undef PAGE_MASK
+#define PAGE_SIZE (1UL << CONFIG_PAGE_SHIFT)
+#define PAGE_MASK (~(PAGE_SIZE - 1))
 
 #define MEMCPY_AND_ZERO_SRC(type, dst, src, len) do {				\
 	while (len >= sizeof(type)) {						\