Re: store_open() unforgiving in bootstrap fs

[John Tobey]

On Mon, Nov 26, 2001 at 06:48:42AM -0500, Roland McGrath wrote:
> > The crash came in file_name_lookup() presumably because there is no
> > working directory port yet.  
> 
> Don't presume, debug!  There is no reason why file_name_lookup should ever
> produce a crash (unless given a bad string argument), and if it does then
> that is the bug (in libc).

I have made a little project of extracting the stack trace.  Here is
my proposed (untested!) patch:

2001-11-26  John Tobey  <jtobey@john-edwin-tobey.org>

        * hurd/hurdinit.c (_hurd_ports_use): Avoid a crash if _hurd_ports
        is null, e.g., in bootstrap filesystems.


Index: hurd/hurdinit.c
===================================================================
RCS file: /cvs/glibc/libc/hurd/hurdinit.c,v
retrieving revision 1.49
diff -u -r1.49 hurdinit.c
--- hurdinit.c  2001/07/06 04:54:47     1.49
+++ hurdinit.c  2001/11/26 23:19:41
@@ -39,6 +39,8 @@
 error_t
 _hurd_ports_use (int which, error_t (*operate) (mach_port_t))
 {
+  if (_hurd_ports == NULL)
+    return ENOENT;
   return HURD_PORT_USE (&_hurd_ports[which], (*operate) (port));
 }
 
END OF PATCH.


Here is the analysis, wherein I manually emulate a debugger: (Needless
to say, I aim to get GDB running under Mach OTOP ASAP.)

EXC_BAD_ACCESS in __spin_try_lock (0)
glibc/sysdeps/mach/i386/machine-lock.h:52
 _EXTERN_INLINE int
 __spin_try_lock (__spin_lock_t *__lock)
 {
   register int __locked;
>  __asm__ __volatile ("xchgl %0, %1"
                       : "=&r" (__locked), "=m" (*__lock) : "0" (1));
   return !__locked;
 }

called from __spin_lock (0)
glibc/mach/lock-intern.h:46
 _EXTERN_INLINE void
 __spin_lock (__spin_lock_t *__lock)
 {
>  if (! __spin_try_lock (__lock))
     __spin_lock_solid (__lock);
 }

called from _hurd_port_get (0, 0x1f90c)
glibc/hurd/hurd/port.h:103
 _HURD_PORT_H_EXTERN_INLINE mach_port_t
 _hurd_port_get (struct hurd_port *port,
                 struct hurd_userlink *link)
 {
   mach_port_t result;
   HURD_CRITICAL_BEGIN;
>  __spin_lock (&port->lock);
   result = _hurd_port_locked_get (port, link);
   HURD_CRITICAL_END;
   return result;
 }

called from HURD_PORT_USE(0, (*operate) (port))
glibc/hurd/hurd/port.h:51
 #define        HURD_PORT_USE(portcell, expr)                         \
   ({ struct hurd_port *const __p = (portcell);                       \
      struct hurd_userlink __link;                                    \
>     const mach_port_t port = _hurd_port_get (__p, &__link);         \
      __typeof(expr) __result = (expr);                               \
      _hurd_port_free (__p, &__link, port);                           \
      __result; })

called from _hurd_ports_use (INIT_PORT_CWDIR, 0x1f95c)
glibc/hurd/hurdinit.c:4
 error_t
 _hurd_ports_use (int which, error_t (*operate) (mach_port_t))
 {
>  return HURD_PORT_USE (&_hurd_ports[which], (*operate) (port));
 }

called from __hurd_file_name_lookup (_hurd_ports_use, __getdport,
        __dir_lookup, "hd0s5", O_RDWR, 0, 0x1fdb0)
glibc/hurd/hurdlookup.c:94
     }

>  err = (*use_init_port) (startport, &lookup_op);
   if (! err)
     err = __hurd_file_name_lookup_retry (use_init_port, get_dtable_port,

called from __file_name_lookup ("hd0s5", O_RDWR, 0)
glibc/hurd/hurdlookup.c:235
   error_t err;
   file_t result;

>  err = __hurd_file_name_lookup (&_hurd_ports_use, &__getdport, 0,
                                  file_name, flags, mode & ~_hurd_umask,
                                  &result);

called from store_open ("hd0s5", 0, &store_std_classes, 0x1fec8)
hurd/libstore/open.c:38
 {
   error_t err;
   int open_flags = (flags & STORE_HARD_READONLY) ? O_RDONLY : O_RDWR;
>  file_t node = file_name_lookup (name, open_flags, 0);

   if (node == MACH_PORT_NULL && !(flags & STORE_HARD_READONLY)
       && (errno == EACCES || errno == EROFS))

called from store_typed_open ("hd0s5", 0, &store_std_classes, 0x1fec8)
hurd/libstore/typed.c:63
       else
         /* Try opening NAME by querying it as a file instead.  */
>        return store_open (name, flags, classes, store);
     }

called from store_parsed_open::open ("hd0s5", 0x1fec8)
hurd/libstore/argp.c:186
               return (*type->open) (pfxed_name, flags, parsed->classes, store);
             }
           else
>            return (*type->open) (name, flags, parsed->classes, store);
         }
       else
         return EOPNOTSUPP;

called from store_parsed_open (0x811a430, 0, 0x1fec8)
hurd/libstore/argp.c:193
   if (num == 1)
>    return open (parsed->names, store);
   else if (num == 0)

called from diskfs_init_main (&startup_argp, 8,
        { "/jtobey/build/gnumach/boot/ext2fs.static",
          "--multiboot-command-line=root=hd0s5", "--host-priv-port=2",
          "--device-master-port=3", "-T", "typed", "hd0s5" },
        &store_parsed, 0x1ff20)
hurd/libdiskfs/init-main.c:43
   if (err)
     error (4, err, "init");

>  err = store_parsed_open (*store_parsed, diskfs_readonly ? STORE_READONLY : 0,
                            &store);
   if (err)
     error (3, err, "%s", diskfs_disk_name);

called from main.

-- 
John Tobey <jtobey@john-edwin-tobey.org>