[Bug gdb/9885] field for register names too narrow

[Bug gdb/9885] field for register names too narrow

[larue at cadence dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=9885

larue at cadence dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |larue at cadence dot com

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[Bug gdb/9885] field for register names too narrow

[larue at cadence dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=9885

--- Comment #1 from larue at cadence dot com ---
I have recently encountered this problem, and found it is much more severe than
indicated in this bug report.  If a register name is > 15 characters then a
negative value is passed to n_spaces().  This causes garbage to be printed, and
occasional crashes of gdb.

This problem still exists in gdb-7.8.1.

The function default_print_one_register_info() calls:
print_spaces_filtered (15 - strlen (name), file);

if the register length is greater than 15, then print_spaces_filtered is called
with a negative value.

The following is a snippet of code from gdb/utils.c.  Notice that if n < 0,
then n_spaces returns pointer to potentially unallocated data in the heap.
This sometimes causes a crash in gdb, and garbage is printed in other cases.

char *
n_spaces (int n)
{
  char *t;
  static char *spaces = 0;
  static int max_spaces = -1;

  if (n > max_spaces)
    {
      if (spaces)
        xfree (spaces);
      spaces = (char *) xmalloc (n + 1);
      for (t = spaces + n; t != spaces;)
        *--t = ' ';
      spaces[n] = '\0';
      max_spaces = n;
    }

  return spaces + max_spaces - n;
}

void
print_spaces_filtered (int n, struct ui_file *stream)
{
  fputs_filtered (n_spaces (n), stream);
}


Ideally, gdb should be able to nicely print with arbitrary length register
names, but at a minimum the crash and garbage output should be fixed. A simple
way to do this is to put this check in n_spaces()

char *
n_spaces (int n)
{
  char *t;
  static char *spaces = 0;
  static int max_spaces = -1;

  if (n > max_spaces)
    {
      if (spaces)
        xfree (spaces);
      spaces = (char *) xmalloc (n + 1);
      for (t = spaces + n; t != spaces;)
        *--t = ' ';
      spaces[n] = '\0';
      max_spaces = n;
    }

  return spaces + max_spaces - n;
}

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[Bug gdb/9885] field for register names too narrow

[larue at cadence dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=9885

--- Comment #2 from larue at cadence dot com ---
Oops, accidentally saved before pasting in the patch (shown below):

char *
n_spaces (int n)
{
  char *t;
  static char *spaces = 0;
  static int max_spaces = -1;
  /* Prevent heap corruption if n is negative (which occurs if
default_print_one_register_info is called with a register whose name
is > 15 characters long */
  if (n < 0)
     n = 0;
  if (n > max_spaces)
    {
      if (spaces)
        xfree (spaces);
      spaces = (char *) xmalloc (n + 1);
      for (t = spaces + n; t != spaces;)
        *--t = ' ';
      spaces[n] = '\0';
      max_spaces = n;
    }

  return spaces + max_spaces - n;
}

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[Bug gdb/9885] field for register names too narrow

[ssbssa at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=9885

Hannes Domani <ssbssa at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|6.8                         |8.2
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |FIXED
                 CC|                            |ssbssa at sourceware dot org

--- Comment #3 from Hannes Domani <ssbssa at sourceware dot org> ---
Fixed since version 8.2, with this commit:
https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=e813d34aaabee0ca034fa5ddd50e76ade80318bc

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