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 <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);
  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
  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
  62         /*
  63          * Restore HW breakpoint registers to sane values
  64          * before debug exceptions are possibly reenabled
  65          * by cpu_suspend()s local_daif_restore() call.
  66          */
  67         if (hw_breakpoint_restore)
  68                 hw_breakpoint_restore(cpu);
  69
  70         /*
  71          * On resume, firmware implementing dynamic mitigation will
  72          * have turned the mitigation on. If the user has forcefully
  73          * disabled it, make sure their wishes are obeyed.
  74          */
  75         spectre_v4_enable_mitigation(NULL);
  76
  77         /* Restore additional MTE-specific configuration */
  78         mte_suspend_exit();
  79 }
  80
  81 /*
  82  * cpu_suspend
  83  *
  84  * arg: argument to pass to the finisher function
  85  * fn: finisher function pointer
  86  *
  87  */
  88 int cpu_suspend(unsigned long arg, int (*fn)(unsigned long))
  89 {
  90         int ret = 0;
  91         unsigned long flags;
  92         struct sleep_stack_data state;
  93
  94         /*
  95          * From this point debug exceptions are disabled to prevent
  96          * updates to mdscr register (saved and restored along with
  97          * general purpose registers) from kernel debuggers.
  98          */
  99         flags = local_daif_save();
 100
 101         /*
 102          * Function graph tracer state gets incosistent when the kernel
 103          * calls functions that never return (aka suspend finishers) hence
 104          * disable graph tracing during their execution.
 105          */
 106         pause_graph_tracing();
 107
 108         if (__cpu_suspend_enter(&state)) {
 109                 /* Call the suspend finisher */
 110                 ret = fn(arg);
 111
 112                 /*
 113                  * Never gets here, unless the suspend finisher fails.
 114                  * Successful cpu_suspend() should return from cpu_resume(),
 115                  * returning through this code path is considered an error
 116                  * If the return value is set to 0 force ret = -EOPNOTSUPP
 117                  * to make sure a proper error condition is propagated
 118                  */
 119                 if (!ret)
 120                         ret = -EOPNOTSUPP;
 121         } else {
 122                 __cpu_suspend_exit();
 123         }
 124
 125         unpause_graph_tracing();
 126
 127         /*
 128          * Restore pstate flags. OS lock and mdscr have been already
 129          * restored, so from this point onwards, debugging is fully
 130          * renabled if it was enabled when core started shutdown.
 131          */
 132         local_daif_restore(flags);
 133
 134         return ret;
 135 }
 136
 137 static int __init cpu_suspend_init(void)
 138 {
 139         /* ctx_ptr is an array of physical addresses */
 140         sleep_save_stash = kcalloc(mpidr_hash_size(), sizeof(*sleep_save_stash),
 141                                    GFP_KERNEL);
 142
 143         if (WARN_ON(!sleep_save_stash))
 144                 return -ENOMEM;
 145
 146         return 0;
 147 }
 148 early_initcall(cpu_suspend_init);