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

Simon Ser
2018-07-24T07:53:31Z

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