In preparation for allowing the user-space to map a ring-buffer, add a set of mapping functions: ring_buffer_{map,unmap}() And controls on the ring-buffer: ring_buffer_map_get_reader() /* swap reader and head */ Mapping the ring-buffer also involves: A unique ID for each subbuf of the ring-buffer, currently they are only identified through their in-kernel VA. A meta-page, where are stored ring-buffer statistics and a description for the current reader The linear mapping exposes the meta-page, and each subbuf of the ring-buffer, ordered following their unique ID, assigned during the first mapping. Once mapped, no subbuf can get in or out of the ring-buffer: the buffer size will remain unmodified and the splice enabling functions will in reality simply memcpy the data instead of swapping subbufs. Link: https://lore.kernel.org/linux-trace-kernel/20240510140435.3550353-3-vdonnefort@google.com
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| 1 | +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ | |
| 2 | +#ifndef _TRACE_MMAP_H_ | |
| 3 | +#define _TRACE_MMAP_H_ | |
| 4 | + | |
| 5 | +#include <linux/types.h> | |
| 6 | + | |
| 7 | +/** | |
| 8 | + * struct trace_buffer_meta - Ring-buffer Meta-page description | |
| 9 | + * @meta_page_size: Size of this meta-page. | |
| 10 | + * @meta_struct_len: Size of this structure. | |
| 11 | + * @subbuf_size: Size of each sub-buffer. | |
| 12 | + * @nr_subbufs: Number of subbfs in the ring-buffer, including the reader. | |
| 13 | + * @reader.lost_events: Number of events lost at the time of the reader swap. | |
| 14 | + * @reader.id: subbuf ID of the current reader. ID range [0 : @nr_subbufs - 1] | |
| 15 | + * @reader.read: Number of bytes read on the reader subbuf. | |
| 16 | + * @flags: Placeholder for now, 0 until new features are supported. | |
| 17 | + * @entries: Number of entries in the ring-buffer. | |
| 18 | + * @overrun: Number of entries lost in the ring-buffer. | |
| 19 | + * @read: Number of entries that have been read. | |
| 20 | + * @Reserved1: Internal use only. | |
| 21 | + * @Reserved2: Internal use only. | |
| 22 | + */ | |
| 23 | +struct trace_buffer_meta { | |
| 24 | + __u32 meta_page_size; | |
| 25 | + __u32 meta_struct_len; | |
| 26 | + | |
| 27 | + __u32 subbuf_size; | |
| 28 | + __u32 nr_subbufs; | |
| 29 | + | |
| 30 | + struct { | |
| 31 | + __u64 lost_events; | |
| 32 | + __u32 id; | |
| 33 | + __u32 read; | |
| 34 | + } reader; | |
| 35 | + | |
| 36 | + __u64 flags; | |
| 37 | + | |
| 38 | + __u64 entries; | |
| 39 | + __u64 overrun; | |
| 40 | + __u64 read; | |
| 41 | + | |
| 42 | + __u64 Reserved1; | |
| 43 | + __u64 Reserved2; | |
| 44 | +}; | |
| 45 | + | |
| 46 | +#endif /* _TRACE_MMAP_H_ */ | |