326 lines
7.6 KiB
C
326 lines
7.6 KiB
C
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#ifndef lint
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static const char rcsid[] =
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"$Id: readelf.c,v 1.4 1998/02/20 04:54:00 jb Exp $";
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#endif /* not lint */
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#ifdef BUILTIN_ELF
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#include <ctype.h>
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#include <err.h>
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#include <errno.h>
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#include <string.h>
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#include <unistd.h>
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#include "readelf.h"
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#include "file.h"
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static void doshn __P((int, off_t, int, size_t, char *));
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static void dophn_exec __P((int, off_t, int, size_t, char *));
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static void dophn_core __P((int, off_t, int, size_t, char *));
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static void
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doshn(fd, off, num, size, buf)
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int fd;
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off_t off;
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int num;
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size_t size;
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char *buf;
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{
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/*
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* This works for both 32-bit and 64-bit ELF formats,
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* because it looks only at the "sh_type" field, which is
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* always 32 bits, and is preceded only by the "sh_name"
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* field which is also always 32 bits, and because it uses
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* the shdr size from the ELF header rather than using
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* the size of an "Elf32_Shdr".
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*/
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Elf32_Shdr *sh = (Elf32_Shdr *) buf;
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if (lseek(fd, off, SEEK_SET) == -1)
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err(1, "lseek failed");
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for ( ; num; num--) {
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if (read(fd, buf, size) == -1)
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err(1, "read failed");
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if (sh->sh_type == SHT_SYMTAB) {
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(void) printf (", not stripped");
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return;
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}
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}
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(void) printf (", stripped");
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}
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/*
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* Look through the program headers of an executable image, searching
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* for a PT_INTERP section; if one is found, it's dynamically linked,
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* otherwise it's statically linked.
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*/
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static void
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dophn_exec(fd, off, num, size, buf)
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int fd;
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off_t off;
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int num;
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size_t size;
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char *buf;
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{
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/* I am not sure if this works for 64 bit elf formats */
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Elf32_Phdr *ph = (Elf32_Phdr *) buf;
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if (lseek(fd, off, SEEK_SET) == -1)
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err(1, "lseek failed");
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for ( ; num; num--) {
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if (read(fd, buf, size) == -1)
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err(1, "read failed");
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if (ph->p_type == PT_INTERP) {
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/*
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* Has an interpreter - must be a dynamically-linked
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* executable.
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*/
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printf(", dynamically linked");
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return;
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}
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}
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printf(", statically linked");
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}
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size_t prpsoffsets[] = {
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8, /* FreeBSD */
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100, /* SunOS 5.x */
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32, /* Linux */
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};
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#define NOFFSETS (sizeof prpsoffsets / sizeof prpsoffsets[0])
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/*
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* Look through the program headers of an executable image, searching
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* for a PT_NOTE section of type NT_PRPSINFO, with a name "CORE" or
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* "FreeBSD"; if one is found, try looking in various places in its
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* contents for a 16-character string containing only printable
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* characters - if found, that string should be the name of the program
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* that dropped core. Note: right after that 16-character string is,
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* at least in SunOS 5.x (and possibly other SVR4-flavored systems) and
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* Linux, a longer string (80 characters, in 5.x, probably other
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* SVR4-flavored systems, and Linux) containing the start of the
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* command line for that program.
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*/
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static void
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dophn_core(fd, off, num, size, buf)
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int fd;
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off_t off;
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int num;
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size_t size;
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char *buf;
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{
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/*
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* This doesn't work for 64-bit ELF, as the "p_offset" field is
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* 64 bits in 64-bit ELF.
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*/
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/*
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* This doesn't work for 64-bit ELF, as the "p_offset" field is
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* 64 bits in 64-bit ELF.
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*/
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Elf32_Phdr *ph = (Elf32_Phdr *) buf;
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Elf32_Nhdr *nh;
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size_t offset, noffset, reloffset;
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unsigned char c;
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int i, j;
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char nbuf[BUFSIZ];
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int bufsize;
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for ( ; num; num--) {
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if (lseek(fd, off, SEEK_SET) == -1)
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err(1, "lseek failed");
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if (read(fd, buf, size) == -1)
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err(1, "read failed");
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off += size;
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if (ph->p_type != PT_NOTE)
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continue;
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if (lseek(fd, ph->p_offset, SEEK_SET) == -1)
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err(1, "lseek failed");
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bufsize = read(fd, nbuf, BUFSIZ);
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if (bufsize == -1)
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err(1, "read failed");
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offset = 0;
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for (;;) {
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if (offset >= bufsize)
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break;
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nh = (Elf32_Nhdr *)&nbuf[offset];
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offset += sizeof *nh;
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/*
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* If this note isn't an NT_PRPSINFO note, it's
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* not what we're looking for.
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*/
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if (nh->n_type != NT_PRPSINFO) {
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offset += nh->n_namesz;
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offset = ((offset + 3)/4)*4;
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offset += nh->n_descsz;
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offset = ((offset + 3)/4)*4;
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continue;
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}
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/*
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* Make sure this note has the name "CORE" or
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* "FreeBSD".
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*/
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if (offset + nh->n_namesz >= bufsize) {
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/*
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* We're past the end of the buffer.
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*/
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break;
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}
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if (nbuf[offset + nh->n_namesz - 1] != '\0' ||
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(strcmp(&nbuf[offset], "CORE") != 0 &&
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strcmp(&nbuf[offset], "FreeBSD") != 0))
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continue;
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offset += nh->n_namesz;
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offset = ((offset + 3)/4)*4;
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/*
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* Extract the program name. We assume it to be
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* 16 characters (that's what it is in SunOS 5.x
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* and Linux).
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*
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* Unfortunately, it's at a different offset in
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* SunOS 5.x and Linux, so try multiple offsets.
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* If the characters aren't all printable, reject
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* it.
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*/
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for (i = 0; i < NOFFSETS; i++) {
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reloffset = prpsoffsets[i];
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noffset = offset + reloffset;
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for (j = 0; j < 16;
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j++, noffset++, reloffset++) {
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/*
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* Make sure we're not past the end
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* of the buffer; if we are, just
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* give up.
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*/
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if (noffset >= bufsize)
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return;
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/*
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* Make sure we're not past the
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* end of the contents; if we
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* are, this obviously isn't
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* the right offset.
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*/
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if (reloffset >= nh->n_descsz)
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goto tryanother;
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c = nbuf[noffset];
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if (c != '\0' && !isprint(c))
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goto tryanother;
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}
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/*
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* Well, that worked.
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*/
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printf(", from '%.16s'",
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&nbuf[offset + prpsoffsets[i]]);
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return;
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tryanother:
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;
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}
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offset += nh->n_descsz;
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offset = ((offset + 3)/4)*4;
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}
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}
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}
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void
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tryelf(fd, buf, nbytes)
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int fd;
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char *buf;
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int nbytes;
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{
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union {
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int32 l;
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char c[sizeof (int32)];
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} u;
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/*
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* ELF executables have multiple section headers in arbitrary
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* file locations and thus file(1) cannot determine it from easily.
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* Instead we traverse thru all section headers until a symbol table
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* one is found or else the binary is stripped.
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*/
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if (buf[EI_MAG0] != ELFMAG0 || buf[EI_MAG1] != ELFMAG1
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|| buf[EI_MAG2] != ELFMAG2 || buf[EI_MAG3] != ELFMAG3)
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return;
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if (buf[4] == ELFCLASS32) {
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Elf32_Ehdr elfhdr;
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if (nbytes <= sizeof (Elf32_Ehdr))
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return;
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u.l = 1;
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(void) memcpy(&elfhdr, buf, sizeof elfhdr);
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/*
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* If the system byteorder does not equal the
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* object byteorder then don't test.
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* XXX - we could conceivably fix up the "dophn_XXX()" and
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* "doshn()" routines to extract stuff in the right
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* byte order....
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*/
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if ((u.c[sizeof(long) - 1] + 1) == elfhdr.e_ident[5]) {
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if (elfhdr.e_type == ET_CORE)
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dophn_core(fd, elfhdr.e_phoff, elfhdr.e_phnum,
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elfhdr.e_phentsize, buf);
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else {
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if (elfhdr.e_type == ET_EXEC) {
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dophn_exec(fd, elfhdr.e_phoff,
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elfhdr.e_phnum,
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elfhdr.e_phentsize, buf);
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}
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doshn(fd, elfhdr.e_shoff, elfhdr.e_shnum,
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elfhdr.e_shentsize, buf);
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}
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}
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return;
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}
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if (buf[4] == ELFCLASS64) {
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Elf64_Ehdr elfhdr;
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if (nbytes <= sizeof (Elf64_Ehdr))
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return;
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u.l = 1;
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(void) memcpy(&elfhdr, buf, sizeof elfhdr);
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/*
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* If the system byteorder does not equal the
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* object byteorder then don't test.
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* XXX - we could conceivably fix up the "dophn_XXX()" and
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* "doshn()" routines to extract stuff in the right
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* byte order....
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*/
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if ((u.c[sizeof(long) - 1] + 1) == elfhdr.e_ident[5]) {
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#ifdef notyet
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if (elfhdr.e_type == ET_CORE)
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dophn_core(fd, elfhdr.e_phoff, elfhdr.e_phnum,
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elfhdr.e_phentsize, buf);
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else
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#endif
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{
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#ifdef notyet
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if (elfhdr.e_type == ET_EXEC) {
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dophn_exec(fd, elfhdr.e_phoff,
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elfhdr.e_phnum,
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elfhdr.e_phentsize, buf);
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}
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#endif
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doshn(fd, elfhdr.e_shoff, elfhdr.e_shnum,
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elfhdr.e_shentsize, buf);
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}
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}
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return;
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}
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}
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#endif
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