Generate NT_PROCSTAT_{AUXV,VMMAP,PS_STRINGS} in FreeBSD coredumps

gcore generates NT_AUXV and NT_FILE notes for Linux targets.  On
FreeBSD auxv is stored in a NT_PROCSTAT_AUXV section, virtual memory
mappings are stored in a NT_PROCSTAT_VMMAP, and both are prefixed with
the struct size.  In addition, store a NT_PROCSTAT_PS_STRINGS note
saving the initial location of the argv[] and environment[] arrays.

gdb/ChangeLog:

	PR gdb/23105
	* fbsd-nat.c (fbsd_nat_target::xfer_partial): Add support for
	TARGET_OBJECT_FREEBSD_VMMAP and TARGET_OBJECT_FREEBSD_PS_STRINGS.
	* fbsd-tdep.c (fbsd_make_note_desc): New.
	(fbsd_make_corefile_notes): Write NT_PROCSTAT_AUXV,
	NT_PROCSTAT_VMMAP and NT_PROCSTAT_PS_STRINGS notes.
	* target.h (enum target_object) Add FreeBSD-specific
	TARGET_OBJECT_FREEBSD_VMMAP and TARGET_OBJECT_FREEBSD_PS_STRINGS.

4 files changed, 126 insertions, 0 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 410fbef..e6f44a3 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,14 @@
+2018-09-06  Simon Ser  <contact@emersion.fr>
+
+	PR gdb/23105
+	* fbsd-nat.c (fbsd_nat_target::xfer_partial): Add support for
+	TARGET_OBJECT_FREEBSD_VMMAP and TARGET_OBJECT_FREEBSD_PS_STRINGS.
+	* fbsd-tdep.c (fbsd_make_note_desc): New.
+	(fbsd_make_corefile_notes): Write NT_PROCSTAT_AUXV,
+	NT_PROCSTAT_VMMAP and NT_PROCSTAT_PS_STRINGS notes.
+	* target.h (enum target_object) Add FreeBSD-specific
+	TARGET_OBJECT_FREEBSD_VMMAP and TARGET_OBJECT_FREEBSD_PS_STRINGS.
+
 2018-09-06  Simon Marchi  <simon.marchi@ericsson.com>
 
 	* compile/compile-c.h (generate_c_for_variable_locations):
diff --git a/gdb/fbsd-nat.c b/gdb/fbsd-nat.c
index 115deac..a255318 100644
--- a/gdb/fbsd-nat.c
+++ b/gdb/fbsd-nat.c
@@ -751,6 +751,61 @@ fbsd_nat_target::xfer_partial (enum target_object object,
 	  }
 	return TARGET_XFER_E_IO;
       }
+    case TARGET_OBJECT_FREEBSD_VMMAP:
+    case TARGET_OBJECT_FREEBSD_PS_STRINGS:
+      {
+	gdb::byte_vector buf_storage;
+	gdb_byte *buf;
+	size_t buflen;
+	int mib[4];
+
+	int proc_target;
+	uint32_t struct_size;
+	switch (object)
+	  {
+	  case TARGET_OBJECT_FREEBSD_VMMAP:
+	    proc_target = KERN_PROC_VMMAP;
+	    struct_size = sizeof (struct kinfo_vmentry);
+	    break;
+	  case TARGET_OBJECT_FREEBSD_PS_STRINGS:
+	    proc_target = KERN_PROC_PS_STRINGS;
+	    struct_size = sizeof (void *);
+	    break;
+	  }
+
+	if (writebuf != NULL)
+	  return TARGET_XFER_E_IO;
+
+	mib[0] = CTL_KERN;
+	mib[1] = KERN_PROC;
+	mib[2] = proc_target;
+	mib[3] = pid;
+
+	if (sysctl (mib, 4, NULL, &buflen, NULL, 0) != 0)
+	  return TARGET_XFER_E_IO;
+	buflen += sizeof (struct_size);
+
+	if (offset >= buflen)
+	  {
+	    *xfered_len = 0;
+	    return TARGET_XFER_EOF;
+	  }
+
+	buf_storage.resize (buflen);
+	buf = buf_storage.data ();
+
+	memcpy (buf, &struct_size, sizeof (struct_size));
+	buflen -= sizeof (struct_size);
+	if (sysctl (mib, 4, buf + sizeof (struct_size), &buflen, NULL, 0) != 0)
+	  return TARGET_XFER_E_IO;
+	buflen += sizeof (struct_size);
+
+	if (buflen - offset < len)
+	  len = buflen - offset;
+	memcpy (readbuf, buf + offset, len);
+	*xfered_len = len;
+	return TARGET_XFER_OK;
+      }
     default:
       return inf_ptrace_target::xfer_partial (object, annex,
 					      readbuf, writebuf, offset,
diff --git a/gdb/fbsd-tdep.c b/gdb/fbsd-tdep.c
index 78d0c3d..ed43087 100644
--- a/gdb/fbsd-tdep.c
+++ b/gdb/fbsd-tdep.c
@@ -512,6 +512,28 @@ fbsd_corefile_thread (struct thread_info *info,
      args->note_size, args->stop_signal);
 }
 
+/* Return a byte_vector containing the contents of a core dump note
+   for the target object of type OBJECT.  If STRUCTSIZE is non-zero,
+   the data is prefixed with a 32-bit integer size to match the format
+   used in FreeBSD NT_PROCSTAT_* notes.  */
+
+static gdb::optional<gdb::byte_vector>
+fbsd_make_note_desc (enum target_object object, uint32_t structsize)
+{
+  gdb::optional<gdb::byte_vector> buf =
+    target_read_alloc (current_top_target (), object, NULL);
+  if (!buf || buf->empty ())
+    return {};
+
+  if (structsize == 0)
+    return buf;
+
+  gdb::byte_vector desc (sizeof (structsize) + buf->size ());
+  memcpy (desc.data (), &structsize, sizeof (structsize));
+  memcpy (desc.data () + sizeof (structsize), buf->data (), buf->size ());
+  return desc;
+}
+
 /* Create appropriate note sections for a corefile, returning them in
    allocated memory.  */
 
@@ -586,6 +608,40 @@ fbsd_make_corefile_notes (struct gdbarch *gdbarch, bfd *obfd, int *note_size)
 
   note_data = thread_args.note_data;
 
+  /* Auxiliary vector.  */
+  uint32_t structsize = gdbarch_ptr_bit (gdbarch) / 4; /* Elf_Auxinfo  */
+  gdb::optional<gdb::byte_vector> note_desc =
+    fbsd_make_note_desc (TARGET_OBJECT_AUXV, structsize);
+  if (note_desc && !note_desc->empty ())
+    {
+      note_data = elfcore_write_note (obfd, note_data, note_size, "FreeBSD",
+				      NT_FREEBSD_PROCSTAT_AUXV,
+				      note_desc->data (), note_desc->size ());
+      if (!note_data)
+	return NULL;
+    }
+
+  /* Virtual memory mappings.  */
+  note_desc = fbsd_make_note_desc (TARGET_OBJECT_FREEBSD_VMMAP, 0);
+  if (note_desc && !note_desc->empty ())
+    {
+      note_data = elfcore_write_note (obfd, note_data, note_size, "FreeBSD",
+				      NT_FREEBSD_PROCSTAT_VMMAP,
+				      note_desc->data (), note_desc->size ());
+      if (!note_data)
+	return NULL;
+    }
+
+  note_desc = fbsd_make_note_desc (TARGET_OBJECT_FREEBSD_PS_STRINGS, 0);
+  if (note_desc && !note_desc->empty ())
+    {
+      note_data = elfcore_write_note (obfd, note_data, note_size, "FreeBSD",
+				      NT_FREEBSD_PROCSTAT_PSSTRINGS,
+				      note_desc->data (), note_desc->size ());
+      if (!note_data)
+	return NULL;
+    }
+
   return note_data;
 }
 
diff --git a/gdb/target.h b/gdb/target.h
index 229b5d0..a3000c8 100644
--- a/gdb/target.h
+++ b/gdb/target.h
@@ -202,6 +202,10 @@ enum target_object
      of the process ID of the process in question, in hexadecimal
      format.  */
   TARGET_OBJECT_EXEC_FILE,
+  /* FreeBSD virtual memory mappings.  */
+  TARGET_OBJECT_FREEBSD_VMMAP,
+  /* FreeBSD process strings.  */
+  TARGET_OBJECT_FREEBSD_PS_STRINGS,
   /* Possible future objects: TARGET_OBJECT_FILE, ...  */
 };