[PATCH v2] Generate NT_PROCSTAT_{AUXV,VMMAP,PS_STRINGS} 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.

2018-07-16  Simon Ser  <contact@emersion.fr>
        * target.h (enum target_object): add FreeBSD-specific
        TARGET_OBJECT_FREEBSD_VMMAP and TARGET_OBJECT_FREEBSD_PS_STRINGS
        * 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_corefile_notes): write NT_PROCSTAT_AUXV,
        NT_PROCSTAT_VMMAP and NT_PROCSTAT_PS_STRINGS notes
---

This patch uses a different approach than the previous one: it adds two
FreeBSD-specific target objects. I chose this approach because there
were already some platform-specific target objects (e.g. for Darwin).
This should fix the issue John pointed out.

 gdb/fbsd-nat.c  | 17 ++++++++++++++-
 gdb/fbsd-tdep.c | 57 +++++++++++++++++++++++++++++++++++++++++++++++++
 gdb/target.h    |  4 ++++
 3 files changed, 77 insertions(+), 1 deletion(-)

diff --git a/gdb/fbsd-nat.c b/gdb/fbsd-nat.c
index 115deac0..2d056676 100644
--- a/gdb/fbsd-nat.c
+++ b/gdb/fbsd-nat.c
@@ -711,17 +711,32 @@ fbsd_nat_target::xfer_partial (enum target_object object,
       }
 #endif
     case TARGET_OBJECT_AUXV:
+    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;
+        switch (object) {
+        case TARGET_OBJECT_AUXV:
+          proc_target = KERN_PROC_AUXV;
+          break;
+        case TARGET_OBJECT_FREEBSD_VMMAP:
+          proc_target = KERN_PROC_VMMAP;
+          break;
+        case TARGET_OBJECT_FREEBSD_PS_STRINGS:
+          proc_target = KERN_PROC_PS_STRINGS;
+          break;
+        }
+
 	if (writebuf != NULL)
 	  return TARGET_XFER_E_IO;
 	mib[0] = CTL_KERN;
 	mib[1] = KERN_PROC;
-	mib[2] = KERN_PROC_AUXV;
+	mib[2] = proc_target;
 	mib[3] = pid;
 	if (offset == 0)
 	  {
diff --git a/gdb/fbsd-tdep.c b/gdb/fbsd-tdep.c
index 9cea0098..2ea76e66 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 +515,20 @@ fbsd_corefile_thread (struct thread_info *info,
      args->note_size, args->stop_signal);
 }
 
+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 {};
+
+  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 +603,46 @@ 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.  */
+  uint32_t structsize = gdbarch_addr_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;
+    }
+  
+  /* File mappings  */
+  structsize = 0x488; /* struct kinfo_vmentry  */
+  note_desc = fbsd_make_note_desc (TARGET_OBJECT_FREEBSD_VMMAP, structsize);
+  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;
+    }
+
+  structsize = gdbarch_addr_bit (gdbarch) / 8; /* void *  */
+  note_desc =
+    fbsd_make_note_desc (TARGET_OBJECT_FREEBSD_PS_STRINGS, structsize);
+  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 18c4a84c..83f1172c 100644
--- a/gdb/target.h
+++ b/gdb/target.h
@@ -203,6 +203,10 @@ enum target_object
      of the process ID of the process in question, in hexadecimal
      format.  */
   TARGET_OBJECT_EXEC_FILE,
+  /* FreeBSD file mappings  */
+  TARGET_OBJECT_FREEBSD_VMMAP,
+  /* FreeBSD process strings  */
+  TARGET_OBJECT_FREEBSD_PS_STRINGS,
   /* Possible future objects: TARGET_OBJECT_FILE, ...  */
 };
 
-- 
2.18.0