btrace, linux: add perf event buffer abstraction
Collect perf event buffer related fields from btrace_target_info into a new struct perf_event_buffer. Update functions that operated on the buffer to take a struct perf_event_buffer pointer rather than a btrace_target_info pointer. 2015-02-09 Markus Metzger <markus.t.metzger@intel.com> * nat/linux-btrace.h (perf_event_buffer): New. (btrace_target_info) <buffer, size, data_head>: Replace with ... <bts>: ... this. * nat/linux-btrace.c (perf_event_header, perf_event_mmap_size) (perf_event_buffer_size, perf_event_buffer_begin) (perf_event_buffer_end, linux_btrace_has_changed): Removed. Updated users. (perf_event_new_data): New.
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Markus Metzger
parent
043c357797
commit
aadf7753fd
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@ -1,3 +1,14 @@
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2015-02-09 Markus Metzger <markus.t.metzger@intel.com>
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* nat/linux-btrace.h (perf_event_buffer): New.
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(btrace_target_info) <buffer, size, data_head>: Replace with ...
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<bts>: ... this.
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* nat/linux-btrace.c (perf_event_header, perf_event_mmap_size)
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(perf_event_buffer_size, perf_event_buffer_begin)
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(perf_event_buffer_end, linux_btrace_has_changed): Removed.
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Updated users.
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(perf_event_new_data): New.
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2015-02-09 Markus Metzger <markus.t.metzger@intel.com>
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* btrace.c (btrace_enable): Pass BTRACE_FORMAT_BTS.
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@ -59,45 +59,12 @@ struct perf_event_sample
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struct perf_event_bts bts;
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};
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/* Get the perf_event header. */
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/* Return non-zero if there is new data in PEVENT; zero otherwise. */
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static inline volatile struct perf_event_mmap_page *
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perf_event_header (struct btrace_target_info* tinfo)
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static int
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perf_event_new_data (const struct perf_event_buffer *pev)
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{
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return tinfo->buffer;
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}
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/* Get the size of the perf_event mmap buffer. */
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static inline size_t
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perf_event_mmap_size (const struct btrace_target_info *tinfo)
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{
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/* The branch trace buffer is preceded by a configuration page. */
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return (tinfo->size + 1) * PAGE_SIZE;
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}
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/* Get the size of the perf_event buffer. */
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static inline size_t
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perf_event_buffer_size (struct btrace_target_info* tinfo)
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{
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return tinfo->size * PAGE_SIZE;
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}
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/* Get the start address of the perf_event buffer. */
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static inline const uint8_t *
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perf_event_buffer_begin (struct btrace_target_info* tinfo)
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{
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return ((const uint8_t *) tinfo->buffer) + PAGE_SIZE;
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}
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/* Get the end address of the perf_event buffer. */
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static inline const uint8_t *
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perf_event_buffer_end (struct btrace_target_info* tinfo)
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{
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return perf_event_buffer_begin (tinfo) + perf_event_buffer_size (tinfo);
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return *pev->data_head != pev->last_head;
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}
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/* Check whether an address is in the kernel. */
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@ -162,11 +129,12 @@ perf_event_sample_ok (const struct perf_event_sample *sample)
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static VEC (btrace_block_s) *
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perf_event_read_bts (struct btrace_target_info* tinfo, const uint8_t *begin,
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const uint8_t *end, const uint8_t *start, size_t size)
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const uint8_t *end, const uint8_t *start,
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unsigned long long size)
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{
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VEC (btrace_block_s) *btrace = NULL;
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struct perf_event_sample sample;
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size_t read = 0;
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unsigned long long read = 0;
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struct btrace_block block = { 0, 0 };
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struct regcache *regcache;
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@ -432,6 +400,7 @@ linux_supports_btrace (struct target_ops *ops, enum btrace_format format)
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struct btrace_target_info *
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linux_enable_btrace (ptid_t ptid)
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{
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struct perf_event_mmap_page *header;
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struct btrace_target_info *tinfo;
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int pid, pg;
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@ -467,15 +436,24 @@ linux_enable_btrace (ptid_t ptid)
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for (pg = 4; pg >= 0; --pg)
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{
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/* The number of pages we request needs to be a power of two. */
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tinfo->size = 1 << pg;
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tinfo->buffer = mmap (NULL, perf_event_mmap_size (tinfo),
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PROT_READ, MAP_SHARED, tinfo->file, 0);
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if (tinfo->buffer == MAP_FAILED)
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continue;
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return tinfo;
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header = mmap (NULL, ((1 << pg) + 1) * PAGE_SIZE, PROT_READ, MAP_SHARED,
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tinfo->file, 0);
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if (header != MAP_FAILED)
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break;
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}
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if (header == MAP_FAILED)
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goto err_file;
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tinfo->header = header;
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tinfo->bts.mem = ((const uint8_t *) header) + PAGE_SIZE;
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tinfo->bts.size = (1 << pg) * PAGE_SIZE;
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tinfo->bts.data_head = &header->data_head;
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tinfo->bts.last_head = 0;
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return tinfo;
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err_file:
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/* We were not able to allocate any buffer. */
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close (tinfo->file);
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@ -489,29 +467,13 @@ linux_enable_btrace (ptid_t ptid)
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enum btrace_error
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linux_disable_btrace (struct btrace_target_info *tinfo)
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{
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int errcode;
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errno = 0;
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errcode = munmap (tinfo->buffer, perf_event_mmap_size (tinfo));
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if (errcode != 0)
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return BTRACE_ERR_UNKNOWN;
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munmap((void *) tinfo->header, tinfo->bts.size + PAGE_SIZE);
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close (tinfo->file);
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xfree (tinfo);
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return BTRACE_ERR_NONE;
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}
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/* Check whether the branch trace has changed. */
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static int
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linux_btrace_has_changed (struct btrace_target_info *tinfo)
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{
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volatile struct perf_event_mmap_page *header = perf_event_header (tinfo);
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return header->data_head != tinfo->data_head;
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}
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/* Read branch trace data in BTS format for the thread given by TINFO into
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BTRACE using the TYPE reading method. */
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@ -520,24 +482,25 @@ linux_read_bts (struct btrace_data_bts *btrace,
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struct btrace_target_info *tinfo,
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enum btrace_read_type type)
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{
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volatile struct perf_event_mmap_page *header;
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struct perf_event_buffer *pevent;
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const uint8_t *begin, *end, *start;
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unsigned long data_head, data_tail, retries = 5;
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size_t buffer_size, size;
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unsigned long long data_head, data_tail, buffer_size, size;
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unsigned int retries = 5;
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pevent = &tinfo->bts;
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/* For delta reads, we return at least the partial last block containing
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the current PC. */
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if (type == BTRACE_READ_NEW && !linux_btrace_has_changed (tinfo))
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if (type == BTRACE_READ_NEW && !perf_event_new_data (pevent))
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return BTRACE_ERR_NONE;
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header = perf_event_header (tinfo);
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buffer_size = perf_event_buffer_size (tinfo);
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data_tail = tinfo->data_head;
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buffer_size = pevent->size;
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data_tail = pevent->last_head;
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/* We may need to retry reading the trace. See below. */
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while (retries--)
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{
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data_head = header->data_head;
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data_head = *pevent->data_head;
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/* Delete any leftover trace from the previous iteration. */
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VEC_free (btrace_block_s, btrace->blocks);
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@ -569,13 +532,13 @@ linux_read_bts (struct btrace_data_bts *btrace,
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}
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/* Data_head keeps growing; the buffer itself is circular. */
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begin = perf_event_buffer_begin (tinfo);
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begin = pevent->mem;
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start = begin + data_head % buffer_size;
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if (data_head <= buffer_size)
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end = start;
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else
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end = perf_event_buffer_end (tinfo);
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end = begin + pevent->size;
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btrace->blocks = perf_event_read_bts (tinfo, begin, end, start, size);
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@ -584,11 +547,11 @@ linux_read_bts (struct btrace_data_bts *btrace,
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kernel might be writing the last branch trace records.
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Let's check whether the data head moved while we read the trace. */
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if (data_head == header->data_head)
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if (data_head == *pevent->data_head)
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break;
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}
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tinfo->data_head = data_head;
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pevent->last_head = data_head;
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/* Prune the incomplete last block (i.e. the first one of inferior execution)
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if we're not doing a delta read. There is no way of filling in its zeroed
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@ -32,6 +32,24 @@
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struct target_ops;
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#if HAVE_LINUX_PERF_EVENT_H
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/* A Linux perf event buffer. */
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struct perf_event_buffer
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{
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/* The mapped memory. */
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const uint8_t *mem;
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/* The size of the mapped memory in bytes. */
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unsigned long long size;
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/* A pointer to the data_head field for this buffer. */
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volatile unsigned long long *data_head;
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/* The data_head value from the last read. */
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unsigned long long last_head;
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};
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#endif /* HAVE_LINUX_PERF_EVENT_H */
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/* Branch trace target information per thread. */
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struct btrace_target_info
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{
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@ -42,16 +60,14 @@ struct btrace_target_info
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/* The ptid of this thread. */
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ptid_t ptid;
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/* The mmap configuration mapping the branch trace perf_event buffer.
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file .. the file descriptor
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buffer .. the mmapped memory buffer
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size .. the buffer's size in pages without the configuration page
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data_head .. the data head from the last read */
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/* The perf event file. */
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int file;
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void *buffer;
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size_t size;
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unsigned long data_head;
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/* The perf event configuration page. */
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volatile struct perf_event_mmap_page *header;
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/* The BTS perf event buffer. */
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struct perf_event_buffer bts;
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#endif /* HAVE_LINUX_PERF_EVENT_H */
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/* The size of a pointer in bits for this thread.
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