1 /* Test program for getting symbol table from vdso module.
2    Copyright (C) 2014 Red Hat, Inc.
3    This file is part of elfutils.
4 
5    This file is free software; you can redistribute it and/or modify
6    it under the terms of the GNU General Public License as published by
7    the Free Software Foundation; either version 3 of the License, or
8    (at your option) any later version.
9 
10    elfutils is distributed in the hope that it will be useful, but
11    WITHOUT ANY WARRANTY; without even the implied warranty of
12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13    GNU General Public License for more details.
14 
15    You should have received a copy of the GNU General Public License
16    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
17 
18 #include <config.h>
19 #include <assert.h>
20 #include <errno.h>
21 #include <inttypes.h>
22 #include <stdio.h>
23 #include <string.h>
24 #include <sys/types.h>
25 #include <unistd.h>
26 #include ELFUTILS_HEADER(dwfl)
27 #include "system.h"
28 
29 #ifndef __linux__
30 int
main(int argc,char ** argv)31 main (int argc __attribute__ ((unused)), char **argv __attribute__ ((unused)))
32 {
33   printf ("Getting the vdso is unsupported.\n");
34   return 77;
35 }
36 #else /* __linux__ */
37 static int vdso_syms = 0;
38 
39 static int
module_callback(Dwfl_Module * mod,void ** userdata,const char * name,Dwarf_Addr start,void * arg)40 module_callback (Dwfl_Module *mod, void **userdata __attribute__((unused)),
41 		 const char *name, Dwarf_Addr start __attribute__((unused)),
42 		 void *arg __attribute__((unused)))
43 {
44   /* We can only recognize the vdso by inspecting the "magic name".  */
45   printf ("module name: %s\n", name);
46   if (strncmp ("[vdso: ", name, 7) == 0)
47     {
48       vdso_syms = dwfl_module_getsymtab (mod);
49       printf ("vdso syms: %d\n", vdso_syms);
50       if (vdso_syms < 0)
51 	error (2, 0, "dwfl_module_getsymtab: %s", dwfl_errmsg (-1));
52 
53       for (int i = 0; i < vdso_syms; i++)
54 	{
55 	  GElf_Sym sym;
56 	  GElf_Addr addr;
57 	  const char *sname = dwfl_module_getsym_info (mod, i, &sym, &addr,
58 						       NULL, NULL, NULL);
59 	  assert (sname != NULL);
60 	  printf ("%d: '%s' %" PRIx64 " (%" PRIx64 ")\n",
61 		  i, sname, sym.st_value, addr);
62 	}
63     }
64 
65   return DWARF_CB_OK;
66 }
67 
68 int
main(int argc,char ** argv)69 main (int argc __attribute__ ((unused)), char **argv __attribute__ ((unused)))
70 {
71   static char *debuginfo_path;
72   static const Dwfl_Callbacks proc_callbacks =
73     {
74       .find_debuginfo = dwfl_standard_find_debuginfo,
75       .debuginfo_path = &debuginfo_path,
76 
77       .find_elf = dwfl_linux_proc_find_elf,
78     };
79   Dwfl *dwfl = dwfl_begin (&proc_callbacks);
80   if (dwfl == NULL)
81     error (2, 0, "dwfl_begin: %s", dwfl_errmsg (-1));
82 
83   /* Take ourself as "arbitrary" process to inspect.  This should work
84      even with "restricted ptrace".  */
85   pid_t pid = getpid();
86 
87   int result = dwfl_linux_proc_report (dwfl, pid);
88   if (result < 0)
89     error (2, 0, "dwfl_linux_proc_report: %s", dwfl_errmsg (-1));
90   else if (result > 0)
91     error (2, result, "dwfl_linux_proc_report");
92 
93   /* Also explicitly attach for older kernels (cannot read vdso otherwise).  */
94   result = dwfl_linux_proc_attach (dwfl, pid, false);
95   if (result < 0)
96     error (2, 0, "dwfl_linux_proc_attach: %s", dwfl_errmsg (-1));
97   else if (result > 0)
98     error (2, result, "dwfl_linux_proc_attach");
99 
100   if (dwfl_report_end (dwfl, NULL, NULL) != 0)
101     error (2, 0, "dwfl_report_end: %s", dwfl_errmsg (-1));
102 
103   if (dwfl_getmodules (dwfl, module_callback, NULL, 0) != 0)
104     error (1, 0, "dwfl_getmodules: %s", dwfl_errmsg (-1));
105 
106   dwfl_end (dwfl);
107 
108   /* No symbols is ok, then we haven't seen the vdso at all on this arch.  */
109   return vdso_syms >= 0 ? 0 : -1;
110 }
111 
112 #endif /* ! __linux__ */
113