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

[John Baldwin <jhb@FreeBSD.org>]

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.  On the one hand this means that there is not an easy way to detect
if if the FIR register is the zero-filled dummy or the true FIR value.
However, it also means that there is no need to deal with multiple
layouts of 'struct fpreg'.  I've chosen to always treat the last register
in 'struct fpreg' as the FIR.  This means that process cores and
ptrace() on older kernels will report a FIR value of 0.  However, FreeBSD
doesn't currently ship a release image for FreeBSD/mips, and releases
prior to 12.0 assume soft-float, so I think this is a reasonable tradeoff
for simplicity.

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.
---
 gdb/ChangeLog        |  8 ++++++++
 gdb/mips-fbsd-nat.c  |  2 +-
 gdb/mips-fbsd-tdep.c | 41 ++++++++++++++++++++++++++++-------------
 3 files changed, 37 insertions(+), 14 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 263d57ff66..0e2a7b5833 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,11 @@
+2017-05-31  John Baldwin  <jhb@FreeBSD.org>
+
+	* 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.
+
 2017-05-31  Simon Marchi  <simon.marchi@ericsson.com>
 
 	* memattr.c (mem_info_command): Rename to ...
diff --git a/gdb/mips-fbsd-nat.c b/gdb/mips-fbsd-nat.c
index 53817d7cd7..c381186535 100644
--- a/gdb/mips-fbsd-nat.c
+++ b/gdb/mips-fbsd-nat.c
@@ -46,7 +46,7 @@ static bool
 getfpregs_supplies (struct gdbarch *gdbarch, int regnum)
 {
   return (regnum >= mips_regnum (gdbarch)->fp0
-	  && regnum < mips_regnum (gdbarch)->fp_implementation_revision);
+	  && regnum <= mips_regnum (gdbarch)->fp_implementation_revision);
 }
 
 /* Fetch register REGNUM from the inferior.  If REGNUM is -1, do this
diff --git a/gdb/mips-fbsd-tdep.c b/gdb/mips-fbsd-tdep.c
index 44b960d4d2..34a19b0ead 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 +73,21 @@ 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)
+    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 +117,21 @@ 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
-- 
2.11.0