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 <linux/cpuidle.h>
8#include <asm/alternative.h>
9#include <asm/cacheflush.h>
10#include <asm/cpufeature.h>
11#include <asm/cpuidle.h>
12#include <asm/daifflags.h>
13#include <asm/debug-monitors.h>
14#include <asm/exec.h>
15#include <asm/fpsimd.h>
16#include <asm/mte.h>
17#include <asm/memory.h>
18#include <asm/mmu_context.h>
19#include <asm/smp_plat.h>
20#include <asm/suspend.h>
21
22/*
23 * This is allocated by cpu_suspend_init(), and used to store a pointer to
24 * the 'struct sleep_stack_data' the contains a particular CPUs state.
25 */
26unsigned long *sleep_save_stash;
27
28/*
29 * This hook is provided so that cpu_suspend code can restore HW
30 * breakpoints as early as possible in the resume path, before reenabling
31 * debug exceptions. Code cannot be run from a CPU PM notifier since by the
32 * time the notifier runs debug exceptions might have been enabled already,
33 * with HW breakpoints registers content still in an unknown state.
34 */
35static int (*hw_breakpoint_restore)(unsigned int);
36void __init cpu_suspend_set_dbg_restorer(int (*hw_bp_restore)(unsigned int))
37{
38	/* Prevent multiple restore hook initializations */
39	if (WARN_ON(hw_breakpoint_restore))
40		return;
41	hw_breakpoint_restore = hw_bp_restore;
42}
43
44void notrace __cpu_suspend_exit(void)
45{
46	unsigned int cpu = smp_processor_id();
47
48	mte_suspend_exit();
49
50	/*
51	 * We are resuming from reset with the idmap active in TTBR0_EL1.
52	 * We must uninstall the idmap and restore the expected MMU
53	 * state before we can possibly return to userspace.
54	 */
55	cpu_uninstall_idmap();
56
57	/* Restore CnP bit in TTBR1_EL1 */
58	if (system_supports_cnp())
59		cpu_enable_swapper_cnp();
60
61	/*
62	 * PSTATE was not saved over suspend/resume, re-enable any detected
63	 * features that might not have been set correctly.
64	 */
65	if (alternative_has_cap_unlikely(ARM64_HAS_DIT))
66		set_pstate_dit(1);
67	__uaccess_enable_hw_pan();
68
69	/*
70	 * Restore HW breakpoint registers to sane values
71	 * before debug exceptions are possibly reenabled
72	 * by cpu_suspend()s local_daif_restore() call.
73	 */
74	if (hw_breakpoint_restore)
75		hw_breakpoint_restore(cpu);
76
77	/*
78	 * On resume, firmware implementing dynamic mitigation will
79	 * have turned the mitigation on. If the user has forcefully
80	 * disabled it, make sure their wishes are obeyed.
81	 */
82	spectre_v4_enable_mitigation(NULL);
83
84	sme_suspend_exit();
85
86	/* Restore additional feature-specific configuration */
87	ptrauth_suspend_exit();
88}
89
90/*
91 * cpu_suspend
92 *
93 * arg: argument to pass to the finisher function
94 * fn: finisher function pointer
95 *
96 */
97int cpu_suspend(unsigned long arg, int (*fn)(unsigned long))
98{
99	int ret = 0;
100	unsigned long flags;
101	struct sleep_stack_data state;
102	struct arm_cpuidle_irq_context context;
103
104	/*
105	 * Some portions of CPU state (e.g. PSTATE.{PAN,DIT}) are initialized
106	 * before alternatives are patched, but are only restored by
107	 * __cpu_suspend_exit() after alternatives are patched. To avoid
108	 * accidentally losing these bits we must not attempt to suspend until
109	 * after alternatives have been patched.
110	 */
111	WARN_ON(!system_capabilities_finalized());
112
113	/* Report any MTE async fault before going to suspend */
114	mte_suspend_enter();
115
116	/*
117	 * From this point debug exceptions are disabled to prevent
118	 * updates to mdscr register (saved and restored along with
119	 * general purpose registers) from kernel debuggers.
120	 *
121	 * Strictly speaking the trace_hardirqs_off() here is superfluous,
122	 * hardirqs should be firmly off by now. This really ought to use
123	 * something like raw_local_daif_save().
124	 */
125	flags = local_daif_save();
126
127	/*
128	 * Function graph tracer state gets inconsistent when the kernel
129	 * calls functions that never return (aka suspend finishers) hence
130	 * disable graph tracing during their execution.
131	 */
132	pause_graph_tracing();
133
134	/*
135	 * Switch to using DAIF.IF instead of PMR in order to reliably
136	 * resume if we're using pseudo-NMIs.
137	 */
138	arm_cpuidle_save_irq_context(&context);
139
140	ct_cpuidle_enter();
141
142	if (__cpu_suspend_enter(&state)) {
143		/* Call the suspend finisher */
144		ret = fn(arg);
145
146		/*
147		 * Never gets here, unless the suspend finisher fails.
148		 * Successful cpu_suspend() should return from cpu_resume(),
149		 * returning through this code path is considered an error
150		 * If the return value is set to 0 force ret = -EOPNOTSUPP
151		 * to make sure a proper error condition is propagated
152		 */
153		if (!ret)
154			ret = -EOPNOTSUPP;
155
156		ct_cpuidle_exit();
157	} else {
158		ct_cpuidle_exit();
159		__cpu_suspend_exit();
160	}
161
162	arm_cpuidle_restore_irq_context(&context);
163
164	unpause_graph_tracing();
165
166	/*
167	 * Restore pstate flags. OS lock and mdscr have been already
168	 * restored, so from this point onwards, debugging is fully
169	 * reenabled if it was enabled when core started shutdown.
170	 */
171	local_daif_restore(flags);
172
173	return ret;
174}
175
176static int __init cpu_suspend_init(void)
177{
178	/* ctx_ptr is an array of physical addresses */
179	sleep_save_stash = kcalloc(mpidr_hash_size(), sizeof(*sleep_save_stash),
180				   GFP_KERNEL);
181
182	if (WARN_ON(!sleep_save_stash))
183		return -ENOMEM;
184
185	return 0;
186}
187early_initcall(cpu_suspend_init);
188