-/* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only) */
-#include <lib/ringbuffer/backend_internal.h>
+/* 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 <ringbuffer/config.h>
+#include <ringbuffer/backend_types.h>
+#include <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:
+ 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 */
projects / lttng-modules.git / blobdiff