fbsd-nat: Add helper routines for register sets using PT_[G]SETREGSET.

FreeBSD's kernel has recently added PT_GETREGSET and PT_SETREGSET
operations to fetch a register set named by an ELF note type.  These
helper routines provide helpers to check for a register set's
existence, fetch registers for a register set, and store registers to
a register set.

gdb/fbsd-nat.c

@@ -49,6 +49,11 @@
 
 #include <list>
 
+#ifndef PT_GETREGSET
+#define	PT_GETREGSET	42	/* Get a target register set */
+#define	PT_SETREGSET	43	/* Set a target register set */
+#endif
+
 /* Return the name of a file that can be opened to get the symbols for
    the child process identified by PID.  */
 
@@ -1774,6 +1779,76 @@ fbsd_nat_target::store_register_set (struct regcache *regcache, int regnum,
 
 /* See fbsd-nat.h.  */
 
+bool
+fbsd_nat_target::have_regset (ptid_t ptid, int note)
+{
+  pid_t pid = get_ptrace_pid (ptid);
+  struct iovec iov;
+
+  iov.iov_base = nullptr;
+  iov.iov_len = 0;
+  if (ptrace (PT_GETREGSET, pid, (PTRACE_TYPE_ARG3) &iov, note) == -1)
+    return 0;
+  return iov.iov_len;
+}
+
+/* See fbsd-nat.h.  */
+
+bool
+fbsd_nat_target::fetch_regset (struct regcache *regcache, int regnum, int note,
+			       const struct regset *regset, void *regs,
+			       size_t size)
+{
+  const struct regcache_map_entry *map
+    = (const struct regcache_map_entry *) regset->regmap;
+  pid_t pid = get_ptrace_pid (regcache->ptid ());
+
+  if (regnum == -1 || regcache_map_supplies (map, regnum, regcache->arch(),
+					     size))
+    {
+      struct iovec iov;
+
+      iov.iov_base = regs;
+      iov.iov_len = size;
+      if (ptrace (PT_GETREGSET, pid, (PTRACE_TYPE_ARG3) &iov, note) == -1)
+	perror_with_name (_("Couldn't get registers"));
+
+      regcache->supply_regset (regset, regnum, regs, size);
+      return true;
+    }
+  return false;
+}
+
+bool
+fbsd_nat_target::store_regset (struct regcache *regcache, int regnum, int note,
+			       const struct regset *regset, void *regs,
+			       size_t size)
+{
+  const struct regcache_map_entry *map
+    = (const struct regcache_map_entry *) regset->regmap;
+  pid_t pid = get_ptrace_pid (regcache->ptid ());
+
+  if (regnum == -1 || regcache_map_supplies (map, regnum, regcache->arch(),
+					     size))
+    {
+      struct iovec iov;
+
+      iov.iov_base = regs;
+      iov.iov_len = size;
+      if (ptrace (PT_GETREGSET, pid, (PTRACE_TYPE_ARG3) &iov, note) == -1)
+	perror_with_name (_("Couldn't get registers"));
+
+      regcache->collect_regset (regset, regnum, regs, size);
+
+      if (ptrace (PT_SETREGSET, pid, (PTRACE_TYPE_ARG3) &iov, note) == -1)
+	perror_with_name (_("Couldn't write registers"));
+      return true;
+    }
+  return false;
+}
+
+/* See fbsd-nat.h.  */
+
 bool
 fbsd_nat_get_siginfo (ptid_t ptid, siginfo_t *siginfo)
 {

gdb/fbsd-nat.h

@@ -151,6 +151,17 @@ private:
   bool store_register_set (struct regcache *regcache, int regnum, int fetch_op,
 			   int store_op, const struct regset *regset,
 			   void *regs, size_t size);
+
+  /* Helper routines which use PT_GETREGSET and PT_SETREGSET for the
+     specified NOTE instead of regset-specific fetch and store
+     ops.  */
+
+  bool fetch_regset (struct regcache *regcache, int regnum, int note,
+		     const struct regset *regset, void *regs, size_t size);
+
+  bool store_regset (struct regcache *regcache, int regnum, int note,
+		     const struct regset *regset, void *regs, size_t size);
+
 protected:
   /* Wrapper versions of the above helpers which accept a register set
      type such as 'struct reg' or 'struct fpreg'.  */
@@ -172,6 +183,33 @@ protected:
     return store_register_set (regcache, regnum, fetch_op, store_op, regset,
 			       &regs, sizeof (regs));
   }
+
+  /* Helper routine for use in read_description in subclasses.  This
+     routine checks if the register set for the specified NOTE is
+     present for a given PTID.  If the register set is present, the
+     the size of the register set is returned.  If the register set is
+     not present, zero is returned.  */
+
+  bool have_regset (ptid_t ptid, int note);
+
+  /* Wrapper versions of the PT_GETREGSET and PT_REGSET helpers which
+     accept a register set type.  */
+
+  template <class Regset>
+  bool fetch_regset (struct regcache *regcache, int regnum, int note,
+		     const struct regset *regset)
+  {
+    Regset regs;
+    return fetch_regset (regcache, regnum, note, regset, &regs, sizeof (regs));
+  }
+
+  template <class Regset>
+  bool store_regset (struct regcache *regcache, int regnum, int note,
+		     const struct regset *regset)
+  {
+    Regset regs;
+    return store_regset (regcache, regnum, note, regset, &regs, sizeof (regs));
+  }
 };
 
 /* Fetch the signal information for PTID and store it in *SIGINFO.