1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/ftrace.h>
3 #include <linux/percpu.h>
4 #include <linux/slab.h>
5 #include <asm/alternative.h>
6 #include <asm/cacheflush.h>
7 #include <asm/cpufeature.h>
8 #include <asm/debug-monitors.h>
9 #include <asm/exec.h>
10 #include <asm/pgtable.h>
11 #include <asm/memory.h>
12 #include <asm/mmu_context.h>
13 #include <asm/smp_plat.h>
14 #include <asm/suspend.h>
15 #include <asm/tlbflush.h>
16
17 /*
18 * This is allocated by cpu_suspend_init(), and used to store a pointer to
19 * the 'struct sleep_stack_data' the contains a particular CPUs state.
20 */
21 unsigned long *sleep_save_stash;
22
23 /*
24 * This hook is provided so that cpu_suspend code can restore HW
25 * breakpoints as early as possible in the resume path, before reenabling
26 * debug exceptions. Code cannot be run from a CPU PM notifier since by the
27 * time the notifier runs debug exceptions might have been enabled already,
28 * with HW breakpoints registers content still in an unknown state.
29 */
30 static int (*hw_breakpoint_restore)(unsigned int);
cpu_suspend_set_dbg_restorer(int (* hw_bp_restore)(unsigned int))31 void __init cpu_suspend_set_dbg_restorer(int (*hw_bp_restore)(unsigned int))
32 {
33 /* Prevent multiple restore hook initializations */
34 if (WARN_ON(hw_breakpoint_restore))
35 return;
36 hw_breakpoint_restore = hw_bp_restore;
37 }
38
__cpu_suspend_exit(void)39 void notrace __cpu_suspend_exit(void)
40 {
41 unsigned int cpu = smp_processor_id();
42
43 /*
44 * We are resuming from reset with the idmap active in TTBR0_EL1.
45 * We must uninstall the idmap and restore the expected MMU
46 * state before we can possibly return to userspace.
47 */
48 cpu_uninstall_idmap();
49
50 /*
51 * PSTATE was not saved over suspend/resume, re-enable any detected
52 * features that might not have been set correctly.
53 */
54 asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_HAS_PAN,
55 CONFIG_ARM64_PAN));
56 uao_thread_switch(current);
57
58 /*
59 * Restore HW breakpoint registers to sane values
60 * before debug exceptions are possibly reenabled
61 * through local_dbg_restore.
62 */
63 if (hw_breakpoint_restore)
64 hw_breakpoint_restore(cpu);
65
66 /*
67 * On resume, firmware implementing dynamic mitigation will
68 * have turned the mitigation on. If the user has forcefully
69 * disabled it, make sure their wishes are obeyed.
70 */
71 if (arm64_get_ssbd_state() == ARM64_SSBD_FORCE_DISABLE)
72 arm64_set_ssbd_mitigation(false);
73 }
74
75 /*
76 * cpu_suspend
77 *
78 * arg: argument to pass to the finisher function
79 * fn: finisher function pointer
80 *
81 */
cpu_suspend(unsigned long arg,int (* fn)(unsigned long))82 int cpu_suspend(unsigned long arg, int (*fn)(unsigned long))
83 {
84 int ret = 0;
85 unsigned long flags;
86 struct sleep_stack_data state;
87
88 /*
89 * From this point debug exceptions are disabled to prevent
90 * updates to mdscr register (saved and restored along with
91 * general purpose registers) from kernel debuggers.
92 */
93 local_dbg_save(flags);
94
95 /*
96 * Function graph tracer state gets incosistent when the kernel
97 * calls functions that never return (aka suspend finishers) hence
98 * disable graph tracing during their execution.
99 */
100 pause_graph_tracing();
101
102 if (__cpu_suspend_enter(&state)) {
103 /* Call the suspend finisher */
104 ret = fn(arg);
105
106 /*
107 * Never gets here, unless the suspend finisher fails.
108 * Successful cpu_suspend() should return from cpu_resume(),
109 * returning through this code path is considered an error
110 * If the return value is set to 0 force ret = -EOPNOTSUPP
111 * to make sure a proper error condition is propagated
112 */
113 if (!ret)
114 ret = -EOPNOTSUPP;
115 } else {
116 __cpu_suspend_exit();
117 }
118
119 unpause_graph_tracing();
120
121 /*
122 * Restore pstate flags. OS lock and mdscr have been already
123 * restored, so from this point onwards, debugging is fully
124 * renabled if it was enabled when core started shutdown.
125 */
126 local_dbg_restore(flags);
127
128 return ret;
129 }
130
cpu_suspend_init(void)131 static int __init cpu_suspend_init(void)
132 {
133 /* ctx_ptr is an array of physical addresses */
134 sleep_save_stash = kcalloc(mpidr_hash_size(), sizeof(*sleep_save_stash),
135 GFP_KERNEL);
136
137 if (WARN_ON(!sleep_save_stash))
138 return -ENOMEM;
139
140 return 0;
141 }
142 early_initcall(cpu_suspend_init);
143