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          * PSTATE was not saved over suspend/resume, re-enable any detected
  51          * features that might not have been set correctly.
  52          */
  53         asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_HAS_PAN,
  54                         CONFIG_ARM64_PAN));
  55         uao_thread_switch(current);
  56
  57         /*
  58          * Restore HW breakpoint registers to sane values
  59          * before debug exceptions are possibly reenabled
  60          * through local_dbg_restore.
  61          */
  62         if (hw_breakpoint_restore)
  63                 hw_breakpoint_restore(cpu);
  64 }
  65
  66 /*
  67  * cpu_suspend
  68  *
  69  * arg: argument to pass to the finisher function
  70  * fn: finisher function pointer
  71  *
  72  */
  73 int cpu_suspend(unsigned long arg, int (*fn)(unsigned long))
  74 {
  75         int ret = 0;
  76         unsigned long flags;
  77         struct sleep_stack_data state;
  78
  79         /*
  80          * From this point debug exceptions are disabled to prevent
  81          * updates to mdscr register (saved and restored along with
  82          * general purpose registers) from kernel debuggers.
  83          */
  84         local_dbg_save(flags);
  85
  86         /*
  87          * Function graph tracer state gets incosistent when the kernel
  88          * calls functions that never return (aka suspend finishers) hence
  89          * disable graph tracing during their execution.
  90          */
  91         pause_graph_tracing();
  92
  93         if (__cpu_suspend_enter(&state)) {
  94                 /* Call the suspend finisher */
  95                 ret = fn(arg);
  96
  97                 /*
  98                  * Never gets here, unless the suspend finisher fails.
  99                  * Successful cpu_suspend() should return from cpu_resume(),
 100                  * returning through this code path is considered an error
 101                  * If the return value is set to 0 force ret = -EOPNOTSUPP
 102                  * to make sure a proper error condition is propagated
 103                  */
 104                 if (!ret)
 105                         ret = -EOPNOTSUPP;
 106         } else {
 107                 __cpu_suspend_exit();
 108         }
 109
 110         unpause_graph_tracing();
 111
 112         /*
 113          * Restore pstate flags. OS lock and mdscr have been already
 114          * restored, so from this point onwards, debugging is fully
 115          * renabled if it was enabled when core started shutdown.
 116          */
 117         local_dbg_restore(flags);
 118
 119         return ret;
 120 }
 121
 122 static int __init cpu_suspend_init(void)
 123 {
 124         /* ctx_ptr is an array of physical addresses */
 125         sleep_save_stash = kcalloc(mpidr_hash_size(), sizeof(*sleep_save_stash),
 126                                    GFP_KERNEL);
 127
 128         if (WARN_ON(!sleep_save_stash))
 129                 return -ENOMEM;
 130
 131         return 0;
 132 }
 133 early_initcall(cpu_suspend_init);