Re: [PATCH v4 3/5] tools/misc: add xen-domctx to present domain context

[Ian Jackson <ian.jackson@xxxxxxxxxx>]

Paul Durrant writes ("[PATCH v4 3/5] tools/misc: add xen-domctx to present 
domain context"):
> This tool is analogous to 'xen-hvmctx' which presents HVM context.
> Subsequent patches will add 'dump' functions when new records are
> introduced.

This looks plausible to me.

Acked-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>

However, I have CC'd Andrew in case he wants to have an opinion.
Andy's done a lot of work on the save/restore stuff and he should be
given a chance to objedt.  Please would committers not commit this
this week, or until Andy also acks it.

Thanks,
Ian.

> Signed-off-by: Paul Durrant <pdurrant@xxxxxxxxxx>
> ---
> Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
> Cc: Wei Liu <wl@xxxxxxx>
> 
> v3:
>  - Re-worked to avoid copying onto stack
>  - Added optional typecode and instance arguments
> 
> v2:
>  - Change name from 'xen-ctx' to 'xen-domctx'
> ---
>  .gitignore              |   1 +
>  tools/misc/Makefile     |   4 +
>  tools/misc/xen-domctx.c | 200 ++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 205 insertions(+)
>  create mode 100644 tools/misc/xen-domctx.c
> 
> diff --git a/.gitignore b/.gitignore
> index 7418ce9829..6da3030f0d 100644
> --- a/.gitignore
> +++ b/.gitignore
> @@ -209,6 +209,7 @@ tools/misc/xen_cpuperf
>  tools/misc/xen-cpuid
>  tools/misc/xen-detect
>  tools/misc/xen-diag
> +tools/misc/xen-domctx
>  tools/misc/xen-tmem-list-parse
>  tools/misc/xen-livepatch
>  tools/misc/xenperf
> diff --git a/tools/misc/Makefile b/tools/misc/Makefile
> index 63947bfadc..ef25524354 100644
> --- a/tools/misc/Makefile
> +++ b/tools/misc/Makefile
> @@ -30,6 +30,7 @@ INSTALL_SBIN                   += xenpm
>  INSTALL_SBIN                   += xenwatchdogd
>  INSTALL_SBIN                   += xen-livepatch
>  INSTALL_SBIN                   += xen-diag
> +INSTALL_SBIN                   += xen-domctx
>  INSTALL_SBIN += $(INSTALL_SBIN-y)
>  
>  # Everything to be installed in a private bin/
> @@ -108,6 +109,9 @@ xen-livepatch: xen-livepatch.o
>  xen-diag: xen-diag.o
>       $(CC) $(LDFLAGS) -o $@ $< $(LDLIBS_libxenctrl) $(APPEND_LDFLAGS)
>  
> +xen-domctx: xen-domctx.o
> +     $(CC) $(LDFLAGS) -o $@ $< $(LDLIBS_libxenctrl) $(APPEND_LDFLAGS)
> +
>  xen-lowmemd: xen-lowmemd.o
>       $(CC) $(LDFLAGS) -o $@ $< $(LDLIBS_libxenevtchn) $(LDLIBS_libxenctrl) 
> $(LDLIBS_libxenstore) $(APPEND_LDFLAGS)
>  
> diff --git a/tools/misc/xen-domctx.c b/tools/misc/xen-domctx.c
> new file mode 100644
> index 0000000000..243325dfce
> --- /dev/null
> +++ b/tools/misc/xen-domctx.c
> @@ -0,0 +1,200 @@
> +/*
> + * xen-domctx.c
> + *
> + * Print out domain save records in a human-readable way.
> + *
> + * Copyright Amazon.com Inc. or its affiliates.
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a
> + * copy of this software and associated documentation files (the "Software"),
> + * to deal in the Software without restriction, including without limitation
> + * the rights to use, copy, modify, merge, publish, distribute, sublicense,
> + * and/or sell copies of the Software, and to permit persons to whom the
> + * Software is furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice shall be included in
> + * all copies or substantial portions of the Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
> + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
> + * DEALINGS IN THE SOFTWARE.
> + */
> +
> +#include <inttypes.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <errno.h>
> +
> +#include <xenctrl.h>
> +#include <xen/xen.h>
> +#include <xen/domctl.h>
> +#include <xen/save.h>
> +
> +static void *buf = NULL;
> +static size_t len, off;
> +
> +#define GET_PTR(_x)                                                        \
> +    do {                                                                   \
> +        if ( len - off < sizeof(*(_x)) )                                   \
> +        {                                                                  \
> +            fprintf(stderr,                                                \
> +                    "error: need another %lu bytes, only %lu available\n", \
> +                    sizeof(*(_x)), len - off);                             \
> +            exit(1);                                                       \
> +        }                                                                  \
> +        (_x) = buf + off;                                                  \
> +    } while (false);
> +
> +static void dump_header(void)
> +{
> +    DOMAIN_SAVE_TYPE(HEADER) *h;
> +
> +    GET_PTR(h);
> +
> +    printf("    HEADER: magic %#x, version %u\n",
> +           h->magic, h->version);
> +
> +}
> +
> +static void dump_end(void)
> +{
> +    DOMAIN_SAVE_TYPE(END) *e;
> +
> +    GET_PTR(e);
> +
> +    printf("    END\n");
> +}
> +
> +static void usage(const char *prog)
> +{
> +    fprintf(stderr, "usage: %s <domid> [ <typecode> [ <instance> ]]\n",
> +            prog);
> +    exit(1);
> +}
> +
> +int main(int argc, char **argv)
> +{
> +    char *s, *e;
> +    long domid;
> +    long typecode = -1;
> +    long instance = -1;
> +    unsigned int entry;
> +    xc_interface *xch;
> +    int rc;
> +
> +    if ( argc < 2 || argc > 4 )
> +        usage(argv[0]);
> +
> +    s = e = argv[1];
> +    domid = strtol(s, &e, 0);
> +
> +    if ( *s == '\0' || *e != '\0' ||
> +         domid < 0 || domid >= DOMID_FIRST_RESERVED )
> +    {
> +        fprintf(stderr, "invalid domid '%s'\n", s);
> +        exit(1);
> +    }
> +
> +    if ( argc >= 3 )
> +    {
> +        s = e = argv[2];
> +        typecode = strtol(s, &e, 0);
> +
> +        if ( *s == '\0' || *e != '\0' )
> +        {
> +            fprintf(stderr, "invalid typecode '%s'\n", s);
> +            exit(1);
> +        }
> +    }
> +
> +    if ( argc == 4 )
> +    {
> +        s = e = argv[3];
> +        instance = strtol(s, &e, 0);
> +
> +        if ( *s == '\0' || *e != '\0' )
> +        {
> +            fprintf(stderr, "invalid instance '%s'\n", s);
> +            exit(1);
> +        }
> +    }
> +
> +    xch = xc_interface_open(0, 0, 0);
> +    if ( !xch )
> +    {
> +        fprintf(stderr, "error: can't open libxc handle\n");
> +        exit(1);
> +    }
> +
> +    rc = xc_domain_getcontext(xch, domid, NULL, &len);
> +    if ( rc < 0 )
> +    {
> +        fprintf(stderr, "error: can't get record length for dom %lu: %s\n",
> +                domid, strerror(errno));
> +        exit(1);
> +    }
> +
> +    buf = malloc(len);
> +    if ( !buf )
> +    {
> +        fprintf(stderr, "error: can't allocate %lu bytes\n", len);
> +        exit(1);
> +    }
> +
> +    rc = xc_domain_getcontext(xch, domid, buf, &len);
> +    if ( rc < 0 )
> +    {
> +        fprintf(stderr, "error: can't get domain record for dom %lu: %s\n",
> +                domid, strerror(errno));
> +        exit(1);
> +    }
> +    off = 0;
> +
> +    entry = 0;
> +    for ( ; ; )
> +    {
> +        struct domain_save_descriptor *desc;
> +
> +        GET_PTR(desc);
> +
> +        off += sizeof(*desc);
> +
> +        if ( (typecode < 0 || typecode == desc->typecode) &&
> +             (instance < 0 || instance == desc->instance) )
> +        {
> +            printf("[%u] type: %u instance: %u length: %u\n", entry++,
> +                   desc->typecode, desc->instance, desc->length);
> +
> +            switch (desc->typecode)
> +            {
> +            case DOMAIN_SAVE_CODE(HEADER): dump_header(); break;
> +            case DOMAIN_SAVE_CODE(END): dump_end(); break;
> +            default:
> +                printf("Unknown type %u: skipping\n", desc->typecode);
> +                break;
> +            }
> +        }
> +
> +        if ( desc->typecode == DOMAIN_SAVE_CODE(END) )
> +            break;
> +
> +        off += desc->length;
> +    }
> +
> +    return 0;
> +}
> +
> +/*
> + * Local variables:
> + * mode: C
> + * c-file-style: "BSD"
> + * c-basic-offset: 4
> + * tab-width: 4
> + * indent-tabs-mode: nil
> + * End:
> + */
> -- 
> 2.20.1
>