1 /* SPDX-License-Identifier: GPL-2.0 */
2
3 #ifndef __ASM_VDSO_GETRANDOM_H
4 #define __ASM_VDSO_GETRANDOM_H
5
6 #ifndef __ASSEMBLY__
7
8 #include <asm/unistd.h>
9 #include <asm/vdso/vsyscall.h>
10 #include <vdso/datapage.h>
11
12 /**
13 * getrandom_syscall - Invoke the getrandom() syscall.
14 * @buffer: Destination buffer to fill with random bytes.
15 * @len: Size of @buffer in bytes.
16 * @flags: Zero or more GRND_* flags.
17 * Returns: The number of random bytes written to @buffer, or a negative value indicating an error.
18 */
19 static __always_inline ssize_t getrandom_syscall(void *_buffer, size_t _len, unsigned int _flags)
20 {
21 register void *buffer asm ("x0") = _buffer;
22 register size_t len asm ("x1") = _len;
23 register unsigned int flags asm ("x2") = _flags;
24 register long ret asm ("x0");
25 register long nr asm ("x8") = __NR_getrandom;
26
27 asm volatile(
28 " svc #0\n"
29 : "=r" (ret)
30 : "r" (buffer), "r" (len), "r" (flags), "r" (nr)
31 : "memory");
32
33 return ret;
34 }
35
36 static __always_inline const struct vdso_rng_data *__arch_get_vdso_rng_data(void)
37 {
38 /*
39 * The RNG data is in the real VVAR data page, but if a task belongs to a time namespace
40 * then VVAR_DATA_PAGE_OFFSET points to the namespace-specific VVAR page and VVAR_TIMENS_
41 * PAGE_OFFSET points to the real VVAR page.
42 */
43 if (IS_ENABLED(CONFIG_TIME_NS) && _vdso_data->clock_mode == VDSO_CLOCKMODE_TIMENS)
44 return (void *)&_vdso_rng_data + VVAR_TIMENS_PAGE_OFFSET * (1UL << CONFIG_PAGE_SHIFT);
45 return &_vdso_rng_data;
46 }
47
48 #endif /* !__ASSEMBLY__ */
49
50 #endif /* __ASM_VDSO_GETRANDOM_H */
51
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