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