Add support for catching system calls to native FreeBSD targets.

All platforms on FreeBSD use a shared system call table, so use a
single XML file to describe the system calls available on each FreeBSD
platform.

Recent versions of FreeBSD include the identifier of the current
system call when reporting a system call entry or exit event in the
ptrace_lwpinfo structure obtained via PT_LWPINFO in fbsd_wait.  As
such, FreeBSD native targets do not use the gdbarch method to fetch
the system call code.  In addition, FreeBSD register sets fetched via
ptrace do not include an equivalent of 'orig_rax' (on amd64 for
example), so the system call code cannot be extracted from the
available registers during a system call exit.  However, GDB assumes
that system call catch points are not supported if the gdbarch method
is not present.  As a workaround, FreeBSD ABIs install a dummy gdbarch
method that throws an internal_error if it is ever invoked.

gdb/ChangeLog:

	* configure.ac: Check for support for system call LWP fields on
	FreeBSD.
	* config.in, configure: Rebuild.
	* data-directory/Makefile.in (SYSCALLS_FILES): Add freebsd.xml.
	* fbsd-nat.c (fbsd_wait) [HAVE_STRUCT_PTRACE_LWPINFO_PL_SYSCALL_CODE]:
	Report system call events.
	[HAVE_STRUCT_PTRACE_LWPINFO_PL_SYSCALL_CODE]
	(fbsd_set_syscall_catchpoint): New function.
	(fbsd_nat_add_target) [HAVE_STRUCT_PTRACE_LWPINFO_PL_SYSCALL_CODE]:
	Set "to_set_syscall_catchpoint" to "fbsd_set_syscall_catchpoint".
	* fbsd-tdep.c: Include xml-syscall.h
	(fbsd_get_syscall_number): New function.
	(fbsd_init_abi): Set XML system call file name.
	Add "get_syscall_number" gdbarch method.
	* syscalls/freebsd.xml: New file.

1 files changed, 21 insertions, 0 deletions

diff --git a/gdb/fbsd-tdep.c b/gdb/fbsd-tdep.c
index e8f8605..4329f97 100644
--- a/gdb/fbsd-tdep.c
+++ b/gdb/fbsd-tdep.c
@@ -24,6 +24,7 @@
 #include "regcache.h"
 #include "regset.h"
 #include "gdbthread.h"
+#include "xml-syscall.h"
 
 #include "elf-bfd.h"
 #include "fbsd-tdep.h"
@@ -317,6 +318,22 @@ fbsd_print_auxv_entry (struct gdbarch *gdbarch, struct ui_file *file,
   fprint_auxv_entry (file, name, description, format, type, val);
 }
 
+/* Implement the "get_syscall_number" gdbarch method.  */
+
+static LONGEST
+fbsd_get_syscall_number (struct gdbarch *gdbarch,
+			 ptid_t ptid)
+{
+
+  /* FreeBSD doesn't use gdbarch_get_syscall_number since FreeBSD
+     native targets fetch the system call number from the
+     'pl_syscall_code' member of struct ptrace_lwpinfo in fbsd_wait.
+     However, system call catching requires this function to be
+     set.  */
+
+  internal_error (__FILE__, __LINE__, _("fbsd_get_sycall_number called"));
+}
+
 /* To be called from GDB_OSABI_FREEBSD_ELF handlers. */
 
 void
@@ -326,4 +343,8 @@ fbsd_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
   set_gdbarch_core_thread_name (gdbarch, fbsd_core_thread_name);
   set_gdbarch_make_corefile_notes (gdbarch, fbsd_make_corefile_notes);
   set_gdbarch_print_auxv_entry (gdbarch, fbsd_print_auxv_entry);
+
+  /* `catch syscall' */
+  set_xml_syscall_file_name (gdbarch, "syscalls/freebsd.xml");
+  set_gdbarch_get_syscall_number (gdbarch, fbsd_get_syscall_number);
 }