106 lines
2.4 KiB
C
106 lines
2.4 KiB
C
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// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Copyright 2022, Athira Rajeev, IBM Corp.
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*/
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#include <unistd.h>
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#include <sys/syscall.h>
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#include <string.h>
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#include <stdio.h>
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#include <sys/ioctl.h>
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#include <sys/mman.h>
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#include <stdlib.h>
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#include <ctype.h>
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#include "misc.h"
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#define PAGE_SIZE sysconf(_SC_PAGESIZE)
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/*
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* Allocate mmap buffer of "mmap_pages" number of
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* pages.
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*/
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void *event_sample_buf_mmap(int fd, int mmap_pages)
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{
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size_t page_size = sysconf(_SC_PAGESIZE);
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size_t mmap_size;
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void *buff;
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if (mmap_pages <= 0)
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return NULL;
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if (fd <= 0)
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return NULL;
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mmap_size = page_size * (1 + mmap_pages);
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buff = mmap(NULL, mmap_size,
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PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
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if (buff == MAP_FAILED) {
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perror("mmap() failed.");
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return NULL;
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}
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return buff;
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}
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/*
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* Post process the mmap buffer.
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* - If sample_count != NULL then return count of total
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* number of samples present in the mmap buffer.
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* - If sample_count == NULL then return the address
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* of first sample from the mmap buffer
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*/
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void *__event_read_samples(void *sample_buff, size_t *size, u64 *sample_count)
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{
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size_t page_size = sysconf(_SC_PAGESIZE);
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struct perf_event_header *header = sample_buff + page_size;
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struct perf_event_mmap_page *metadata_page = sample_buff;
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unsigned long data_head, data_tail;
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/*
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* PERF_RECORD_SAMPLE:
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* struct {
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* struct perf_event_header hdr;
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* u64 data[];
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* };
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*/
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data_head = metadata_page->data_head;
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/* sync memory before reading sample */
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mb();
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data_tail = metadata_page->data_tail;
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/* Check for sample_count */
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if (sample_count)
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*sample_count = 0;
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while (1) {
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/*
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* Reads the mmap data buffer by moving
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* the data_tail to know the last read data.
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* data_head points to head in data buffer.
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* refer "struct perf_event_mmap_page" in
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* "include/uapi/linux/perf_event.h".
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*/
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if (data_head - data_tail < sizeof(header))
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return NULL;
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data_tail += sizeof(header);
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if (header->type == PERF_RECORD_SAMPLE) {
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*size = (header->size - sizeof(header));
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if (!sample_count)
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return sample_buff + page_size + data_tail;
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data_tail += *size;
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*sample_count += 1;
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} else {
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*size = (header->size - sizeof(header));
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if ((metadata_page->data_tail + *size) > metadata_page->data_head)
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data_tail = metadata_page->data_head;
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else
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data_tail += *size;
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}
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header = (struct perf_event_header *)((void *)header + header->size);
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}
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return NULL;
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}
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