1// SPDX-License-Identifier: GPL-2.0+
2
3#include <errno.h>
4#include <setjmp.h>
5#include <signal.h>
6#include <sys/types.h>
7#include <sys/wait.h>
8
9#include "dexcr.h"
10#include "reg.h"
11#include "utils.h"
12
13static jmp_buf generic_signal_jump_buf;
14
15static void generic_signal_handler(int signum, siginfo_t *info, void *context)
16{
17	longjmp(generic_signal_jump_buf, 0);
18}
19
20bool dexcr_exists(void)
21{
22	struct sigaction old;
23	volatile bool exists;
24
25	old = push_signal_handler(SIGILL, generic_signal_handler);
26	if (setjmp(generic_signal_jump_buf))
27		goto out;
28
29	/*
30	 * If the SPR is not recognised by the hardware it triggers
31	 * a hypervisor emulation interrupt. If the kernel does not
32	 * recognise/try to emulate it, we receive a SIGILL signal.
33	 *
34	 * If we do not receive a signal, assume we have the SPR or the
35	 * kernel is trying to emulate it correctly.
36	 */
37	exists = false;
38	mfspr(SPRN_DEXCR_RO);
39	exists = true;
40
41out:
42	pop_signal_handler(SIGILL, old);
43	return exists;
44}
45
46/*
47 * Just test if a bad hashchk triggers a signal, without checking
48 * for support or if the NPHIE aspect is enabled.
49 */
50bool hashchk_triggers(void)
51{
52	struct sigaction old;
53	volatile bool triggers;
54
55	old = push_signal_handler(SIGILL, generic_signal_handler);
56	if (setjmp(generic_signal_jump_buf))
57		goto out;
58
59	triggers = true;
60	do_bad_hashchk();
61	triggers = false;
62
63out:
64	pop_signal_handler(SIGILL, old);
65	return triggers;
66}
67
68unsigned int get_dexcr(enum dexcr_source source)
69{
70	switch (source) {
71	case DEXCR:
72		return mfspr(SPRN_DEXCR_RO);
73	case HDEXCR:
74		return mfspr(SPRN_HDEXCR_RO);
75	case EFFECTIVE:
76		return mfspr(SPRN_DEXCR_RO) | mfspr(SPRN_HDEXCR_RO);
77	default:
78		FAIL_IF_EXIT_MSG(true, "bad enum dexcr_source");
79	}
80}
81
82void await_child_success(pid_t pid)
83{
84	int wstatus;
85
86	FAIL_IF_EXIT_MSG(pid == -1, "fork failed");
87	FAIL_IF_EXIT_MSG(waitpid(pid, &wstatus, 0) == -1, "wait failed");
88	FAIL_IF_EXIT_MSG(!WIFEXITED(wstatus), "child did not exit cleanly");
89	FAIL_IF_EXIT_MSG(WEXITSTATUS(wstatus) != 0, "child exit error");
90}
91
92/*
93 * Perform a hashst instruction. The following components determine the result
94 *
95 * 1. The LR value (any register technically)
96 * 2. The SP value (also any register, but it must be a valid address)
97 * 3. A secret key managed by the kernel
98 *
99 * The result is stored to the address held in SP.
100 */
101void hashst(unsigned long lr, void *sp)
102{
103	asm volatile ("addi 31, %0, 0;"		/* set r31 (pretend LR) to lr */
104		      "addi 30, %1, 8;"		/* set r30 (pretend SP) to sp + 8 */
105		      PPC_RAW_HASHST(31, -8, 30)	/* compute hash into stack location */
106		      : : "r" (lr), "r" (sp) : "r31", "r30", "memory");
107}
108
109/*
110 * Perform a hashchk instruction. A hash is computed as per hashst(),
111 * however the result is not stored to memory. Instead the existing
112 * value is read and compared against the computed hash.
113 *
114 * If they match, execution continues.
115 * If they differ, an interrupt triggers.
116 */
117void hashchk(unsigned long lr, void *sp)
118{
119	asm volatile ("addi 31, %0, 0;"		/* set r31 (pretend LR) to lr */
120		      "addi 30, %1, 8;"		/* set r30 (pretend SP) to sp + 8 */
121		      PPC_RAW_HASHCHK(31, -8, 30)	/* check hash at stack location */
122		      : : "r" (lr), "r" (sp) : "r31", "r30", "memory");
123}
124
125void do_bad_hashchk(void)
126{
127	unsigned long hash = 0;
128
129	hashst(0, &hash);
130	hash += 1;
131	hashchk(0, &hash);
132}
133