include/lttng/ust-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_UST_RING_BUFFER_CONTEXT_H
  10 #define _LTTNG_UST_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-utils.h>
  20 #include <lttng/ust-compiler.h>
  21
  22 struct lttng_ust_ring_buffer;
  23 struct lttng_ust_ring_buffer_channel;
  24 struct lttng_ust_ring_buffer_ctx;
  25 struct lttng_ust_ring_buffer_ctx_private;
  26 struct lttng_ust_probe_ctx;
  27
  28 /*
  29  * ring buffer context
  30  *
  31  * IMPORTANT: this structure is part of the ABI between the probe and
  32  * UST. Fields need to be only added at the end, never reordered, never
  33  * removed.
  34  *
  35  * The field @struct_size should be used to determine the size of the
  36  * structure. It should be queried before using additional fields added
  37  * at the end of the structure.
  38  */
  39 struct lttng_ust_ring_buffer_ctx {
  40         uint32_t struct_size;                   /* Size of this structure. */
  41
  42         void *client_priv;                      /* Ring buffer client private data */
  43         size_t data_size;                       /* size of payload */
  44         int largest_align;                      /*
  45                                                  * alignment of the largest element
  46                                                  * in the payload
  47                                                  */
  48         struct lttng_ust_probe_ctx *probe_ctx;  /* Probe context */
  49
  50         /* Private ring buffer context, set by reserve callback. */
  51         struct lttng_ust_ring_buffer_ctx_private *priv;
  52
  53         /* End of base ABI. Fields below should be used after checking struct_size. */
  54 };
  55
  56 /**
  57  * lttng_ust_ring_buffer_ctx_init - initialize ring buffer context
  58  * @ctx: ring buffer context to initialize
  59  * @client_priv: client private data
  60  * @data_size: size of record data payload
  61  * @largest_align: largest alignment within data payload types
  62  * @ip: caller ip address
  63  */
  64 static inline
  65 void lttng_ust_ring_buffer_ctx_init(struct lttng_ust_ring_buffer_ctx *ctx,
  66                                         void *client_priv, size_t data_size, int largest_align,
  67                                         struct lttng_ust_probe_ctx *probe_ctx)
  68         lttng_ust_notrace;
  69 static inline
  70 void lttng_ust_ring_buffer_ctx_init(struct lttng_ust_ring_buffer_ctx *ctx,
  71                                         void *client_priv, size_t data_size, int largest_align,
  72                                         struct lttng_ust_probe_ctx *probe_ctx)
  73 {
  74         ctx->struct_size = sizeof(struct lttng_ust_ring_buffer_ctx);
  75         ctx->client_priv = client_priv;
  76         ctx->data_size = data_size;
  77         ctx->largest_align = largest_align;
  78         ctx->probe_ctx = probe_ctx;
  79         ctx->priv = NULL;
  80 }
  81
  82 /*
  83  * We need to define LTTNG_UST_RING_BUFFER_ALIGN_ATTR so it is known early at
  84  * compile-time. We have to duplicate the "config->align" information and the
  85  * definition here because config->align is used both in the slow and fast
  86  * paths, but LTTNG_UST_RING_BUFFER_ALIGN_ATTR is only available for the client
  87  * code.
  88  */
  89 #ifdef LTTNG_UST_RING_BUFFER_NATURAL_ALIGN
  90
  91 # define LTTNG_UST_RING_BUFFER_ALIGN_ATTR       /* Default arch alignment */
  92
  93 /*
  94  * lttng_ust_ring_buffer_align - Calculate the offset needed to align the type.
  95  * @align_drift:  object offset from an "alignment"-aligned address.
  96  * @size_of_type: Must be non-zero, power of 2.
  97  */
  98 static inline
  99 unsigned int lttng_ust_ring_buffer_align(size_t align_drift, size_t size_of_type)
 100         lttng_ust_notrace;
 101 static inline
 102 unsigned int lttng_ust_ring_buffer_align(size_t align_drift, size_t size_of_type)
 103 {
 104         return lttng_ust_offset_align(align_drift, size_of_type);
 105 }
 106
 107 #else
 108
 109 # define LTTNG_UST_RING_BUFFER_ALIGN_ATTR __attribute__((packed))
 110
 111 /*
 112  * lttng_ust_ring_buffer_align - Calculate the offset needed to align the type.
 113  * @align_drift:  object offset from an "alignment"-aligned address.
 114  * @size_of_type: Must be non-zero, power of 2.
 115  */
 116 static inline
 117 unsigned int lttng_ust_ring_buffer_align(size_t align_drift, size_t size_of_type)
 118         lttng_ust_notrace;
 119 static inline
 120 unsigned int lttng_ust_ring_buffer_align(size_t align_drift __attribute__((unused)),
 121                 size_t size_of_type __attribute__((unused)))
 122 {
 123         /*
 124          * On architectures with efficient unaligned memory access, the content
 125          * of the ringbuffer is packed and so the offset is always zero.
 126          */
 127         return 0;
 128 }
 129
 130 #endif
 131
 132 #endif /* _LTTNG_UST_RING_BUFFER_CONTEXT_H */