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/mte.h>
16 #include <asm/memory.h>
17 #include <asm/mmu_context.h>
18 #include <asm/smp_plat.h>
19 #include <asm/suspend.h>
20
21 /*
22 * This is allocated by cpu_suspend_init(), and used to store a pointer to
23 * the 'struct sleep_stack_data' the contains a particular CPUs state.
24 */
25 unsigned long *sleep_save_stash;
26
27 /*
28 * This hook is provided so that cpu_suspend code can restore HW
29 * breakpoints as early as possible in the resume path, before reenabling
30 * debug exceptions. Code cannot be run from a CPU PM notifier since by the
31 * time the notifier runs debug exceptions might have been enabled already,
32 * with HW breakpoints registers content still in an unknown state.
33 */
34 static int (*hw_breakpoint_restore)(unsigned int);
cpu_suspend_set_dbg_restorer(int (* hw_bp_restore)(unsigned int))35 void __init cpu_suspend_set_dbg_restorer(int (*hw_bp_restore)(unsigned int))
36 {
37 /* Prevent multiple restore hook initializations */
38 if (WARN_ON(hw_breakpoint_restore))
39 return;
40 hw_breakpoint_restore = hw_bp_restore;
41 }
42
__cpu_suspend_exit(void)43 void notrace __cpu_suspend_exit(void)
44 {
45 unsigned int cpu = smp_processor_id();
46
47 mte_suspend_exit();
48
49 /*
50 * We are resuming from reset with the idmap active in TTBR0_EL1.
51 * We must uninstall the idmap and restore the expected MMU
52 * state before we can possibly return to userspace.
53 */
54 cpu_uninstall_idmap();
55
56 /* Restore CnP bit in TTBR1_EL1 */
57 if (system_supports_cnp())
58 cpu_replace_ttbr1(lm_alias(swapper_pg_dir), idmap_pg_dir);
59
60 /*
61 * PSTATE was not saved over suspend/resume, re-enable any detected
62 * features that might not have been set correctly.
63 */
64 if (cpus_have_const_cap(ARM64_HAS_DIT))
65 set_pstate_dit(1);
66 __uaccess_enable_hw_pan();
67
68 /*
69 * Restore HW breakpoint registers to sane values
70 * before debug exceptions are possibly reenabled
71 * by cpu_suspend()s local_daif_restore() call.
72 */
73 if (hw_breakpoint_restore)
74 hw_breakpoint_restore(cpu);
75
76 /*
77 * On resume, firmware implementing dynamic mitigation will
78 * have turned the mitigation on. If the user has forcefully
79 * disabled it, make sure their wishes are obeyed.
80 */
81 spectre_v4_enable_mitigation(NULL);
82
83 /* Restore additional feature-specific configuration */
84 ptrauth_suspend_exit();
85 }
86
87 /*
88 * cpu_suspend
89 *
90 * arg: argument to pass to the finisher function
91 * fn: finisher function pointer
92 *
93 */
cpu_suspend(unsigned long arg,int (* fn)(unsigned long))94 int cpu_suspend(unsigned long arg, int (*fn)(unsigned long))
95 {
96 int ret = 0;
97 unsigned long flags;
98 struct sleep_stack_data state;
99 struct arm_cpuidle_irq_context context;
100
101 /* Report any MTE async fault before going to suspend */
102 mte_suspend_enter();
103
104 /*
105 * From this point debug exceptions are disabled to prevent
106 * updates to mdscr register (saved and restored along with
107 * general purpose registers) from kernel debuggers.
108 *
109 * Strictly speaking the trace_hardirqs_off() here is superfluous,
110 * hardirqs should be firmly off by now. This really ought to use
111 * something like raw_local_daif_save().
112 */
113 flags = local_daif_save();
114
115 /*
116 * Function graph tracer state gets inconsistent when the kernel
117 * calls functions that never return (aka suspend finishers) hence
118 * disable graph tracing during their execution.
119 */
120 pause_graph_tracing();
121
122 /*
123 * Switch to using DAIF.IF instead of PMR in order to reliably
124 * resume if we're using pseudo-NMIs.
125 */
126 arm_cpuidle_save_irq_context(&context);
127
128 ct_cpuidle_enter();
129
130 if (__cpu_suspend_enter(&state)) {
131 /* Call the suspend finisher */
132 ret = fn(arg);
133
134 /*
135 * Never gets here, unless the suspend finisher fails.
136 * Successful cpu_suspend() should return from cpu_resume(),
137 * returning through this code path is considered an error
138 * If the return value is set to 0 force ret = -EOPNOTSUPP
139 * to make sure a proper error condition is propagated
140 */
141 if (!ret)
142 ret = -EOPNOTSUPP;
143
144 ct_cpuidle_exit();
145 } else {
146 ct_cpuidle_exit();
147 __cpu_suspend_exit();
148 }
149
150 arm_cpuidle_restore_irq_context(&context);
151
152 unpause_graph_tracing();
153
154 /*
155 * Restore pstate flags. OS lock and mdscr have been already
156 * restored, so from this point onwards, debugging is fully
157 * reenabled if it was enabled when core started shutdown.
158 */
159 local_daif_restore(flags);
160
161 return ret;
162 }
163
cpu_suspend_init(void)164 static int __init cpu_suspend_init(void)
165 {
166 /* ctx_ptr is an array of physical addresses */
167 sleep_save_stash = kcalloc(mpidr_hash_size(), sizeof(*sleep_save_stash),
168 GFP_KERNEL);
169
170 if (WARN_ON(!sleep_save_stash))
171 return -ENOMEM;
172
173 return 0;
174 }
175 early_initcall(cpu_suspend_init);
176