diff mbox

[v4] PR 20569, segv in follow_exec

Message ID 1477415521-22010-1-git-send-email-lgustavo@codesourcery.com
State New
Headers show

Commit Message

Luis Machado Oct. 25, 2016, 5:12 p.m. UTC
Adjusted a few more bits.

I ended up using the ugly explicit cast for an enum that is being used as a
bitfield. I'm guessing we'll want to convert this to the macro-fied
template-fied version that is more appropriate to C++?

If so then i can come up with a follow up patch that does the conversion. I
didn't want to disrupt v4 with more unrelated changes.

I have regression-tested v4 on Ubuntu 16.04 x86-64 to make sure the new changes
to try_open_exec_file were sane.

How does this version look?

Changes in v4:

* Adjusted source files based on overall comments.
* Renamed maybe_open_exec_file to try_open_exec_file as suggested.
* Simplified try_maybe_open_exec_file by exporting symbol_file_add_main_1
  and calling it from within the function.
* Consolidated a couple flags into a single argument to try_open_exec_file.
* Adjusted testcase based on comments.

Changes in v3:

Follows the updated patch with the comments addressed and a few more things
adjusted. I can't say i like the name "maybe_open_exec_file", but that was
the best that came to mind on a Monday. :-)

How does it look now?

* Addressed overal review comments (explicit NULL check, misleading variable
  name and trailing whitespaces).
* Separated bug fixes for exception_print_same and NULL dereferences. They
  were submitted as a couple separate (obvious?) patches.
* Moved duplicate code from exec_file_locate_attach and follow_exec to a
  shared function maybe_open_exec_file that gets called from both places.
* Addressed comments for the testcase, cleaned it up and made it expect a
  different output message.

Changes in v2:

* Changed exec_file_target cleanup to a exec_file_host cleanup inside
  exec.c:exec_file_locate_attach. It was a typo that caused a crash.
* Added the gdb.base/exec-invalid-sysroot.exp testcase.

As I noted in PR20569, several exec-related tests cause GDB to segv when sysroot translation fails on the executable pathname reported by gdbserver.  The immediate cause of the segv is that follow_exec is passing a NULL argument (the result of exec_file_find) to strlen, but as I looked at the code in more detail it seemed like follow_exec simply isn't prepared for the case where sysroot translation fails to locate the new executable, and there is no obvious recovery strategy.

I thought I could copy logic from the other caller of exec_file_find, exec_file_locate_attach, but I think it's doing the wrong thing there as well.  Plus, from reading the code I found other bugs in both callers of exec_file_find due to confusion between host and target pathnames.

The attached patch attempts to fix all the bugs.  In terms of the testcases that were formerly segv'ing, GDB now prints a warning but continues execution of the new program, so that the tests now mostly FAIL instead.  You could argue the FAILs are due to a legitimate problem with the test environment setting up the sysroot translation incorrectly, but I'm not sure continuing execution rather than leaving the target stopped is the most user-friendly fallback behavior, either.  E.g. the GDB manual suggests that you can set a breakpoint on main and GDB will stop on main of the newly exec'ed program, too, but it can't do that if it can't find the symbol information, and there's no way for the user to specify the executable file to GDB explicitly before it resumes execution.  But, seemed better not to complicate this already-too-complicated patch further by trying to address that in the first cut.

The following testcases will make GDB crash whenever an invalid sysroot is provided, causing GDB to be unabled to find a valid path to the symbol file.

gdb.base/catch-syscall.exp
gdb.base/execl-update-breakpoints.exp
gdb.base/foll-exec-mode.exp
gdb.base/foll-exec.exp
gdb.base/foll-vfork.exp
gdb.base/pie-execl.exp
gdb.multi/bkpt-multi-exec.exp
gdb.python/py-finish-breakpoint.exp
gdb.threads/execl.exp
gdb.threads/non-ldr-exc-1.exp
gdb.threads/non-ldr-exc-2.exp
gdb.threads/non-ldr-exc-3.exp
gdb.threads/non-ldr-exc-4.exp
gdb.threads/thread-execl.exp

gdb/ChangeLog:
2016-10-25  Sandra Loosemore  <sandra@codesourcery.com>
	    Luis Machado  <lgustavo@codesourcery.com>

	PR gdb/20569
	* exceptions.c (exception_print_same): Moved here from exec.c.
	* exceptions.h (exception_print_same): Declare.
	* exec.h (try_open_exec_file): New declaration.
	Include symfile.h.
	* exec.c (exception_print_same): Moved to exceptions.c.
	(try_open_exec_file): New function.
	(exec_file_locate_attach): Rename exec_file and full_exec_path
	variables to avoid confusion between target and host pathnames.
	Move pathname processing logic to exec_file_find.  Do not return
	early if pathname lookup fails;
	Call try_open_exec_file.
	* infrun.c (follow_exec): Split and rename execd_pathname variable
	to avoid confusion between target and host pathnames.  Replace
	brokenpathname copy with cleanup to free malloc'ed string.  Warn
	if pathname lookup fails.  Pass target pathname to
	target_follow_exec, not hostpathname.
	Call try_open_exec_file.
	* solib.c (exec_file_find): Incorporate fallback logic for relative
	pathnames formerly in exec_file_locate_attach.
	* symfile.c (symbol_file_add_main_1): Make non-static.
	Move declaration to ...
	* symfile.h (symbol_file_add_main_1): ... here and make extern.

gdb/testsuite/ChangeLog:
2016-10-25  Luis Machado  <lgustavo@codesourcery.com>

	* gdb.base/exec-invalid-sysroot.exp: New file.
---
 gdb/ChangeLog                                   |  27 +++++
 gdb/exceptions.c                                |  19 ++++
 gdb/exceptions.h                                |   3 +
 gdb/exec.c                                      | 131 +++++++++++-------------
 gdb/exec.h                                      |   9 ++
 gdb/infrun.c                                    |  44 ++++----
 gdb/solib.c                                     |  32 ++++--
 gdb/symfile.c                                   |   4 +-
 gdb/symfile.h                                   |   2 +
 gdb/testsuite/ChangeLog                         |   4 +
 gdb/testsuite/gdb.base/exec-invalid-sysroot.exp |  70 +++++++++++++
 11 files changed, 238 insertions(+), 107 deletions(-)
 create mode 100644 gdb/testsuite/gdb.base/exec-invalid-sysroot.exp

Comments

Pedro Alves Oct. 25, 2016, 6:04 p.m. UTC | #1
On 10/25/2016 06:12 PM, Luis Machado wrote:
> Adjusted a few more bits.
> 
> I ended up using the ugly explicit cast for an enum that is being used as a
> bitfield. I'm guessing we'll want to convert this to the macro-fied
> template-fied version that is more appropriate to C++?

Yup.  I actually have a patch for that in one of my C++ branches
somewhere.

> 
> If so then i can come up with a follow up patch that does the conversion. I
> didn't want to disrupt v4 with more unrelated changes.

Use 'int' in this patch like the rest of the functions that pass
around this enum, and remove the casts.  Then when the enum
is made a proper enum-flags with DEF_ENUM_FLAGS_TYPE, you won't
have to remove the casts then, and all functions that need adjustment
will get the same adjustment at the same time.  No need for a partial
transition.

> 

>  void
> -exec_file_locate_attach (int pid, int defer_bp_reset, int from_tty)
> +try_open_exec_file (const char *exec_file_host, struct inferior *inf,
> +		    enum symfile_add_flags flags, int from_tty)

Use int.

>  {
> -  char *exec_file, *full_exec_path = NULL;
>    struct cleanup *old_chain;
>    struct gdb_exception prev_err = exception_none;
>  
> -  /* Do nothing if we already have an executable filename.  */
> -  exec_file = (char *) get_exec_file (0);
> -  if (exec_file != NULL)
> -    return;
> -
> -  /* Try to determine a filename from the process itself.  */
> -  exec_file = target_pid_to_exec_file (pid);
> -  if (exec_file == NULL)
> -    {
> -      warning (_("No executable has been specified and target does not "
> -		 "support\n"
> -		 "determining executable automatically.  "
> -		 "Try using the \"file\" command."));
> -      return;
> -    }
> -
> -  /* If gdb_sysroot is not empty and the discovered filename
> -     is absolute then prefix the filename with gdb_sysroot.  */
> -  if (*gdb_sysroot != '\0' && IS_ABSOLUTE_PATH (exec_file))
> -    {
> -      full_exec_path = exec_file_find (exec_file, NULL);
> -      if (full_exec_path == NULL)
> -	return;
> -    }
> -  else
> -    {
> -      /* It's possible we don't have a full path, but rather just a
> -	 filename.  Some targets, such as HP-UX, don't provide the
> -	 full path, sigh.
> -
> -	 Attempt to qualify the filename against the source path.
> -	 (If that fails, we'll just fall back on the original
> -	 filename.  Not much more we can do...)  */
> -      if (!source_full_path_of (exec_file, &full_exec_path))
> -	full_exec_path = xstrdup (exec_file);
> -    }
> -
> -  old_chain = make_cleanup (xfree, full_exec_path);
> -  make_cleanup (free_current_contents, &prev_err.message);
> +  old_chain = make_cleanup (free_current_contents, &prev_err.message);
>  
>    /* exec_file_attach and symbol_file_add_main may throw an error if the file
>       cannot be opened either locally or remotely.
> @@ -217,7 +160,9 @@ exec_file_locate_attach (int pid, int defer_bp_reset, int from_tty)
>       errors/exceptions in the following code.  */
>    TRY
>      {
> -      exec_file_attach (full_exec_path, from_tty);
> +      /* We must do this step even if exec_file_host is NULL, so that
> +	 exec_file_attach will clear state.  */
> +      exec_file_attach (exec_file_host, from_tty);
>      }
>    CATCH (err, RETURN_MASK_ERROR)
>      {
> @@ -232,20 +177,64 @@ exec_file_locate_attach (int pid, int defer_bp_reset, int from_tty)
>      }
>    END_CATCH
>  
> -  TRY
> +  if (exec_file_host != NULL)
>      {
> -      if (defer_bp_reset)
> -	current_inferior ()->symfile_flags |= SYMFILE_DEFER_BP_RESET;
> -      symbol_file_add_main (full_exec_path, from_tty);
> +      /* SYMFILE_DEFER_BP_RESET is used as the proper displacement for PIE
> +	 (Position Independent Executable) main symbol file will get applied by
> +	 solib_create_inferior_hook below.  breakpoint_re_set would fail to insert
> +	 the breakpoints with the zero displacement.  */
> +      TRY

I don't understand how it makes sense to this comment _here_.
Move this to where the flag is first passed down.  Note how there's
no "solib_create_inferior_hook below" at all here.  This function
just passes down the "flags" argument unmodified.

> +	{
> +	  symbol_file_add_main_1 (exec_file_host, from_tty, flags);
> +
> +	  if ((inf->symfile_flags & SYMFILE_NO_READ) == 0)
> +	    set_initial_language ();

This is already done by symbol_file_add_main_1..

> +	}
> +      CATCH (err, RETURN_MASK_ERROR)
> +	{
> +	  if (!exception_print_same (prev_err, err))
> +	    warning ("%s", err.message);
> +	}
> +      END_CATCH
> +
> +      inf->symfile_flags &= ~SYMFILE_DEFER_BP_RESET;

Before the patch, inf->symfile_flags is enabled/disabled
around the body of the code.  But now you pass down
SYMFILE_DEFER_BP_RESET in 'flags'.  I think we should
be able to remove this?

>      }
> -  CATCH (err, RETURN_MASK_ERROR)
> +
> +  do_cleanups (old_chain);
> +}
> +
> +/* See gdbcore.h.  */
> +
> +void
> +exec_file_locate_attach (int pid, int defer_bp_reset, int from_tty)
> +{
> +  char *exec_file_target, *exec_file_host;
> +  struct cleanup *old_chain;
> +  symfile_add_flags flags = SYMFILE_MAINLINE;

Use int for now.  Start with 0.  try_open_exec_file
always adds the SYMFILE_MAINLINE for you.

> +
> +  /* Do nothing if we already have an executable filename.  */
> +  if (get_exec_file (0) != NULL)
> +    return;
> +
> +  /* Try to determine a filename from the process itself.  */
> +  exec_file_target = target_pid_to_exec_file (pid);
> +  if (exec_file_target == NULL)
>      {
> -      if (!exception_print_same (prev_err, err))
> -	warning ("%s", err.message);
> +      warning (_("No executable has been specified and target does not "
> +		 "support\n"
> +		 "determining executable automatically.  "
> +		 "Try using the \"file\" command."));
> +      return;
>      }
> -  END_CATCH
> -  current_inferior ()->symfile_flags &= ~SYMFILE_DEFER_BP_RESET;
>  
> +  exec_file_host = exec_file_find (exec_file_target, NULL);
> +  old_chain = make_cleanup (xfree, exec_file_host);
> +
> +  if (defer_bp_reset)
> +    flags = (enum symfile_add_flags) (flags | SYMFILE_DEFER_BP_RESET);

Now with int, you can write:

    flags |= SYMFILE_DEFER_BP_RESET;

>    gdb_assert (current_program_space == inf->pspace);
>  
> -  /* That a.out is now the one to use.  */
> -  exec_file_attach (execd_pathname, 0);
> +  /* Attempt to open the exec file.  */
> +  try_open_exec_file (exec_file_host, inf, (enum symfile_add_flags) 0, 0);

Hmm, doesn't thi lose the SYMFILE_DEFER_BP_RESET described ...

>  
> -  /* SYMFILE_DEFER_BP_RESET is used as the proper displacement for PIE
> -     (Position Independent Executable) main symbol file will get applied by
> -     solib_create_inferior_hook below.  breakpoint_re_set would fail to insert
> -     the breakpoints with the zero displacement.  */
> -
> -  symbol_file_add (execd_pathname,
> -		   (inf->symfile_flags
> -		    | SYMFILE_MAINLINE | SYMFILE_DEFER_BP_RESET),
> -		   NULL, 0);

... here, in the code that you're replacing?

Seems to be that you should leave the comment here, and do:

  /* SYMFILE_DEFER_BP_RESET is used as the proper displacement for PIE
     (Position Independent Executable) main symbol file will get applied by
     solib_create_inferior_hook below.  breakpoint_re_set would fail to insert
     the breakpoints with the zero displacement.  */
  try_open_exec_file (exec_file_host, inf, SYMFILE_DEFER_BP_RESET, 0);

Here is where it makes sense to talk about the solib_create_inferior_hook
call below, because there's actually such a call below.

> -
> -  if ((inf->symfile_flags & SYMFILE_NO_READ) == 0)
> -    set_initial_language ();
> +  do_cleanups (old_chain);
>  
>    /* If the target can specify a description, read it.  Must do this
>       after flipping to the new executable (because the target supplied

BTW, symbol_file_add_main_1 doesn't actually add "flags" to
its add_flags local, so it seems like we're actually losing 
the passed down SYMFILE_DEFER_BP_RESET?  Or is there some confusion
regarding symfile_add_flags vs objfile flags here?  Oh looks
like there is...

I think I'll go dig up my enum-flags patch, and that will I think
help clear this up a lot.

Thanks,
Pedro Alves
Luis Machado Oct. 25, 2016, 6:15 p.m. UTC | #2
On 10/25/2016 01:04 PM, Pedro Alves wrote:
> On 10/25/2016 06:12 PM, Luis Machado wrote:
>> Adjusted a few more bits.
>>
>> I ended up using the ugly explicit cast for an enum that is being used as a
>> bitfield. I'm guessing we'll want to convert this to the macro-fied
>> template-fied version that is more appropriate to C++?
>
> Yup.  I actually have a patch for that in one of my C++ branches
> somewhere.
>
>>
>> If so then i can come up with a follow up patch that does the conversion. I
>> didn't want to disrupt v4 with more unrelated changes.
>
> Use 'int' in this patch like the rest of the functions that pass
> around this enum, and remove the casts.  Then when the enum
> is made a proper enum-flags with DEF_ENUM_FLAGS_TYPE, you won't
> have to remove the casts then, and all functions that need adjustment
> will get the same adjustment at the same time.  No need for a partial
> transition.
>
>>
>
>>  void
>> -exec_file_locate_attach (int pid, int defer_bp_reset, int from_tty)
>> +try_open_exec_file (const char *exec_file_host, struct inferior *inf,
>> +		    enum symfile_add_flags flags, int from_tty)
>
> Use int.
>
>>  {
>> -  char *exec_file, *full_exec_path = NULL;
>>    struct cleanup *old_chain;
>>    struct gdb_exception prev_err = exception_none;
>>
>> -  /* Do nothing if we already have an executable filename.  */
>> -  exec_file = (char *) get_exec_file (0);
>> -  if (exec_file != NULL)
>> -    return;
>> -
>> -  /* Try to determine a filename from the process itself.  */
>> -  exec_file = target_pid_to_exec_file (pid);
>> -  if (exec_file == NULL)
>> -    {
>> -      warning (_("No executable has been specified and target does not "
>> -		 "support\n"
>> -		 "determining executable automatically.  "
>> -		 "Try using the \"file\" command."));
>> -      return;
>> -    }
>> -
>> -  /* If gdb_sysroot is not empty and the discovered filename
>> -     is absolute then prefix the filename with gdb_sysroot.  */
>> -  if (*gdb_sysroot != '\0' && IS_ABSOLUTE_PATH (exec_file))
>> -    {
>> -      full_exec_path = exec_file_find (exec_file, NULL);
>> -      if (full_exec_path == NULL)
>> -	return;
>> -    }
>> -  else
>> -    {
>> -      /* It's possible we don't have a full path, but rather just a
>> -	 filename.  Some targets, such as HP-UX, don't provide the
>> -	 full path, sigh.
>> -
>> -	 Attempt to qualify the filename against the source path.
>> -	 (If that fails, we'll just fall back on the original
>> -	 filename.  Not much more we can do...)  */
>> -      if (!source_full_path_of (exec_file, &full_exec_path))
>> -	full_exec_path = xstrdup (exec_file);
>> -    }
>> -
>> -  old_chain = make_cleanup (xfree, full_exec_path);
>> -  make_cleanup (free_current_contents, &prev_err.message);
>> +  old_chain = make_cleanup (free_current_contents, &prev_err.message);
>>
>>    /* exec_file_attach and symbol_file_add_main may throw an error if the file
>>       cannot be opened either locally or remotely.
>> @@ -217,7 +160,9 @@ exec_file_locate_attach (int pid, int defer_bp_reset, int from_tty)
>>       errors/exceptions in the following code.  */
>>    TRY
>>      {
>> -      exec_file_attach (full_exec_path, from_tty);
>> +      /* We must do this step even if exec_file_host is NULL, so that
>> +	 exec_file_attach will clear state.  */
>> +      exec_file_attach (exec_file_host, from_tty);
>>      }
>>    CATCH (err, RETURN_MASK_ERROR)
>>      {
>> @@ -232,20 +177,64 @@ exec_file_locate_attach (int pid, int defer_bp_reset, int from_tty)
>>      }
>>    END_CATCH
>>
>> -  TRY
>> +  if (exec_file_host != NULL)
>>      {
>> -      if (defer_bp_reset)
>> -	current_inferior ()->symfile_flags |= SYMFILE_DEFER_BP_RESET;
>> -      symbol_file_add_main (full_exec_path, from_tty);
>> +      /* SYMFILE_DEFER_BP_RESET is used as the proper displacement for PIE
>> +	 (Position Independent Executable) main symbol file will get applied by
>> +	 solib_create_inferior_hook below.  breakpoint_re_set would fail to insert
>> +	 the breakpoints with the zero displacement.  */
>> +      TRY
>
> I don't understand how it makes sense to this comment _here_.
> Move this to where the flag is first passed down.  Note how there's
> no "solib_create_inferior_hook below" at all here.  This function
> just passes down the "flags" argument unmodified.
>
>> +	{
>> +	  symbol_file_add_main_1 (exec_file_host, from_tty, flags);
>> +
>> +	  if ((inf->symfile_flags & SYMFILE_NO_READ) == 0)
>> +	    set_initial_language ();
>
> This is already done by symbol_file_add_main_1..
>
>> +	}
>> +      CATCH (err, RETURN_MASK_ERROR)
>> +	{
>> +	  if (!exception_print_same (prev_err, err))
>> +	    warning ("%s", err.message);
>> +	}
>> +      END_CATCH
>> +
>> +      inf->symfile_flags &= ~SYMFILE_DEFER_BP_RESET;
>
> Before the patch, inf->symfile_flags is enabled/disabled
> around the body of the code.  But now you pass down
> SYMFILE_DEFER_BP_RESET in 'flags'.  I think we should
> be able to remove this?
>
>>      }
>> -  CATCH (err, RETURN_MASK_ERROR)
>> +
>> +  do_cleanups (old_chain);
>> +}
>> +
>> +/* See gdbcore.h.  */
>> +
>> +void
>> +exec_file_locate_attach (int pid, int defer_bp_reset, int from_tty)
>> +{
>> +  char *exec_file_target, *exec_file_host;
>> +  struct cleanup *old_chain;
>> +  symfile_add_flags flags = SYMFILE_MAINLINE;
>
> Use int for now.  Start with 0.  try_open_exec_file
> always adds the SYMFILE_MAINLINE for you.
>
>> +
>> +  /* Do nothing if we already have an executable filename.  */
>> +  if (get_exec_file (0) != NULL)
>> +    return;
>> +
>> +  /* Try to determine a filename from the process itself.  */
>> +  exec_file_target = target_pid_to_exec_file (pid);
>> +  if (exec_file_target == NULL)
>>      {
>> -      if (!exception_print_same (prev_err, err))
>> -	warning ("%s", err.message);
>> +      warning (_("No executable has been specified and target does not "
>> +		 "support\n"
>> +		 "determining executable automatically.  "
>> +		 "Try using the \"file\" command."));
>> +      return;
>>      }
>> -  END_CATCH
>> -  current_inferior ()->symfile_flags &= ~SYMFILE_DEFER_BP_RESET;
>>
>> +  exec_file_host = exec_file_find (exec_file_target, NULL);
>> +  old_chain = make_cleanup (xfree, exec_file_host);
>> +
>> +  if (defer_bp_reset)
>> +    flags = (enum symfile_add_flags) (flags | SYMFILE_DEFER_BP_RESET);
>
> Now with int, you can write:
>
>     flags |= SYMFILE_DEFER_BP_RESET;
>
>>    gdb_assert (current_program_space == inf->pspace);
>>
>> -  /* That a.out is now the one to use.  */
>> -  exec_file_attach (execd_pathname, 0);
>> +  /* Attempt to open the exec file.  */
>> +  try_open_exec_file (exec_file_host, inf, (enum symfile_add_flags) 0, 0);
>
> Hmm, doesn't thi lose the SYMFILE_DEFER_BP_RESET described ...
>
>>
>> -  /* SYMFILE_DEFER_BP_RESET is used as the proper displacement for PIE
>> -     (Position Independent Executable) main symbol file will get applied by
>> -     solib_create_inferior_hook below.  breakpoint_re_set would fail to insert
>> -     the breakpoints with the zero displacement.  */
>> -
>> -  symbol_file_add (execd_pathname,
>> -		   (inf->symfile_flags
>> -		    | SYMFILE_MAINLINE | SYMFILE_DEFER_BP_RESET),
>> -		   NULL, 0);
>
> ... here, in the code that you're replacing?
>
> Seems to be that you should leave the comment here, and do:
>
>   /* SYMFILE_DEFER_BP_RESET is used as the proper displacement for PIE
>      (Position Independent Executable) main symbol file will get applied by
>      solib_create_inferior_hook below.  breakpoint_re_set would fail to insert
>      the breakpoints with the zero displacement.  */
>   try_open_exec_file (exec_file_host, inf, SYMFILE_DEFER_BP_RESET, 0);
>
> Here is where it makes sense to talk about the solib_create_inferior_hook
> call below, because there's actually such a call below.
>
>> -
>> -  if ((inf->symfile_flags & SYMFILE_NO_READ) == 0)
>> -    set_initial_language ();
>> +  do_cleanups (old_chain);
>>
>>    /* If the target can specify a description, read it.  Must do this
>>       after flipping to the new executable (because the target supplied
>
> BTW, symbol_file_add_main_1 doesn't actually add "flags" to
> its add_flags local, so it seems like we're actually losing
> the passed down SYMFILE_DEFER_BP_RESET?  Or is there some confusion
> regarding symfile_add_flags vs objfile flags here?  Oh looks
> like there is...
>
> I think I'll go dig up my enum-flags patch, and that will I think
> help clear this up a lot.

Before i go ahead and adjust this even more, what's your plan and ETA 
for the above? This is disturbing more code as we try to consolidade 
slightly different functions into a single one in order to make things a 
bit more clean. But i'm afraid this is besides the point of the original 
patch itself?

I just want to understand what's the end goal, because the scope seems 
to be changing slightly with each iteration. :-)

Thanks,
Luis
Pedro Alves Oct. 25, 2016, 6:20 p.m. UTC | #3
On 10/25/2016 07:15 PM, Luis Machado wrote:

> Before i go ahead and adjust this even more, what's your plan and ETA
> for the above? 

I'll try to post this today.

> This is disturbing more code as we try to consolidade
> slightly different functions into a single one in order to make things a
> bit more clean. But i'm afraid this is besides the point of the original
> patch itself?
> 
> I just want to understand what's the end goal, because the scope seems
> to be changing slightly with each iteration. :-)

No, the scope has not changed at all.  Your original version duplicated
a large chunk of code, and then the attempt to refactor things did it
incorrectly.  Still the same scope, but the patch as is, is buggy.

Between accepted duplicated code, and fixing the patch, I take the latter.

Thanks,
Pedro Alves
Luis Machado Oct. 25, 2016, 6:30 p.m. UTC | #4
On 10/25/2016 01:20 PM, Pedro Alves wrote:
> On 10/25/2016 07:15 PM, Luis Machado wrote:
>
>> Before i go ahead and adjust this even more, what's your plan and ETA
>> for the above?
>
> I'll try to post this today.
>

Sounds good.

>> This is disturbing more code as we try to consolidade
>> slightly different functions into a single one in order to make things a
>> bit more clean. But i'm afraid this is besides the point of the original
>> patch itself?
>>
>> I just want to understand what's the end goal, because the scope seems
>> to be changing slightly with each iteration. :-)
>
> No, the scope has not changed at all.  Your original version duplicated
> a large chunk of code, and then the attempt to refactor things did it
> incorrectly.  Still the same scope, but the patch as is, is buggy.
>
> Between accepted duplicated code, and fixing the patch, I take the latter.

Fine by me.

Thanks,
Luis
Luis Machado Oct. 25, 2016, 7:41 p.m. UTC | #5
On 10/25/2016 01:30 PM, Luis Machado wrote:
> On 10/25/2016 01:20 PM, Pedro Alves wrote:
>> On 10/25/2016 07:15 PM, Luis Machado wrote:
>>
>>> Before i go ahead and adjust this even more, what's your plan and ETA
>>> for the above?
>>
>> I'll try to post this today.
>>
>
> Sounds good.
>
>>> This is disturbing more code as we try to consolidade
>>> slightly different functions into a single one in order to make things a
>>> bit more clean. But i'm afraid this is besides the point of the original
>>> patch itself?
>>>
>>> I just want to understand what's the end goal, because the scope seems
>>> to be changing slightly with each iteration. :-)
>>
>> No, the scope has not changed at all.  Your original version duplicated
>> a large chunk of code, and then the attempt to refactor things did it
>> incorrectly.  Still the same scope, but the patch as is, is buggy.
>>
>> Between accepted duplicated code, and fixing the patch, I take the
>> latter.
>
> Fine by me.
>
> Thanks,
> Luis

Going back to the flags problem, maybe adding "add_flags" as argument to 
symbol_file_add_main_1, just like symbol_file_add, and appending those 
flags to the existing flag variable there would make things work?
Pedro Alves Oct. 25, 2016, 7:46 p.m. UTC | #6
On 10/25/2016 08:41 PM, Luis Machado wrote:

> Going back to the flags problem, maybe adding "add_flags" as argument to
> symbol_file_add_main_1, just like symbol_file_add, and appending those
> flags to the existing flag variable there would make things work?

I've now cleaned up that patch, and simply rebasing yours on top
shows what I meant:

 src/gdb/exec.c:184:59: error: could not convert ‘flags’ from
‘symfile_add_flags {aka enum_flags<symfile_add_flag>}’ to
‘objfile_flags {aka enum_flags<objfile_flag>}’
     symbol_file_add_main_1 (exec_file_host, from_tty, flags);
                                                           ^
 Makefile:1138: recipe for target 'exec.o' failed

I.e., the existing flags parameter to symbol_file_add_main_1
is _not_ a symfile_add_flags.  We can't just use it as is.

So yes, I think so.  I was just doing that here, this minute.
But I was replacing the from_tty parameter symbol_file_add_main
with a symfile_add_flags instead.  Let me do that and send
both patches.
Luis Machado Oct. 25, 2016, 7:50 p.m. UTC | #7
On 10/25/2016 02:46 PM, Pedro Alves wrote:
> On 10/25/2016 08:41 PM, Luis Machado wrote:
>
>> Going back to the flags problem, maybe adding "add_flags" as argument to
>> symbol_file_add_main_1, just like symbol_file_add, and appending those
>> flags to the existing flag variable there would make things work?
>
> I've now cleaned up that patch, and simply rebasing yours on top
> shows what I meant:
>
>  src/gdb/exec.c:184:59: error: could not convert ‘flags’ from
> ‘symfile_add_flags {aka enum_flags<symfile_add_flag>}’ to
> ‘objfile_flags {aka enum_flags<objfile_flag>}’
>      symbol_file_add_main_1 (exec_file_host, from_tty, flags);
>                                                            ^

Ah yes. Confusing names in those functions.

>  Makefile:1138: recipe for target 'exec.o' failed
>
> I.e., the existing flags parameter to symbol_file_add_main_1
> is _not_ a symfile_add_flags.  We can't just use it as is.
>
> So yes, I think so.  I was just doing that here, this minute.
> But I was replacing the from_tty parameter symbol_file_add_main
> with a symfile_add_flags instead.  Let me do that and send
> both patches.
>

Oki!

Thanks.
diff mbox

Patch

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 43175ff..c9cf146 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,30 @@ 
+2016-10-25  Sandra Loosemore  <sandra@codesourcery.com>
+	    Luis Machado  <lgustavo@codesourcery.com>
+
+	PR gdb/20569
+	* exceptions.c (exception_print_same): Moved here from exec.c.
+	* exceptions.h (exception_print_same): Declare.
+	* exec.h (try_open_exec_file): New declaration.
+	Include symfile.h.
+	* exec.c (exception_print_same): Moved to exceptions.c.
+	(try_open_exec_file): New function.
+	(exec_file_locate_attach): Rename exec_file and full_exec_path
+	variables to avoid confusion between target and host pathnames.
+	Move pathname processing logic to exec_file_find.  Do not return
+	early if pathname lookup fails;
+	Call try_open_exec_file.
+	* infrun.c (follow_exec): Split and rename execd_pathname variable
+	to avoid confusion between target and host pathnames.  Replace
+	brokenpathname copy with cleanup to free malloc'ed string.  Warn
+	if pathname lookup fails.  Pass target pathname to
+	target_follow_exec, not hostpathname.
+	Call try_open_exec_file.
+	* solib.c (exec_file_find): Incorporate fallback logic for relative
+	pathnames formerly in exec_file_locate_attach.
+	* symfile.c (symbol_file_add_main_1): Make non-static.
+	Move declaration to ...
+	* symfile.h (symbol_file_add_main_1): ... here and make extern.
+
 2016-10-24  Luis Machado  <lgustavo@codesourcery.com>
 
 	* exec.c (exec_file_locate_attach): Prevent NULL pointer dereference
diff --git a/gdb/exceptions.c b/gdb/exceptions.c
index 9a10f66..0e269de 100644
--- a/gdb/exceptions.c
+++ b/gdb/exceptions.c
@@ -256,3 +256,22 @@  catch_errors (catch_errors_ftype *func, void *func_args, char *errstring,
     return 0;
   return val;
 }
+
+/* Returns non-zero if exceptions E1 and E2 are equal.  Returns zero
+   otherwise.  */
+
+int
+exception_print_same (struct gdb_exception e1, struct gdb_exception e2)
+{
+  const char *msg1 = e1.message;
+  const char *msg2 = e2.message;
+
+  if (msg1 == NULL)
+    msg1 = "";
+  if (msg2 == NULL)
+    msg2 = "";
+
+  return (e1.reason == e2.reason
+	  && e1.error == e2.error
+	  && strcmp (msg1, msg2) == 0);
+}
diff --git a/gdb/exceptions.h b/gdb/exceptions.h
index 5711c1a..a2d39d7 100644
--- a/gdb/exceptions.h
+++ b/gdb/exceptions.h
@@ -88,4 +88,7 @@  extern int catch_exceptions_with_msg (struct ui_out *uiout,
 typedef int (catch_errors_ftype) (void *);
 extern int catch_errors (catch_errors_ftype *, void *, char *, return_mask);
 
+/* Compare two exception objects for print equality.  */
+extern int exception_print_same (struct gdb_exception e1,
+				 struct gdb_exception e2);
 #endif
diff --git a/gdb/exec.c b/gdb/exec.c
index 6e2a296..09c456e 100644
--- a/gdb/exec.c
+++ b/gdb/exec.c
@@ -136,73 +136,16 @@  exec_file_clear (int from_tty)
     printf_unfiltered (_("No executable file now.\n"));
 }
 
-/* Returns non-zero if exceptions E1 and E2 are equal.  Returns zero
-   otherwise.  */
-
-static int
-exception_print_same (struct gdb_exception e1, struct gdb_exception e2)
-{
-  const char *msg1 = e1.message;
-  const char *msg2 = e2.message;
-
-  if (msg1 == NULL)
-    msg1 = "";
-  if (msg2 == NULL)
-    msg2 = "";
-
-  return (e1.reason == e2.reason
-	  && e1.error == e2.error
-	  && strcmp (msg1, msg2) == 0);
-}
-
-/* See gdbcore.h.  */
+/* See exec.h.  */
 
 void
-exec_file_locate_attach (int pid, int defer_bp_reset, int from_tty)
+try_open_exec_file (const char *exec_file_host, struct inferior *inf,
+		    enum symfile_add_flags flags, int from_tty)
 {
-  char *exec_file, *full_exec_path = NULL;
   struct cleanup *old_chain;
   struct gdb_exception prev_err = exception_none;
 
-  /* Do nothing if we already have an executable filename.  */
-  exec_file = (char *) get_exec_file (0);
-  if (exec_file != NULL)
-    return;
-
-  /* Try to determine a filename from the process itself.  */
-  exec_file = target_pid_to_exec_file (pid);
-  if (exec_file == NULL)
-    {
-      warning (_("No executable has been specified and target does not "
-		 "support\n"
-		 "determining executable automatically.  "
-		 "Try using the \"file\" command."));
-      return;
-    }
-
-  /* If gdb_sysroot is not empty and the discovered filename
-     is absolute then prefix the filename with gdb_sysroot.  */
-  if (*gdb_sysroot != '\0' && IS_ABSOLUTE_PATH (exec_file))
-    {
-      full_exec_path = exec_file_find (exec_file, NULL);
-      if (full_exec_path == NULL)
-	return;
-    }
-  else
-    {
-      /* It's possible we don't have a full path, but rather just a
-	 filename.  Some targets, such as HP-UX, don't provide the
-	 full path, sigh.
-
-	 Attempt to qualify the filename against the source path.
-	 (If that fails, we'll just fall back on the original
-	 filename.  Not much more we can do...)  */
-      if (!source_full_path_of (exec_file, &full_exec_path))
-	full_exec_path = xstrdup (exec_file);
-    }
-
-  old_chain = make_cleanup (xfree, full_exec_path);
-  make_cleanup (free_current_contents, &prev_err.message);
+  old_chain = make_cleanup (free_current_contents, &prev_err.message);
 
   /* exec_file_attach and symbol_file_add_main may throw an error if the file
      cannot be opened either locally or remotely.
@@ -217,7 +160,9 @@  exec_file_locate_attach (int pid, int defer_bp_reset, int from_tty)
      errors/exceptions in the following code.  */
   TRY
     {
-      exec_file_attach (full_exec_path, from_tty);
+      /* We must do this step even if exec_file_host is NULL, so that
+	 exec_file_attach will clear state.  */
+      exec_file_attach (exec_file_host, from_tty);
     }
   CATCH (err, RETURN_MASK_ERROR)
     {
@@ -232,20 +177,64 @@  exec_file_locate_attach (int pid, int defer_bp_reset, int from_tty)
     }
   END_CATCH
 
-  TRY
+  if (exec_file_host != NULL)
     {
-      if (defer_bp_reset)
-	current_inferior ()->symfile_flags |= SYMFILE_DEFER_BP_RESET;
-      symbol_file_add_main (full_exec_path, from_tty);
+      /* SYMFILE_DEFER_BP_RESET is used as the proper displacement for PIE
+	 (Position Independent Executable) main symbol file will get applied by
+	 solib_create_inferior_hook below.  breakpoint_re_set would fail to insert
+	 the breakpoints with the zero displacement.  */
+      TRY
+	{
+	  symbol_file_add_main_1 (exec_file_host, from_tty, flags);
+
+	  if ((inf->symfile_flags & SYMFILE_NO_READ) == 0)
+	    set_initial_language ();
+	}
+      CATCH (err, RETURN_MASK_ERROR)
+	{
+	  if (!exception_print_same (prev_err, err))
+	    warning ("%s", err.message);
+	}
+      END_CATCH
+
+      inf->symfile_flags &= ~SYMFILE_DEFER_BP_RESET;
     }
-  CATCH (err, RETURN_MASK_ERROR)
+
+  do_cleanups (old_chain);
+}
+
+/* See gdbcore.h.  */
+
+void
+exec_file_locate_attach (int pid, int defer_bp_reset, int from_tty)
+{
+  char *exec_file_target, *exec_file_host;
+  struct cleanup *old_chain;
+  symfile_add_flags flags = SYMFILE_MAINLINE;
+
+  /* Do nothing if we already have an executable filename.  */
+  if (get_exec_file (0) != NULL)
+    return;
+
+  /* Try to determine a filename from the process itself.  */
+  exec_file_target = target_pid_to_exec_file (pid);
+  if (exec_file_target == NULL)
     {
-      if (!exception_print_same (prev_err, err))
-	warning ("%s", err.message);
+      warning (_("No executable has been specified and target does not "
+		 "support\n"
+		 "determining executable automatically.  "
+		 "Try using the \"file\" command."));
+      return;
     }
-  END_CATCH
-  current_inferior ()->symfile_flags &= ~SYMFILE_DEFER_BP_RESET;
 
+  exec_file_host = exec_file_find (exec_file_target, NULL);
+  old_chain = make_cleanup (xfree, exec_file_host);
+
+  if (defer_bp_reset)
+    flags = (enum symfile_add_flags) (flags | SYMFILE_DEFER_BP_RESET);
+
+  /* Attempt to open the exec file.  */
+  try_open_exec_file (exec_file_host, current_inferior (), flags, from_tty);
   do_cleanups (old_chain);
 }
 
diff --git a/gdb/exec.h b/gdb/exec.h
index 4044cb7..151ac62 100644
--- a/gdb/exec.h
+++ b/gdb/exec.h
@@ -23,6 +23,7 @@ 
 #include "target.h"
 #include "progspace.h"
 #include "memrange.h"
+#include "symfile.h"
 
 struct target_section;
 struct target_ops;
@@ -113,4 +114,12 @@  extern void print_section_info (struct target_section_table *table,
 
 extern void exec_close (void);
 
+/* Helper function that attempts to open the symbol file at EXEC_FILE_HOST.
+   If successful, it proceeds to add the symbol file as the main symbol file.
+
+   FLAGS is passed on to the function adding the symbol file as well as
+   FROM_TTY.  */
+extern void try_open_exec_file (const char *exec_file_host,
+				struct inferior *inf,
+				enum symfile_add_flags flags, int from_tty);
 #endif
diff --git a/gdb/infrun.c b/gdb/infrun.c
index 00bba16..d198dc8 100644
--- a/gdb/infrun.c
+++ b/gdb/infrun.c
@@ -1077,15 +1077,17 @@  show_follow_exec_mode_string (struct ui_file *file, int from_tty,
   fprintf_filtered (file, _("Follow exec mode is \"%s\".\n"),  value);
 }
 
-/* EXECD_PATHNAME is assumed to be non-NULL.  */
+/* EXEC_FILE_TARGET is assumed to be non-NULL.  */
 
 static void
-follow_exec (ptid_t ptid, char *execd_pathname)
+follow_exec (ptid_t ptid, char *exec_file_target)
 {
   struct thread_info *th, *tmp;
   struct inferior *inf = current_inferior ();
   int pid = ptid_get_pid (ptid);
   ptid_t process_ptid;
+  char *exec_file_host;
+  struct cleanup *old_chain;
 
   /* This is an exec event that we actually wish to pay attention to.
      Refresh our symbol table to the newly exec'd program, remove any
@@ -1155,7 +1157,7 @@  follow_exec (ptid_t ptid, char *execd_pathname)
   process_ptid = pid_to_ptid (pid);
   printf_unfiltered (_("%s is executing new program: %s\n"),
 		     target_pid_to_str (process_ptid),
-		     execd_pathname);
+		     exec_file_target);
 
   /* We've followed the inferior through an exec.  Therefore, the
      inferior has essentially been killed & reborn.  */
@@ -1164,14 +1166,17 @@  follow_exec (ptid_t ptid, char *execd_pathname)
 
   breakpoint_init_inferior (inf_execd);
 
-  if (*gdb_sysroot != '\0')
-    {
-      char *name = exec_file_find (execd_pathname, NULL);
+  exec_file_host = exec_file_find (exec_file_target, NULL);
+  old_chain = make_cleanup (xfree, exec_file_host);
 
-      execd_pathname = (char *) alloca (strlen (name) + 1);
-      strcpy (execd_pathname, name);
-      xfree (name);
-    }
+  /* If we were unable to map the executable target pathname onto a host
+     pathname, tell the user that.  Otherwise GDB's subsequent behavior
+     is confusing.  Maybe it would even be better to stop at this point
+     so that the user can specify a file manually before continuing.  */
+  if (exec_file_host == NULL)
+    warning (_("Could not load symbols for executable %s.\n"
+	       "Do you need \"set sysroot\"?"),
+	     exec_file_target);
 
   /* Reset the shared library package.  This ensures that we get a
      shlib event when the child reaches "_start", at which point the
@@ -1193,7 +1198,7 @@  follow_exec (ptid_t ptid, char *execd_pathname)
 
       inf = add_inferior_with_spaces ();
       inf->pid = pid;
-      target_follow_exec (inf, execd_pathname);
+      target_follow_exec (inf, exec_file_target);
 
       set_current_inferior (inf);
       set_current_program_space (inf->pspace);
@@ -1212,21 +1217,10 @@  follow_exec (ptid_t ptid, char *execd_pathname)
 
   gdb_assert (current_program_space == inf->pspace);
 
-  /* That a.out is now the one to use.  */
-  exec_file_attach (execd_pathname, 0);
+  /* Attempt to open the exec file.  */
+  try_open_exec_file (exec_file_host, inf, (enum symfile_add_flags) 0, 0);
 
-  /* SYMFILE_DEFER_BP_RESET is used as the proper displacement for PIE
-     (Position Independent Executable) main symbol file will get applied by
-     solib_create_inferior_hook below.  breakpoint_re_set would fail to insert
-     the breakpoints with the zero displacement.  */
-
-  symbol_file_add (execd_pathname,
-		   (inf->symfile_flags
-		    | SYMFILE_MAINLINE | SYMFILE_DEFER_BP_RESET),
-		   NULL, 0);
-
-  if ((inf->symfile_flags & SYMFILE_NO_READ) == 0)
-    set_initial_language ();
+  do_cleanups (old_chain);
 
   /* If the target can specify a description, read it.  Must do this
      after flipping to the new executable (because the target supplied
diff --git a/gdb/solib.c b/gdb/solib.c
index b8c2b42..d49dd99 100644
--- a/gdb/solib.c
+++ b/gdb/solib.c
@@ -380,21 +380,22 @@  solib_find_1 (char *in_pathname, int *fd, int is_solib)
 /* Return the full pathname of the main executable, or NULL if not
    found.  The returned pathname is malloc'ed and must be freed by
    the caller.  If FD is non-NULL, *FD is set to either -1 or an open
-   file handle for the main executable.
-
-   The search algorithm used is described in solib_find_1's comment
-   above.  */
+   file handle for the main executable.  */
 
 char *
 exec_file_find (char *in_pathname, int *fd)
 {
-  char *result = solib_find_1 (in_pathname, fd, 0);
+  char *result;
+  const char *fskind = effective_target_file_system_kind ();
+
+  if (in_pathname == NULL)
+    return NULL;
 
-  if (result == NULL)
+  if (*gdb_sysroot != '\0' && IS_TARGET_ABSOLUTE_PATH (fskind, in_pathname))
     {
-      const char *fskind = effective_target_file_system_kind ();
+      result = solib_find_1 (in_pathname, fd, 0);
 
-      if (fskind == file_system_kind_dos_based)
+      if (result == NULL && fskind == file_system_kind_dos_based)
 	{
 	  char *new_pathname;
 
@@ -405,6 +406,21 @@  exec_file_find (char *in_pathname, int *fd)
 	  result = solib_find_1 (new_pathname, fd, 0);
 	}
     }
+  else
+    {
+      /* It's possible we don't have a full path, but rather just a
+	 filename.  Some targets, such as HP-UX, don't provide the
+	 full path, sigh.
+
+	 Attempt to qualify the filename against the source path.
+	 (If that fails, we'll just fall back on the original
+	 filename.  Not much more we can do...)  */
+
+      if (!source_full_path_of (in_pathname, &result))
+	result = xstrdup (in_pathname);
+      if (fd != NULL)
+	*fd = -1;
+    }
 
   return result;
 }
diff --git a/gdb/symfile.c b/gdb/symfile.c
index 7eb6cdc..210badb 100644
--- a/gdb/symfile.c
+++ b/gdb/symfile.c
@@ -85,8 +85,6 @@  int readnow_symbol_files;	/* Read full symbols immediately.  */
 
 static void load_command (char *, int);
 
-static void symbol_file_add_main_1 (const char *args, int from_tty, int flags);
-
 static void add_symbol_file_command (char *, int);
 
 static const struct sym_fns *find_sym_fns (bfd *);
@@ -1306,7 +1304,7 @@  symbol_file_add_main (const char *args, int from_tty)
   symbol_file_add_main_1 (args, from_tty, 0);
 }
 
-static void
+void
 symbol_file_add_main_1 (const char *args, int from_tty, int flags)
 {
   const int add_flags = (current_inferior ()->symfile_flags
diff --git a/gdb/symfile.h b/gdb/symfile.h
index 32902cb..cc54530 100644
--- a/gdb/symfile.h
+++ b/gdb/symfile.h
@@ -475,6 +475,8 @@  extern struct objfile *symbol_file_add_from_bfd (bfd *, const char *, int,
 extern void symbol_file_add_separate (bfd *, const char *, int,
 				      struct objfile *);
 
+extern void symbol_file_add_main_1 (const char *args, int from_tty, int flags);
+
 extern char *find_separate_debug_file_by_debuglink (struct objfile *);
 
 /* Create a new section_addr_info, with room for NUM_SECTIONS.  */
diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 460e6b9..d0a2bc9 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,7 @@ 
+2016-10-25  Luis Machado  <lgustavo@codesourcery.com>
+
+	* gdb.base/exec-invalid-sysroot.exp: New file.
+
 2016-10-24  Jan Kratochvil  <jan.kratochvil@redhat.com>
 
 	* gdb.base/morestack.exp: Try to build it using -fuse-ld=gold first.
diff --git a/gdb/testsuite/gdb.base/exec-invalid-sysroot.exp b/gdb/testsuite/gdb.base/exec-invalid-sysroot.exp
new file mode 100644
index 0000000..a42de0b
--- /dev/null
+++ b/gdb/testsuite/gdb.base/exec-invalid-sysroot.exp
@@ -0,0 +1,70 @@ 
+#   Copyright 1997-2016 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# This test exercises PR20569.  GDB would crash when attempting to follow
+# an exec call when it could not resolve the path to the symbol file.
+# This was the case when an invalid sysroot is provided.
+
+standard_testfile foll-exec.c
+
+global binfile
+set binfile [standard_output_file "foll-exec"]
+set testfile2 "execd-prog"
+set srcfile2 ${testfile2}.c
+set binfile2 [standard_output_file ${testfile2}]
+
+set compile_options debug
+
+# build the first test case
+if  { [gdb_compile "${srcdir}/${subdir}/${srcfile2}" "${binfile2}" executable $compile_options] != "" } {
+    untested "could not compile test program ${binfile2}"
+    return -1
+}
+
+if  { [gdb_compile "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable $compile_options] != "" } {
+    untested "could not compile test program ${binfile}"
+    return -1
+}
+
+proc do_exec_sysroot_test {} {
+    global binfile srcfile srcfile2 testfile testfile2
+    global gdb_prompt
+
+    gdb_test_no_output "set sysroot /a/path/that/does/not/exist"
+
+    # Start the program running, and stop at main.
+    #
+    if ![runto_main] then {
+	fail "Couldn't run ${testfile}"
+	return
+    }
+
+    # Verify that the system supports "catch exec".
+    gdb_test "catch exec" "Catchpoint \[0-9\]* \\(exec\\)" "insert exec catchpoint"
+    set test "continue to first exec catchpoint"
+    gdb_test_multiple "continue" $test {
+	-re ".*Your system does not support this type\r\nof catchpoint.*$gdb_prompt $" {
+	    unsupported $test
+	    return
+	}
+	-re ".*Could not load symbols for executable.*$gdb_prompt $" {
+	    pass $test
+	}
+    }
+}
+
+# Start with a fresh gdb
+clean_restart $binfile
+do_exec_sysroot_test