1 // SPDX-License-Identifier: GPL-2.0
2
3 /*
4 * simple_ring_buffer is used by the pKVM hypervisor which does not have access
5 * to all kernel symbols. Whatever is undefined when compiling this file is
6 * compiler and tooling-generated symbols that can safely be ignored for
7 * simple_ring_buffer.
8 */
9
10 #include <linux/atomic.h>
11 #include <linux/string.h>
12 #include <asm/page.h>
13
14 void undefsyms_base(void *p, int n);
15
16 static char page[PAGE_SIZE] __aligned(PAGE_SIZE);
17
undefsyms_base(void * p,int n)18 void undefsyms_base(void *p, int n)
19 {
20 char buffer[256] = { 0 };
21
22 u32 u = 0;
23 memset((char * volatile)page, 8, PAGE_SIZE);
24 memset((char * volatile)buffer, 8, sizeof(buffer));
25 memcpy((void * volatile)p, buffer, sizeof(buffer));
26 cmpxchg((u32 * volatile)&u, 0, 8);
27 WARN_ON(n == 0xdeadbeef);
28 }
29