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

Simon Ser
2018-08-01T16:33:32Z

Hi John,

What do you think of this patch?

Thanks!

Simon Ser

On July 24, 2018 8:17 AM, Simon Ser <contact@emersion.fr> wrote:
> Hi John,
>
> Do you think this approach is acceptable?
>
> Thanks,
>
> Simon Ser
>
> On July 16, 2018 2:38 PM, Simon Ser <contact@emersion.fr> wrote:
> > 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