arch/arm64/kernel/suspend.c

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