addr2line.c

Go to the documentation of this file.

/**********************************************************************

  addr2line.c -

  $Author$

  Copyright (C) 2010 Shinichiro Hamaji

**********************************************************************/

#include "ruby/config.h"
#include "ruby/missing.h"
#include "addr2line.h"

#include <stdio.h>
#include <errno.h>

#ifdef USE_ELF

#include <fcntl.h>
#include <limits.h>
#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>

#ifdef __OpenBSD__
#include <elf_abi.h>
#else
#include <elf.h>
#endif

/* Make alloca work the best possible way.  */
#ifdef __GNUC__
# ifndef atarist
#  ifndef alloca
#   define alloca __builtin_alloca
#  endif
# endif /* atarist */
#else
# ifdef HAVE_ALLOCA_H
#  include <alloca.h>
# else
#  ifdef _AIX
#pragma alloca
#  else
#   ifndef alloca               /* predefined by HP cc +Olibcalls */
void *alloca();
#   endif
#  endif /* AIX */
# endif /* HAVE_ALLOCA_H */
#endif /* __GNUC__ */

#ifdef HAVE_DL_ITERATE_PHDR
# ifndef _GNU_SOURCE
#  define _GNU_SOURCE
# endif
# include <link.h>
#endif

#define DW_LNS_copy                     0x01
#define DW_LNS_advance_pc               0x02
#define DW_LNS_advance_line             0x03
#define DW_LNS_set_file                 0x04
#define DW_LNS_set_column               0x05
#define DW_LNS_negate_stmt              0x06
#define DW_LNS_set_basic_block          0x07
#define DW_LNS_const_add_pc             0x08
#define DW_LNS_fixed_advance_pc         0x09
#define DW_LNS_set_prologue_end         0x0a /* DWARF3 */
#define DW_LNS_set_epilogue_begin       0x0b /* DWARF3 */
#define DW_LNS_set_isa                  0x0c /* DWARF3 */

/* Line number extended opcode name. */
#define DW_LNE_end_sequence             0x01
#define DW_LNE_set_address              0x02
#define DW_LNE_define_file              0x03
#define DW_LNE_set_discriminator        0x04  /* DWARF4 */

#ifndef ElfW
# if SIZEOF_VOIDP == 8
#  define ElfW(x) Elf64##_##x
# else
#  define ElfW(x) Elf32##_##x
# endif
#endif
#ifndef PATH_MAX
#define PATH_MAX 4096
#endif

int kprintf(const char *fmt, ...);

typedef struct {
    const char *dirname;
    const char *filename;
    int line;

    int fd;
    void *mapped;
    size_t mapped_size;
    unsigned long base_addr;
} line_info_t;

/* Avoid consuming stack as this module may be used from signal handler */
static char binary_filename[PATH_MAX];

static unsigned long
uleb128(char **p)
{
    unsigned long r = 0;
    int s = 0;
    for (;;) {
        unsigned char b = *(unsigned char *)(*p)++;
        if (b < 0x80) {
            r += (unsigned long)b << s;
            break;
        }
        r += (b & 0x7f) << s;
        s += 7;
    }
    return r;
}

static long
sleb128(char **p)
{
    long r = 0;
    int s = 0;
    for (;;) {
        unsigned char b = *(unsigned char *)(*p)++;
        if (b < 0x80) {
            if (b & 0x40) {
                r -= (0x80 - b) << s;
            }
            else {
                r += (b & 0x3f) << s;
            }
            break;
        }
        r += (b & 0x7f) << s;
        s += 7;
    }
    return r;
}

static const char *
get_nth_dirname(unsigned long dir, char *p)
{
    if (!dir--) {
        return "";
    }
    while (dir--) {
        while (*p) p++;
        p++;
        if (!*p) {
            kprintf("Unexpected directory number %lu in %s\n",
                    dir, binary_filename);
            return "";
        }
    }
    return p;
}

static void
fill_filename(int file, char *include_directories, char *filenames,
              line_info_t *line)
{
    int i;
    char *p = filenames;
    char *filename;
    unsigned long dir;
    for (i = 1; i <= file; i++) {
        filename = p;
        if (!*p) {
            /* Need to output binary file name? */
            kprintf("Unexpected file number %d in %s\n",
                    file, binary_filename);
            return;
        }
        while (*p) p++;
        p++;
        dir = uleb128(&p);
        /* last modified. */
        uleb128(&p);
        /* size of the file. */
        uleb128(&p);

        if (i == file) {
            line->filename = filename;
            line->dirname = get_nth_dirname(dir, include_directories);
        }
    }
}

static int
get_path_from_symbol(const char *symbol, const char **p, size_t *len)
{
    if (symbol[0] == '0') {
        /* libexecinfo */
        *p   = strchr(symbol, '/');
        if (*p == NULL) return 0;
        *len = strlen(*p);
    }
    else {
        /* glibc */
        const char *q;
        *p   = symbol;
        q   = strchr(symbol, '(');
        if (q == NULL) return 0;
        *len = q - symbol;
    }
    return 1;
}

static void
fill_line(int num_traces, void **traces,
          unsigned long addr, int file, int line,
          char *include_directories, char *filenames, line_info_t *lines)
{
    int i;
    for (i = 0; i < num_traces; i++) {
        unsigned long a = (unsigned long)traces[i] - lines[i].base_addr;
        /* We assume one line code doesn't result >100 bytes of native code.
       We may want more reliable way eventually... */
        if (addr < a && a < addr + 100) {
            fill_filename(file, include_directories, filenames, &lines[i]);
            lines[i].line = line;
        }
    }
}

static void
parse_debug_line_cu(int num_traces, void **traces,
                    char **debug_line, line_info_t *lines)
{
    char *p, *cu_end, *cu_start, *include_directories, *filenames;
    unsigned long unit_length;
    int default_is_stmt, line_base;
    unsigned int header_length, minimum_instruction_length, line_range,
                 opcode_base;
    /* unsigned char *standard_opcode_lengths; */

    /* The registers. */
    unsigned long addr = 0;
    unsigned int file = 1;
    unsigned int line = 1;
    /* unsigned int column = 0; */
    int is_stmt;
    /* int basic_block = 0; */
    /* int end_sequence = 0; */
    /* int prologue_end = 0; */
    /* int epilogue_begin = 0; */
    /* unsigned int isa = 0; */

    p = *debug_line;

    unit_length = *(unsigned int *)p;
    p += sizeof(unsigned int);
    if (unit_length == 0xffffffff) {
        unit_length = *(unsigned long *)p;
        p += sizeof(unsigned long);
    }

    cu_end = p + unit_length;

    /*dwarf_version = *(unsigned short *)p;*/
    p += 2;

    header_length = *(unsigned int *)p;
    p += sizeof(unsigned int);

    cu_start = p + header_length;

    minimum_instruction_length = *(unsigned char *)p;
    p++;

    is_stmt = default_is_stmt = *(unsigned char *)p;
    p++;

    line_base = *(char *)p;
    p++;

    line_range = *(unsigned char *)p;
    p++;

    opcode_base = *(unsigned char *)p;
    p++;

    /* standard_opcode_lengths = (unsigned char *)p - 1; */
    p += opcode_base - 1;

    include_directories = p;

    /* skip include directories */
    while (*p) {
        while (*p) p++;
        p++;
    }
    p++;

    filenames = p;

    p = cu_start;

#define FILL_LINE()                                                 \
    do {                                                            \
        fill_line(num_traces, traces, addr, file, line,             \
                  include_directories, filenames, lines);           \
        /*basic_block = prologue_end = epilogue_begin = 0;*/        \
    } while (0)

    while (p < cu_end) {
        unsigned long a;
        unsigned char op = *p++;
        switch (op) {
        case DW_LNS_copy:
            FILL_LINE();
            break;
        case DW_LNS_advance_pc:
            a = uleb128(&p);
            addr += a;
            break;
        case DW_LNS_advance_line: {
            long a = sleb128(&p);
            line += a;
            break;
        }
        case DW_LNS_set_file:
            file = (unsigned int)uleb128(&p);
            break;
        case DW_LNS_set_column:
            /*column = (unsigned int)*/(void)uleb128(&p);
            break;
        case DW_LNS_negate_stmt:
            is_stmt = !is_stmt;
            break;
        case DW_LNS_set_basic_block:
            /*basic_block = 1; */
            break;
        case DW_LNS_const_add_pc:
            a = ((255 - opcode_base) / line_range) *
                minimum_instruction_length;
            addr += a;
            break;
        case DW_LNS_fixed_advance_pc:
            a = *(unsigned char *)p++;
            addr += a;
            break;
        case DW_LNS_set_prologue_end:
            /* prologue_end = 1; */
            break;
        case DW_LNS_set_epilogue_begin:
            /* epilogue_begin = 1; */
            break;
        case DW_LNS_set_isa:
            /* isa = (unsigned int)*/(void)uleb128(&p);
            break;
        case 0:
            a = *(unsigned char *)p++;
            op = *p++;
            switch (op) {
            case DW_LNE_end_sequence:
                /* end_sequence = 1; */
                FILL_LINE();
                addr = 0;
                file = 1;
                line = 1;
                /* column = 0; */
                is_stmt = default_is_stmt;
                /* end_sequence = 0; */
                /* isa = 0; */
                break;
            case DW_LNE_set_address:
                addr = *(unsigned long *)p;
                p += sizeof(unsigned long);
                break;
            case DW_LNE_define_file:
                kprintf("Unsupported operation in %s\n",
                        binary_filename);
                break;
            case DW_LNE_set_discriminator:
                /* TODO:currently ignore */
                uleb128(&p);
                break;
            default:
                kprintf("Unknown extended opcode: %d in %s\n",
                        op, binary_filename);
            }
            break;
        default: {
            unsigned long addr_incr;
            unsigned long line_incr;
            a = op - opcode_base;
            addr_incr = (a / line_range) * minimum_instruction_length;
            line_incr = line_base + (a % line_range);
            addr += (unsigned int)addr_incr;
            line += (unsigned int)line_incr;
            FILL_LINE();
        }
        }
    }
    *debug_line = p;
}

static void
parse_debug_line(int num_traces, void **traces,
                 char *debug_line, unsigned long size, line_info_t *lines)
{
    char *debug_line_end = debug_line + size;
    while (debug_line < debug_line_end) {
        parse_debug_line_cu(num_traces, traces, &debug_line, lines);
    }
    if (debug_line != debug_line_end) {
        kprintf("Unexpected size of .debug_line in %s\n",
                binary_filename);
    }
}

/* read file and fill lines */
static void
fill_lines(int num_traces, void **traces, char **syms, int check_debuglink,
           line_info_t *current_line, line_info_t *lines);

static void
follow_debuglink(char *debuglink, int num_traces, void **traces, char **syms,
                 line_info_t *current_line, line_info_t *lines)
{
    /* Ideally we should check 4 paths to follow gnu_debuglink,
       but we handle only one case for now as this format is used
       by some linux distributions. See GDB's info for detail. */
    static const char global_debug_dir[] = "/usr/lib/debug";
    char *p, *subdir;

    p = strrchr(binary_filename, '/');
    if (!p) {
        return;
    }
    p[1] = '\0';

    subdir = (char *)alloca(strlen(binary_filename) + 1);
    strcpy(subdir, binary_filename);
    strcpy(binary_filename, global_debug_dir);
    strncat(binary_filename, subdir,
            PATH_MAX - strlen(binary_filename) - 1);
    strncat(binary_filename, debuglink,
            PATH_MAX - strlen(binary_filename) - 1);

    munmap(current_line->mapped, current_line->mapped_size);
    close(current_line->fd);
    fill_lines(num_traces, traces, syms, 0, current_line, lines);
}

/* read file and fill lines */
static void
fill_lines(int num_traces, void **traces, char **syms, int check_debuglink,
           line_info_t *current_line, line_info_t *lines)
{
    int i;
    char *shstr;
    char *section_name;
    ElfW(Ehdr) *ehdr;
    ElfW(Shdr) *shdr, *shstr_shdr;
    ElfW(Shdr) *debug_line_shdr = NULL, *gnu_debuglink_shdr = NULL;
    int fd;
    off_t filesize;
    char *file;

    fd = open(binary_filename, O_RDONLY);
    if (fd < 0) {
        return;
    }
    filesize = lseek(fd, 0, SEEK_END);
    if (filesize < 0) {
        int e = errno;
        close(fd);
        kprintf("lseek: %s\n", strerror(e));
        return;
    }
#if SIZEOF_OFF_T > SIZEOF_SIZE_T
    if (filesize > (off_t)SIZE_MAX) {
        close(fd);
        kprintf("Too large file %s\n", binary_filename);
        return;
    }
#endif
    lseek(fd, 0, SEEK_SET);
    /* async-signal unsafe */
    file = (char *)mmap(NULL, (size_t)filesize, PROT_READ, MAP_SHARED, fd, 0);
    if (file == MAP_FAILED) {
        int e = errno;
        close(fd);
        kprintf("mmap: %s\n", strerror(e));
        return;
    }

    ehdr = (ElfW(Ehdr) *)file;
    if (memcmp(ehdr->e_ident, "\177ELF", 4) != 0) {
        /*
         * Huh? Maybe filename was overridden by setproctitle() and
         * it match non-elf file.
         */
        close(fd);
        return;
    }

    current_line->fd = fd;
    current_line->mapped = file;
    current_line->mapped_size = (size_t)filesize;

    for (i = 0; i < num_traces; i++) {
        const char *path;
        size_t len;
        if (get_path_from_symbol(syms[i], &path, &len) &&
                !strncmp(path, binary_filename, len)) {
            lines[i].line = -1;
        }
    }

    shdr = (ElfW(Shdr) *)(file + ehdr->e_shoff);

    shstr_shdr = shdr + ehdr->e_shstrndx;
    shstr = file + shstr_shdr->sh_offset;

    for (i = 0; i < ehdr->e_shnum; i++) {
        section_name = shstr + shdr[i].sh_name;
        if (!strcmp(section_name, ".debug_line")) {
            debug_line_shdr = shdr + i;
            break;
        } else if (!strcmp(section_name, ".gnu_debuglink")) {
            gnu_debuglink_shdr = shdr + i;
        }
    }

    if (!debug_line_shdr) {
        /* This file doesn't have .debug_line section,
           let's check .gnu_debuglink section instead. */
        if (gnu_debuglink_shdr && check_debuglink) {
            follow_debuglink(file + gnu_debuglink_shdr->sh_offset,
                             num_traces, traces, syms,
                             current_line, lines);
        }
        return;
    }

    parse_debug_line(num_traces, traces,
                     file + debug_line_shdr->sh_offset,
                     debug_line_shdr->sh_size,
                     lines);
}

#ifdef HAVE_DL_ITERATE_PHDR

typedef struct {
    int num_traces;
    char **syms;
    line_info_t *lines;
} fill_base_addr_state_t;

static int
fill_base_addr(struct dl_phdr_info *info, size_t size, void *data)
{
    int i;
    fill_base_addr_state_t *st = (fill_base_addr_state_t *)data;
    for (i = 0; i < st->num_traces; i++) {
        const char *path;
        size_t len;
        size_t name_len = strlen(info->dlpi_name);

        if (get_path_from_symbol(st->syms[i], &path, &len) &&
                (len == name_len || (len > name_len && path[len-name_len-1] == '/')) &&
                !strncmp(path+len-name_len, info->dlpi_name, name_len)) {
            st->lines[i].base_addr = info->dlpi_addr;
        }
    }
    return 0;
}

#endif /* HAVE_DL_ITERATE_PHDR */

void
rb_dump_backtrace_with_lines(int num_traces, void **trace, char **syms)
{
    int i;
    /* async-signal unsafe */
    line_info_t *lines = (line_info_t *)calloc(num_traces,
                                               sizeof(line_info_t));

    /* Note that line info of shared objects might not be shown
       if we don't have dl_iterate_phdr */
#ifdef HAVE_DL_ITERATE_PHDR
    fill_base_addr_state_t fill_base_addr_state;

    fill_base_addr_state.num_traces = num_traces;
    fill_base_addr_state.syms = syms;
    fill_base_addr_state.lines = lines;
    /* maybe async-signal unsafe */
    dl_iterate_phdr(fill_base_addr, &fill_base_addr_state);
#endif /* HAVE_DL_ITERATE_PHDR */

    for (i = 0; i < num_traces; i++) {
        const char *path;
        size_t len;
        if (lines[i].line) {
            continue;
        }

        if (!get_path_from_symbol(syms[i], &path, &len)) {
            continue;
        }

        strncpy(binary_filename, path, len);
        binary_filename[len] = '\0';

        fill_lines(num_traces, trace, syms, 1, &lines[i], lines);
    }

    for (i = 0; i < num_traces; i++) {
        line_info_t *line = &lines[i];

        if (line->line > 0) {
            if (line->filename) {
                if (line->dirname && line->dirname[0]) {
                    kprintf("%s %s/%s:%d\n", syms[i], line->dirname, line->filename, line->line);
                }
                else {
                    kprintf("%s %s:%d\n", syms[i], line->filename, line->line);
                }
            } else {
                kprintf("%s ???:%d\n", syms[i], line->line);
            }
        } else {
            kprintf("%s\n", syms[i]);
        }
    }

    for (i = 0; i < num_traces; i++) {
        line_info_t *line = &lines[i];
        if (line->fd) {
            munmap(line->mapped, line->mapped_size);
            close(line->fd);
        }
    }
    free(lines);
}

/* From FreeBSD's lib/libstand/printf.c */
/*-
 * Copyright (c) 1986, 1988, 1991, 1993
 *      The Regents of the University of California.  All rights reserved.
 * (c) UNIX System Laboratories, Inc.
 * All or some portions of this file are derived from material licensed
 * to the University of California by American Telephone and Telegraph
 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
 * the permission of UNIX System Laboratories, Inc.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      @(#)subr_prf.c  8.3 (Berkeley) 1/21/94
 */

#include <stdarg.h>
#define MAXNBUF (sizeof(intmax_t) * CHAR_BIT + 1)
extern int rb_toupper(int c);
#define    toupper(c)  rb_toupper(c)
#define    hex2ascii(hex)  (hex2ascii_data[hex])
char const hex2ascii_data[] = "0123456789abcdefghijklmnopqrstuvwxyz";
static inline int imax(int a, int b) { return (a > b ? a : b); }
static int kvprintf(char const *fmt, void (*func)(int), void *arg, int radix, va_list ap);

static void putce(int c)
{
    char s[1];
    ssize_t ret;

    s[0] = (char)c;
    ret = write(2, s, 1);
    (void)ret;
}

int
kprintf(const char *fmt, ...)
{
        va_list ap;
        int retval;

        va_start(ap, fmt);
        retval = kvprintf(fmt, putce, NULL, 10, ap);
        va_end(ap);
        return retval;
}

/*
 * Put a NUL-terminated ASCII number (base <= 36) in a buffer in reverse
 * order; return an optional length and a pointer to the last character
 * written in the buffer (i.e., the first character of the string).
 * The buffer pointed to by `nbuf' must have length >= MAXNBUF.
 */
static char *
ksprintn(char *nbuf, uintmax_t num, int base, int *lenp, int upper)
{
        char *p, c;

        p = nbuf;
        *p = '\0';
        do {
                c = hex2ascii(num % base);
                *++p = upper ? toupper(c) : c;
        } while (num /= base);
        if (lenp)
                *lenp = (int)(p - nbuf);
        return (p);
}

/*
 * Scaled down version of printf(3).
 *
 * Two additional formats:
 *
 * The format %b is supported to decode error registers.
 * Its usage is:
 *
 *      printf("reg=%b\n", regval, "<base><arg>*");
 *
 * where <base> is the output base expressed as a control character, e.g.
 * \10 gives octal; \20 gives hex.  Each arg is a sequence of characters,
 * the first of which gives the bit number to be inspected (origin 1), and
 * the next characters (up to a control character, i.e. a character <= 32),
 * give the name of the register.  Thus:
 *
 *      kvprintf("reg=%b\n", 3, "\10\2BITTWO\1BITONE\n");
 *
 * would produce output:
 *
 *      reg=3<BITTWO,BITONE>
 *
 * XXX:  %D  -- Hexdump, takes pointer and separator string:
 *              ("%6D", ptr, ":")   -> XX:XX:XX:XX:XX:XX
 *              ("%*D", len, ptr, " " -> XX XX XX XX ...
 */
static int
kvprintf(char const *fmt, void (*func)(int), void *arg, int radix, va_list ap)
{
#define PCHAR(c) {int cc=(c); if (func) (*func)(cc); else *d++ = cc; retval++; }
        char nbuf[MAXNBUF];
        char *d;
        const char *p, *percent, *q;
        unsigned char *up;
        int ch, n;
        uintmax_t num;
        int base, lflag, qflag, tmp, width, ladjust, sharpflag, neg, sign, dot;
        int cflag, hflag, jflag, tflag, zflag;
        int dwidth, upper;
        char padc;
        int stop = 0, retval = 0;

        num = 0;
        if (!func)
                d = (char *) arg;
        else
                d = NULL;

        if (fmt == NULL)
                fmt = "(fmt null)\n";

        if (radix < 2 || radix > 36)
                radix = 10;

        for (;;) {
                padc = ' ';
                width = 0;
                while ((ch = (unsigned char)*fmt++) != '%' || stop) {
                        if (ch == '\0')
                                return (retval);
                        PCHAR(ch);
                }
                percent = fmt - 1;
                qflag = 0; lflag = 0; ladjust = 0; sharpflag = 0; neg = 0;
                sign = 0; dot = 0; dwidth = 0; upper = 0;
                cflag = 0; hflag = 0; jflag = 0; tflag = 0; zflag = 0;
reswitch:       switch (ch = (unsigned char)*fmt++) {
                case '.':
                        dot = 1;
                        goto reswitch;
                case '#':
                        sharpflag = 1;
                        goto reswitch;
                case '+':
                        sign = 1;
                        goto reswitch;
                case '-':
                        ladjust = 1;
                        goto reswitch;
                case '%':
                        PCHAR(ch);
                        break;
                case '*':
                        if (!dot) {
                                width = va_arg(ap, int);
                                if (width < 0) {
                                        ladjust = !ladjust;
                                        width = -width;
                                }
                        } else {
                                dwidth = va_arg(ap, int);
                        }
                        goto reswitch;
                case '0':
                        if (!dot) {
                                padc = '0';
                                goto reswitch;
                        }
                case '1': case '2': case '3': case '4':
                case '5': case '6': case '7': case '8': case '9':
                                for (n = 0;; ++fmt) {
                                        n = n * 10 + ch - '0';
                                        ch = *fmt;
                                        if (ch < '0' || ch > '9')
                                                break;
                                }
                        if (dot)
                                dwidth = n;
                        else
                                width = n;
                        goto reswitch;
                case 'b':
                        num = (unsigned int)va_arg(ap, int);
                        p = va_arg(ap, char *);
                        for (q = ksprintn(nbuf, num, *p++, NULL, 0); *q;)
                                PCHAR(*q--);

                        if (num == 0)
                                break;

                        for (tmp = 0; *p;) {
                                n = *p++;
                                if (num & (1 << (n - 1))) {
                                        PCHAR(tmp ? ',' : '<');
                                        for (; (n = *p) > ' '; ++p)
                                                PCHAR(n);
                                        tmp = 1;
                                } else
                                        for (; *p > ' '; ++p)
                                                continue;
                        }
                        if (tmp)
                                PCHAR('>');
                        break;
                case 'c':
                        PCHAR(va_arg(ap, int));
                        break;
                case 'D':
                        up = va_arg(ap, unsigned char *);
                        p = va_arg(ap, char *);
                        if (!width)
                                width = 16;
                        while(width--) {
                                PCHAR(hex2ascii(*up >> 4));
                                PCHAR(hex2ascii(*up & 0x0f));
                                up++;
                                if (width)
                                        for (q=p;*q;q++)
                                                PCHAR(*q);
                        }
                        break;
                case 'd':
                case 'i':
                        base = 10;
                        sign = 1;
                        goto handle_sign;
                case 'h':
                        if (hflag) {
                                hflag = 0;
                                cflag = 1;
                        } else
                                hflag = 1;
                        goto reswitch;
                case 'j':
                        jflag = 1;
                        goto reswitch;
                case 'l':
                        if (lflag) {
                                lflag = 0;
                                qflag = 1;
                        } else
                                lflag = 1;
                        goto reswitch;
                case 'n':
                        if (jflag)
                                *(va_arg(ap, intmax_t *)) = retval;
                        else if (qflag)
                                *(va_arg(ap, int64_t *)) = retval;
                        else if (lflag)
                                *(va_arg(ap, long *)) = retval;
                        else if (zflag)
                                *(va_arg(ap, size_t *)) = retval;
                        else if (hflag)
                                *(va_arg(ap, short *)) = retval;
                        else if (cflag)
                                *(va_arg(ap, char *)) = retval;
                        else
                                *(va_arg(ap, int *)) = retval;
                        break;
                case 'o':
                        base = 8;
                        goto handle_nosign;
                case 'p':
                        base = 16;
                        sharpflag = (width == 0);
                        sign = 0;
                        num = (uintptr_t)va_arg(ap, void *);
                        goto number;
                case 'q':
                        qflag = 1;
                        goto reswitch;
                case 'r':
                        base = radix;
                        if (sign)
                                goto handle_sign;
                        goto handle_nosign;
                case 's':
                        p = va_arg(ap, char *);
                        if (p == NULL)
                                p = "(null)";
                        if (!dot)
                                n = (int)strlen (p);
                        else
                                for (n = 0; n < dwidth && p[n]; n++)
                                        continue;

                        width -= n;

                        if (!ladjust && width > 0)
                                while (width--)
                                        PCHAR(padc);
                        while (n--)
                                PCHAR(*p++);
                        if (ladjust && width > 0)
                                while (width--)
                                        PCHAR(padc);
                        break;
                case 't':
                        tflag = 1;
                        goto reswitch;
                case 'u':
                        base = 10;
                        goto handle_nosign;
                case 'X':
                        upper = 1;
                case 'x':
                        base = 16;
                        goto handle_nosign;
                case 'y':
                        base = 16;
                        sign = 1;
                        goto handle_sign;
                case 'z':
                        zflag = 1;
                        goto reswitch;
handle_nosign:
                        sign = 0;
                        if (jflag)
                                num = va_arg(ap, uintmax_t);
                        else if (qflag)
                                num = va_arg(ap, uint64_t);
                        else if (tflag)
                                num = va_arg(ap, ptrdiff_t);
                        else if (lflag)
                                num = va_arg(ap, unsigned long);
                        else if (zflag)
                                num = va_arg(ap, size_t);
                        else if (hflag)
                                num = (unsigned short)va_arg(ap, int);
                        else if (cflag)
                                num = (unsigned char)va_arg(ap, int);
                        else
                                num = va_arg(ap, unsigned int);
                        goto number;
handle_sign:
                        if (jflag)
                                num = va_arg(ap, intmax_t);
                        else if (qflag)
                                num = va_arg(ap, int64_t);
                        else if (tflag)
                                num = va_arg(ap, ptrdiff_t);
                        else if (lflag)
                                num = va_arg(ap, long);
                        else if (zflag)
                                num = va_arg(ap, ssize_t);
                        else if (hflag)
                                num = (short)va_arg(ap, int);
                        else if (cflag)
                                num = (char)va_arg(ap, int);
                        else
                                num = va_arg(ap, int);
number:
                        if (sign && (intmax_t)num < 0) {
                                neg = 1;
                                num = -(intmax_t)num;
                        }
                        p = ksprintn(nbuf, num, base, &n, upper);
                        tmp = 0;
                        if (sharpflag && num != 0) {
                                if (base == 8)
                                        tmp++;
                                else if (base == 16)
                                        tmp += 2;
                        }
                        if (neg)
                                tmp++;

                        if (!ladjust && padc == '0')
                                dwidth = width - tmp;
                        width -= tmp + imax(dwidth, n);
                        dwidth -= n;
                        if (!ladjust)
                                while (width-- > 0)
                                        PCHAR(' ');
                        if (neg)
                                PCHAR('-');
                        if (sharpflag && num != 0) {
                                if (base == 8) {
                                        PCHAR('0');
                                } else if (base == 16) {
                                        PCHAR('0');
                                        PCHAR('x');
                                }
                        }
                        while (dwidth-- > 0)
                                PCHAR('0');

                        while (*p)
                                PCHAR(*p--);

                        if (ladjust)
                                while (width-- > 0)
                                        PCHAR(' ');

                        break;
                default:
                        while (percent < fmt)
                                PCHAR(*percent++);
                        /*
                         * Since we ignore an formatting argument it is no
                         * longer safe to obey the remaining formatting
                         * arguments as the arguments will no longer match
                         * the format specs.
                         */
                        stop = 1;
                        break;
                }
        }
#undef PCHAR
}
#else /* defined(USE_ELF) */
#error not supported
#endif

---