vdso.c

Go to the documentation of this file.

#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>
#include <linux/kernel.h>

#include "vdso.h"
#include "util.h"
#include "symbol.h"
#include "linux/string.h"

static bool vdso_found;
static char vdso_file[] = "/tmp/perf-vdso.so-XXXXXX";

static int find_vdso_map(void **start, void **end)
{
    FILE *maps;
    char line[128];
    int found = 0;

    maps = fopen("/proc/self/maps", "r");
    if (!maps) {
        pr_err("vdso: cannot open maps\n");
        return -1;
    }

    while (!found && fgets(line, sizeof(line), maps)) {
        int m = -1;

        /* We care only about private r-x mappings. */
        if (2 != sscanf(line, "%p-%p r-xp %*x %*x:%*x %*u %n",
                start, end, &m))
            continue;
        if (m < 0)
            continue;

        if (!strncmp(&line[m], VDSO__MAP_NAME,
                 sizeof(VDSO__MAP_NAME) - 1))
            found = 1;
    }

    fclose(maps);
    return !found;
}

static char *get_file(void)
{
    char *vdso = NULL;
    char *buf = NULL;
    void *start, *end;
    size_t size;
    int fd;

    if (vdso_found)
        return vdso_file;

    if (find_vdso_map(&start, &end))
        return NULL;

    size = end - start;

    buf = memdup(start, size);
    if (!buf)
        return NULL;

    fd = mkstemp(vdso_file);
    if (fd < 0)
        goto out;

    if (size == (size_t) write(fd, buf, size))
        vdso = vdso_file;

    close(fd);

 out:
    free(buf);

    vdso_found = (vdso != NULL);
    return vdso;
}

void vdso__exit(void)
{
    if (vdso_found)
        unlink(vdso_file);
}

struct dso *vdso__dso_findnew(struct list_head *head)
{
    struct dso *dso = dsos__find(head, VDSO__MAP_NAME);

    if (!dso) {
        char *file;

        file = get_file();
        if (!file)
            return NULL;

        dso = dso__new(VDSO__MAP_NAME);
        if (dso != NULL) {
            dsos__add(head, dso);
            dso__set_long_name(dso, file);
        }
    }

    return dso;
}