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 /*
46 * We are resuming from reset with the idmap active in TTBR0_EL1.
47 * We must uninstall the idmap and restore the expected MMU
48 * state before we can possibly return to userspace.
49 */
50 cpu_uninstall_idmap();
51
52 /* Restore CnP bit in TTBR1_EL1 */
53 if (system_supports_cnp())
54 cpu_replace_ttbr1(lm_alias(swapper_pg_dir));
55
56 /*
57 * PSTATE was not saved over suspend/resume, re-enable any detected
58 * features that might not have been set correctly.
59 */
60 __uaccess_enable_hw_pan();
61 uao_thread_switch(current);
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 MTE-specific configuration */
79 mte_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
95 /*
96 * From this point debug exceptions are disabled to prevent
97 * updates to mdscr register (saved and restored along with
98 * general purpose registers) from kernel debuggers.
99 */
100 flags = local_daif_save();
101
102 /*
103 * Function graph tracer state gets incosistent when the kernel
104 * calls functions that never return (aka suspend finishers) hence
105 * disable graph tracing during their execution.
106 */
107 pause_graph_tracing();
108
109 if (__cpu_suspend_enter(&state)) {
110 /* Call the suspend finisher */
111 ret = fn(arg);
112
113 /*
114 * Never gets here, unless the suspend finisher fails.
115 * Successful cpu_suspend() should return from cpu_resume(),
116 * returning through this code path is considered an error
117 * If the return value is set to 0 force ret = -EOPNOTSUPP
118 * to make sure a proper error condition is propagated
119 */
120 if (!ret)
121 ret = -EOPNOTSUPP;
122 } else {
123 __cpu_suspend_exit();
124 }
125
126 unpause_graph_tracing();
127
128 /*
129 * Restore pstate flags. OS lock and mdscr have been already
130 * restored, so from this point onwards, debugging is fully
131 * renabled if it was enabled when core started shutdown.
132 */
133 local_daif_restore(flags);
134
135 return ret;
136 }
137
cpu_suspend_init(void)138 static int __init cpu_suspend_init(void)
139 {
140 /* ctx_ptr is an array of physical addresses */
141 sleep_save_stash = kcalloc(mpidr_hash_size(), sizeof(*sleep_save_stash),
142 GFP_KERNEL);
143
144 if (WARN_ON(!sleep_save_stash))
145 return -ENOMEM;
146
147 return 0;
148 }
149 early_initcall(cpu_suspend_init);
150
