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Diffstat (limited to 'arch/mips/include/asm/vdso.h')
| -rw-r--r-- | arch/mips/include/asm/vdso.h | 136 |
1 files changed, 136 insertions, 0 deletions
diff --git a/arch/mips/include/asm/vdso.h b/arch/mips/include/asm/vdso.h new file mode 100644 index 000000000..91bf0c2c2 --- /dev/null +++ b/arch/mips/include/asm/vdso.h @@ -0,0 +1,136 @@ +/* + * 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; + u64 wall_to_mono_sec; + u64 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 = READ_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 */ |