+++ /dev/null
-/* SPDX-License-Identifier: (GPL-2.0-only OR LGPL-2.1-only)
- *
- * lib/ringbuffer/backend_internal.h
- *
- * Ring buffer backend (internal helpers).
- *
- * Copyright (C) 2008-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
- */
-
-#ifndef _LIB_RING_BUFFER_BACKEND_INTERNAL_H
-#define _LIB_RING_BUFFER_BACKEND_INTERNAL_H
-
-#include <wrapper/compiler.h>
-#include <wrapper/ringbuffer/config.h>
-#include <wrapper/ringbuffer/backend_types.h>
-#include <wrapper/ringbuffer/frontend_types.h>
-#include <linux/string.h>
-#include <linux/uaccess.h>
-
-/* Ring buffer backend API presented to the frontend */
-
-/* Ring buffer and channel backend create/free */
-
-int lib_ring_buffer_backend_create(struct lib_ring_buffer_backend *bufb,
- struct channel_backend *chan, int cpu);
-void channel_backend_unregister_notifiers(struct channel_backend *chanb);
-void lib_ring_buffer_backend_free(struct lib_ring_buffer_backend *bufb);
-int channel_backend_init(struct channel_backend *chanb,
- const char *name,
- const struct lib_ring_buffer_config *config,
- void *priv, size_t subbuf_size,
- size_t num_subbuf);
-void channel_backend_free(struct channel_backend *chanb);
-
-void lib_ring_buffer_backend_reset(struct lib_ring_buffer_backend *bufb);
-void channel_backend_reset(struct channel_backend *chanb);
-
-int lib_ring_buffer_backend_init(void);
-void lib_ring_buffer_backend_exit(void);
-
-extern void _lib_ring_buffer_write(struct lib_ring_buffer_backend *bufb,
- size_t offset, const void *src, size_t len,
- size_t pagecpy);
-extern void _lib_ring_buffer_memset(struct lib_ring_buffer_backend *bufb,
- size_t offset, int c, size_t len,
- size_t pagecpy);
-extern void _lib_ring_buffer_strcpy(struct lib_ring_buffer_backend *bufb,
- size_t offset, const char *src, size_t len,
- size_t pagecpy, int pad);
-extern void _lib_ring_buffer_copy_from_user_inatomic(struct lib_ring_buffer_backend *bufb,
- size_t offset, const void *src,
- size_t len, size_t pagecpy);
-extern void _lib_ring_buffer_strcpy_from_user_inatomic(struct lib_ring_buffer_backend *bufb,
- size_t offset, const char __user *src, size_t len,
- size_t pagecpy, int pad);
-
-/*
- * Subbuffer ID bits for overwrite mode. Need to fit within a single word to be
- * exchanged atomically.
- *
- * Top half word, except lowest bit, belongs to "offset", which is used to keep
- * to count the produced buffers. For overwrite mode, this provides the
- * consumer with the capacity to read subbuffers in order, handling the
- * situation where producers would write up to 2^15 buffers (or 2^31 for 64-bit
- * systems) concurrently with a single execution of get_subbuf (between offset
- * sampling and subbuffer ID exchange).
- */
-
-#define HALF_ULONG_BITS (BITS_PER_LONG >> 1)
-
-#define SB_ID_OFFSET_SHIFT (HALF_ULONG_BITS + 1)
-#define SB_ID_OFFSET_COUNT (1UL << SB_ID_OFFSET_SHIFT)
-#define SB_ID_OFFSET_MASK (~(SB_ID_OFFSET_COUNT - 1))
-/*
- * Lowest bit of top word half belongs to noref. Used only for overwrite mode.
- */
-#define SB_ID_NOREF_SHIFT (SB_ID_OFFSET_SHIFT - 1)
-#define SB_ID_NOREF_COUNT (1UL << SB_ID_NOREF_SHIFT)
-#define SB_ID_NOREF_MASK SB_ID_NOREF_COUNT
-/*
- * In overwrite mode: lowest half of word is used for index.
- * Limit of 2^16 subbuffers per buffer on 32-bit, 2^32 on 64-bit.
- * In producer-consumer mode: whole word used for index.
- */
-#define SB_ID_INDEX_SHIFT 0
-#define SB_ID_INDEX_COUNT (1UL << SB_ID_INDEX_SHIFT)
-#define SB_ID_INDEX_MASK (SB_ID_NOREF_COUNT - 1)
-
-/*
- * Construct the subbuffer id from offset, index and noref. Use only the index
- * for producer-consumer mode (offset and noref are only used in overwrite
- * mode).
- */
-static inline
-unsigned long subbuffer_id(const struct lib_ring_buffer_config *config,
- unsigned long offset, unsigned long noref,
- unsigned long index)
-{
- if (config->mode == RING_BUFFER_OVERWRITE)
- return (offset << SB_ID_OFFSET_SHIFT)
- | (noref << SB_ID_NOREF_SHIFT)
- | index;
- else
- return index;
-}
-
-/*
- * Compare offset with the offset contained within id. Return 1 if the offset
- * bits are identical, else 0.
- */
-static inline
-int subbuffer_id_compare_offset(const struct lib_ring_buffer_config *config,
- unsigned long id, unsigned long offset)
-{
- return (id & SB_ID_OFFSET_MASK) == (offset << SB_ID_OFFSET_SHIFT);
-}
-
-static inline
-unsigned long subbuffer_id_get_index(const struct lib_ring_buffer_config *config,
- unsigned long id)
-{
- if (config->mode == RING_BUFFER_OVERWRITE)
- return id & SB_ID_INDEX_MASK;
- else
- return id;
-}
-
-static inline
-unsigned long subbuffer_id_is_noref(const struct lib_ring_buffer_config *config,
- unsigned long id)
-{
- if (config->mode == RING_BUFFER_OVERWRITE)
- return !!(id & SB_ID_NOREF_MASK);
- else
- return 1;
-}
-
-/*
- * Only used by reader on subbuffer ID it has exclusive access to. No volatile
- * needed.
- */
-static inline
-void subbuffer_id_set_noref(const struct lib_ring_buffer_config *config,
- unsigned long *id)
-{
- if (config->mode == RING_BUFFER_OVERWRITE)
- *id |= SB_ID_NOREF_MASK;
-}
-
-static inline
-void subbuffer_id_set_noref_offset(const struct lib_ring_buffer_config *config,
- unsigned long *id, unsigned long offset)
-{
- unsigned long tmp;
-
- if (config->mode == RING_BUFFER_OVERWRITE) {
- tmp = *id;
- tmp &= ~SB_ID_OFFSET_MASK;
- tmp |= offset << SB_ID_OFFSET_SHIFT;
- tmp |= SB_ID_NOREF_MASK;
- /* Volatile store, read concurrently by readers. */
- WRITE_ONCE(*id, tmp);
- }
-}
-
-/* No volatile access, since already used locally */
-static inline
-void subbuffer_id_clear_noref(const struct lib_ring_buffer_config *config,
- unsigned long *id)
-{
- if (config->mode == RING_BUFFER_OVERWRITE)
- *id &= ~SB_ID_NOREF_MASK;
-}
-
-/*
- * For overwrite mode, cap the number of subbuffers per buffer to:
- * 2^16 on 32-bit architectures
- * 2^32 on 64-bit architectures
- * This is required to fit in the index part of the ID. Return 0 on success,
- * -EPERM on failure.
- */
-static inline
-int subbuffer_id_check_index(const struct lib_ring_buffer_config *config,
- unsigned long num_subbuf)
-{
- if (config->mode == RING_BUFFER_OVERWRITE)
- return (num_subbuf > (1UL << HALF_ULONG_BITS)) ? -EPERM : 0;
- else
- return 0;
-}
-
-static inline
-void lib_ring_buffer_backend_get_pages(const struct lib_ring_buffer_config *config,
- struct lib_ring_buffer_ctx *ctx,
- struct lib_ring_buffer_backend_pages **backend_pages)
-{
- struct lib_ring_buffer_backend *bufb = &ctx->buf->backend;
- struct channel_backend *chanb = &ctx->chan->backend;
- size_t sbidx, offset = ctx->buf_offset;
- unsigned long sb_bindex, id;
- struct lib_ring_buffer_backend_pages *rpages;
-
- offset &= chanb->buf_size - 1;
- sbidx = offset >> chanb->subbuf_size_order;
- id = bufb->buf_wsb[sbidx].id;
- sb_bindex = subbuffer_id_get_index(config, id);
- rpages = bufb->array[sb_bindex];
- CHAN_WARN_ON(ctx->chan,
- config->mode == RING_BUFFER_OVERWRITE
- && subbuffer_id_is_noref(config, id));
- *backend_pages = rpages;
-}
-
-/* Get backend pages from cache. */
-static inline
-struct lib_ring_buffer_backend_pages *
- lib_ring_buffer_get_backend_pages_from_ctx(const struct lib_ring_buffer_config *config,
- struct lib_ring_buffer_ctx *ctx)
-{
- return ctx->backend_pages;
-}
-
-/*
- * The ring buffer can count events recorded and overwritten per buffer,
- * but it is disabled by default due to its performance overhead.
- */
-#ifdef LTTNG_RING_BUFFER_COUNT_EVENTS
-static inline
-void subbuffer_count_record(const struct lib_ring_buffer_config *config,
- struct lib_ring_buffer_backend *bufb,
- unsigned long idx)
-{
- unsigned long sb_bindex;
-
- sb_bindex = subbuffer_id_get_index(config, bufb->buf_wsb[idx].id);
- v_inc(config, &bufb->array[sb_bindex]->records_commit);
-}
-#else /* LTTNG_RING_BUFFER_COUNT_EVENTS */
-static inline
-void subbuffer_count_record(const struct lib_ring_buffer_config *config,
- struct lib_ring_buffer_backend *bufb,
- unsigned long idx)
-{
-}
-#endif /* #else LTTNG_RING_BUFFER_COUNT_EVENTS */
-
-/*
- * Reader has exclusive subbuffer access for record consumption. No need to
- * perform the decrement atomically.
- */
-static inline
-void subbuffer_consume_record(const struct lib_ring_buffer_config *config,
- struct lib_ring_buffer_backend *bufb)
-{
- unsigned long sb_bindex;
-
- sb_bindex = subbuffer_id_get_index(config, bufb->buf_rsb.id);
- CHAN_WARN_ON(bufb->chan,
- !v_read(config, &bufb->array[sb_bindex]->records_unread));
- /* Non-atomic decrement protected by exclusive subbuffer access */
- _v_dec(config, &bufb->array[sb_bindex]->records_unread);
- v_inc(config, &bufb->records_read);
-}
-
-static inline
-unsigned long subbuffer_get_records_count(
- const struct lib_ring_buffer_config *config,
- struct lib_ring_buffer_backend *bufb,
- unsigned long idx)
-{
- unsigned long sb_bindex;
-
- sb_bindex = subbuffer_id_get_index(config, bufb->buf_wsb[idx].id);
- return v_read(config, &bufb->array[sb_bindex]->records_commit);
-}
-
-/*
- * Must be executed at subbuffer delivery when the writer has _exclusive_
- * subbuffer access. See lib_ring_buffer_check_deliver() for details.
- * lib_ring_buffer_get_records_count() must be called to get the records
- * count before this function, because it resets the records_commit
- * count.
- */
-static inline
-unsigned long subbuffer_count_records_overrun(
- const struct lib_ring_buffer_config *config,
- struct lib_ring_buffer_backend *bufb,
- unsigned long idx)
-{
- struct lib_ring_buffer_backend_pages *pages;
- unsigned long overruns, sb_bindex;
-
- sb_bindex = subbuffer_id_get_index(config, bufb->buf_wsb[idx].id);
- pages = bufb->array[sb_bindex];
- overruns = v_read(config, &pages->records_unread);
- v_set(config, &pages->records_unread,
- v_read(config, &pages->records_commit));
- v_set(config, &pages->records_commit, 0);
-
- return overruns;
-}
-
-static inline
-void subbuffer_set_data_size(const struct lib_ring_buffer_config *config,
- struct lib_ring_buffer_backend *bufb,
- unsigned long idx,
- unsigned long data_size)
-{
- struct lib_ring_buffer_backend_pages *pages;
- unsigned long sb_bindex;
-
- sb_bindex = subbuffer_id_get_index(config, bufb->buf_wsb[idx].id);
- pages = bufb->array[sb_bindex];
- pages->data_size = data_size;
-}
-
-static inline
-unsigned long subbuffer_get_read_data_size(
- const struct lib_ring_buffer_config *config,
- struct lib_ring_buffer_backend *bufb)
-{
- struct lib_ring_buffer_backend_pages *pages;
- unsigned long sb_bindex;
-
- sb_bindex = subbuffer_id_get_index(config, bufb->buf_rsb.id);
- pages = bufb->array[sb_bindex];
- return pages->data_size;
-}
-
-static inline
-unsigned long subbuffer_get_data_size(
- const struct lib_ring_buffer_config *config,
- struct lib_ring_buffer_backend *bufb,
- unsigned long idx)
-{
- struct lib_ring_buffer_backend_pages *pages;
- unsigned long sb_bindex;
-
- sb_bindex = subbuffer_id_get_index(config, bufb->buf_wsb[idx].id);
- pages = bufb->array[sb_bindex];
- return pages->data_size;
-}
-
-static inline
-void subbuffer_inc_packet_count(const struct lib_ring_buffer_config *config,
- struct lib_ring_buffer_backend *bufb,
- unsigned long idx)
-{
- bufb->buf_cnt[idx].seq_cnt++;
-}
-
-/**
- * lib_ring_buffer_clear_noref - Clear the noref subbuffer flag, called by
- * writer.
- */
-static inline
-void lib_ring_buffer_clear_noref(const struct lib_ring_buffer_config *config,
- struct lib_ring_buffer_backend *bufb,
- unsigned long idx)
-{
- unsigned long id, new_id;
-
- if (config->mode != RING_BUFFER_OVERWRITE)
- return;
-
- /*
- * Performing a volatile access to read the sb_pages, because we want to
- * read a coherent version of the pointer and the associated noref flag.
- */
- id = READ_ONCE(bufb->buf_wsb[idx].id);
- for (;;) {
- /* This check is called on the fast path for each record. */
- if (likely(!subbuffer_id_is_noref(config, id))) {
- /*
- * Store after load dependency ordering the writes to
- * the subbuffer after load and test of the noref flag
- * matches the memory barrier implied by the cmpxchg()
- * in update_read_sb_index().
- */
- return; /* Already writing to this buffer */
- }
- new_id = id;
- subbuffer_id_clear_noref(config, &new_id);
- new_id = cmpxchg(&bufb->buf_wsb[idx].id, id, new_id);
- if (likely(new_id == id))
- break;
- id = new_id;
- }
-}
-
-/**
- * lib_ring_buffer_set_noref_offset - Set the noref subbuffer flag and offset,
- * called by writer.
- */
-static inline
-void lib_ring_buffer_set_noref_offset(const struct lib_ring_buffer_config *config,
- struct lib_ring_buffer_backend *bufb,
- unsigned long idx, unsigned long offset)
-{
- if (config->mode != RING_BUFFER_OVERWRITE)
- return;
-
- /*
- * Because ring_buffer_set_noref() is only called by a single thread
- * (the one which updated the cc_sb value), there are no concurrent
- * updates to take care of: other writers have not updated cc_sb, so
- * they cannot set the noref flag, and concurrent readers cannot modify
- * the pointer because the noref flag is not set yet.
- * The smp_wmb() in ring_buffer_commit() takes care of ordering writes
- * to the subbuffer before this set noref operation.
- * subbuffer_set_noref() uses a volatile store to deal with concurrent
- * readers of the noref flag.
- */
- CHAN_WARN_ON(bufb->chan,
- subbuffer_id_is_noref(config, bufb->buf_wsb[idx].id));
- /*
- * Memory barrier that ensures counter stores are ordered before set
- * noref and offset.
- */
- smp_mb();
- subbuffer_id_set_noref_offset(config, &bufb->buf_wsb[idx].id, offset);
-}
-
-/**
- * update_read_sb_index - Read-side subbuffer index update.
- */
-static inline
-int update_read_sb_index(const struct lib_ring_buffer_config *config,
- struct lib_ring_buffer_backend *bufb,
- struct channel_backend *chanb,
- unsigned long consumed_idx,
- unsigned long consumed_count)
-{
- unsigned long old_id, new_id;
-
- if (config->mode == RING_BUFFER_OVERWRITE) {
- /*
- * Exchange the target writer subbuffer with our own unused
- * subbuffer. No need to use READ_ONCE() here to read the
- * old_wpage, because the value read will be confirmed by the
- * following cmpxchg().
- */
- old_id = bufb->buf_wsb[consumed_idx].id;
- if (unlikely(!subbuffer_id_is_noref(config, old_id)))
- return -EAGAIN;
- /*
- * Make sure the offset count we are expecting matches the one
- * indicated by the writer.
- */
- if (unlikely(!subbuffer_id_compare_offset(config, old_id,
- consumed_count)))
- return -EAGAIN;
- CHAN_WARN_ON(bufb->chan,
- !subbuffer_id_is_noref(config, bufb->buf_rsb.id));
- subbuffer_id_set_noref_offset(config, &bufb->buf_rsb.id,
- consumed_count);
- new_id = cmpxchg(&bufb->buf_wsb[consumed_idx].id, old_id,
- bufb->buf_rsb.id);
- if (unlikely(old_id != new_id))
- return -EAGAIN;
- bufb->buf_rsb.id = new_id;
- } else {
- /* No page exchange, use the writer page directly */
- bufb->buf_rsb.id = bufb->buf_wsb[consumed_idx].id;
- }
- return 0;
-}
-
-static inline __attribute__((always_inline))
-void lttng_inline_memcpy(void *dest, const void *src,
- unsigned long len)
-{
- switch (len) {
- case 1:
- *(uint8_t *) dest = *(const uint8_t *) src;
- break;
- case 2:
- *(uint16_t *) dest = *(const uint16_t *) src;
- break;
- case 4:
- *(uint32_t *) dest = *(const uint32_t *) src;
- break;
- case 8:
- *(uint64_t *) dest = *(const uint64_t *) src;
- break;
- default:
- inline_memcpy(dest, src, len);
- }
-}
-
-/*
- * Use the architecture-specific memcpy implementation for constant-sized
- * inputs, but rely on an inline memcpy for length statically unknown.
- * The function call to memcpy is just way too expensive for a fast path.
- */
-#define lib_ring_buffer_do_copy(config, dest, src, len) \
-do { \
- size_t __len = (len); \
- if (__builtin_constant_p(len)) \
- memcpy(dest, src, __len); \
- else \
- lttng_inline_memcpy(dest, src, __len); \
-} while (0)
-
-/*
- * We use __copy_from_user_inatomic to copy userspace data since we already
- * did the access_ok for the whole range.
- *
- * Return 0 if OK, nonzero on error.
- */
-static inline
-unsigned long lib_ring_buffer_do_copy_from_user_inatomic(void *dest,
- const void __user *src,
- unsigned long len)
-{
- return __copy_from_user_inatomic(dest, src, len);
-}
-
-/*
- * write len bytes to dest with c
- */
-static inline
-void lib_ring_buffer_do_memset(char *dest, int c,
- unsigned long len)
-{
- unsigned long i;
-
- for (i = 0; i < len; i++)
- dest[i] = c;
-}
-
-#endif /* _LIB_RING_BUFFER_BACKEND_INTERNAL_H */