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/daifflags.h>
11 #include <asm/debug-monitors.h>
12 #include <asm/exec.h>
13 #include <asm/mte.h>
14 #include <asm/memory.h>
15 #include <asm/mmu_context.h>
16 #include <asm/smp_plat.h>
17 #include <asm/suspend.h>
18
19 /*
20 * This is allocated by cpu_suspend_init(), and used to store a pointer to
21 * the 'struct sleep_stack_data' the contains a particular CPUs state.
22 */
23 unsigned long *sleep_save_stash;
24
25 /*
26 * This hook is provided so that cpu_suspend code can restore HW
27 * breakpoints as early as possible in the resume path, before reenabling
28 * debug exceptions. Code cannot be run from a CPU PM notifier since by the
29 * time the notifier runs debug exceptions might have been enabled already,
30 * with HW breakpoints registers content still in an unknown state.
31 */
32 static int (*hw_breakpoint_restore)(unsigned int);
cpu_suspend_set_dbg_restorer(int (* hw_bp_restore)(unsigned int))33 void __init cpu_suspend_set_dbg_restorer(int (*hw_bp_restore)(unsigned int))
34 {
35 /* Prevent multiple restore hook initializations */
36 if (WARN_ON(hw_breakpoint_restore))
37 return;
38 hw_breakpoint_restore = hw_bp_restore;
39 }
40
__cpu_suspend_exit(void)41 void notrace __cpu_suspend_exit(void)
42 {
43 unsigned int cpu = smp_processor_id();
44
45 mte_suspend_exit();
46
47 /*
48 * We are resuming from reset with the idmap active in TTBR0_EL1.
49 * We must uninstall the idmap and restore the expected MMU
50 * state before we can possibly return to userspace.
51 */
52 cpu_uninstall_idmap();
53
54 /* Restore CnP bit in TTBR1_EL1 */
55 if (system_supports_cnp())
56 cpu_replace_ttbr1(lm_alias(swapper_pg_dir));
57
58 /*
59 * PSTATE was not saved over suspend/resume, re-enable any detected
60 * features that might not have been set correctly.
61 */
62 __uaccess_enable_hw_pan();
63 uao_thread_switch(current);
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
97 /* Report any MTE async fault before going to suspend */
98 mte_suspend_enter();
99
100 /*
101 * From this point debug exceptions are disabled to prevent
102 * updates to mdscr register (saved and restored along with
103 * general purpose registers) from kernel debuggers.
104 */
105 flags = local_daif_save();
106
107 /*
108 * Function graph tracer state gets incosistent when the kernel
109 * calls functions that never return (aka suspend finishers) hence
110 * disable graph tracing during their execution.
111 */
112 pause_graph_tracing();
113
114 if (__cpu_suspend_enter(&state)) {
115 /* Call the suspend finisher */
116 ret = fn(arg);
117
118 /*
119 * Never gets here, unless the suspend finisher fails.
120 * Successful cpu_suspend() should return from cpu_resume(),
121 * returning through this code path is considered an error
122 * If the return value is set to 0 force ret = -EOPNOTSUPP
123 * to make sure a proper error condition is propagated
124 */
125 if (!ret)
126 ret = -EOPNOTSUPP;
127 } else {
128 RCU_NONIDLE(__cpu_suspend_exit());
129 }
130
131 unpause_graph_tracing();
132
133 /*
134 * Restore pstate flags. OS lock and mdscr have been already
135 * restored, so from this point onwards, debugging is fully
136 * renabled if it was enabled when core started shutdown.
137 */
138 local_daif_restore(flags);
139
140 return ret;
141 }
142
cpu_suspend_init(void)143 static int __init cpu_suspend_init(void)
144 {
145 /* ctx_ptr is an array of physical addresses */
146 sleep_save_stash = kcalloc(mpidr_hash_size(), sizeof(*sleep_save_stash),
147 GFP_KERNEL);
148
149 if (WARN_ON(!sleep_save_stash))
150 return -ENOMEM;
151
152 return 0;
153 }
154 early_initcall(cpu_suspend_init);
155