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(), lttng_ust_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  * lttng_ust_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 lttng_ust_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 lttng_ust_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 LTTNG_UST_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 LTTNG_UST_RING_BUFFER_ALIGN_ATTR is only available for the client
 108  * code.
 109  */
 110 #ifdef LTTNG_UST_RING_BUFFER_NATURAL_ALIGN
 111
 112 # define LTTNG_UST_RING_BUFFER_ALIGN_ATTR       /* Default arch alignment */
 113
 114 /*
 115  * lttng_ust_lib_ring_buffer_align - Calculate the offset needed to align the type.
 116  * @align_drift:  object offset from an "alignment"-aligned address.
 117  * @size_of_type: Must be non-zero, power of 2.
 118  */
 119 static inline lttng_ust_notrace
 120 unsigned int lttng_ust_lib_ring_buffer_align(size_t align_drift, size_t size_of_type);
 121 static inline
 122 unsigned int lttng_ust_lib_ring_buffer_align(size_t align_drift, size_t size_of_type)
 123 {
 124         return lttng_ust_offset_align(align_drift, size_of_type);
 125 }
 126
 127 #else
 128
 129 # define LTTNG_UST_RING_BUFFER_ALIGN_ATTR __attribute__((packed))
 130
 131 /*
 132  * lttng_ust_lib_ring_buffer_align - Calculate the offset needed to align the type.
 133  * @align_drift:  object offset from an "alignment"-aligned address.
 134  * @size_of_type: Must be non-zero, power of 2.
 135  */
 136 static inline lttng_ust_notrace
 137 unsigned int lttng_ust_lib_ring_buffer_align(size_t align_drift, size_t size_of_type);
 138 static inline
 139 unsigned int lttng_ust_lib_ring_buffer_align(size_t align_drift, size_t size_of_type)
 140 {
 141         /*
 142          * On architectures with efficient unaligned memory access, the content
 143          * of the ringbuffer is packed and so the offset is always zero.
 144          */
 145         return 0;
 146 }
 147
 148 #endif
 149
 150 /**
 151  * lttng_ust_lib_ring_buffer_align_ctx - Align context offset on "alignment"
 152  * @ctx: ring buffer context.
 153  */
 154 static inline lttng_ust_notrace
 155 void lttng_ust_lib_ring_buffer_align_ctx(struct lttng_ust_lib_ring_buffer_ctx *ctx,
 156                            size_t alignment);
 157 static inline
 158 void lttng_ust_lib_ring_buffer_align_ctx(struct lttng_ust_lib_ring_buffer_ctx *ctx,
 159                            size_t alignment)
 160 {
 161         ctx->buf_offset += lttng_ust_lib_ring_buffer_align(ctx->buf_offset,
 162                                                  alignment);
 163 }
 164
 165 #endif /* _LTTNG_RING_BUFFER_CONTEXT_H */