vdso.h
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/*
* Copyright (C) 2015 Imagination Technologies
* Author: Alex Smith <alex.smith@imgtec.com>
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation; either version 2 of the License, or (at your
* option) any later version.
*/
#ifndef __ASM_VDSO_H
#define __ASM_VDSO_H
#include <linux/mm_types.h>
#include <asm/barrier.h>
/**
* struct mips_vdso_image - Details of a VDSO image.
* @data: Pointer to VDSO image data (page-aligned).
* @size: Size of the VDSO image data (page-aligned).
* @off_sigreturn: Offset of the sigreturn() trampoline.
* @off_rt_sigreturn: Offset of the rt_sigreturn() trampoline.
* @mapping: Special mapping structure.
*
* This structure contains details of a VDSO image, including the image data
* and offsets of certain symbols required by the kernel. It is generated as
* part of the VDSO build process, aside from the mapping page array, which is
* populated at runtime.
*/
struct mips_vdso_image {
void *data;
unsigned long size;
unsigned long off_sigreturn;
unsigned long off_rt_sigreturn;
struct vm_special_mapping mapping;
};
/*
* The following structures are auto-generated as part of the build for each
* ABI by genvdso, see arch/mips/vdso/Makefile.
*/
extern struct mips_vdso_image vdso_image;
#ifdef CONFIG_MIPS32_O32
extern struct mips_vdso_image vdso_image_o32;
#endif
#ifdef CONFIG_MIPS32_N32
extern struct mips_vdso_image vdso_image_n32;
#endif
/**
* union mips_vdso_data - Data provided by the kernel for the VDSO.
* @xtime_sec: Current real time (seconds part).
* @xtime_nsec: Current real time (nanoseconds part, shifted).
* @wall_to_mono_sec: Wall-to-monotonic offset (seconds part).
* @wall_to_mono_nsec: Wall-to-monotonic offset (nanoseconds part).
* @seq_count: Counter to synchronise updates (odd = updating).
* @cs_shift: Clocksource shift value.
* @clock_mode: Clocksource to use for time functions.
* @cs_mult: Clocksource multiplier value.
* @cs_cycle_last: Clock cycle value at last update.
* @cs_mask: Clocksource mask value.
* @tz_minuteswest: Minutes west of Greenwich (from timezone).
* @tz_dsttime: Type of DST correction (from timezone).
*
* This structure contains data needed by functions within the VDSO. It is
* populated by the kernel and mapped read-only into user memory. The time
* fields are mirrors of internal data from the timekeeping infrastructure.
*
* Note: Care should be taken when modifying as the layout must remain the same
* for both 64- and 32-bit (for 32-bit userland on 64-bit kernel).
*/
union mips_vdso_data {
struct {
u64 xtime_sec;
u64 xtime_nsec;
u32 wall_to_mono_sec;
u32 wall_to_mono_nsec;
u32 seq_count;
u32 cs_shift;
u8 clock_mode;
u32 cs_mult;
u64 cs_cycle_last;
u64 cs_mask;
s32 tz_minuteswest;
s32 tz_dsttime;
};
u8 page[PAGE_SIZE];
};
static inline u32 vdso_data_read_begin(const union mips_vdso_data *data)
{
u32 seq;
while (true) {
seq = ACCESS_ONCE(data->seq_count);
if (likely(!(seq & 1))) {
/* Paired with smp_wmb() in vdso_data_write_*(). */
smp_rmb();
return seq;
}
cpu_relax();
}
}
static inline bool vdso_data_read_retry(const union mips_vdso_data *data,
u32 start_seq)
{
/* Paired with smp_wmb() in vdso_data_write_*(). */
smp_rmb();
return unlikely(data->seq_count != start_seq);
}
static inline void vdso_data_write_begin(union mips_vdso_data *data)
{
++data->seq_count;
/* Ensure sequence update is written before other data page values. */
smp_wmb();
}
static inline void vdso_data_write_end(union mips_vdso_data *data)
{
/* Ensure data values are written before updating sequence again. */
smp_wmb();
++data->seq_count;
}
#endif /* __ASM_VDSO_H */