libdwfl/linux-proc-maps.c

/* Standard libdwfl callbacks for debugging a live Linux process.
   Copyright (C) 2005 Red Hat, Inc.

   This program is Open Source software; you can redistribute it and/or
   modify it under the terms of the Open Software License version 1.0 as
   published by the Open Source Initiative.

   You should have received a copy of the Open Software License along
   with this program; if not, you may obtain a copy of the Open Software
   License version 1.0 from http://www.opensource.org/licenses/osl.php or
   by writing the Open Source Initiative c/o Lawrence Rosen, Esq.,
   3001 King Ranch Road, Ukiah, CA 95482.   */

#include "libdwflP.h"
#include <inttypes.h>
#include <sys/types.h>
#include <errno.h>
#include <stdio.h>
#include <stdio_ext.h>
#include <stdbool.h>
#include <string.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <assert.h>
#include <endian.h>


#define PROCMAPSFMT	"/proc/%d/maps"
#define PROCMEMFMT	"/proc/%d/mem"
#define PROCAUXVFMT	"/proc/%d/auxv"


/* Search /proc/PID/auxv for the AT_SYSINFO_EHDR tag.  */

static int
find_sysinfo_ehdr (pid_t pid, GElf_Addr *sysinfo_ehdr)
{
  char *fname = NULL;
  asprintf (&fname, PROCAUXVFMT, pid);
  if (fname == NULL)
    return ENOMEM;

  int fd = open64 (fname, O_RDONLY);
  free (fname);
  if (fd < 0)
    return errno == ENOENT ? 0 : errno;

  ssize_t nread;
  do
    {
      union
      {
	char buffer[sizeof (long int) * 2 * 64];
	Elf64_auxv_t a64[sizeof (long int) * 2 * 64 / sizeof (Elf64_auxv_t)];
	Elf32_auxv_t a32[sizeof (long int) * 2 * 32 / sizeof (Elf32_auxv_t)];
      } d;
      nread = read (fd, &d, sizeof d);
      if (nread > 0)
	{
	  switch (sizeof (long int))
	    {
	    case 4:
	      for (size_t i = 0; (char *) &d.a32[i] < &d.buffer[nread]; ++i)
		if (d.a32[i].a_type == AT_SYSINFO_EHDR)
		  {
		    *sysinfo_ehdr = d.a32[i].a_un.a_val;
		    nread = 0;
		    break;
		  }
	      break;
	    case 8:
	      for (size_t i = 0; (char *) &d.a64[i] < &d.buffer[nread]; ++i)
		if (d.a64[i].a_type == AT_SYSINFO_EHDR)
		  {
		    *sysinfo_ehdr = d.a64[i].a_un.a_val;
		    nread = 0;
		    break;
		  }
	      break;
	    default:
	      abort ();
	      break;
	    }
	}
    }
  while (nread > 0);

  close (fd);

  return nread < 0 ? errno : 0;
}

int
dwfl_linux_proc_report (Dwfl *dwfl, pid_t pid)
{
  if (dwfl == NULL)
    return -1;

  /* We'll notice the AT_SYSINFO_EHDR address specially when we hit it.  */
  GElf_Addr sysinfo_ehdr = 0;
  int result = find_sysinfo_ehdr (pid, &sysinfo_ehdr);
  if (result != 0)
    return result;

  char *fname = NULL;
  asprintf (&fname, PROCMAPSFMT, pid);
  if (fname == NULL)
    return ENOMEM;

  FILE *f = fopen (fname, "r");
  free (fname);
  if (f == NULL)
    return errno;

  (void) __fsetlocking (f, FSETLOCKING_BYCALLER);

  unsigned int last_dmajor = -1, last_dminor = -1;
  uint64_t last_ino = -1;
  char *last_file = NULL;
  Dwarf_Addr low = 0, high = 0;

  inline bool report (void)
    {
      if (last_file != NULL)
	{
	  if (INTUSE(dwfl_report_module) (dwfl, last_file, low, high) == NULL)
	    {
	      free (last_file);
	      return true;
	    }
	  last_file = NULL;
	}
      return false;
    }

  char *line = NULL;
  size_t linesz;
  ssize_t len;
  while ((len = getline (&line, &linesz, f)) > 0)
    {
      if (line[len - 1] == '\n')
	line[len - 1] = '\0';

      Dwarf_Addr start, end, offset;
      unsigned int dmajor, dminor;
      uint64_t ino;
      int nread = -1;
      if (sscanf (line, "%" PRIx64 "-%" PRIx64 " %*s %" PRIx64
		  " %x:%x %" PRIi64 " %n",
		  &start, &end, &offset, &dmajor, &dminor, &ino, &nread) < 6
	  || nread <= 0)
	{
	  free (line);
	  return ENOEXEC;
	}

      /* If this is the special mapping AT_SYSINFO_EHDR pointed us at,
	 report the last one and then this special one.  */
      if (start == sysinfo_ehdr && start != 0)
	{
	  if (report ())
	    {
	    bad_report:
	      free (line);
	      fclose (f);
	      return -1;
	    }

	  low = start;
	  high = end;
	  if (asprintf (&last_file, "[vdso: %d]", (int) pid) < 0
	      || report ())
	    goto bad_report;
	}

      char *file = line + nread + strspn (line + nread, " \t");
      if (file[0] == '\0' || (ino == 0 && dmajor == 0 && dminor == 0))
	/* This line doesn't indicate a file mapping.  */
	continue;

      if (last_file != NULL
	  && ino == last_ino && dmajor == last_dmajor && dminor == last_dminor)
	{
	  /* This is another portion of the same file's mapping.  */
	  assert (!strcmp (last_file, file));
	  high = end;
	}
      else
	{
	  /* This is a different file mapping.  Report the last one.  */
	  if (report ())
	    goto bad_report;
	  low = start;
	  high = end;
	  last_file = strdup (file);
	  last_ino = ino;
	  last_dmajor = dmajor;
	  last_dminor = dminor;
	}
    }
  free (line);

  result = ferror_unlocked (f) ? errno : feof_unlocked (f) ? 0 : ENOEXEC;
  fclose (f);

  /* Report the final one.  */
  bool lose = report ();

  return result != 0 ? result : lose ? -1 : 0;
}
INTDEF (dwfl_linux_proc_report)


static ssize_t
read_proc_memory (void *arg, void *data, GElf_Addr address,
		  size_t minread, size_t maxread)
{
  const int fd = *(const int *) arg;
  ssize_t nread = pread64 (fd, data, maxread, (off64_t) address);
  if (nread > 0 && (size_t) nread < minread)
    nread = 0;
  return nread;
}

extern Elf *elf_from_remote_memory (GElf_Addr ehdr_vma,
				    GElf_Addr *loadbasep,
				    ssize_t (*read_memory) (void *arg,
							    void *data,
							    GElf_Addr address,
							    size_t minread,
							    size_t maxread),
				    void *arg);


/* Dwfl_Callbacks.find_elf */

int
dwfl_linux_proc_find_elf (Dwfl_Module *mod __attribute__ ((unused)),
			  void **userdata __attribute__ ((unused)),
			  const char *module_name, Dwarf_Addr base,
			  char **file_name, Elf **elfp)
{
  if (module_name[0] == '/')
    {
      int fd = open64 (module_name, O_RDONLY);
      if (fd >= 0)
	{
	  *file_name = strdup (module_name);
	  if (*file_name == NULL)
	    {
	      close (fd);
	      return ENOMEM;
	    }
	}
      return fd;
    }

  int pid;
  if (sscanf (module_name, "[vdso: %d]", &pid) == 1)
    {
      /* Special case for in-memory ELF image.  */

      char *fname = NULL;
      asprintf (&fname, PROCMEMFMT, pid);
      if (fname == NULL)
	return -1;

      int fd = open64 (fname, O_RDONLY);
      free (fname);
      if (fd < 0)
	return -1;

      *elfp = elf_from_remote_memory (base, NULL, &read_proc_memory, &fd);

      close (fd);

      *file_name = NULL;
      return -1;
    }

  abort ();
  return -1;
}
INTDEF (dwfl_linux_proc_find_elf)