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