path: root/loc2c-test.c

/* Simple test program for loc2c code.  */

#include <config.h>
#include <assert.h>
#include <inttypes.h>
#include <sys/types.h>
#include <stdio.h>
#include <stdio_ext.h>
#include <stdlib.h>
#include <string.h>
#include <error.h>
#include <locale.h>
#include <argp.h>
#include <elfutils/libdwfl.h>
#include <dwarf.h>
#include <obstack.h>
#include <unistd.h>
#include <stdarg.h>
#include "loc2c.h"

#define _(msg) msg

static const char *
dwarf_diename_integrate (Dwarf_Die *die)
{
  Dwarf_Attribute attr_mem;
  return dwarf_formstring (dwarf_attr_integrate (die, DW_AT_name, &attr_mem));
}


static void __attribute__ ((noreturn))
fail (void *arg __attribute__ ((unused)), const char *fmt, ...)
{
  va_list ap;

  fprintf (stderr, "%s: ", program_invocation_short_name);

  va_start (ap, fmt);
  vfprintf (stderr, _(fmt), ap);
  va_end (ap);

  exit (2);
}

static void
handle_variable (Dwarf_Die *scopes, int nscopes, int out,
		 Dwarf_Addr cubias, Dwarf_Die *vardie, Dwarf_Addr pc,
		 char **fields)
{
#define obstack_chunk_alloc malloc
#define obstack_chunk_free free
  struct obstack pool;
  obstack_init (&pool);

   /* Figure out the appropriate frame base for accessing this variable.
     XXX not handling nested functions
     XXX inlines botched
  */
  Dwarf_Attribute fb_attr_mem, *fb_attr = NULL;
  for (int inner = 0; inner < nscopes; ++inner)
    {
      switch (dwarf_tag (&scopes[inner]))
	{
	default:
	  continue;
	case DW_TAG_subprogram:
	case DW_TAG_entry_point:
	case DW_TAG_inlined_subroutine:	/* XXX */
	  if (inner >= out)
	    fb_attr = dwarf_attr_integrate (&scopes[inner],
					    DW_AT_frame_base,
					    &fb_attr_mem);
	  break;
	}
      break;
    }

  Dwarf_Attribute attr_mem;

  if (dwarf_attr_integrate (vardie, DW_AT_location, &attr_mem) == NULL)
    error (2, 0, _("cannot get location of variable: %s"),
	   dwarf_errmsg (-1));

#define FIELD "addr"
#define emit(fmt, ...) printf ("  addr = " fmt "\n", ## __VA_ARGS__)

  struct location *head, *tail = NULL;
  head = c_translate_location (&pool, &fail, NULL, NULL,
			       1, cubias, &attr_mem, pc,
			       &tail, fb_attr);

  if (dwarf_attr_integrate (vardie, DW_AT_type, &attr_mem) == NULL)
    error (2, 0, _("cannot get type of variable: %s"),
	   dwarf_errmsg (-1));

  bool store = false;
  Dwarf_Die die_mem, *die = vardie;
  while (*fields != NULL)
    {
      die = dwarf_formref_die (&attr_mem, &die_mem);

      if (!strcmp (*fields, "="))
	{
	  store = true;
	  if (fields[1] != NULL)
	    error (2, 0, _("extra fields after ="));
	  break;
	}

      const int typetag = dwarf_tag (die);
      switch (typetag)
	{
	case DW_TAG_typedef:
	  /* Just iterate on the referent type.  */
	  break;

	case DW_TAG_pointer_type:
	  if (**fields == '+')
	    goto subscript;
	  /* A "" field means explicit pointer dereference and we consume it.
	     Otherwise the next field implicitly gets the dereference.  */
	  if (**fields == '\0')
	    ++fields;
	  c_translate_pointer (&pool, 1, cubias, die, &tail);
	  break;

	case DW_TAG_array_type:
	  if (**fields == '+')
	    {
	    subscript:;
	      char *endp = *fields + 1;
	      uintmax_t idx = strtoumax (*fields + 1, &endp, 0);
	      if (endp == NULL || endp == *fields || *endp != '\0')
		c_translate_array (&pool, 1, cubias, die, &tail,
				   *fields + 1, 0);
	      else
		c_translate_array (&pool, 1, cubias, die, &tail,
				   NULL, idx);
	      ++fields;
	    }
	  else
	    error (2, 0, _("bad field for array type: %s"), *fields);
	  break;

	case DW_TAG_structure_type:
	case DW_TAG_union_type:
	  switch (dwarf_child (die, &die_mem))
	    {
	    case 1:		/* No children.  */
	      error (2, 0, _("empty struct %s"),
		     dwarf_diename_integrate (die) ?: "<anonymous>");
	      break;
	    case -1:		/* Error.  */
	    default:		/* Shouldn't happen */
	      error (2, 0, _("%s %s: %s"),
		     typetag == DW_TAG_union_type ? "union" : "struct",
		     dwarf_diename_integrate (die) ?: "<anonymous>",
		     dwarf_errmsg (-1));
	      break;

	    case 0:
	      break;
	    }
	  while (dwarf_tag (die) != DW_TAG_member
		 || ({ const char *member = dwarf_diename_integrate (die);
		       member == NULL || strcmp (member, *fields); }))
	    if (dwarf_siblingof (die, &die_mem) != 0)
	      error (2, 0, _("field name %s not found"), *fields);

	  if (dwarf_attr_integrate (die, DW_AT_data_member_location,
				    &attr_mem) == NULL)
	    {
	      /* Union members don't usually have a location,
		 but just use the containing union's location.  */
	      if (typetag != DW_TAG_union_type)
		error (2, 0, _("no location for field %s: %s"),
		       *fields, dwarf_errmsg (-1));
	    }
	  else
	    c_translate_location (&pool, NULL, NULL, NULL,
				  1, cubias, &attr_mem, pc,
				  &tail, NULL);
	  ++fields;
	  break;

	case DW_TAG_base_type:
	  error (2, 0, _("field %s vs base type %s"),
		 *fields, dwarf_diename_integrate (die) ?: "<anonymous type>");
	  break;

	case -1:
	  error (2, 0, _("cannot find type: %s"), dwarf_errmsg (-1));
	  break;

	default:
	  error (2, 0, _("%s: unexpected type tag %#x"),
		 dwarf_diename_integrate (die) ?: "<anonymous type>",
		 dwarf_tag (die));
	  break;
	}

      /* Now iterate on the type in DIE's attribute.  */
      if (dwarf_attr_integrate (die, DW_AT_type, &attr_mem) == NULL)
	error (2, 0, _("cannot get type of field: %s"), dwarf_errmsg (-1));
    }

  /* Fetch the type DIE corresponding to the final location to be accessed.
     It must be a base type or a typedef for one.  */

  Dwarf_Die typedie_mem;
  Dwarf_Die *typedie;
  int typetag;
  while (1)
    {
      typedie = dwarf_formref_die (&attr_mem, &typedie_mem);
      if (typedie == NULL)
	error (2, 0, _("cannot get type of field: %s"), dwarf_errmsg (-1));
      typetag = dwarf_tag (typedie);
      if (typetag != DW_TAG_typedef)
	break;
      if (dwarf_attr_integrate (typedie, DW_AT_type, &attr_mem) == NULL)
	error (2, 0, _("cannot get type of field: %s"), dwarf_errmsg (-1));
    }

  switch (typetag)
    {
    case DW_TAG_base_type:
      if (store)
	c_translate_store (&pool, 1, cubias, die, typedie, &tail, "value");
      else
	c_translate_fetch (&pool, 1, cubias, die, typedie, &tail, "value");
      break;

    case DW_TAG_pointer_type:
      if (store)
	error (2, 0, _("store not supported for pointer type"));
      c_translate_pointer (&pool, 1, cubias, typedie, &tail);
      c_translate_addressof (&pool, 1, cubias, die, typedie, &tail, "value");
      break;

    default:
      if (store)
	error (2, 0, _("store supported only for base type"));
      else
	error (2, 0, _("fetch supported only for base type or pointer"));
      break;
    }

  printf ("#define PROBEADDR %#" PRIx64 "ULL\n", pc);

  puts (store
	? "static void set_value(struct pt_regs *regs, intptr_t value)\n{"
	: "static void print_value(struct pt_regs *regs)\n"
	"{\n"
	"  intptr_t value;");

  bool deref = c_emit_location (stdout, head, 1);

  puts (store ? " return;" :
	"  printk (\" ---> %ld\\n\", (unsigned long) value);\n"
	"  return;");

  if (deref)
    puts ("\n"
	  " deref_fault:\n"
	  "  printk (\" => BAD ACCESS\\n\");");

  puts ("}");
}

int
main (int argc, char **argv)
{
  /* We use no threads here which can interfere with handling a stream.  */
  (void) __fsetlocking (stdout, FSETLOCKING_BYCALLER);

  /* Set locale.  */
  (void) setlocale (LC_ALL, "");

  Dwfl *dwfl = NULL;
  int argi;
  (void) argp_parse (dwfl_standard_argp (), argc, argv, 0, &argi, &dwfl);
  assert (dwfl != NULL);

  if (argi == argc)
    error (2, 0, "need address argument");

  char *endp;
  uintmax_t pc = strtoumax (argv[argi], &endp, 0);
  if (endp == argv[argi])
    error (2, 0, "bad address argument");

  Dwarf_Addr cubias;
  Dwarf_Die *cudie = dwfl_addrdie (dwfl, pc, &cubias);
  if (cudie == NULL)
    error (EXIT_FAILURE, 0, "dwfl_addrdie: %s", dwfl_errmsg (-1));

  Dwarf_Die *scopes;
  int n = dwarf_getscopes (cudie, pc - cubias, &scopes);
  if (n < 0)
    error (EXIT_FAILURE, 0, "dwarf_getscopes: %s", dwarf_errmsg (-1));
  else if (n == 0)
    error (EXIT_FAILURE, 0, "%#" PRIx64 ": not in any scope\n", pc);

  if (++argi == argc)
    error (2, 0, "need variable arguments");

  char *spec = argv[argi++];

  int lineno = 0, colno = 0, shadow = 0;
  char *at = strchr (spec, '@');
  if (at != NULL)
    {
      *at++ = '\0';
      if (sscanf (at, "%*[^:]:%i:%i", &lineno, &colno) < 1)
	lineno = 0;
    }
  else
    {
      int len;
      if (sscanf (spec, "%*[^+]%n+%i", &len, &shadow) == 2)
	spec[len] = '\0';
    }

  Dwarf_Die vardie;
  int out = dwarf_getscopevar (scopes, n, spec, shadow, at, lineno, colno,
			       &vardie);
  if (out == -2)
    error (0, 0, "no match for %s (+%d, %s:%d:%d)",
	   spec, shadow, at, lineno, colno);
  else if (out < 0)
    error (0, 0, "dwarf_getscopevar: %s (+%d, %s:%d:%d): %s",
	   spec, shadow, at, lineno, colno, dwarf_errmsg (-1));
  else
    handle_variable (scopes, n, out, cubias, &vardie, pc, &argv[argi]);

  dwfl_end (dwfl);

  return 0;
}