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

Joel Brobecker
2005-03-25T05:49:27Z

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?

Thanks,
--
Joel

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];

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

@@ -164,9 +165,17 @@ supply_fpregset (fpregset_t *fpregsetp)
regcache_raw_supply (current_regcache, FP0_REGNUM + regi,
(char *) &fpregsetp->fp_r.fp_regs[regi]);

+ /* We can't supply the FSR register directly to the regcache,
+ because there is a size issue: On one hand, fpregsetp->fp_csr
+ is 32bits long, while the regcache expects a 64bits long value.
+ So we use a buffer of the correct size and copy into it the register
+ value at the proper location. */
+ memset (fsrbuf, 0, 4);
+ memcpy (fsrbuf + 4, &fpregsetp->fp_csr, 4);
+
regcache_raw_supply (current_regcache,
mips_regnum (current_gdbarch)->fp_control_status,
- (char *) &fpregsetp->fp_csr);
+ fsrbuf);

/* FIXME: how can we supply FCRIR? SGI doesn't tell us. */
regcache_raw_supply (current_regcache,
@@ -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);
+ }
}