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 /*
47 * We are resuming from reset with the idmap active in TTBR0_EL1.
48 * We must uninstall the idmap and restore the expected MMU
49 * state before we can possibly return to userspace.
50 */
51 cpu_uninstall_idmap();
52
53 /* Restore CnP bit in TTBR1_EL1 */
54 if (system_supports_cnp())
55 cpu_replace_ttbr1(lm_alias(swapper_pg_dir));
56
57 /*
58 * PSTATE was not saved over suspend/resume, re-enable any detected
59 * features that might not have been set correctly.
60 */
61 __uaccess_enable_hw_pan();
62
63 /*
64 * Restore HW breakpoint registers to sane values
65 * before debug exceptions are possibly reenabled
66 * by cpu_suspend()s local_daif_restore() call.
67 */
68 if (hw_breakpoint_restore)
69 hw_breakpoint_restore(cpu);
70
71 /*
72 * On resume, firmware implementing dynamic mitigation will
73 * have turned the mitigation on. If the user has forcefully
74 * disabled it, make sure their wishes are obeyed.
75 */
76 spectre_v4_enable_mitigation(NULL);
77
78 /* Restore additional feature-specific configuration */
79 ptrauth_suspend_exit();
80 }
81
82 /*
83 * cpu_suspend
84 *
85 * arg: argument to pass to the finisher function
86 * fn: finisher function pointer
87 *
88 */
cpu_suspend(unsigned long arg,int (* fn)(unsigned long))89 int cpu_suspend(unsigned long arg, int (*fn)(unsigned long))
90 {
91 int ret = 0;
92 unsigned long flags;
93 struct sleep_stack_data state;
94 struct arm_cpuidle_irq_context context;
95
96 /* Report any MTE async fault before going to suspend */
97 mte_suspend_enter();
98
99 /*
100 * From this point debug exceptions are disabled to prevent
101 * updates to mdscr register (saved and restored along with
102 * general purpose registers) from kernel debuggers.
103 */
104 flags = local_daif_save();
105
106 /*
107 * Function graph tracer state gets inconsistent when the kernel
108 * calls functions that never return (aka suspend finishers) hence
109 * disable graph tracing during their execution.
110 */
111 pause_graph_tracing();
112
113 /*
114 * Switch to using DAIF.IF instead of PMR in order to reliably
115 * resume if we're using pseudo-NMIs.
116 */
117 arm_cpuidle_save_irq_context(&context);
118
119 if (__cpu_suspend_enter(&state)) {
120 /* Call the suspend finisher */
121 ret = fn(arg);
122
123 /*
124 * Never gets here, unless the suspend finisher fails.
125 * Successful cpu_suspend() should return from cpu_resume(),
126 * returning through this code path is considered an error
127 * If the return value is set to 0 force ret = -EOPNOTSUPP
128 * to make sure a proper error condition is propagated
129 */
130 if (!ret)
131 ret = -EOPNOTSUPP;
132 } else {
133 RCU_NONIDLE(__cpu_suspend_exit());
134 }
135
136 arm_cpuidle_restore_irq_context(&context);
137
138 unpause_graph_tracing();
139
140 /*
141 * Restore pstate flags. OS lock and mdscr have been already
142 * restored, so from this point onwards, debugging is fully
143 * reenabled if it was enabled when core started shutdown.
144 */
145 local_daif_restore(flags);
146
147 return ret;
148 }
149
cpu_suspend_init(void)150 static int __init cpu_suspend_init(void)
151 {
152 /* ctx_ptr is an array of physical addresses */
153 sleep_save_stash = kcalloc(mpidr_hash_size(), sizeof(*sleep_save_stash),
154 GFP_KERNEL);
155
156 if (WARN_ON(!sleep_save_stash))
157 return -ENOMEM;
158
159 return 0;
160 }
161 early_initcall(cpu_suspend_init);
162