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
13 static jmp_buf generic_signal_jump_buf;
14
generic_signal_handler(int signum,siginfo_t * info,void * context)15 static void generic_signal_handler(int signum, siginfo_t *info, void *context)
16 {
17 longjmp(generic_signal_jump_buf, 0);
18 }
19
dexcr_exists(void)20 bool 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
41 out:
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 */
hashchk_triggers(void)50 bool 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
63 out:
64 pop_signal_handler(SIGILL, old);
65 return triggers;
66 }
67
get_dexcr(enum dexcr_source source)68 unsigned 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
await_child_success(pid_t pid)82 void 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 */
hashst(unsigned long lr,void * sp)101 void 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 */
hashchk(unsigned long lr,void * sp)117 void 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
do_bad_hashchk(void)125 void do_bad_hashchk(void)
126 {
127 unsigned long hash = 0;
128
129 hashst(0, &hash);
130 hash += 1;
131 hashchk(0, &hash);
132 }
133