Add a new gdbarch method to fetch signal information from core files.

Previously the core_xfer_partial method used core_get_siginfo to handle
TARGET_OBJECT_SIGNAL_INFO requests.  However, core_get_siginfo looked for
Linux-specific sections in the core file.  To support fetching siginfo
from cores on other systems, add a new gdbarch method (`core_xfer_siginfo`)
and move the body of the existing core_get_siginfo into a
linux_core_xfer_siginfo implementation of this method in linux-tdep.c.

gdb/ChangeLog:

	* corelow.c (get_core_siginfo): Remove.
	(core_xfer_partial): Use the gdbarch "core_xfer_siginfo" method
	instead of get_core_siginfo.
	* gdbarch.sh (core_xfer_siginfo): New gdbarch callback.
	* gdbarch.h: Re-generate.
	* gdbarch.c: Re-generate.
	* linux-tdep.c (linux_core_xfer_siginfo): New.
	(linux_init_abi): Install gdbarch "core_xfer_siginfo" method.

gdb/ChangeLog

@@ -1,3 +1,14 @@
+2017-07-07  John Baldwin  <jhb@FreeBSD.org>
+
+	* corelow.c (get_core_siginfo): Remove.
+	(core_xfer_partial): Use the gdbarch "core_xfer_siginfo" method
+	instead of get_core_siginfo.
+	* gdbarch.sh (core_xfer_siginfo): New gdbarch callback.
+	* gdbarch.h: Re-generate.
+	* gdbarch.c: Re-generate.
+	* linux-tdep.c (linux_core_xfer_siginfo): New.
+	(linux_init_abi): Install gdbarch "core_xfer_siginfo" method.
+
 2017-07-07  John Baldwin  <jhb@FreeBSD.org>
 
 	* corelow.c (thread_section_name): Move to ...

gdb/corelow.c

@@ -668,25 +668,6 @@ add_to_spuid_list (bfd *abfd, asection *asect, void *list_p)
   list->pos += 4;
 }
 
-/* Read siginfo data from the core, if possible.  Returns -1 on
-   failure.  Otherwise, returns the number of bytes read.  ABFD is the
-   core file's BFD; READBUF, OFFSET, and LEN are all as specified by
-   the to_xfer_partial interface.  */
-
-static LONGEST
-get_core_siginfo (bfd *abfd, gdb_byte *readbuf, ULONGEST offset, ULONGEST len)
-{
-  thread_section_name section_name (".note.linuxcore.siginfo", inferior_ptid);
-  asection *section = bfd_get_section_by_name (abfd, section_name.c_str ());
-  if (section == NULL)
-    return -1;
-
-  if (!bfd_get_section_contents (abfd, section, readbuf, offset, len))
-    return -1;
-
-  return len;
-}
-
 static enum target_xfer_status
 core_xfer_partial (struct target_ops *ops, enum target_object object,
 		   const char *annex, gdb_byte *readbuf,
@@ -874,12 +855,20 @@ core_xfer_partial (struct target_ops *ops, enum target_object object,
     case TARGET_OBJECT_SIGNAL_INFO:
       if (readbuf)
 	{
-	  LONGEST l = get_core_siginfo (core_bfd, readbuf, offset, len);
+	  if (core_gdbarch
-
+	      && gdbarch_core_xfer_siginfo_p (core_gdbarch))
-	  if (l > 0)
 	    {
-	      *xfered_len = len;
+	      LONGEST l = gdbarch_core_xfer_siginfo  (core_gdbarch, readbuf,
-	      return TARGET_XFER_OK;
+						      offset, len);
+
+	      if (l >= 0)
+		{
+		  *xfered_len = l;
+		  if (l == 0)
+		    return TARGET_XFER_EOF;
+		  else
+		    return TARGET_XFER_OK;
+		}
 	    }
 	}
       return TARGET_XFER_E_IO;

gdb/gdbarch.c

@@ -287,6 +287,7 @@ struct gdbarch
   gdbarch_core_xfer_shared_libraries_aix_ftype *core_xfer_shared_libraries_aix;
   gdbarch_core_pid_to_str_ftype *core_pid_to_str;
   gdbarch_core_thread_name_ftype *core_thread_name;
+  gdbarch_core_xfer_siginfo_ftype *core_xfer_siginfo;
   const char * gcore_bfd_target;
   int vtable_function_descriptors;
   int vbit_in_delta;
@@ -646,6 +647,7 @@ verify_gdbarch (struct gdbarch *gdbarch)
   /* Skip verify of core_xfer_shared_libraries_aix, has predicate.  */
   /* Skip verify of core_pid_to_str, has predicate.  */
   /* Skip verify of core_thread_name, has predicate.  */
+  /* Skip verify of core_xfer_siginfo, has predicate.  */
   /* Skip verify of gcore_bfd_target, has predicate.  */
   /* Skip verify of vtable_function_descriptors, invalid_p == 0 */
   /* Skip verify of vbit_in_delta, invalid_p == 0 */
@@ -883,6 +885,12 @@ gdbarch_dump (struct gdbarch *gdbarch, struct ui_file *file)
   fprintf_unfiltered (file,
                       "gdbarch_dump: core_xfer_shared_libraries_aix = <%s>\n",
                       host_address_to_string (gdbarch->core_xfer_shared_libraries_aix));
+  fprintf_unfiltered (file,
+                      "gdbarch_dump: gdbarch_core_xfer_siginfo_p() = %d\n",
+                      gdbarch_core_xfer_siginfo_p (gdbarch));
+  fprintf_unfiltered (file,
+                      "gdbarch_dump: core_xfer_siginfo = <%s>\n",
+                      host_address_to_string (gdbarch->core_xfer_siginfo));
   fprintf_unfiltered (file,
                       "gdbarch_dump: decr_pc_after_break = %s\n",
                       core_addr_to_string_nz (gdbarch->decr_pc_after_break));
@@ -3796,6 +3804,30 @@ set_gdbarch_core_thread_name (struct gdbarch *gdbarch,
   gdbarch->core_thread_name = core_thread_name;
 }
 
+int
+gdbarch_core_xfer_siginfo_p (struct gdbarch *gdbarch)
+{
+  gdb_assert (gdbarch != NULL);
+  return gdbarch->core_xfer_siginfo != NULL;
+}
+
+LONGEST
+gdbarch_core_xfer_siginfo (struct gdbarch *gdbarch, gdb_byte *readbuf, ULONGEST offset, ULONGEST len)
+{
+  gdb_assert (gdbarch != NULL);
+  gdb_assert (gdbarch->core_xfer_siginfo != NULL);
+  if (gdbarch_debug >= 2)
+    fprintf_unfiltered (gdb_stdlog, "gdbarch_core_xfer_siginfo called\n");
+  return gdbarch->core_xfer_siginfo (gdbarch,  readbuf, offset, len);
+}
+
+void
+set_gdbarch_core_xfer_siginfo (struct gdbarch *gdbarch,
+                               gdbarch_core_xfer_siginfo_ftype core_xfer_siginfo)
+{
+  gdbarch->core_xfer_siginfo = core_xfer_siginfo;
+}
+
 int
 gdbarch_gcore_bfd_target_p (struct gdbarch *gdbarch)
 {

gdb/gdbarch.h

@@ -933,6 +933,16 @@ typedef const char * (gdbarch_core_thread_name_ftype) (struct gdbarch *gdbarch,
 extern const char * gdbarch_core_thread_name (struct gdbarch *gdbarch, struct thread_info *thr);
 extern void set_gdbarch_core_thread_name (struct gdbarch *gdbarch, gdbarch_core_thread_name_ftype *core_thread_name);
 
+/* Read offset OFFSET of TARGET_OBJECT_SIGNAL_INFO signal information
+   from core file into buffer READBUF with length LEN.  Return the number
+   of bytes read (zero indicates EOF, a negative value indicates failure). */
+
+extern int gdbarch_core_xfer_siginfo_p (struct gdbarch *gdbarch);
+
+typedef LONGEST (gdbarch_core_xfer_siginfo_ftype) (struct gdbarch *gdbarch, gdb_byte *readbuf, ULONGEST offset, ULONGEST len);
+extern LONGEST gdbarch_core_xfer_siginfo (struct gdbarch *gdbarch, gdb_byte *readbuf, ULONGEST offset, ULONGEST len);
+extern void set_gdbarch_core_xfer_siginfo (struct gdbarch *gdbarch, gdbarch_core_xfer_siginfo_ftype *core_xfer_siginfo);
+
 /* BFD target to use when generating a core file. */
 
 extern int gdbarch_gcore_bfd_target_p (struct gdbarch *gdbarch);

gdb/gdbarch.sh

@@ -755,6 +755,11 @@ M;const char *;core_pid_to_str;ptid_t ptid;ptid
 # How the core target extracts the name of a thread from a core file.
 M;const char *;core_thread_name;struct thread_info *thr;thr
 
+# Read offset OFFSET of TARGET_OBJECT_SIGNAL_INFO signal information
+# from core file into buffer READBUF with length LEN.  Return the number
+# of bytes read (zero indicates EOF, a negative value indicates failure).
+M;LONGEST;core_xfer_siginfo;gdb_byte *readbuf, ULONGEST offset, ULONGEST len; readbuf, offset, len
+
 # BFD target to use when generating a core file.
 V;const char *;gcore_bfd_target;;;0;0;;;pstring (gdbarch->gcore_bfd_target)
 

gdb/linux-tdep.c

@@ -1127,6 +1127,26 @@ linux_core_info_proc (struct gdbarch *gdbarch, const char *args,
     error (_("unable to handle request"));
 }
 
+/* Read siginfo data from the core, if possible.  Returns -1 on
+   failure.  Otherwise, returns the number of bytes read.  READBUF,
+   OFFSET, and LEN are all as specified by the to_xfer_partial
+   interface.  */
+
+static LONGEST
+linux_core_xfer_siginfo (struct gdbarch *gdbarch, gdb_byte *readbuf,
+			 ULONGEST offset, ULONGEST len)
+{
+  thread_section_name section_name (".note.linuxcore.siginfo", inferior_ptid);
+  asection *section = bfd_get_section_by_name (core_bfd, section_name.c_str ());
+  if (section == NULL)
+    return -1;
+
+  if (!bfd_get_section_contents (core_bfd, section, readbuf, offset, len))
+    return -1;
+
+  return len;
+}
+
 typedef int linux_find_memory_region_ftype (ULONGEST vaddr, ULONGEST size,
 					    ULONGEST offset, ULONGEST inode,
 					    int read, int write,
@@ -2516,6 +2536,7 @@ linux_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
   set_gdbarch_core_pid_to_str (gdbarch, linux_core_pid_to_str);
   set_gdbarch_info_proc (gdbarch, linux_info_proc);
   set_gdbarch_core_info_proc (gdbarch, linux_core_info_proc);
+  set_gdbarch_core_xfer_siginfo (gdbarch, linux_core_xfer_siginfo);
   set_gdbarch_find_memory_regions (gdbarch, linux_find_memory_regions);
   set_gdbarch_make_corefile_notes (gdbarch, linux_make_corefile_notes);
   set_gdbarch_has_shared_address_space (gdbarch,