[PATCH] Generate NT_PROCSTAT_{AUXV,VMMAP} in FreeBSD coredumps

[Simon Ser <contact@emersion.fr>]

gcore generates NT_AUXV and NT_FILE notes for Linux targets. On
FreeBSD auxv is stored in a NT_PROCSTAT_AUXV section, file mappings
are stored in a NT_PROCSTAT_VMMAP and both are prefixed with the
struct size.

2018-07-11  Simon Ser  <contact@emersion.fr>
        * fbsd-tdep.c (fbsd_make_corefile_notes): write NT_PROCSTAT_AUXV
        and NT_PROCSTAT_VMMAP notes

---

This is an improvement of my v2 patch [1]. Thanks John for your review!

Changes from v2 to v3:
- Use NT_FREEBSD_PROCSTAT_* enums instead or re-defining these
- Simplify Elf_Auxinfo struct size expression
- Also write NT_PROCSTAT_VMMAP notes
- Directly use sysctl as this will allow to support more notes in
  the future (all of these work in the same way)
- Use gdb::unique_xmalloc_ptr()

[1]: https://sourceware.org/ml/gdb-patches/2018-07/msg00267.html

 gdb/fbsd-tdep.c | 58 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 58 insertions(+)

diff --git a/gdb/fbsd-tdep.c b/gdb/fbsd-tdep.c
index 9cea0098..e335ee6f 100644
--- a/gdb/fbsd-tdep.c
+++ b/gdb/fbsd-tdep.c
@@ -25,6 +25,9 @@
 #include "regset.h"
 #include "gdbthread.h"
 #include "xml-syscall.h"
+#include <sys/user.h>
+#include <sys/sysctl.h>
+#include <sys/types.h>
 
 #include "elf-bfd.h"
 #include "fbsd-tdep.h"
@@ -512,6 +515,32 @@ fbsd_corefile_thread (struct thread_info *info,
      args->note_size, args->stop_signal);
 }
 
+static gdb::unique_xmalloc_ptr<char>
+procstat_sysctl (pid_t pid, int what, size_t structsz, size_t *sizep)
+{
+  int name[4];
+  name[0] = CTL_KERN;
+  name[1] = KERN_PROC;
+  name[2] = what;
+  name[3] = pid;
+  size_t len = 0;
+  if (sysctl (name, 4, NULL, &len, NULL, 0) == -1)
+    return NULL;
+ 
+  int structsize = structsz;
+  gdb::unique_xmalloc_ptr<char> buf
+    ((char *) xmalloc (sizeof (structsize) + len));
+  if (buf == NULL)
+    return NULL;
+  memcpy (buf.get (), &structsize, sizeof (structsize));
+  void *p = buf.get () + sizeof (structsize);
+  if (sysctl (name, 4, p, &len, NULL, 0) == -1)
+    return NULL;
+
+  *sizep = sizeof (structsize) + len;
+  return buf;
+}
+
 /* Create appropriate note sections for a corefile, returning them in
    allocated memory.  */
 
@@ -586,6 +615,35 @@ fbsd_make_corefile_notes (struct gdbarch *gdbarch, bfd *obfd, int *note_size)
 
   note_data = thread_args.note_data;
 
+  pid_t pid = inferior_ptid.pid ();
+
+  /* Auxillary vector.  */
+  size_t auxinfo_size = gdbarch_addr_bit (gdbarch) / 4; /* Elf_Auxinfo */
+  size_t note_desc_size;
+  gdb::unique_xmalloc_ptr<char> note_desc;
+  note_desc = procstat_sysctl (pid, KERN_PROC_AUXV, auxinfo_size,
+                               &note_desc_size);
+  if (note_desc != NULL)
+    {
+      note_data = elfcore_write_note (obfd, note_data, note_size,
+                                      "FreeBSD", NT_FREEBSD_PROCSTAT_AUXV,
+                                      note_desc.get (), note_desc_size);
+      if (!note_data)
+        return NULL;
+    }
+
+  /* File mappings */
+  note_desc = procstat_sysctl (pid, KERN_PROC_VMMAP,
+                               sizeof(struct kinfo_vmentry), &note_desc_size);
+  if (note_desc != NULL)
+    {
+      note_data = elfcore_write_note (obfd, note_data, note_size,
+                                      "FreeBSD", NT_FREEBSD_PROCSTAT_VMMAP,
+                                      note_desc.get (), note_desc_size);
+      if (!note_data)
+        return NULL;
+    }
+
   return note_data;
 }
 
-- 
2.18.0