arch/mips/include/asm/vdso.h

   1 /* SPDX-License-Identifier: GPL-2.0-or-later */
   2 /*
   3  * Copyright (C) 2015 Imagination Technologies
   4  * Author: Alex Smith <alex.smith@imgtec.com>
   5  */
   6
   7 #ifndef __ASM_VDSO_H
   8 #define __ASM_VDSO_H
   9
  10 #include <linux/mm_types.h>
  11
  12 #include <asm/barrier.h>
  13
  14 /**
  15  * struct mips_vdso_image - Details of a VDSO image.
  16  * @data: Pointer to VDSO image data (page-aligned).
  17  * @size: Size of the VDSO image data (page-aligned).
  18  * @off_sigreturn: Offset of the sigreturn() trampoline.
  19  * @off_rt_sigreturn: Offset of the rt_sigreturn() trampoline.
  20  * @mapping: Special mapping structure.
  21  *
  22  * This structure contains details of a VDSO image, including the image data
  23  * and offsets of certain symbols required by the kernel. It is generated as
  24  * part of the VDSO build process, aside from the mapping page array, which is
  25  * populated at runtime.
  26  */
  27 struct mips_vdso_image {
  28         void *data;
  29         unsigned long size;
  30
  31         unsigned long off_sigreturn;
  32         unsigned long off_rt_sigreturn;
  33
  34         struct vm_special_mapping mapping;
  35 };
  36
  37 /*
  38  * The following structures are auto-generated as part of the build for each
  39  * ABI by genvdso, see arch/mips/vdso/Makefile.
  40  */
  41
  42 extern struct mips_vdso_image vdso_image;
  43
  44 #ifdef CONFIG_MIPS32_O32
  45 extern struct mips_vdso_image vdso_image_o32;
  46 #endif
  47
  48 #ifdef CONFIG_MIPS32_N32
  49 extern struct mips_vdso_image vdso_image_n32;
  50 #endif
  51
  52 /**
  53  * union mips_vdso_data - Data provided by the kernel for the VDSO.
  54  * @xtime_sec:          Current real time (seconds part).
  55  * @xtime_nsec:         Current real time (nanoseconds part, shifted).
  56  * @wall_to_mono_sec:   Wall-to-monotonic offset (seconds part).
  57  * @wall_to_mono_nsec:  Wall-to-monotonic offset (nanoseconds part).
  58  * @seq_count:          Counter to synchronise updates (odd = updating).
  59  * @cs_shift:           Clocksource shift value.
  60  * @clock_mode:         Clocksource to use for time functions.
  61  * @cs_mult:            Clocksource multiplier value.
  62  * @cs_cycle_last:      Clock cycle value at last update.
  63  * @cs_mask:            Clocksource mask value.
  64  * @tz_minuteswest:     Minutes west of Greenwich (from timezone).
  65  * @tz_dsttime:         Type of DST correction (from timezone).
  66  *
  67  * This structure contains data needed by functions within the VDSO. It is
  68  * populated by the kernel and mapped read-only into user memory. The time
  69  * fields are mirrors of internal data from the timekeeping infrastructure.
  70  *
  71  * Note: Care should be taken when modifying as the layout must remain the same
  72  * for both 64- and 32-bit (for 32-bit userland on 64-bit kernel).
  73  */
  74 union mips_vdso_data {
  75         struct {
  76                 u64 xtime_sec;
  77                 u64 xtime_nsec;
  78                 u64 wall_to_mono_sec;
  79                 u64 wall_to_mono_nsec;
  80                 u32 seq_count;
  81                 u32 cs_shift;
  82                 u8 clock_mode;
  83                 u32 cs_mult;
  84                 u64 cs_cycle_last;
  85                 u64 cs_mask;
  86                 s32 tz_minuteswest;
  87                 s32 tz_dsttime;
  88         };
  89
  90         u8 page[PAGE_SIZE];
  91 };
  92
  93 static inline u32 vdso_data_read_begin(const union mips_vdso_data *data)
  94 {
  95         u32 seq;
  96
  97         while (true) {
  98                 seq = READ_ONCE(data->seq_count);
  99                 if (likely(!(seq & 1))) {
 100                         /* Paired with smp_wmb() in vdso_data_write_*(). */
 101                         smp_rmb();
 102                         return seq;
 103                 }
 104
 105                 cpu_relax();
 106         }
 107 }
 108
 109 static inline bool vdso_data_read_retry(const union mips_vdso_data *data,
 110                                         u32 start_seq)
 111 {
 112         /* Paired with smp_wmb() in vdso_data_write_*(). */
 113         smp_rmb();
 114         return unlikely(data->seq_count != start_seq);
 115 }
 116
 117 static inline void vdso_data_write_begin(union mips_vdso_data *data)
 118 {
 119         ++data->seq_count;
 120
 121         /* Ensure sequence update is written before other data page values. */
 122         smp_wmb();
 123 }
 124
 125 static inline void vdso_data_write_end(union mips_vdso_data *data)
 126 {
 127         /* Ensure data values are written before updating sequence again. */
 128         smp_wmb();
 129         ++data->seq_count;
 130 }
 131
 132 #endif /* __ASM_VDSO_H */