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gdb: Avoid signed integer overflow when printing source lines

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When printing source lines with calls to print_source_lines we need to
pass a start line number and an end line number.  The end line number
is calculated by calling get_lines_to_list and adding this value to
the start line number.  For example this code from list_command:

    print_source_lines (cursal.symtab, first,
                        first + get_lines_to_list (), 0);

The problem is that get_lines_to_list returns a value based on the
GDB setting `set listsize LISTSIZE`.  By default LISTSIZE is 10,
however, its also possible to set LISTSIZE to unlimited, in which
case get_lines_to_list will return INT_MAX.

As the parameter signature for print_source_lines is:

  void print_source_lines (struct symtab *, int, int,
                           print_source_lines_flags);

and `first` in the above code is an `int`, then when LISTSIZE is
`unlimited` the above code will result in signed integer overflow,
which is undefined.

The solution in this patch is a new class source_lines_range that can
be constructed from a single line number and a direction (forward or
backward).  The range is then constructed from the line number and the
value of get_lines_to_list.

gdb/ChangeLog:

	* cli/cli-cmds.c (list_command): Pass a source_lines_range to
	print_source_lines.
	* source.c (print_source_lines_base): Update line number check.
	(print_source_lines): New function.
	(source_lines_range::source_lines_range): New function.
	* source.h (class source_lines_range): New class.
	(print_source_lines): New declaration.
This commit is contained in:
Andrew Burgess
2019-01-07 07:26:35 +00:00
parent 8379fac67e
commit 0e2a21335b
4 changed files with 115 additions and 26 deletions
Download Patch File Download Diff File Expand all files Collapse all files

10
gdb/ChangeLog
View File

@@ -1,3 +1,13 @@
2019-01-09 Andrew Burgess <andrew.burgess@embecosm.com>
* cli/cli-cmds.c (list_command): Pass a source_lines_range to
print_source_lines.
* source.c (print_source_lines_base): Update line number check.
(print_source_lines): New function.
(source_lines_range::source_lines_range): New function.
* source.h (class source_lines_range): New class.
(print_source_lines): New declaration.
2019-01-09 Philippe Waroquiers <philippe.waroquiers@skynet.be>
* linespec.c (linespec_state_destructor): Free self->canonical_names.

35
gdb/cli/cli-cmds.c
View File

@@ -895,14 +895,13 @@ list_command (const char *arg, int from_tty)
&& get_lines_to_list () == 1 && first > 1)
first -= 1;
print_source_lines (cursal.symtab, first,
first + get_lines_to_list (), 0);
print_source_lines (cursal.symtab, source_lines_range (first), 0);
}
/* "l" or "l +" lists next ten lines. */
else if (arg == NULL || arg[0] == '+')
print_source_lines (cursal.symtab, cursal.line,
cursal.line + get_lines_to_list (), 0);
print_source_lines (cursal.symtab,
source_lines_range (cursal.line), 0);
/* "l -" lists previous ten lines, the ones before the ten just
listed. */
@@ -911,10 +910,9 @@ list_command (const char *arg, int from_tty)
if (get_first_line_listed () == 1)
error (_("Already at the start of %s."),
symtab_to_filename_for_display (cursal.symtab));
print_source_lines (cursal.symtab,
std::max (get_first_line_listed ()
- get_lines_to_list (), 1),
get_first_line_listed (), 0);
source_lines_range range (get_first_line_listed (),
source_lines_range::BACKWARD);
print_source_lines (cursal.symtab, range, 0);
}
return;
@@ -1059,9 +1057,11 @@ list_command (const char *arg, int from_tty)
if (dummy_beg && sal_end.symtab == 0)
error (_("No default source file yet. Do \"help list\"."));
if (dummy_beg)
print_source_lines (sal_end.symtab,
std::max (sal_end.line - (get_lines_to_list () - 1), 1),
sal_end.line + 1, 0);
{
source_lines_range range (sal_end.line + 1,
source_lines_range::BACKWARD);
print_source_lines (sal_end.symtab, range, 0);
}
else if (sal.symtab == 0)
error (_("No default source file yet. Do \"help list\"."));
else if (no_end)
@@ -1074,17 +1074,14 @@ list_command (const char *arg, int from_tty)
first_line = 1;
if (sals.size () > 1)
print_sal_location (sal);
print_source_lines (sal.symtab,
first_line,
first_line + get_lines_to_list (),
0);
print_source_lines (sal.symtab, source_lines_range (first_line), 0);
}
}
else if (dummy_end)
print_source_lines (sal.symtab, source_lines_range (sal.line), 0);
else
print_source_lines (sal.symtab, sal.line,
(dummy_end
? sal.line + get_lines_to_list ()
: sal_end.line + 1),
print_source_lines (sal.symtab,
source_lines_range (sal.line, (sal_end.line + 1)),
0);
}

48
gdb/source.c
View File

@@ -1331,13 +1331,8 @@ print_source_lines_base (struct symtab *s, int line, int stopline,
last_source_error = 0;
/* If the user requested a sequence of lines that seems to go backward
(from high to low line numbers) then we don't print anything.
The use of '- 1' here instead of '<=' is currently critical, we rely
on the undefined wrap around behaviour of 'int' for stopline. When
the use has done: 'set listsize unlimited' then stopline can overflow
and appear as MIN_INT. This is a long-standing bug that needs
fixing. */
if (stopline - 1 < line)
(from high to low line numbers) then we don't print anything. */
if (stopline <= line)
return;
std::string lines;
@@ -1399,6 +1394,18 @@ print_source_lines (struct symtab *s, int line, int stopline,
{
print_source_lines_base (s, line, stopline, flags);
}
/* See source.h. */
void
print_source_lines (struct symtab *s, source_lines_range line_range,
print_source_lines_flags flags)
{
print_source_lines_base (s, line_range.startline (),
line_range.stopline (), flags);
}
/* Print info on range of pc's in a specified line. */
@@ -1822,6 +1829,33 @@ set_substitute_path_command (const char *args, int from_tty)
forget_cached_source_info ();
}
/* See source.h. */
source_lines_range::source_lines_range (int startline,
source_lines_range::direction dir)
{
if (dir == source_lines_range::FORWARD)
{
LONGEST end = static_cast <LONGEST> (startline) + get_lines_to_list ();
if (end > INT_MAX)
end = INT_MAX;
m_startline = startline;
m_stopline = static_cast <int> (end);
}
else
{
LONGEST start = static_cast <LONGEST> (startline) - get_lines_to_list ();
if (start < 1)
start = 1;
m_startline = static_cast <int> (start);
m_stopline = startline;
}
}
void
_initialize_source (void)

48
gdb/source.h
View File

@@ -157,6 +157,54 @@ DEF_ENUM_FLAGS_TYPE (enum print_source_lines_flag, print_source_lines_flags);
extern void print_source_lines (struct symtab *s, int line, int stopline,
print_source_lines_flags flags);
/* Wrap up the logic to build a line number range for passing to
print_source_lines when using get_lines_to_list. An instance of this
class can be built from a single line number and a direction (forward or
backward) the range is then computed using get_lines_to_list. */
class source_lines_range
{
public:
/* When constructing the range from a single line number, does the line
range extend forward, or backward. */
enum direction
{
FORWARD,
BACKWARD
};
/* Construct a SOURCE_LINES_RANGE starting at STARTLINE and extending in
direction DIR. The number of lines is from GET_LINES_TO_LIST. If the
direction is backward then the start is actually (STARTLINE -
GET_LINES_TO_LIST). There is also logic in place to ensure the start
is always 1 or more, and the end will be at most INT_MAX. */
explicit source_lines_range (int startline, direction dir = FORWARD);
/* Construct a SOURCE_LINES_RANGE from STARTLINE to STOPLINE. */
explicit source_lines_range (int startline, int stopline)
: m_startline (startline),
m_stopline (stopline)
{ /* Nothing. */ }
/* Return the line to start listing from. */
int startline () const
{ return m_startline; }
/* Return the line after the last line that should be listed. */
int stopline () const
{ return m_stopline; }
private:
/* The start and end of the range. */
int m_startline;
int m_stopline;
};
/* Variation of previous print_source_lines that takes a range instead of a
start and end line number. */
extern void print_source_lines (struct symtab *s, source_lines_range r,
print_source_lines_flags flags);
/* Forget line positions and file names for the symtabs in a
particular objfile. */
extern void forget_cached_source_info_for_objfile (struct objfile *);