+++ /dev/null
-/*
- * SPDX-License-Identifier: LGPL-2.1-only
- *
- * Copyright (C) 2011-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
- *
- * Ring buffer backend (API).
- *
- * Credits to Steven Rostedt for proposing to use an extra-subbuffer owned by
- * the reader in flight recorder mode.
- */
-
-#ifndef _LTTNG_RING_BUFFER_BACKEND_H
-#define _LTTNG_RING_BUFFER_BACKEND_H
-
-#include <stddef.h>
-#include <unistd.h>
-
-/* Internal helpers */
-#include "backend_internal.h"
-#include "frontend_internal.h"
-
-/* Ring buffer backend API */
-
-/* Ring buffer backend access (read/write) */
-
-extern size_t lib_ring_buffer_read(struct lttng_ust_lib_ring_buffer_backend *bufb,
- size_t offset, void *dest, size_t len,
- struct lttng_ust_shm_handle *handle)
- __attribute__((visibility("hidden")));
-
-extern int lib_ring_buffer_read_cstr(struct lttng_ust_lib_ring_buffer_backend *bufb,
- size_t offset, void *dest, size_t len,
- struct lttng_ust_shm_handle *handle)
- __attribute__((visibility("hidden")));
-
-/*
- * Return the address where a given offset is located.
- * Should be used to get the current subbuffer header pointer. Given we know
- * it's never on a page boundary, it's safe to write directly to this address,
- * as long as the write is never bigger than a page size.
- */
-extern void *
-lib_ring_buffer_offset_address(struct lttng_ust_lib_ring_buffer_backend *bufb,
- size_t offset,
- struct lttng_ust_shm_handle *handle)
- __attribute__((visibility("hidden")));
-
-extern void *
-lib_ring_buffer_read_offset_address(struct lttng_ust_lib_ring_buffer_backend *bufb,
- size_t offset,
- struct lttng_ust_shm_handle *handle)
- __attribute__((visibility("hidden")));
-
-/**
- * lib_ring_buffer_write - write data to a buffer backend
- * @config : ring buffer instance configuration
- * @ctx: ring buffer context. (input arguments only)
- * @src : source pointer to copy from
- * @len : length of data to copy
- *
- * This function copies "len" bytes of data from a source pointer to a buffer
- * backend, at the current context offset. This is more or less a buffer
- * backend-specific memcpy() operation. Calls the slow path (_ring_buffer_write)
- * if copy is crossing a page boundary.
- */
-static inline
-void lib_ring_buffer_write(const struct lttng_ust_lib_ring_buffer_config *config,
- struct lttng_ust_lib_ring_buffer_ctx *ctx,
- const void *src, size_t len)
- __attribute__((always_inline));
-static inline
-void lib_ring_buffer_write(const struct lttng_ust_lib_ring_buffer_config *config,
- struct lttng_ust_lib_ring_buffer_ctx *ctx,
- const void *src, size_t len)
-{
- struct lttng_ust_lib_ring_buffer_ctx_private *ctx_private = ctx->priv;
- struct channel_backend *chanb = &ctx_private->chan->backend;
- struct lttng_ust_shm_handle *handle = ctx_private->chan->handle;
- size_t offset = ctx_private->buf_offset;
- struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages;
- void *p;
-
- if (caa_unlikely(!len))
- return;
- /*
- * Underlying layer should never ask for writes across
- * subbuffers.
- */
- CHAN_WARN_ON(chanb, (offset & (chanb->buf_size - 1)) + len > chanb->buf_size);
- backend_pages = lib_ring_buffer_get_backend_pages_from_ctx(config, ctx);
- if (caa_unlikely(!backend_pages)) {
- if (lib_ring_buffer_backend_get_pages(config, ctx, &backend_pages))
- return;
- }
- p = shmp_index(handle, backend_pages->p, offset & (chanb->subbuf_size - 1));
- if (caa_unlikely(!p))
- return;
- lib_ring_buffer_do_copy(config, p, src, len);
- ctx_private->buf_offset += len;
-}
-
-/*
- * Copy up to @len string bytes from @src to @dest. Stop whenever a NULL
- * terminating character is found in @src. Returns the number of bytes
- * copied. Does *not* terminate @dest with NULL terminating character.
- */
-static inline
-size_t lib_ring_buffer_do_strcpy(const struct lttng_ust_lib_ring_buffer_config *config,
- char *dest, const char *src, size_t len)
- __attribute__((always_inline));
-static inline
-size_t lib_ring_buffer_do_strcpy(const struct lttng_ust_lib_ring_buffer_config *config,
- char *dest, const char *src, size_t len)
-{
- size_t count;
-
- for (count = 0; count < len; count++) {
- char c;
-
- /*
- * Only read source character once, in case it is
- * modified concurrently.
- */
- c = CMM_LOAD_SHARED(src[count]);
- if (!c)
- break;
- lib_ring_buffer_do_copy(config, &dest[count], &c, 1);
- }
- return count;
-}
-
-/**
- * lib_ring_buffer_strcpy - write string data to a buffer backend
- * @config : ring buffer instance configuration
- * @ctx: ring buffer context. (input arguments only)
- * @src : source pointer to copy from
- * @len : length of data to copy
- * @pad : character to use for padding
- *
- * This function copies @len - 1 bytes of string data from a source
- * pointer to a buffer backend, followed by a terminating '\0'
- * character, at the current context offset. This is more or less a
- * buffer backend-specific strncpy() operation. If a terminating '\0'
- * character is found in @src before @len - 1 characters are copied, pad
- * the buffer with @pad characters (e.g. '#').
- */
-static inline
-void lib_ring_buffer_strcpy(const struct lttng_ust_lib_ring_buffer_config *config,
- struct lttng_ust_lib_ring_buffer_ctx *ctx,
- const char *src, size_t len, char pad)
- __attribute__((always_inline));
-static inline
-void lib_ring_buffer_strcpy(const struct lttng_ust_lib_ring_buffer_config *config,
- struct lttng_ust_lib_ring_buffer_ctx *ctx,
- const char *src, size_t len, char pad)
-{
- struct lttng_ust_lib_ring_buffer_ctx_private *ctx_private = ctx->priv;
- struct channel_backend *chanb = &ctx_private->chan->backend;
- struct lttng_ust_shm_handle *handle = ctx_private->chan->handle;
- size_t count;
- size_t offset = ctx_private->buf_offset;
- struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages;
- void *p;
-
- if (caa_unlikely(!len))
- return;
- /*
- * Underlying layer should never ask for writes across
- * subbuffers.
- */
- CHAN_WARN_ON(chanb, (offset & (chanb->buf_size - 1)) + len > chanb->buf_size);
- backend_pages = lib_ring_buffer_get_backend_pages_from_ctx(config, ctx);
- if (caa_unlikely(!backend_pages)) {
- if (lib_ring_buffer_backend_get_pages(config, ctx, &backend_pages))
- return;
- }
- p = shmp_index(handle, backend_pages->p, offset & (chanb->subbuf_size - 1));
- if (caa_unlikely(!p))
- return;
-
- count = lib_ring_buffer_do_strcpy(config, p, src, len - 1);
- offset += count;
- /* Padding */
- if (caa_unlikely(count < len - 1)) {
- size_t pad_len = len - 1 - count;
-
- p = shmp_index(handle, backend_pages->p, offset & (chanb->subbuf_size - 1));
- if (caa_unlikely(!p))
- return;
- lib_ring_buffer_do_memset(p, pad, pad_len);
- offset += pad_len;
- }
- /* Final '\0' */
- p = shmp_index(handle, backend_pages->p, offset & (chanb->subbuf_size - 1));
- if (caa_unlikely(!p))
- return;
- lib_ring_buffer_do_memset(p, '\0', 1);
- ctx_private->buf_offset += len;
-}
-
-/**
- * lib_ring_buffer_pstrcpy - write to a buffer backend P-string
- * @config : ring buffer instance configuration
- * @ctx: ring buffer context. (input arguments only)
- * @src : source pointer to copy from
- * @len : length of data to copy
- * @pad : character to use for padding
- *
- * This function copies up to @len bytes of data from a source pointer
- * to a Pascal String into the buffer backend. If a terminating '\0'
- * character is found in @src before @len characters are copied, pad the
- * buffer with @pad characters (e.g. '\0').
- *
- * The length of the pascal strings in the ring buffer is explicit: it
- * is either the array or sequence length.
- */
-static inline
-void lib_ring_buffer_pstrcpy(const struct lttng_ust_lib_ring_buffer_config *config,
- struct lttng_ust_lib_ring_buffer_ctx *ctx,
- const char *src, size_t len, char pad)
- __attribute__((always_inline));
-static inline
-void lib_ring_buffer_pstrcpy(const struct lttng_ust_lib_ring_buffer_config *config,
- struct lttng_ust_lib_ring_buffer_ctx *ctx,
- const char *src, size_t len, char pad)
-{
- struct lttng_ust_lib_ring_buffer_ctx_private *ctx_private = ctx->priv;
- struct channel_backend *chanb = &ctx_private->chan->backend;
- struct lttng_ust_shm_handle *handle = ctx_private->chan->handle;
- size_t count;
- size_t offset = ctx_private->buf_offset;
- struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages;
- void *p;
-
- if (caa_unlikely(!len))
- return;
- /*
- * Underlying layer should never ask for writes across
- * subbuffers.
- */
- CHAN_WARN_ON(chanb, (offset & (chanb->buf_size - 1)) + len > chanb->buf_size);
- backend_pages = lib_ring_buffer_get_backend_pages_from_ctx(config, ctx);
- if (caa_unlikely(!backend_pages)) {
- if (lib_ring_buffer_backend_get_pages(config, ctx, &backend_pages))
- return;
- }
- p = shmp_index(handle, backend_pages->p, offset & (chanb->subbuf_size - 1));
- if (caa_unlikely(!p))
- return;
-
- count = lib_ring_buffer_do_strcpy(config, p, src, len);
- offset += count;
- /* Padding */
- if (caa_unlikely(count < len)) {
- size_t pad_len = len - count;
-
- p = shmp_index(handle, backend_pages->p, offset & (chanb->subbuf_size - 1));
- if (caa_unlikely(!p))
- return;
- lib_ring_buffer_do_memset(p, pad, pad_len);
- }
- ctx_private->buf_offset += len;
-}
-
-/*
- * This accessor counts the number of unread records in a buffer.
- * It only provides a consistent value if no reads not writes are performed
- * concurrently.
- */
-static inline
-unsigned long lib_ring_buffer_get_records_unread(
- const struct lttng_ust_lib_ring_buffer_config *config,
- struct lttng_ust_lib_ring_buffer *buf,
- struct lttng_ust_shm_handle *handle)
-{
- struct lttng_ust_lib_ring_buffer_backend *bufb = &buf->backend;
- unsigned long records_unread = 0, sb_bindex;
- unsigned int i;
- struct lttng_ust_lib_ring_buffer_channel *chan;
-
- chan = shmp(handle, bufb->chan);
- if (!chan)
- return 0;
- for (i = 0; i < chan->backend.num_subbuf; i++) {
- struct lttng_ust_lib_ring_buffer_backend_subbuffer *wsb;
- struct lttng_ust_lib_ring_buffer_backend_pages_shmp *rpages;
- struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages;
-
- wsb = shmp_index(handle, bufb->buf_wsb, i);
- if (!wsb)
- return 0;
- sb_bindex = subbuffer_id_get_index(config, wsb->id);
- rpages = shmp_index(handle, bufb->array, sb_bindex);
- if (!rpages)
- return 0;
- backend_pages = shmp(handle, rpages->shmp);
- if (!backend_pages)
- return 0;
- records_unread += v_read(config, &backend_pages->records_unread);
- }
- if (config->mode == RING_BUFFER_OVERWRITE) {
- struct lttng_ust_lib_ring_buffer_backend_pages_shmp *rpages;
- struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages;
-
- sb_bindex = subbuffer_id_get_index(config, bufb->buf_rsb.id);
- rpages = shmp_index(handle, bufb->array, sb_bindex);
- if (!rpages)
- return 0;
- backend_pages = shmp(handle, rpages->shmp);
- if (!backend_pages)
- return 0;
- records_unread += v_read(config, &backend_pages->records_unread);
- }
- return records_unread;
-}
-
-#endif /* _LTTNG_RING_BUFFER_BACKEND_H */
projects / lttng-ust.git / blobdiff