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 <asm/alternative.h>
7 #include <asm/cacheflush.h>
8 #include <asm/cpufeature.h>
9 #include <asm/daifflags.h>
10 #include <asm/debug-monitors.h>
11 #include <asm/exec.h>
12 #include <asm/pgtable.h>
13 #include <asm/memory.h>
14 #include <asm/mmu_context.h>
15 #include <asm/smp_plat.h>
16 #include <asm/suspend.h>
17
18 /*
19 * This is allocated by cpu_suspend_init(), and used to store a pointer to
20 * the 'struct sleep_stack_data' the contains a particular CPUs state.
21 */
22 unsigned long *sleep_save_stash;
23
24 /*
25 * This hook is provided so that cpu_suspend code can restore HW
26 * breakpoints as early as possible in the resume path, before reenabling
27 * debug exceptions. Code cannot be run from a CPU PM notifier since by the
28 * time the notifier runs debug exceptions might have been enabled already,
29 * with HW breakpoints registers content still in an unknown state.
30 */
31 static int (*hw_breakpoint_restore)(unsigned int);
32 void __init cpu_suspend_set_dbg_restorer(int (*hw_bp_restore)(unsigned int))
33 {
34 /* Prevent multiple restore hook initializations */
35 if (WARN_ON(hw_breakpoint_restore))
36 return;
37 hw_breakpoint_restore = hw_bp_restore;
38 }
39
40 void notrace __cpu_suspend_exit(void)
41 {
42 unsigned int cpu = smp_processor_id();
43
44 /*
45 * We are resuming from reset with the idmap active in TTBR0_EL1.
46 * We must uninstall the idmap and restore the expected MMU
47 * state before we can possibly return to userspace.
48 */
49 cpu_uninstall_idmap();
50
51 /* Restore CnP bit in TTBR1_EL1 */
52 if (system_supports_cnp())
53 cpu_replace_ttbr1(lm_alias(swapper_pg_dir));
54
55 /*
56 * PSTATE was not saved over suspend/resume, re-enable any detected
57 * features that might not have been set correctly.
58 */
59 __uaccess_enable_hw_pan();
60 uao_thread_switch(current);
61
62 /*
63 * Restore HW breakpoint registers to sane values
64 * before debug exceptions are possibly reenabled
65 * by cpu_suspend()s local_daif_restore() call.
66 */
67 if (hw_breakpoint_restore)
68 hw_breakpoint_restore(cpu);
69
70 /*
71 * On resume, firmware implementing dynamic mitigation will
72 * have turned the mitigation on. If the user has forcefully
73 * disabled it, make sure their wishes are obeyed.
74 */
75 if (arm64_get_ssbd_state() == ARM64_SSBD_FORCE_DISABLE)
76 arm64_set_ssbd_mitigation(false);
77 }
78
79 /*
80 * cpu_suspend
81 *
82 * arg: argument to pass to the finisher function
83 * fn: finisher function pointer
84 *
85 */
86 int cpu_suspend(unsigned long arg, int (*fn)(unsigned long))
87 {
88 int ret = 0;
89 unsigned long flags;
90 struct sleep_stack_data state;
91
92 /*
93 * From this point debug exceptions are disabled to prevent
94 * updates to mdscr register (saved and restored along with
95 * general purpose registers) from kernel debuggers.
96 */
97 flags = local_daif_save();
98
99 /*
100 * Function graph tracer state gets incosistent when the kernel
101 * calls functions that never return (aka suspend finishers) hence
102 * disable graph tracing during their execution.
103 */
104 pause_graph_tracing();
105
106 if (__cpu_suspend_enter(&state)) {
107 /* Call the suspend finisher */
108 ret = fn(arg);
109
110 /*
111 * Never gets here, unless the suspend finisher fails.
112 * Successful cpu_suspend() should return from cpu_resume(),
113 * returning through this code path is considered an error
114 * If the return value is set to 0 force ret = -EOPNOTSUPP
115 * to make sure a proper error condition is propagated
116 */
117 if (!ret)
118 ret = -EOPNOTSUPP;
119 } else {
120 __cpu_suspend_exit();
121 }
122
123 unpause_graph_tracing();
124
125 /*
126 * Restore pstate flags. OS lock and mdscr have been already
127 * restored, so from this point onwards, debugging is fully
128 * renabled if it was enabled when core started shutdown.
129 */
130 local_daif_restore(flags);
131
132 return ret;
133 }
134
135 static int __init cpu_suspend_init(void)
136 {
137 /* ctx_ptr is an array of physical addresses */
138 sleep_save_stash = kcalloc(mpidr_hash_size(), sizeof(*sleep_save_stash),
139 GFP_KERNEL);
140
141 if (WARN_ON(!sleep_save_stash))
142 return -ENOMEM;
143
144 return 0;
145 }
146 early_initcall(cpu_suspend_init);