Re: [RFC/mips] Problem with fetching/setting 32 bit registers

[Mark Kettenis <mark.kettenis@xs4all.nl>]

   Date: Thu, 24 Mar 2005 21:49:17 -0800
   From: Joel Brobecker <brobecker@adacore.com>

   Daniel,

   > This appears to be a bug in your native support, at least relative to
   > the rest of the MIPS port.

   Thanks to your help, I think I actually better what happens, now. It's a
   size issue: fpregsetp->fp_csr is 32bits long, while the value stored int
   the raw part of the regcache is 64 bits. So when we do the memcpy inside
   regcache_raw_supply(), we end up copying the FSR register value at the
   first 4 bytes of the regcache buffer, and then some other junk. When
   comes the time to transform this raw register into a cooked register, we
   naturally look at the last 4 bytes...

   I am currently testing the attached patch. Doesn't it look better?

Looks better but:

   Index: irix5-nat.c
   ===================================================================
   RCS file: /gnat.dev/cvs/Dev/gdb/gdb-6.3/gdb/irix5-nat.c,v
   retrieving revision 1.2
   diff -u -p -r1.2 irix5-nat.c
   --- irix5-nat.c	18 Nov 2004 10:49:32 -0000	1.2
   +++ irix5-nat.c	25 Mar 2005 05:46:56 -0000
   @@ -157,6 +157,7 @@ supply_fpregset (fpregset_t *fpregsetp)
    {
      int regi;
      static char zerobuf[32] = {0};
   +  char fsrbuf[64];

Looks like you're confused about bits and bytes.  Guess 8 is large
enough here ;-).

      /* FIXME, this is wrong for the N32 ABI which has 64 bit FP regs. */

Could you remove the redundant parenthesis here while you're at it:

   @@ -194,7 +203,20 @@ fill_fpregset (fpregset_t *fpregsetp, in

      if ((regno == -1)
	  || (regno == mips_regnum (current_gdbarch)->fp_control_status))
   -    fpregsetp->fp_csr = *(unsigned *) &deprecated_registers[DEPRECATED_REGISTER_BYTE (mips_regnum (current_gdbarch)->fp_control_status)];
   +    {
   +      char fsrbuf[64];
   +
   +    /* We can't fill the FSR register directly from the regcache,
   +       because there is a size issue: On one hand, fpregsetp->fp_csr
   +       is 32bits long, while the regcache expects a 64bits long buffer.
   +       So we use a buffer of the correct size and copy the register
   +       value from that buffer.  */
   +      regcache_raw_read (current_regcache,
   +                         mips_regnum (current_gdbarch)->fp_control_status,
   +                         fsrbuf);
   +
   +      memcpy (&fpregsetp->fp_csr, fsrbuf + 4, 4);
   +    }
    }