[PATCH v2] Generate NT_PROCSTAT_{AUXV,VMMAP,PS_STRINGS} in FreeBSD coredumps

Simon Ser
2018-07-16T13:39:10Z

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