Generate NT_PROCSTAT_{AUXV,VMMAP} in FreeBSD coredumps
Commit Message
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(+)
Comments
On 7/11/18 5:35 AM, Simon Ser 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.
>
> 2018-07-11 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;
> +}
> +
You can't use a sysctl like this in a tdep.c file. fbsd-tdep.c runs on
any OS, (so for example you could be running gdb with a FreeBSD binary
on Linux or OS X against a debug server (gdbserver or lldb-server or some
such) running on a remote FreeBSD host (or VM) and use 'gcore' on the
debugging host to generate a local core file.
Native code that would only run on a FreeBSD host would live in fbsd-nat.c,
and when I have thought about handling other procstat notes in FreeBSD cores
I've mostly thought about adding some kind of hook that fbsd-tdep.c would
invoke to write extra core notes and setting that hook only for native
targets in fbsd-nat.c for the native gdbarchs.
Your previous patch for AUXV still works because the target_foo function
you called previously will talk to either the debug server or the
native target to fetch the AUXV data, so I think your previous patch
for NT_PROCSTAT_AUXV is a better approach for that note.
On July 11, 2018 5:16 PM, John Baldwin <jhb@FreeBSD.org> wrote:
> You can't use a sysctl like this in a tdep.c file. fbsd-tdep.c runs on
> any OS, (so for example you could be running gdb with a FreeBSD binary
> on Linux or OS X against a debug server (gdbserver or lldb-server or some
> such) running on a remote FreeBSD host (or VM) and use 'gcore' on the
> debugging host to generate a local core file.
Ah, that's what I feared when choosing this approach.
> Native code that would only run on a FreeBSD host would live in fbsd-nat.c,
> and when I have thought about handling other procstat notes in FreeBSD cores
> I've mostly thought about adding some kind of hook that fbsd-tdep.c would
> invoke to write extra core notes and setting that hook only for native
> targets in fbsd-nat.c for the native gdbarchs.
>
> Your previous patch for AUXV still works because the target_foo function
> you called previously will talk to either the debug server or the
> native target to fetch the AUXV data, so I think your previous patch
> for NT_PROCSTAT_AUXV is a better approach for that note.
Hmm, I need those other notes too. Would it be possible to add some
FreeBSD-specific TARGET_OBJECT_* constants? If not, could you explain
how one would add this hook?
Thanks,
Simon
@@ -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,
+ ¬e_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), ¬e_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;
}