Linux i387 fix

[Mark Kettenis <kettenis at wins dot uva dot nl>]

Hi Jim,

The current i386-linux.c:supply_fpregset() passes whatever is in the
reserved bits on to the GDB register file.  Since the coporocessor
seems to be initialized in a state where these reserved bits are
turned on (at least in non-fpu using threads, see
linux/arch/i386/kernel/ptrace.c) this means that `info float' and
`info all-registers' will print some funny numbers.  At the end of
this message you'll find a patch that fixes this.

I don't know if supply_xfpregs needs to be fixed too.  Depends on the
Cygnus-specific Linux kernel patch I guess.

Maybe we should make some changes to convert_to_fpregset() too, such
that it doesn't change the reserved bits in *FPREGSETP.  Right now it
overwrites those with the padding that's present in the GDB register
file.

Mark


1999-12-13  Mark Kettenis  <kettenis@gnu.org>

	* i386-linux-nat.c (supply_fpregset): Mask off the reserved bits
	in *FPREGSETP before storing the values in the GDB register file.


Index: gdb/i386-linux-nat.c
===================================================================
RCS file: /var/cvsroot/gdb/gdb/i386-linux-nat.c,v
retrieving revision 1.1.1.4
diff -u -r1.1.1.4 i386-linux-nat.c
--- gdb/i386-linux-nat.c	1999/12/13 21:10:21	1.1.1.4
+++ gdb/i386-linux-nat.c	1999/12/13 22:44:20
@@ -195,29 +195,36 @@
 void 
 supply_fpregset (fpregset_t *fpregsetp)
 {
+  long l;
   int i;
 
   /* Supply the floating-point registers.  */
   for (i = 0; i < 8; i++)
     supply_register (FP0_REGNUM + i, FPREGSET_T_FPREG_ADDR (fpregsetp, i));
 
-  supply_register (FCTRL_REGNUM, (char *) &fpregsetp->cwd);
-  supply_register (FSTAT_REGNUM, (char *) &fpregsetp->swd);
-  supply_register (FTAG_REGNUM,  (char *) &fpregsetp->twd);
+  /* We have to mask off the reserved bits in *FPREGSETP before
+     storing the values in the GDB register file, since the reserved
+     parts of the structure typically are initialized with all bits
+     turned on.  */
+#define supply(REGNO, MEMBER)					        \
+  l = fpregsetp->MEMBER & 0xffff;                                       \
+  supply_register (REGNO, (char *) &l)
+  
+  supply (FCTRL_REGNUM, cwd);
+  supply (FSTAT_REGNUM, swd);
+  supply (FTAG_REGNUM, twd);
   supply_register (FCOFF_REGNUM, (char *) &fpregsetp->fip);
-  supply_register (FDS_REGNUM,   (char *) &fpregsetp->fos);
+  supply (FDS_REGNUM, fos);
   supply_register (FDOFF_REGNUM, (char *) &fpregsetp->foo);
-  
-  /* Extract the code segment and opcode from the  "fcs" member.  */
-  {
-    long l;
 
-    l = fpregsetp->fcs & 0xffff;
-    supply_register (FCS_REGNUM, (char *) &l);
+#undef supply
+
+  /* Extract the code segment and opcode from the  "fcs" member.  */
+  l = fpregsetp->fcs & 0xffff;
+  supply_register (FCS_REGNUM, (char *) &l);
 
-    l = (fpregsetp->fcs >> 16) & ((1 << 11) - 1);
-    supply_register (FOP_REGNUM, (char *) &l);
-  }
+  l = (fpregsetp->fcs >> 16) & ((1 << 11) - 1);
+  supply_register (FOP_REGNUM, (char *) &l);
 }