Re: [Xen-devel] [PATCH] Add xentrace/xen_crash.

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Mon, 2013-10-14 at 10:07 -0400, Don Slutz wrote:
> From: Don Slutz <Don@xxxxxxxxxxxxxxx>
> 
> This allows crash to connect to a domU. Usage:
> 
> usage: xen_crash <domid> [<optional port>]
> 
>   xen_crash 1&
>   crash localhost:5001 
> /usr/lib/debug/lib/modules/3.8.11-100.fc17.x86_64/vmlinux
> 
> The domU will be paused while crash is connected.  Currently the code exits 
> when crash disconnects.

Could you supply some docs please, ideally a simple man page but a txt
would do too. Under docs/ probably so they get published on xenbits etc.

> diff --git a/tools/xentrace/Makefile b/tools/xentrace/Makefile
> index 63b09c0..a2313c6 100644
> --- a/tools/xentrace/Makefile
> +++ b/tools/xentrace/Makefile
> @@ -7,7 +7,7 @@ CFLAGS += $(CFLAGS_libxenctrl)
>  LDLIBS += $(LDLIBS_libxenctrl)
>  
>  BIN      = xentrace xentrace_setsize
> -LIBBIN   = xenctx
> +LIBBIN   = xenctx xen_crash

It appears to be x86 specific, at least right now.

So please do something like:
LIBBIN-$(CONFIG_X86) += xen_crash
...

LIBBIN += $(LIBBIN-y)

> diff --git a/tools/xentrace/xen_crash.c b/tools/xentrace/xen_crash.c
> new file mode 100644
> index 0000000..6a4bb34
> --- /dev/null
> +++ b/tools/xentrace/xen_crash.c
> @@ -0,0 +1,697 @@
> +/******************************************************************************
> + * tools/xentrace/xen_crash.c
> + *
> + * Connect crash to DOMu.
> + *
> + * Copyright (C) 2012 by Cloud Switch, Inc.
> + *
> + */
> +
> +#include <ctype.h>
> +#include <time.h>
> +#include <stdlib.h>
> +#include <sys/mman.h>
> +#include <stdio.h>
> +#include <sys/types.h>
> +#include <sys/socket.h>
> +#include <sys/ioctl.h>
> +#include <sys/time.h>
> +#include <sys/stat.h>
> +#include <netinet/in.h>
> +#include <netdb.h>
> +#include <fcntl.h>
> +#include <unistd.h>
> +#include <errno.h>
> +#include <signal.h>
> +#include <string.h>
> +#include <inttypes.h>
> +#include <getopt.h>
> +
> +#include "xenctrl.h"
> +#include <xen/foreign/x86_32.h>
> +#include <xen/foreign/x86_64.h>
> +#include <xen/hvm/save.h>
> +
> +xc_interface *xc_handle = 0;
> +int domid = 0;
> +int debug = 0;
> +
> +typedef unsigned long long guest_word_t;
> +#define FMT_32B_WORD "%08llx"
> +#define FMT_64B_WORD "%016llx"
> +
> +/* Word-length of the guest's own data structures */
> +int guest_word_size = sizeof (unsigned long);
> +/* Word-length of the context record we get from xen */
> +int ctxt_word_size = sizeof (unsigned long);
> +int guest_protected_mode = 1;
> +
> +#define MACHINE_TYPE       "X86_64"

This looks to be used regardless of the type of the guest?

> +
> +#define STRNEQ(A, B)     (B && \
> +        (strncmp((char *)(A), (char *)(B), strlen((char *)(B))) == 0))
> +#define FAILMSG "FAIL "
> +#define DONEMSG "DONE "
> +#define DATAMSG "DATA "
> +
> +#define DATA_HDRSIZE    13   /* strlen("XXXX ") + strlen("0131072") + NULL */

I think you could use the strlen calls, which should be statically
evaluated directly and avoid the possibility of having miscounted.

Is this some protocol defined by crash? Can you include a reference to
their specification somewhere please. Is it intended for consumption
externally to the crash tools -- i.e. is it a stable protocol? (it
smells a bit ad-hoc is why I'm asking).

If it's not intended to be consumed like this perhaps the tool would be
better off living in the crash source base?

Ian.


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