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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 */
26unsigned 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 */
35static int (*hw_breakpoint_restore)(unsigned int);
36void __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
44void 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 */
97int 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
103 /*
104 * Some portions of CPU state (e.g. PSTATE.{PAN,DIT}) are initialized
105 * before alternatives are patched, but are only restored by
106 * __cpu_suspend_exit() after alternatives are patched. To avoid
107 * accidentally losing these bits we must not attempt to suspend until
108 * after alternatives have been patched.
109 */
110 WARN_ON(!system_capabilities_finalized());
111
112 /* Report any MTE async fault before going to suspend */
113 mte_suspend_enter();
114
115 /*
116 * From this point debug exceptions are disabled to prevent
117 * updates to mdscr register (saved and restored along with
118 * general purpose registers) from kernel debuggers.
119 *
120 * Strictly speaking the trace_hardirqs_off() here is superfluous,
121 * hardirqs should be firmly off by now. This really ought to use
122 * something like raw_local_daif_save().
123 *
124 * This also unmasks interrupts in PMR in order to reliably
125 * resume if we're using pseudo-NMIs.
126 */
127 flags = local_daif_save();
128
129 /*
130 * Function graph tracer state gets inconsistent when the kernel
131 * calls functions that never return (aka suspend finishers) hence
132 * disable graph tracing during their execution.
133 */
134 pause_graph_tracing();
135
136 ct_cpuidle_enter();
137
138 if (__cpu_suspend_enter(&state)) {
139 /* Call the suspend finisher */
140 ret = fn(arg);
141
142 /*
143 * Never gets here, unless the suspend finisher fails.
144 * Successful cpu_suspend() should return from cpu_resume(),
145 * returning through this code path is considered an error
146 * If the return value is set to 0 force ret = -EOPNOTSUPP
147 * to make sure a proper error condition is propagated
148 */
149 if (!ret)
150 ret = -EOPNOTSUPP;
151
152 ct_cpuidle_exit();
153 } else {
154 ct_cpuidle_exit();
155 __cpu_suspend_exit();
156 }
157
158 unpause_graph_tracing();
159
160 /*
161 * Restore pstate flags. OS lock and mdscr have been already
162 * restored, so from this point onwards, debugging is fully
163 * reenabled if it was enabled when core started shutdown.
164 */
165 local_daif_restore(flags);
166
167 return ret;
168}
169
170static int __init cpu_suspend_init(void)
171{
172 /* ctx_ptr is an array of physical addresses */
173 sleep_save_stash = kcalloc(mpidr_hash_size(), sizeof(*sleep_save_stash),
174 GFP_KERNEL);
175
176 if (WARN_ON(!sleep_save_stash))
177 return -ENOMEM;
178
179 return 0;
180}
181early_initcall(cpu_suspend_init);