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