usr/src/uts/i86pc/sys/comm_page.h

root/usr/src/uts/i86pc/sys/comm_page.h
/*
 * This file and its contents are supplied under the terms of the
 * Common Development and Distribution License ("CDDL"), version 1.0.
 * You may only use this file in accordance with the terms of version
 * 1.0 of the CDDL.
 *
 * A full copy of the text of the CDDL should have accompanied this
 * source.  A copy of the CDDL is also available via the Internet at
 * http://www.illumos.org/license/CDDL.
 */

/*
 * Copyright 2016 Joyent, Inc.
 * Copyright 2025 Oxide Computer Company
 */

#ifndef _COMM_PAGE_H
#define _COMM_PAGE_H

#ifndef _ASM
#include <sys/types.h>
#include <sys/param.h>
#include <sys/time.h>
#include <sys/sysmacros.h>
#endif /* _ASM */

#ifdef __cplusplus
extern "C" {
#endif

#ifndef _ASM

/*
 * x86 comm page
 *
 * This struct defines the data format for the "comm page": kernel data made
 * directly available to userspace for read-only operations.  This enables
 * facilities such as clock_gettime to operate entirely in userspace without
 * the need for a trap or fasttrap.
 *
 * A note about 32-bit/64-bit compatibility:
 * The current format of the comm page is designed to be consistent for both
 * 32-bit and 64-bit programs running in a 64-bit kernel.  On 32-bit kernels,
 * the comm page is not exposed to userspace due to the difference in
 * timespec_t sizing.
 *
 * This struct is instantiated "by hand" in assembly to preserve the global
 * symbols it contains.  That layout must be kept in sync with the structure
 * defined here.
 * See: "uts/i86pc/ml/comm_page.S"
 */
typedef struct comm_page_s {
        hrtime_t                cp_tsc_last;
        hrtime_t                cp_tsc_hrtime_base;
        hrtime_t                cp_tsc_resume_cap;
        uint32_t                cp_tsc_type;
        uint32_t                cp_tsc_max_delta;

        volatile uint32_t       cp_hres_lock;   /* must be 8-byte aligned */
        uint32_t                cp_nsec_scale;
        int64_t                 cp_hrestime_adj;
        hrtime_t                cp_hres_last_tick;
        uint32_t                cp_tsc_ncpu;
        uint32_t                _cp_pad0;
        volatile int64_t        cp_hrestime[2];
        uint64_t                _cp_pad1[502];  /* pad to page boundary */
#if defined(_MACHDEP)
        hrtime_t                cp_tsc_sync_tick_delta[NCPU];
        /* fill any remaining space in page with padding */
#define _CP_PAD2_SZ     P2ROUNDUP(NCPU, PAGESIZE / sizeof (hrtime_t)) - NCPU
        uint64_t                _cp_pad2[_CP_PAD2_SZ];
#else
        /* length resides in cp_tsc_ncpu */
        hrtime_t                cp_tsc_sync_tick_delta[];
#endif /* defined(_MACHDEP) */
} comm_page_t;

#if defined(_KERNEL)
extern comm_page_t comm_page;

#if defined(_MACHDEP)

#include <sys/debug.h>
CTASSERT((offsetof(comm_page_t, cp_tsc_sync_tick_delta) & PAGEOFFSET) == 0);
CTASSERT((sizeof (comm_page_t) & PAGEOFFSET) == 0);

extern hrtime_t tsc_last;
extern hrtime_t tsc_hrtime_base;
extern hrtime_t tsc_resume_cap;
extern uint32_t tsc_type;
extern uint32_t tsc_max_delta;
extern volatile uint32_t hres_lock;
extern uint32_t nsec_scale;
extern int64_t hrestime_adj;
extern hrtime_t hres_last_tick;
extern uint32_t tsc_ncpu;
extern volatile timestruc_t hrestime;
extern hrtime_t tsc_sync_tick_delta[NCPU];

#endif /* defined(_MACHDEP) */
#endif /* defined(_KERNEL) */

#endif  /* _ASM */

#ifdef __cplusplus
}
#endif

#endif /* _COMM_PAGE_H */
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