Look for FIR in the last FreeBSD/mips floating-point register.

FreeBSD/mips kernels were recently changed to include the floating
point implementation revision register in the floating point register
set exported in process cores and via ptrace() (r318067).  This change
will first ship in FreeBSD 12.0 when it is eventually released.  The
space used to hold FIR was previously reserved in 'struct fpreg' as a
zero-filled dummy for padding, so 'struct fpreg' has not changed in
size.  Since FIR should be non-zero on all MIPS processors supported
by FreeBSD, ignore a value of 0 from 'struct fpreg' and only report
non-zero values as a valid FIR register.

gdb/ChangeLog:

	* mips-fbsd-nat.c (getfpregs_supplies): Return true for FIR.
	* mips-fbsd-tdep.c (mips_fbsd_supply_fpregs): Split supply of FSR
	out of loop and add supply of FIR.
	(mips_fbsd_collect_fpregs): Split collect of FSR out of loop and
	add collect of FIR.

1 files changed, 30 insertions, 13 deletions

diff --git a/gdb/mips-fbsd-tdep.c b/gdb/mips-fbsd-tdep.c
index 44b960d..feb18e1 100644
--- a/gdb/mips-fbsd-tdep.c
+++ b/gdb/mips-fbsd-tdep.c
@@ -39,7 +39,8 @@
 
 /* Number of registers in `struct fpreg' from <machine/reg.h>.  The
    first 32 hold floating point registers.  33 holds the FSR.  The
-   34th is a dummy for padding.  */
+   34th holds FIR on FreeBSD 12.0 and newer kernels.  On older kernels
+   it was a zero-filled dummy for padding.  */
 #define MIPS_FBSD_NUM_FPREGS	34
 
 /* Supply a single register.  The register size might not match, so use
@@ -72,14 +73,23 @@ mips_fbsd_supply_fpregs (struct regcache *regcache, int regnum,
 {
   struct gdbarch *gdbarch = get_regcache_arch (regcache);
   const gdb_byte *regs = (const gdb_byte *) fpregs;
-  int i, fp0num, fsrnum;
+  int i, fp0num;
 
   fp0num = mips_regnum (gdbarch)->fp0;
-  fsrnum = mips_regnum (gdbarch)->fp_control_status;
-  for (i = fp0num; i <= fsrnum; i++)
-    if (regnum == i || regnum == -1)
-      mips_fbsd_supply_reg (regcache, i,
-			    regs + (i - fp0num) * regsize, regsize);
+  for (i = 0; i <= 32; i++)
+    if (regnum == fp0num + i || regnum == -1)
+      mips_fbsd_supply_reg (regcache, fp0num + i,
+			    regs + i * regsize, regsize);
+  if (regnum == mips_regnum (gdbarch)->fp_control_status || regnum == -1)
+    mips_fbsd_supply_reg (regcache, mips_regnum (gdbarch)->fp_control_status,
+			  regs + 32 * regsize, regsize);
+  if ((regnum == mips_regnum (gdbarch)->fp_implementation_revision
+       || regnum == -1)
+      && extract_unsigned_integer (regs + 33 * regsize, regsize,
+				   gdbarch_byte_order (gdbarch)) != 0)
+    mips_fbsd_supply_reg (regcache,
+			  mips_regnum (gdbarch)->fp_implementation_revision,
+			  regs + 33 * regsize, regsize);
 }
 
 /* Supply the general-purpose registers stored in GREGS to REGCACHE.
@@ -109,14 +119,21 @@ mips_fbsd_collect_fpregs (const struct regcache *regcache, int regnum,
 {
   struct gdbarch *gdbarch = get_regcache_arch (regcache);
   gdb_byte *regs = (gdb_byte *) fpregs;
-  int i, fp0num, fsrnum;
+  int i, fp0num;
 
   fp0num = mips_regnum (gdbarch)->fp0;
-  fsrnum = mips_regnum (gdbarch)->fp_control_status;
-  for (i = fp0num; i <= fsrnum; i++)
-    if (regnum == i || regnum == -1)
-      mips_fbsd_collect_reg (regcache, i,
-			     regs + (i - fp0num) * regsize, regsize);
+  for (i = 0; i < 32; i++)
+    if (regnum == fp0num + i || regnum == -1)
+      mips_fbsd_collect_reg (regcache, fp0num + i,
+			     regs + i * regsize, regsize);
+  if (regnum == mips_regnum (gdbarch)->fp_control_status || regnum == -1)
+    mips_fbsd_collect_reg (regcache, mips_regnum (gdbarch)->fp_control_status,
+			   regs + 32 * regsize, regsize);
+  if (regnum == mips_regnum (gdbarch)->fp_implementation_revision
+      || regnum == -1)
+    mips_fbsd_collect_reg (regcache,
+			   mips_regnum (gdbarch)->fp_implementation_revision,
+			   regs + 33 * regsize, regsize);
 }
 
 /* Collect the general-purpose registers from REGCACHE and store them