Re: gdbserver with reversed arguments goes into an infinite loop

Denis PILAT
2006-12-13T15:46:17Z

Daniel Jacobowitz wrote:
> On Wed, Dec 13, 2006 at 10:58:14AM +0100, Denis PILAT wrote:
>> I've found that if you revert the argument of gdbserver, means writing
>> the program's name before the COMM argument, it goes into an infinite
>> loop, and as the CTRL+C does not work, you have to kill the process from
>> an other shell.
>>
>> In gdbserver/server.c, the loop in question does the remote_open on the
>> wrong passed argument (argv[1]) which unfortunately is the binary file
>> you'd expect to open so remote_open does not exit on error.
>>
>> I think either we could check that we pass correct argument before using
>> start_inferior(), this is executing before the loop. The bellow patch is
>> in that sense.
>>
>> Or we find a way to exit the loop by adding a test in it. May be by
>> adding something in remote_open to let it fail.
>
> I doubt it's in an infinite loop. It's probably sleeping, "waiting"
> for a connection. We ought to allow C-c when no debugger is
> connected yet. It'd be nice if remote_open wouldn't open ordinary
> files, too.
>
Yes it's waiting for a connection but as arguments are wrongs it can
wait for long ...

You're right, preventing remote_open from opening ordinary files would
exit the loop.
But may be it would be better to open only character device (S_ISCHR
macro) than excluding ordinary files (S_ISREG macro). It's up to you !
Here is a patch where I made a test to open only character device. If
you right with that solution I'll propose a patch with a ChangeLog and
so on.
I took this opportunity to remove a warning on a strncpy() usage.

I'm wondering about the compilation of this code under windows. I never
compiled a gdbserver on windows, is there any gdbserver hosted under
windows ?

--
Denis

Index: remote-utils.c
===================================================================
--- remote-utils.c (revision 544)
+++ remote-utils.c (working copy)
@@ -36,6 +36,7 @@
#include <sys/time.h>
#include <unistd.h>
#include <arpa/inet.h>
+#include <sys/stat.h>

#ifndef HAVE_SOCKLEN_T
typedef int socklen_t;
@@ -68,10 +69,24 @@ void
remote_open (char *name)
{
int save_fcntl_flags;
-
- if (!strchr (name, ':'))
+ char *port_str;
+
+ port_str = strchr (name, ':');
+
+ /* if name is not of kind "HOST:PORT" it must be tty device. */
+ if (!port_str)
{
- remote_desc = open (name, O_RDWR);
+ struct stat status;
+ int stat_result;
+ remote_desc = -1;
+
+ /* Open only character device. */
+ stat_result = stat(name, &status);
+ if (!stat_result && S_ISCHR(status.st_mode))
+ {
+ remote_desc = open (name, O_RDWR);
+ }
+
if (remote_desc < 0)
perror_with_name ("Could not open remote device");

@@ -123,14 +138,11 @@ remote_open (char *name)
}
else
{
- char *port_str;
int port;
struct sockaddr_in sockaddr;
socklen_t tmp;
int tmp_desc;

- port_str = strchr (name, ':');
-
port = atoi (port_str + 1);

tmp_desc = socket (PF_INET, SOCK_STREAM, 0);
@@ -650,7 +662,7 @@ prepare_resume_reply (char *buf, char st
CORE_ADDR addr;
int i;

- strncpy (buf, "watch:", 6);
+ buf = strncpy (buf, "watch:", 6);
buf += 6;

addr = (*the_target->stopped_data_address) ();