include/lttng/ringbuffer-context.h

   1 /*
   2  * SPDX-License-Identifier: MIT
   3  *
   4  * Copyright (C) 2010-2021 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   5  *
   6  * Ring buffer context header.
   7  */
   8
   9 #ifndef _LTTNG_RING_BUFFER_CONTEXT_H
  10 #define _LTTNG_RING_BUFFER_CONTEXT_H
  11
  12 #include <errno.h>
  13 #include <stdint.h>
  14 #include <stddef.h>
  15 #include <urcu/arch.h>
  16 #include <string.h>
  17
  18 #include <lttng/ust-tracer.h>
  19 #include <lttng/ust-align.h>
  20 #include <lttng/ust-compiler.h>
  21
  22 struct lttng_ust_lib_ring_buffer;
  23 struct lttng_ust_lib_ring_buffer_channel;
  24 struct lttng_ust_lib_ring_buffer_ctx;
  25 struct lttng_ust_shm_handle;
  26
  27 /*
  28  * ring buffer context
  29  *
  30  * Context passed to lib_ring_buffer_reserve(), lib_ring_buffer_commit(),
  31  * lib_ring_buffer_try_discard_reserve(), lib_ring_buffer_align_ctx() and
  32  * lib_ring_buffer_write().
  33  *
  34  * IMPORTANT: this structure is part of the ABI between the probe and
  35  * UST. Fields need to be only added at the end, never reordered, never
  36  * removed.
  37  *
  38  * The field @struct_size should be used to determine the size of the
  39  * structure. It should be queried before using additional fields added
  40  * at the end of the structure.
  41  */
  42 struct lttng_ust_lib_ring_buffer_ctx {
  43         uint32_t struct_size;           /* Size of this structure. */
  44
  45         /* input received by lib_ring_buffer_reserve(), saved here. */
  46         struct lttng_ust_lib_ring_buffer_channel *chan; /* channel */
  47         void *priv;                     /* client private data */
  48         struct lttng_ust_shm_handle *handle;    /* shared-memory handle */
  49         size_t data_size;               /* size of payload */
  50         int largest_align;              /*
  51                                          * alignment of the largest element
  52                                          * in the payload
  53                                          */
  54
  55         /* output from lib_ring_buffer_reserve() */
  56         int reserve_cpu;                /* processor id updated by the reserve */
  57         struct lttng_ust_lib_ring_buffer *buf;  /*
  58                                          * buffer corresponding to processor id
  59                                          * for this channel
  60                                          */
  61         size_t slot_size;               /* size of the reserved slot */
  62         unsigned long buf_offset;       /* offset following the record header */
  63         unsigned long pre_offset;       /*
  64                                          * Initial offset position _before_
  65                                          * the record is written. Positioned
  66                                          * prior to record header alignment
  67                                          * padding.
  68                                          */
  69         uint64_t tsc;                   /* time-stamp counter value */
  70         unsigned int rflags;            /* reservation flags */
  71         void *ip;                       /* caller ip address */
  72         struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages;
  73
  74         /* End of base ABI. Fields below should be used after checking struct_size. */
  75 };
  76
  77 /**
  78  * lib_ring_buffer_ctx_init - initialize ring buffer context
  79  * @ctx: ring buffer context to initialize
  80  * @chan: channel
  81  * @priv: client private data
  82  * @data_size: size of record data payload
  83  * @largest_align: largest alignment within data payload types
  84  */
  85 static inline lttng_ust_notrace
  86 void lib_ring_buffer_ctx_init(struct lttng_ust_lib_ring_buffer_ctx *ctx,
  87                               struct lttng_ust_lib_ring_buffer_channel *chan,
  88                               void *priv, size_t data_size, int largest_align,
  89                               struct lttng_ust_shm_handle *handle);
  90 static inline
  91 void lib_ring_buffer_ctx_init(struct lttng_ust_lib_ring_buffer_ctx *ctx,
  92                               struct lttng_ust_lib_ring_buffer_channel *chan,
  93                               void *priv, size_t data_size, int largest_align,
  94                               struct lttng_ust_shm_handle *handle)
  95 {
  96         ctx->struct_size = sizeof(struct lttng_ust_lib_ring_buffer_ctx);
  97         ctx->chan = chan;
  98         ctx->priv = priv;
  99         ctx->data_size = data_size;
 100         ctx->reserve_cpu = -1;
 101         ctx->largest_align = largest_align;
 102         ctx->rflags = 0;
 103         ctx->handle = handle;
 104         ctx->ip = 0;
 105 }
 106
 107 /*
 108  * We need to define RING_BUFFER_ALIGN_ATTR so it is known early at
 109  * compile-time. We have to duplicate the "config->align" information and the
 110  * definition here because config->align is used both in the slow and fast
 111  * paths, but RING_BUFFER_ALIGN_ATTR is only available for the client code.
 112  */
 113 #ifdef RING_BUFFER_ALIGN
 114
 115 # define RING_BUFFER_ALIGN_ATTR         /* Default arch alignment */
 116
 117 /*
 118  * Calculate the offset needed to align the type.
 119  * size_of_type must be non-zero.
 120  */
 121 static inline lttng_ust_notrace
 122 unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type);
 123 static inline
 124 unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type)
 125 {
 126         return lttng_ust_offset_align(align_drift, size_of_type);
 127 }
 128
 129 #else
 130
 131 # define RING_BUFFER_ALIGN_ATTR __attribute__((packed))
 132
 133 /*
 134  * Calculate the offset needed to align the type.
 135  * size_of_type must be non-zero.
 136  */
 137 static inline lttng_ust_notrace
 138 unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type);
 139 static inline
 140 unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type)
 141 {
 142         return 0;
 143 }
 144
 145 #endif
 146
 147 /**
 148  * lib_ring_buffer_align_ctx - Align context offset on "alignment"
 149  * @ctx: ring buffer context.
 150  */
 151 static inline lttng_ust_notrace
 152 void lib_ring_buffer_align_ctx(struct lttng_ust_lib_ring_buffer_ctx *ctx,
 153                            size_t alignment);
 154 static inline
 155 void lib_ring_buffer_align_ctx(struct lttng_ust_lib_ring_buffer_ctx *ctx,
 156                            size_t alignment)
 157 {
 158         ctx->buf_offset += lib_ring_buffer_align(ctx->buf_offset,
 159                                                  alignment);
 160 }
 161
 162 #endif /* _LTTNG_RING_BUFFER_CONTEXT_H */