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