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