1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright 2019, Gustavo Romero, Michael Neuling, IBM Corp.
4 *
5 * This test will spawn two processes. Both will be attached to the same
6 * CPU (CPU 0). The child will be in a loop writing to FP register f31 and
7 * VMX/VEC/Altivec register vr31 a known value, called poison, calling
8 * sched_yield syscall after to allow the parent to switch on the CPU.
9 * Parent will set f31 and vr31 to 1 and in a loop will check if f31 and
10 * vr31 remain 1 as expected until a given timeout (2m). If the issue is
11 * present child's poison will leak into parent's f31 or vr31 registers,
12 * otherwise, poison will never leak into parent's f31 and vr31 registers.
13 */
14
15#define _GNU_SOURCE
16#include <stdio.h>
17#include <stdlib.h>
18#include <unistd.h>
19#include <inttypes.h>
20#include <sched.h>
21#include <sys/types.h>
22#include <signal.h>
23
24#include "tm.h"
25
26int tm_poison_test(void)
27{
28	int cpu, pid;
29	cpu_set_t cpuset;
30	uint64_t poison = 0xdeadbeefc0dec0fe;
31	uint64_t unknown = 0;
32	bool fail_fp = false;
33	bool fail_vr = false;
34
35	SKIP_IF(!have_htm());
36	SKIP_IF(htm_is_synthetic());
37
38	cpu = pick_online_cpu();
39	FAIL_IF(cpu < 0);
40
41	// Attach both Child and Parent to the same CPU
42	CPU_ZERO(&cpuset);
43	CPU_SET(cpu, &cpuset);
44	FAIL_IF(sched_setaffinity(0, sizeof(cpuset), &cpuset) != 0);
45
46	pid = fork();
47	if (!pid) {
48		/**
49		 * child
50		 */
51		while (1) {
52			sched_yield();
53			asm (
54				"mtvsrd 31, %[poison];" // f31 = poison
55				"mtvsrd 63, %[poison];" // vr31 = poison
56
57				: : [poison] "r" (poison) : );
58		}
59	}
60
61	/**
62	 * parent
63	 */
64	asm (
65		/*
66		 * Set r3, r4, and f31 to known value 1 before entering
67		 * in transaction. They won't be written after that.
68		 */
69		"       li      3, 0x1          ;"
70		"       li      4, 0x1          ;"
71		"       mtvsrd  31, 4           ;"
72
73		/*
74		 * The Time Base (TB) is a 64-bit counter register that is
75		 * independent of the CPU clock and which is incremented
76		 * at a frequency of 512000000 Hz, so every 1.953125ns.
77		 * So it's necessary 120s/0.000000001953125s = 61440000000
78		 * increments to get a 2 minutes timeout. Below we set that
79		 * value in r5 and then use r6 to track initial TB value,
80		 * updating TB values in r7 at every iteration and comparing it
81		 * to r6. When r7 (current) - r6 (initial) > 61440000000 we bail
82		 * out since for sure we spent already 2 minutes in the loop.
83		 * SPR 268 is the TB register.
84		 */
85		"       lis     5, 14           ;"
86		"       ori     5, 5, 19996     ;"
87		"       sldi    5, 5, 16        ;" // r5 = 61440000000
88
89		"       mfspr   6, 268          ;" // r6 (TB initial)
90		"1:     mfspr   7, 268          ;" // r7 (TB current)
91		"       subf    7, 6, 7         ;" // r7 - r6 > 61440000000 ?
92		"       cmpd    7, 5            ;"
93		"       bgt     3f              ;" // yes, exit
94
95		/*
96		 * Main loop to check f31
97		 */
98		"       tbegin.                 ;" // no, try again
99		"       beq     1b              ;" // restart if no timeout
100		"       mfvsrd  3, 31           ;" // read f31
101		"       cmpd    3, 4            ;" // f31 == 1 ?
102		"       bne     2f              ;" // broken :-(
103		"       tabort. 3               ;" // try another transaction
104		"2:     tend.                   ;" // commit transaction
105		"3:     mr    %[unknown], 3     ;" // record r3
106
107		: [unknown] "=r" (unknown)
108		:
109		: "cr0", "r3", "r4", "r5", "r6", "r7", "vs31"
110
111		);
112
113	/*
114	 * On leak 'unknown' will contain 'poison' value from child,
115	 * otherwise (no leak) 'unknown' will contain the same value
116	 * as r3 before entering in transactional mode, i.e. 0x1.
117	 */
118	fail_fp = unknown != 0x1;
119	if (fail_fp)
120		printf("Unknown value %#"PRIx64" leaked into f31!\n", unknown);
121	else
122		printf("Good, no poison or leaked value into FP registers\n");
123
124	asm (
125		/*
126		 * Set r3, r4, and vr31 to known value 1 before entering
127		 * in transaction. They won't be written after that.
128		 */
129		"       li      3, 0x1          ;"
130		"       li      4, 0x1          ;"
131		"       mtvsrd  63, 4           ;"
132
133		"       lis     5, 14           ;"
134		"       ori     5, 5, 19996     ;"
135		"       sldi    5, 5, 16        ;" // r5 = 61440000000
136
137		"       mfspr   6, 268          ;" // r6 (TB initial)
138		"1:     mfspr   7, 268          ;" // r7 (TB current)
139		"       subf    7, 6, 7         ;" // r7 - r6 > 61440000000 ?
140		"       cmpd    7, 5            ;"
141		"       bgt     3f              ;" // yes, exit
142
143		/*
144		 * Main loop to check vr31
145		 */
146		"       tbegin.                 ;" // no, try again
147		"       beq     1b              ;" // restart if no timeout
148		"       mfvsrd  3, 63           ;" // read vr31
149		"       cmpd    3, 4            ;" // vr31 == 1 ?
150		"       bne     2f              ;" // broken :-(
151		"       tabort. 3               ;" // try another transaction
152		"2:     tend.                   ;" // commit transaction
153		"3:     mr    %[unknown], 3     ;" // record r3
154
155		: [unknown] "=r" (unknown)
156		:
157		: "cr0", "r3", "r4", "r5", "r6", "r7", "vs63"
158
159		);
160
161	/*
162	 * On leak 'unknown' will contain 'poison' value from child,
163	 * otherwise (no leak) 'unknown' will contain the same value
164	 * as r3 before entering in transactional mode, i.e. 0x1.
165	 */
166	fail_vr = unknown != 0x1;
167	if (fail_vr)
168		printf("Unknown value %#"PRIx64" leaked into vr31!\n", unknown);
169	else
170		printf("Good, no poison or leaked value into VEC registers\n");
171
172	kill(pid, SIGKILL);
173
174	return (fail_fp | fail_vr);
175}
176
177int main(int argc, char *argv[])
178{
179	/* Test completes in about 4m */
180	test_harness_set_timeout(250);
181	return test_harness(tm_poison_test, "tm_poison_test");
182}
183