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
  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(). */
  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         size_t slot_size;                       /* size of the reserved slot */
  56         unsigned long buf_offset;               /* offset following the record header */
  57         unsigned long pre_offset;               /*
  58                                                  * Initial offset position _before_
  59                                                  * the record is written. Positioned
  60                                                  * prior to record header alignment
  61                                                  * padding.
  62                                                  */
  63         uint64_t tsc;                           /* time-stamp counter value */
  64         unsigned int rflags;                    /* reservation flags */
  65         void *ip;                               /* caller ip address */
  66
  67         struct lttng_ust_lib_ring_buffer *buf;  /*
  68                                                  * buffer corresponding to processor id
  69                                                  * for this channel
  70                                                  */
  71         struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages;
  72
  73         /* End of base ABI. Fields below should be used after checking struct_size. */
  74 };
  75
  76 /**
  77  * lib_ring_buffer_ctx_init - initialize ring buffer context
  78  * @ctx: ring buffer context to initialize
  79  * @chan: channel
  80  * @priv: client private data
  81  * @data_size: size of record data payload
  82  * @largest_align: largest alignment within data payload types
  83  */
  84 static inline lttng_ust_notrace
  85 void lib_ring_buffer_ctx_init(struct lttng_ust_lib_ring_buffer_ctx *ctx,
  86                               struct lttng_ust_lib_ring_buffer_channel *chan,
  87                               void *priv, size_t data_size, int largest_align);
  88 static inline
  89 void lib_ring_buffer_ctx_init(struct lttng_ust_lib_ring_buffer_ctx *ctx,
  90                               struct lttng_ust_lib_ring_buffer_channel *chan,
  91                               void *priv, size_t data_size, int largest_align)
  92 {
  93         ctx->struct_size = sizeof(struct lttng_ust_lib_ring_buffer_ctx);
  94         ctx->chan = chan;
  95         ctx->priv = priv;
  96         ctx->data_size = data_size;
  97         ctx->reserve_cpu = -1;
  98         ctx->largest_align = largest_align;
  99         ctx->rflags = 0;
 100         ctx->ip = 0;
 101 }
 102
 103 /*
 104  * We need to define RING_BUFFER_ALIGN_ATTR so it is known early at
 105  * compile-time. We have to duplicate the "config->align" information and the
 106  * definition here because config->align is used both in the slow and fast
 107  * paths, but RING_BUFFER_ALIGN_ATTR is only available for the client code.
 108  */
 109 #ifdef RING_BUFFER_ALIGN
 110
 111 # define RING_BUFFER_ALIGN_ATTR         /* Default arch alignment */
 112
 113 /*
 114  * Calculate the offset needed to align the type.
 115  * size_of_type must be non-zero.
 116  */
 117 static inline lttng_ust_notrace
 118 unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type);
 119 static inline
 120 unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type)
 121 {
 122         return lttng_ust_offset_align(align_drift, size_of_type);
 123 }
 124
 125 #else
 126
 127 # define RING_BUFFER_ALIGN_ATTR __attribute__((packed))
 128
 129 /*
 130  * Calculate the offset needed to align the type.
 131  * size_of_type must be non-zero.
 132  */
 133 static inline lttng_ust_notrace
 134 unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type);
 135 static inline
 136 unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type)
 137 {
 138         return 0;
 139 }
 140
 141 #endif
 142
 143 /**
 144  * lib_ring_buffer_align_ctx - Align context offset on "alignment"
 145  * @ctx: ring buffer context.
 146  */
 147 static inline lttng_ust_notrace
 148 void lib_ring_buffer_align_ctx(struct lttng_ust_lib_ring_buffer_ctx *ctx,
 149                            size_t alignment);
 150 static inline
 151 void lib_ring_buffer_align_ctx(struct lttng_ust_lib_ring_buffer_ctx *ctx,
 152                            size_t alignment)
 153 {
 154         ctx->buf_offset += lib_ring_buffer_align(ctx->buf_offset,
 155                                                  alignment);
 156 }
 157
 158 #endif /* _LTTNG_RING_BUFFER_CONTEXT_H */