jvmti_agent.c

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/*
 * jvmti_agent.c: JVMTI agent interface
 *
 * Adapted from the Oprofile code in opagent.c:
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * Copyright 2007 OProfile authors
 * Jens Wilke
 * Daniel Hansel
 * Copyright IBM Corporation 2007
 */
#include <sys/types.h>
#include <sys/stat.h> /* for mkdir() */
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>
#include <stdint.h>
#include <limits.h>
#include <fcntl.h>
#include <unistd.h>
#include <time.h>
#include <sys/mman.h>
#include <syscall.h> /* for gettid() */
#include <err.h>

#include "jvmti_agent.h"
#include "../util/jitdump.h"

#define JIT_LANG "java"

static char jit_path[PATH_MAX];
static void *marker_addr;

static inline pid_t gettid(void)
{
    return (pid_t)syscall(__NR_gettid);
}

static int get_e_machine(struct jitheader *hdr)
{
    ssize_t sret;
    char id[16];
    int fd, ret = -1;
    struct {
        uint16_t e_type;
        uint16_t e_machine;
    } info;

    fd = open("/proc/self/exe", O_RDONLY);
    if (fd == -1)
        return -1;

    sret = read(fd, id, sizeof(id));
    if (sret != sizeof(id))
        goto error;

    /* check ELF signature */
    if (id[0] != 0x7f || id[1] != 'E' || id[2] != 'L' || id[3] != 'F')
        goto error;

    sret = read(fd, &info, sizeof(info));
    if (sret != sizeof(info))
        goto error;

    hdr->elf_mach = info.e_machine;
    ret = 0;
error:
    close(fd);
    return ret;
}

static int use_arch_timestamp;

static inline uint64_t
get_arch_timestamp(void)
{
#if defined(__i386__) || defined(__x86_64__)
    unsigned int low, high;

    asm volatile("rdtsc" : "=a" (low), "=d" (high));

    return low | ((uint64_t)high) << 32;
#else
    return 0;
#endif
}

#define NSEC_PER_SEC    1000000000
static int perf_clk_id = CLOCK_MONOTONIC;

static inline uint64_t
timespec_to_ns(const struct timespec *ts)
{
        return ((uint64_t) ts->tv_sec * NSEC_PER_SEC) + ts->tv_nsec;
}

static inline uint64_t
perf_get_timestamp(void)
{
    struct timespec ts;
    int ret;

    if (use_arch_timestamp)
        return get_arch_timestamp();

    ret = clock_gettime(perf_clk_id, &ts);
    if (ret)
        return 0;

    return timespec_to_ns(&ts);
}

static int
debug_cache_init(void)
{
    char str[32];
    char *base, *p;
    struct tm tm;
    time_t t;
    int ret;

    time(&t);
    localtime_r(&t, &tm);

    base = getenv("JITDUMPDIR");
    if (!base)
        base = getenv("HOME");
    if (!base)
        base = ".";

    strftime(str, sizeof(str), JIT_LANG"-jit-%Y%m%d", &tm);

    snprintf(jit_path, PATH_MAX - 1, "%s/.debug/", base);

    ret = mkdir(jit_path, 0755);
    if (ret == -1) {
        if (errno != EEXIST) {
            warn("jvmti: cannot create jit cache dir %s", jit_path);
            return -1;
        }
    }

    snprintf(jit_path, PATH_MAX - 1, "%s/.debug/jit", base);
    ret = mkdir(jit_path, 0755);
    if (ret == -1) {
        if (errno != EEXIST) {
            warn("cannot create jit cache dir %s", jit_path);
            return -1;
        }
    }

    snprintf(jit_path, PATH_MAX - 1, "%s/.debug/jit/%s.XXXXXXXX", base, str);

    p = mkdtemp(jit_path);
    if (p != jit_path) {
        warn("cannot create jit cache dir %s", jit_path);
        return -1;
    }

    return 0;
}

static int
perf_open_marker_file(int fd)
{
    long pgsz;

    pgsz = sysconf(_SC_PAGESIZE);
    if (pgsz == -1)
        return -1;

    /*
     * we mmap the jitdump to create an MMAP RECORD in perf.data file.
     * The mmap is captured either live (perf record running when we mmap)
     * or  in deferred mode, via /proc/PID/maps
     * the MMAP record is used as a marker of a jitdump file for more meta
     * data info about the jitted code. Perf report/annotate detect this
     * special filename and process the jitdump file.
     *
     * mapping must be PROT_EXEC to ensure it is captured by perf record
     * even when not using -d option
     */
    marker_addr = mmap(NULL, pgsz, PROT_READ|PROT_EXEC, MAP_PRIVATE, fd, 0);
    return (marker_addr == MAP_FAILED) ? -1 : 0;
}

static void
perf_close_marker_file(void)
{
    long pgsz;

    if (!marker_addr)
        return;

    pgsz = sysconf(_SC_PAGESIZE);
    if (pgsz == -1)
        return;

    munmap(marker_addr, pgsz);
}

static void
init_arch_timestamp(void)
{
    char *str = getenv("JITDUMP_USE_ARCH_TIMESTAMP");

    if (!str || !*str || !strcmp(str, "0"))
        return;

    use_arch_timestamp = 1;
}

void *jvmti_open(void)
{
    char dump_path[PATH_MAX];
    struct jitheader header;
    int fd;
    FILE *fp;

    init_arch_timestamp();

    /*
     * check if clockid is supported
     */
    if (!perf_get_timestamp()) {
        if (use_arch_timestamp)
            warnx("jvmti: arch timestamp not supported");
        else
            warnx("jvmti: kernel does not support %d clock id", perf_clk_id);
    }

    memset(&header, 0, sizeof(header));

    debug_cache_init();

    /*
     * jitdump file name
     */
    snprintf(dump_path, PATH_MAX, "%s/jit-%i.dump", jit_path, getpid());

    fd = open(dump_path, O_CREAT|O_TRUNC|O_RDWR, 0666);
    if (fd == -1)
        return NULL;

    /*
     * create perf.data maker for the jitdump file
     */
    if (perf_open_marker_file(fd)) {
        warnx("jvmti: failed to create marker file");
        return NULL;
    }

    fp = fdopen(fd, "w+");
    if (!fp) {
        warn("jvmti: cannot create %s", dump_path);
        close(fd);
        goto error;
    }

    warnx("jvmti: jitdump in %s", dump_path);

    if (get_e_machine(&header)) {
        warn("get_e_machine failed\n");
        goto error;
    }

    header.magic      = JITHEADER_MAGIC;
    header.version    = JITHEADER_VERSION;
    header.total_size = sizeof(header);
    header.pid        = getpid();

    header.timestamp = perf_get_timestamp();

    if (use_arch_timestamp)
        header.flags |= JITDUMP_FLAGS_ARCH_TIMESTAMP;

    if (!fwrite(&header, sizeof(header), 1, fp)) {
        warn("jvmti: cannot write dumpfile header");
        goto error;
    }
    return fp;
error:
    fclose(fp);
    return NULL;
}

int
jvmti_close(void *agent)
{
    struct jr_code_close rec;
    FILE *fp = agent;

    if (!fp) {
        warnx("jvmti: invalid fd in close_agent");
        return -1;
    }

    rec.p.id = JIT_CODE_CLOSE;
    rec.p.total_size = sizeof(rec);

    rec.p.timestamp = perf_get_timestamp();

    if (!fwrite(&rec, sizeof(rec), 1, fp))
        return -1;

    fclose(fp);

    fp = NULL;

    perf_close_marker_file();

    return 0;
}

int
jvmti_write_code(void *agent, char const *sym,
    uint64_t vma, void const *code, unsigned int const size)
{
    static int code_generation = 1;
    struct jr_code_load rec;
    size_t sym_len;
    FILE *fp = agent;
    int ret = -1;

    /* don't care about 0 length function, no samples */
    if (size == 0)
        return 0;

    if (!fp) {
        warnx("jvmti: invalid fd in write_native_code");
        return -1;
    }

    sym_len = strlen(sym) + 1;

    rec.p.id           = JIT_CODE_LOAD;
    rec.p.total_size   = sizeof(rec) + sym_len;
    rec.p.timestamp    = perf_get_timestamp();

    rec.code_size  = size;
    rec.vma        = vma;
    rec.code_addr  = vma;
    rec.pid        = getpid();
    rec.tid        = gettid();

    if (code)
        rec.p.total_size += size;

    /*
     * If JVM is multi-threaded, nultiple concurrent calls to agent
     * may be possible, so protect file writes
     */
    flockfile(fp);

    /*
     * get code index inside lock to avoid race condition
     */
    rec.code_index = code_generation++;

    ret = fwrite_unlocked(&rec, sizeof(rec), 1, fp);
    fwrite_unlocked(sym, sym_len, 1, fp);

    if (code)
        fwrite_unlocked(code, size, 1, fp);

    funlockfile(fp);

    ret = 0;

    return ret;
}

int
jvmti_write_debug_info(void *agent, uint64_t code,
    int nr_lines, jvmti_line_info_t *li,
    const char * const * file_names)
{
    struct jr_code_debug_info rec;
    size_t sret, len, size, flen = 0;
    uint64_t addr;
    FILE *fp = agent;
    int i;

    /*
     * no entry to write
     */
    if (!nr_lines)
        return 0;

    if (!fp) {
        warnx("jvmti: invalid fd in write_debug_info");
        return -1;
    }

    for (i = 0; i < nr_lines; ++i) {
        flen += strlen(file_names[i]) + 1;
    }

    rec.p.id        = JIT_CODE_DEBUG_INFO;
    size            = sizeof(rec);
    rec.p.timestamp = perf_get_timestamp();
    rec.code_addr   = (uint64_t)(uintptr_t)code;
    rec.nr_entry    = nr_lines;

    /*
     * on disk source line info layout:
     * uint64_t : addr
     * int      : line number
     * int      : column discriminator
     * file[]   : source file name
     */
    size += nr_lines * sizeof(struct debug_entry);
    size += flen;
    rec.p.total_size = size;

    /*
     * If JVM is multi-threaded, nultiple concurrent calls to agent
     * may be possible, so protect file writes
     */
    flockfile(fp);

    sret = fwrite_unlocked(&rec, sizeof(rec), 1, fp);
    if (sret != 1)
        goto error;

    for (i = 0; i < nr_lines; i++) {

        addr = (uint64_t)li[i].pc;
        len  = sizeof(addr);
        sret = fwrite_unlocked(&addr, len, 1, fp);
        if (sret != 1)
            goto error;

        len  = sizeof(li[0].line_number);
        sret = fwrite_unlocked(&li[i].line_number, len, 1, fp);
        if (sret != 1)
            goto error;

        len  = sizeof(li[0].discrim);
        sret = fwrite_unlocked(&li[i].discrim, len, 1, fp);
        if (sret != 1)
            goto error;

        sret = fwrite_unlocked(file_names[i], strlen(file_names[i]) + 1, 1, fp);
        if (sret != 1)
            goto error;
    }
    funlockfile(fp);
    return 0;
error:
    funlockfile(fp);
    return -1;
}