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// SPDX-License-Identifier: Apache-2.0
/*
* This example code shows how to read from the trace buffer.
*
* Copyright 2013-2019 IBM Corp.
*/
#include <external/trace/trace.h>
#include "../ccan/endian/endian.h"
#include "../ccan/short_types/short_types.h"
#include "trace.h"
#include <trace_types.h>
#include <errno.h>
#if defined(__powerpc__) || defined(__powerpc64__)
#define rmb() lwsync()
#else
#define rmb()
#endif
bool trace_empty(const struct trace_reader *tr)
{
const struct trace_repeat *rep;
if (tr->rpos == be64_to_cpu(tr->tb->end))
return true;
/*
* If we have a single element only, and it's a repeat buffer
* we've already seen every repeat for (yet which may be
* incremented in future), we're also empty.
*/
rep = (void *)tr->tb->buf + tr->rpos % be64_to_cpu(tr->tb->buf_size);
if (be64_to_cpu(tr->tb->end) != tr->rpos + sizeof(*rep))
return false;
if (rep->type != TRACE_REPEAT)
return false;
if (be16_to_cpu(rep->num) != tr->last_repeat)
return false;
return true;
}
/* You can't read in parallel, so some locking required in caller. */
bool trace_get(union trace *t, struct trace_reader *tr)
{
u64 start, rpos;
size_t len;
len = sizeof(*t) < be32_to_cpu(tr->tb->max_size) ? sizeof(*t) :
be32_to_cpu(tr->tb->max_size);
if (trace_empty(tr))
return false;
again:
/*
* The actual buffer is slightly larger than tbsize, so this
* memcpy is always valid.
*/
memcpy(t, tr->tb->buf + tr->rpos % be64_to_cpu(tr->tb->buf_size), len);
rmb(); /* read barrier, so we read tr->tb->start after copying record. */
start = be64_to_cpu(tr->tb->start);
rpos = tr->rpos;
/* Now, was that overwritten? */
if (rpos < start) {
/* Create overflow record. */
t->overflow.unused64 = 0;
t->overflow.type = TRACE_OVERFLOW;
t->overflow.len_div_8 = sizeof(t->overflow) / 8;
t->overflow.bytes_missed = cpu_to_be64(start - rpos);
tr->rpos = start;
return true;
}
/* Repeat entries need special handling */
if (t->hdr.type == TRACE_REPEAT) {
u32 num = be16_to_cpu(t->repeat.num);
/* In case we've read some already... */
t->repeat.num = cpu_to_be16(num - tr->last_repeat);
/* Record how many repeats we saw this time. */
tr->last_repeat = num;
/* Don't report an empty repeat buffer. */
if (t->repeat.num == 0) {
/*
* This can't be the last buffer, otherwise
* trace_empty would have returned true.
*/
assert(be64_to_cpu(tr->tb->end) >
rpos + t->hdr.len_div_8 * 8);
/* Skip to next entry. */
tr->rpos = rpos + t->hdr.len_div_8 * 8;
tr->last_repeat = 0;
goto again;
}
} else {
tr->last_repeat = 0;
tr->rpos = rpos + t->hdr.len_div_8 * 8;
}
return true;
}
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