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         int cpu;                        /* processor id */
  55
  56         /* output from lib_ring_buffer_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  * @cpu: processor id
  85  */
  86 static inline lttng_ust_notrace
  87 void lib_ring_buffer_ctx_init(struct lttng_ust_lib_ring_buffer_ctx *ctx,
  88                               struct lttng_ust_lib_ring_buffer_channel *chan,
  89                               void *priv, size_t data_size, int largest_align,
  90                               int cpu, struct lttng_ust_shm_handle *handle);
  91 static inline
  92 void lib_ring_buffer_ctx_init(struct lttng_ust_lib_ring_buffer_ctx *ctx,
  93                               struct lttng_ust_lib_ring_buffer_channel *chan,
  94                               void *priv, size_t data_size, int largest_align,
  95                               int cpu, struct lttng_ust_shm_handle *handle)
  96 {
  97         ctx->struct_size = sizeof(struct lttng_ust_lib_ring_buffer_ctx);
  98         ctx->chan = chan;
  99         ctx->priv = priv;
 100         ctx->data_size = data_size;
 101         ctx->largest_align = largest_align;
 102         ctx->cpu = cpu;
 103         ctx->rflags = 0;
 104         ctx->handle = handle;
 105         ctx->ip = 0;
 106 }
 107
 108 /*
 109  * We need to define RING_BUFFER_ALIGN_ATTR so it is known early at
 110  * compile-time. We have to duplicate the "config->align" information and the
 111  * definition here because config->align is used both in the slow and fast
 112  * paths, but RING_BUFFER_ALIGN_ATTR is only available for the client code.
 113  */
 114 #ifdef RING_BUFFER_ALIGN
 115
 116 # define RING_BUFFER_ALIGN_ATTR         /* Default arch alignment */
 117
 118 /*
 119  * Calculate the offset needed to align the type.
 120  * size_of_type must be non-zero.
 121  */
 122 static inline lttng_ust_notrace
 123 unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type);
 124 static inline
 125 unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type)
 126 {
 127         return lttng_ust_offset_align(align_drift, size_of_type);
 128 }
 129
 130 #else
 131
 132 # define RING_BUFFER_ALIGN_ATTR __attribute__((packed))
 133
 134 /*
 135  * Calculate the offset needed to align the type.
 136  * size_of_type must be non-zero.
 137  */
 138 static inline lttng_ust_notrace
 139 unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type);
 140 static inline
 141 unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type)
 142 {
 143         return 0;
 144 }
 145
 146 #endif
 147
 148 /**
 149  * lib_ring_buffer_align_ctx - Align context offset on "alignment"
 150  * @ctx: ring buffer context.
 151  */
 152 static inline lttng_ust_notrace
 153 void lib_ring_buffer_align_ctx(struct lttng_ust_lib_ring_buffer_ctx *ctx,
 154                            size_t alignment);
 155 static inline
 156 void lib_ring_buffer_align_ctx(struct lttng_ust_lib_ring_buffer_ctx *ctx,
 157                            size_t alignment)
 158 {
 159         ctx->buf_offset += lib_ring_buffer_align(ctx->buf_offset,
 160                                                  alignment);
 161 }
 162
 163 #endif /* _LTTNG_RING_BUFFER_CONTEXT_H */