Author: emaste
Date: Sun Mar  8 21:11:49 2020
New Revision: 358783
URL: https://svnweb.freebsd.org/changeset/base/358783

Log:
  MFC r340169 (brooks): elfdump: Add -E to test if a file is an ELF binary.
  
  This is intended to replace potentially unreliable checks like:
  
      file -b $1 | grep -q '^ELF ..-bit .SB executable'

Modified:
  stable/12/usr.bin/elfdump/elfdump.1
  stable/12/usr.bin/elfdump/elfdump.c
Directory Properties:
  stable/12/   (props changed)

Modified: stable/12/usr.bin/elfdump/elfdump.1
==============================================================================
--- stable/12/usr.bin/elfdump/elfdump.1 Sun Mar  8 21:10:16 2020        
(r358782)
+++ stable/12/usr.bin/elfdump/elfdump.1 Sun Mar  8 21:11:49 2020        
(r358783)
@@ -24,7 +24,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd January 15, 2003
+.Dd November 5, 2018
 .Dt ELFDUMP 1
 .Os
 .Sh NAME
@@ -34,7 +34,7 @@
 files
 .Sh SYNOPSIS
 .Nm
-.Fl a | cdeGhinprs
+.Fl a | E | cdeGhinprs
 .Op Fl w Ar file
 .Ar file
 .Sh DESCRIPTION
@@ -55,6 +55,11 @@ Dump section headers.
 Dump dynamic symbols.
 .It Fl e
 Dump ELF header.
+.It Fl E
+Return success if
+.Ar file
+is an ELF file and failure if it is not.
+This option is exclusive with other options.
 .It Fl G
 Dump the GOT.
 .It Fl h

Modified: stable/12/usr.bin/elfdump/elfdump.c
==============================================================================
--- stable/12/usr.bin/elfdump/elfdump.c Sun Mar  8 21:10:16 2020        
(r358782)
+++ stable/12/usr.bin/elfdump/elfdump.c Sun Mar  8 21:11:49 2020        
(r358783)
@@ -60,6 +60,7 @@ __FBSDID("$FreeBSD$");
 #define        ED_SHDR         (1<<8)
 #define        ED_SYMTAB       (1<<9)
 #define        ED_ALL          ((1<<10)-1)
+#define        ED_IS_ELF       (1<<10) /* Exclusive with other flags */
 
 #define        elf_get_addr    elf_get_quad
 #define        elf_get_off     elf_get_quad
@@ -527,7 +528,7 @@ main(int ac, char **av)
 
        out = stdout;
        flags = 0;
-       while ((ch = getopt(ac, av, "acdeiGhnprsw:")) != -1)
+       while ((ch = getopt(ac, av, "acdEeiGhnprsw:")) != -1)
                switch (ch) {
                case 'a':
                        flags = ED_ALL;
@@ -538,6 +539,9 @@ main(int ac, char **av)
                case 'd':
                        flags |= ED_DYN;
                        break;
+               case 'E':
+                       flags = ED_IS_ELF;
+                       break;
                case 'e':
                        flags |= ED_EHDR;
                        break;
@@ -575,7 +579,8 @@ main(int ac, char **av)
                }
        ac -= optind;
        av += optind;
-       if (ac == 0 || flags == 0)
+       if (ac == 0 || flags == 0 || ((flags & ED_IS_ELF) &&
+           (ac != 1 || (flags & ~ED_IS_ELF) || out != stdout)))
                usage();
        if ((fd = open(*av, O_RDONLY)) < 0 ||
            fstat(fd, &sb) < 0)
@@ -593,8 +598,12 @@ main(int ac, char **av)
        e = mmap(NULL, sb.st_size, PROT_READ, MAP_SHARED, fd, 0);
        if (e == MAP_FAILED)
                err(1, NULL);
-       if (!IS_ELF(*(Elf32_Ehdr *)e))
+       if (!IS_ELF(*(Elf32_Ehdr *)e)) {
+               if (flags & ED_IS_ELF)
+                       exit(1);
                errx(1, "not an elf file");
+       } else if (flags & ED_IS_ELF)
+               exit (0);
        phoff = elf_get_off(e, e, E_PHOFF);
        shoff = elf_get_off(e, e, E_SHOFF);
        phentsize = elf_get_quarter(e, e, E_PHENTSIZE);
@@ -1270,6 +1279,7 @@ elf_get_quad(Elf32_Ehdr *e, void *base, elf_member_t m
 static void
 usage(void)
 {
-       fprintf(stderr, "usage: elfdump -a | -cdeGhinprs [-w file] file\n");
+       fprintf(stderr,
+           "usage: elfdump -a | -E | -cdeGhinprs [-w file] file\n");
        exit(1);
 }
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