1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/ftrace.h>
3 #include <linux/percpu.h>
4 #include <linux/slab.h>
5 #include <linux/uaccess.h>
6 #include <linux/pgtable.h>
7 #include <linux/cpuidle.h>
8 #include <asm/alternative.h>
9 #include <asm/cacheflush.h>
10 #include <asm/cpufeature.h>
11 #include <asm/cpuidle.h>
12 #include <asm/daifflags.h>
13 #include <asm/debug-monitors.h>
14 #include <asm/exec.h>
15 #include <asm/fpsimd.h>
16 #include <asm/mte.h>
17 #include <asm/memory.h>
18 #include <asm/mmu_context.h>
19 #include <asm/smp_plat.h>
20 #include <asm/suspend.h>
21
22 /*
23 * This is allocated by cpu_suspend_init(), and used to store a pointer to
24 * the 'struct sleep_stack_data' the contains a particular CPUs state.
25 */
26 unsigned long *sleep_save_stash;
27
28 /*
29 * This hook is provided so that cpu_suspend code can restore HW
30 * breakpoints as early as possible in the resume path, before reenabling
31 * debug exceptions. Code cannot be run from a CPU PM notifier since by the
32 * time the notifier runs debug exceptions might have been enabled already,
33 * with HW breakpoints registers content still in an unknown state.
34 */
35 static int (*hw_breakpoint_restore)(unsigned int);
36 void __init cpu_suspend_set_dbg_restorer(int (*hw_bp_restore)(unsigned int))
37 {
38 /* Prevent multiple restore hook initializations */
39 if (WARN_ON(hw_breakpoint_restore))
40 return;
41 hw_breakpoint_restore = hw_bp_restore;
42 }
43
44 void notrace __cpu_suspend_exit(void)
45 {
46 unsigned int cpu = smp_processor_id();
47
48 mte_suspend_exit();
49
50 /*
51 * We are resuming from reset with the idmap active in TTBR0_EL1.
52 * We must uninstall the idmap and restore the expected MMU
53 * state before we can possibly return to userspace.
54 */
55 cpu_uninstall_idmap();
56
57 /* Restore CnP bit in TTBR1_EL1 */
58 if (system_supports_cnp())
59 cpu_enable_swapper_cnp();
60
61 /*
62 * PSTATE was not saved over suspend/resume, re-enable any detected
63 * features that might not have been set correctly.
64 */
65 if (alternative_has_cap_unlikely(ARM64_HAS_DIT))
66 set_pstate_dit(1);
67 __uaccess_enable_hw_pan();
68
69 /*
70 * Restore HW breakpoint registers to sane values
71 * before debug exceptions are possibly reenabled
72 * by cpu_suspend()s local_daif_restore() call.
73 */
74 if (hw_breakpoint_restore)
75 hw_breakpoint_restore(cpu);
76
77 /*
78 * On resume, firmware implementing dynamic mitigation will
79 * have turned the mitigation on. If the user has forcefully
80 * disabled it, make sure their wishes are obeyed.
81 */
82 spectre_v4_enable_mitigation(NULL);
83
84 sme_suspend_exit();
85
86 /* Restore additional feature-specific configuration */
87 ptrauth_suspend_exit();
88 }
89
90 /*
91 * cpu_suspend
92 *
93 * arg: argument to pass to the finisher function
94 * fn: finisher function pointer
95 *
96 */
97 int cpu_suspend(unsigned long arg, int (*fn)(unsigned long))
98 {
99 int ret = 0;
100 unsigned long flags;
101 struct sleep_stack_data state;
102 struct arm_cpuidle_irq_context context;
103
104 /*
105 * Some portions of CPU state (e.g. PSTATE.{PAN,DIT}) are initialized
106 * before alternatives are patched, but are only restored by
107 * __cpu_suspend_exit() after alternatives are patched. To avoid
108 * accidentally losing these bits we must not attempt to suspend until
109 * after alternatives have been patched.
110 */
111 WARN_ON(!system_capabilities_finalized());
112
113 /* Report any MTE async fault before going to suspend */
114 mte_suspend_enter();
115
116 /*
117 * From this point debug exceptions are disabled to prevent
118 * updates to mdscr register (saved and restored along with
119 * general purpose registers) from kernel debuggers.
120 *
121 * Strictly speaking the trace_hardirqs_off() here is superfluous,
122 * hardirqs should be firmly off by now. This really ought to use
123 * something like raw_local_daif_save().
124 */
125 flags = local_daif_save();
126
127 /*
128 * Function graph tracer state gets inconsistent when the kernel
129 * calls functions that never return (aka suspend finishers) hence
130 * disable graph tracing during their execution.
131 */
132 pause_graph_tracing();
133
134 /*
135 * Switch to using DAIF.IF instead of PMR in order to reliably
136 * resume if we're using pseudo-NMIs.
137 */
138 arm_cpuidle_save_irq_context(&context);
139
140 ct_cpuidle_enter();
141
142 if (__cpu_suspend_enter(&state)) {
143 /* Call the suspend finisher */
144 ret = fn(arg);
145
146 /*
147 * Never gets here, unless the suspend finisher fails.
148 * Successful cpu_suspend() should return from cpu_resume(),
149 * returning through this code path is considered an error
150 * If the return value is set to 0 force ret = -EOPNOTSUPP
151 * to make sure a proper error condition is propagated
152 */
153 if (!ret)
154 ret = -EOPNOTSUPP;
155
156 ct_cpuidle_exit();
157 } else {
158 ct_cpuidle_exit();
159 __cpu_suspend_exit();
160 }
161
162 arm_cpuidle_restore_irq_context(&context);
163
164 unpause_graph_tracing();
165
166 /*
167 * Restore pstate flags. OS lock and mdscr have been already
168 * restored, so from this point onwards, debugging is fully
169 * reenabled if it was enabled when core started shutdown.
170 */
171 local_daif_restore(flags);
172
173 return ret;
174 }
175
176 static int __init cpu_suspend_init(void)
177 {
178 /* ctx_ptr is an array of physical addresses */
179 sleep_save_stash = kcalloc(mpidr_hash_size(), sizeof(*sleep_save_stash),
180 GFP_KERNEL);
181
182 if (WARN_ON(!sleep_save_stash))
183 return -ENOMEM;
184
185 return 0;
186 }
187 early_initcall(cpu_suspend_init);
188
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