[3/3] Use signal information to determine SIGTRAP type for FreeBSD.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index b8412304b6..50363d5e60 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,19 @@ 
+2018-02-28  John Baldwin  <jhb@FreeBSD.org>
+
+	* fbsd-nat.c: Include "inf-ptrace.h".
+	(USE_SIGTRAP_SIGINFO): Conditionally define.
+	[USE_SIGTRAP_SIGINFO] (fbsd_handle_debug_trap): New function.
+	(fbsd_wait) [USE_SIGTRAP_SIGINFO]: Call "fbsd_handle_debug_trap".
+	[USE_SIGTRAP_SIGINFO] (fbsd_stopped_by_sw_breakpoint): New
+	function.
+	[USE_SIGTRAP_SIGINFO] (fbsd_supports_stopped_by_sw_breakpoint):
+	Likewise.
+	[USE_SIGTRAP_SIGINFO] (fbsd_supports_stopped_by_hw_breakpoint):
+	Likewise.
+	(fbsd_nat_add_target) [USE_SIGTRAP_SIGINFO]: Set
+	"stopped_by_sw_breakpoint", "supports_stopped_by_sw_breakpoint",
+	"supports_stopped_by_hw_breakpoint" target methods.
+
 2018-02-28  John Baldwin  <jhb@FreeBSD.org>
 
 	* NEWS (Changes since GDB 8.1): Add "set/show debug fbsd-nat".
diff --git a/gdb/fbsd-nat.c b/gdb/fbsd-nat.c
index 2516ac5552..d36d4c9299 100644
--- a/gdb/fbsd-nat.c
+++ b/gdb/fbsd-nat.c
@@ -26,6 +26,7 @@ 
 #include "gdbcmd.h"
 #include "gdbthread.h"
 #include "gdb_wait.h"
+#include "inf-ptrace.h"
 #include <sys/types.h>
 #include <sys/procfs.h>
 #include <sys/ptrace.h>
@@ -45,6 +46,16 @@ 
 
 #include <list>
 
+#ifdef TRAP_BRKPT
+/*
+ * MIPS does not set si_code for SIGTRAP.  sparc64 reports
+ * non-standard values in si_code for SIGTRAP.
+ */
+#if !defined(__mips__) && !defined(__sparc64__)
+#define	USE_SIGTRAP_SIGINFO
+#endif
+#endif
+
 /* Return the name of a file that can be opened to get the symbols for
    the child process identified by PID.  */
 
@@ -1187,6 +1198,56 @@  fbsd_resume (struct target_ops *ops,
   super_resume (ops, ptid, step, signo);
 }
 
+#ifdef USE_SIGTRAP_SIGINFO
+/* Handle breakpoint and trace traps reported via SIGTRAP.  If the
+   trap was a breakpoint or trace trap that should be reported to the
+   core, return true.  */
+
+static bool
+fbsd_handle_debug_trap (struct target_ops *ops, ptid_t ptid,
+			const struct ptrace_lwpinfo &pl)
+{
+
+  /* Ignore traps without valid siginfo or for signals other than
+     SIGTRAP.  */
+  if (! (pl.pl_flags & PL_FLAG_SI) || pl.pl_siginfo.si_signo != SIGTRAP)
+    return false;
+
+  /* Trace traps are either a single step or a hardware watchpoint or
+     breakpoint.  */
+  if (pl.pl_siginfo.si_code == TRAP_TRACE)
+    {
+      if (debug_fbsd_nat)
+	fprintf_unfiltered (gdb_stdlog,
+			    "FNAT: trace trap for LWP %ld\n", ptid.lwp ());
+      return true;
+    }
+
+  if (pl.pl_siginfo.si_code == TRAP_BRKPT)
+    {
+      /* Fixup PC for the software breakpoint.  */
+      struct regcache *regcache = get_thread_regcache (ptid);
+      struct gdbarch *gdbarch = regcache->arch ();
+      int decr_pc = gdbarch_decr_pc_after_break (gdbarch);
+
+      if (debug_fbsd_nat)
+	fprintf_unfiltered (gdb_stdlog,
+			    "FNAT: sw breakpoint trap for LWP %ld\n",
+			    ptid.lwp ());
+      if (decr_pc != 0)
+	{
+	  CORE_ADDR pc;
+
+	  pc = regcache_read_pc (regcache);
+	  regcache_write_pc (regcache, pc - decr_pc);
+	}
+      return true;
+    }
+
+  return false;
+}
+#endif
+
 /* Wait for the child specified by PTID to do something.  Return the
    process ID of the child, or MINUS_ONE_PTID in case of error; store
    the status in *OURSTATUS.  */
@@ -1372,6 +1433,13 @@  fbsd_wait (struct target_ops *ops,
 	    }
 #endif
 
+#ifdef USE_SIGTRAP_SIGINFO
+	  if (fbsd_handle_debug_trap (ops, wptid, pl))
+	    {
+	      return wptid;
+	    }
+#endif
+
 	  /* Note that PL_FLAG_SCE is set for any event reported while
 	     a thread is executing a system call in the kernel.  In
 	     particular, signals that interrupt a sleep in a system
@@ -1410,6 +1478,41 @@  fbsd_wait (struct target_ops *ops,
     }
 }
 
+#ifdef USE_SIGTRAP_SIGINFO
+/* Implement the "to_stopped_by_sw_breakpoint" target_ops method.  */
+
+static int
+fbsd_stopped_by_sw_breakpoint (struct target_ops *ops)
+{
+  struct ptrace_lwpinfo pl;
+
+  if (ptrace (PT_LWPINFO, get_ptrace_pid (inferior_ptid), (caddr_t) &pl,
+	      sizeof pl) == -1)
+    return 0;
+
+  return (pl.pl_flags & PL_FLAG_SI) && pl.pl_siginfo.si_signo == SIGTRAP
+    && pl.pl_siginfo.si_code == TRAP_BRKPT;
+}
+
+/* Implement the "to_supports_stopped_by_sw_breakpoint" target_ops
+   method.  */
+
+static int
+fbsd_supports_stopped_by_sw_breakpoint (struct target_ops *ops)
+{
+  return 1;
+}
+
+/* Implement the "to_supports_stopped_by_hw_breakpoint" target_ops
+   method.  */
+
+static int
+fbsd_supports_stopped_by_hw_breakpoint (struct target_ops *ops)
+{
+  return ops->to_stopped_by_hw_breakpoint != NULL;
+}
+#endif
+
 #ifdef TDP_RFPPWAIT
 /* Target hook for follow_fork.  On entry and at return inferior_ptid is
    the ptid of the followed inferior.  */
@@ -1560,6 +1663,13 @@  fbsd_nat_add_target (struct target_ops *t)
   t->to_wait = fbsd_wait;
   t->to_post_startup_inferior = fbsd_post_startup_inferior;
   t->to_post_attach = fbsd_post_attach;
+#ifdef USE_SIGTRAP_SIGINFO
+  t->to_stopped_by_sw_breakpoint = fbsd_stopped_by_sw_breakpoint;
+  t->to_supports_stopped_by_sw_breakpoint =
+    fbsd_supports_stopped_by_sw_breakpoint;
+  t->to_supports_stopped_by_hw_breakpoint =
+    fbsd_supports_stopped_by_hw_breakpoint;
+#endif
 #ifdef TDP_RFPPWAIT
   t->to_follow_fork = fbsd_follow_fork;
   t->to_insert_fork_catchpoint = fbsd_insert_fork_catchpoint;