auxtrace.c

/*
 * auxtrace.c: AUX area trace support
 * Copyright (c) 2013-2015, Intel Corporation.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 */

#include <sys/types.h>
#include <sys/mman.h>
#include <stdbool.h>

#include <linux/kernel.h>
#include <linux/perf_event.h>
#include <linux/types.h>
#include <linux/bitops.h>
#include <linux/log2.h>

#include "../perf.h"
#include "util.h"
#include "evlist.h"
#include "cpumap.h"
#include "thread_map.h"
#include "asm/bug.h"
#include "auxtrace.h"

int auxtrace_mmap__mmap(struct auxtrace_mmap *mm,
			struct auxtrace_mmap_params *mp,
			void *userpg, int fd)
{
	struct perf_event_mmap_page *pc = userpg;

#if BITS_PER_LONG != 64 && !defined(HAVE_SYNC_COMPARE_AND_SWAP_SUPPORT)
	pr_err("Cannot use AUX area tracing mmaps\n");
	return -1;
#endif

	WARN_ONCE(mm->base, "Uninitialized auxtrace_mmap\n");

	mm->userpg = userpg;
	mm->mask = mp->mask;
	mm->len = mp->len;
	mm->prev = 0;
	mm->idx = mp->idx;
	mm->tid = mp->tid;
	mm->cpu = mp->cpu;

	if (!mp->len) {
		mm->base = NULL;
		return 0;
	}

	pc->aux_offset = mp->offset;
	pc->aux_size = mp->len;

	mm->base = mmap(NULL, mp->len, mp->prot, MAP_SHARED, fd, mp->offset);
	if (mm->base == MAP_FAILED) {
		pr_debug2("failed to mmap AUX area\n");
		mm->base = NULL;
		return -1;
	}

	return 0;
}

void auxtrace_mmap__munmap(struct auxtrace_mmap *mm)
{
	if (mm->base) {
		munmap(mm->base, mm->len);
		mm->base = NULL;
	}
}

void auxtrace_mmap_params__init(struct auxtrace_mmap_params *mp,
				off_t auxtrace_offset,
				unsigned int auxtrace_pages,
				bool auxtrace_overwrite)
{
	if (auxtrace_pages) {
		mp->offset = auxtrace_offset;
		mp->len = auxtrace_pages * (size_t)page_size;
		mp->mask = is_power_of_2(mp->len) ? mp->len - 1 : 0;
		mp->prot = PROT_READ | (auxtrace_overwrite ? 0 : PROT_WRITE);
		pr_debug2("AUX area mmap length %zu\n", mp->len);
	} else {
		mp->len = 0;
	}
}

void auxtrace_mmap_params__set_idx(struct auxtrace_mmap_params *mp,
				   struct perf_evlist *evlist, int idx,
				   bool per_cpu)
{
	mp->idx = idx;

	if (per_cpu) {
		mp->cpu = evlist->cpus->map[idx];
		if (evlist->threads)
			mp->tid = evlist->threads->map[0];
		else
			mp->tid = -1;
	} else {
		mp->cpu = -1;
		mp->tid = evlist->threads->map[idx];
	}
}