arch/arm64/kernel/suspend.c

   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  */
  26 unsigned 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  */
  35 static int (*hw_breakpoint_restore)(unsigned int);
  36 void __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
  44 void 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  */
  97 int 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
 176 static 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 }
 187 early_initcall(cpu_suspend_init);