[Crash-utility] Fix pvops Xen detection for kernels >= v4.20

[lijiang]

On Tue, Jun 29, 2021 at 10:13 AM HAGIO KAZUHITO(萩尾　一仁)
<k-hagio-ab at nec.com> wrote:
>
> -----Original Message-----
> > Kernel commit 5c83511bdb9832c86be20fb86b783356e2f58062 removed
> > pv_init_ops, and later commit 054ac8ad5ebe4a69e1f0e842483821ddbe560121
> > removed the Xen-specific paravirt patch function. As a result, pvops Xen
> > dumps are no longer recognized as Xen dumps, and virtual-to-physical
> > translation fails.
> >
> > Use the value of xen_start_info to determine whether the kernel is
> > running in Xen PV mode. This pointer is set during the initialization of
> > a PV domain. Kudos to Juergen Gross, who suggested this check.
> >
> > Signed-off-by: Petr Tesarik <ptesarik at suse.com>
>
> Thank you, the patch looks good to me.
>
> Acked-by: Kazuhito Hagio <k-hagio-ab at nec.com>
>
> Lianbo, the patch needs some space adjustment to apply, here is a
> modified patch:
> https://github.com/k-hagio/crash/commit/a7d5cd4169a994b1faa1f646c149d1f54e9dfefd.patch
>
Looks good.  Thanks.
Acked-by: Lianbo Jiang <lijiang at redhat.com>

> Kazu
>
> > ---
> >   kernel.c |   34 ++++++++++++++++++++++++++++------
> >   1 file changed, 28 insertions(+), 6 deletions(-)
> >
> > diff --git a/kernel.c b/kernel.c
> > index e123f76..36fdea2 100644
> > --- a/kernel.c
> > +++ b/kernel.c
> > @@ -95,6 +95,7 @@ static ulong __dump_audit(char *);
> >   static void dump_audit(void);
> >   static char *vmcoreinfo_read_string(const char *);
> >   static void check_vmcoreinfo(void);
> > +static int is_pvops_xen(void);
> >
> >
> >   /*
> > @@ -109,7 +110,6 @@ kernel_init()
> >       char *rqstruct;
> >       char *rq_timestamp_name = NULL;
> >       char *irq_desc_type_name;
> > -     ulong pv_init_ops;
> >       struct gnu_request req;
> >
> >       if (pc->flags & KERNEL_DEBUG_QUERY)
> > @@ -169,11 +169,7 @@ kernel_init()
> >                               error(FATAL, "cannot malloc m2p page.");
> >       }
> >
> > -     if (PVOPS() && symbol_exists("pv_init_ops") &&
> > -         readmem(symbol_value("pv_init_ops"), KVADDR, &pv_init_ops,
> > -         sizeof(void *), "pv_init_ops", RETURN_ON_ERROR) &&
> > -         ((p1 = value_symbol(pv_init_ops)) &&
> > -         (STREQ(p1, "xen_patch") || STREQ(p1, "paravirt_patch_default")))) {
> > +     if (is_pvops_xen()) {
> >               kt->flags |= ARCH_XEN | ARCH_PVOPS_XEN;
> >               kt->xen_flags |= WRITABLE_PAGE_TABLES;
> >               if (machine_type("X86"))
> > @@ -10709,6 +10705,32 @@ paravirt_init(void)
> >       }
> >   }
> >
> > +static int
> > +is_pvops_xen(void)
> > +{
> > +     ulong addr;
> > +     char *sym;
> > +
> > +     if (!PVOPS())
> > +             return FALSE;
> > +
> > +     if (symbol_exists("pv_init_ops") &&
> > +         readmem(symbol_value("pv_init_ops"), KVADDR, &addr,
> > +         sizeof(void *), "pv_init_ops", RETURN_ON_ERROR) &&
> > +         (sym = value_symbol(addr)) &&
> > +         (STREQ(sym, "xen_patch") ||
> > +          STREQ(sym, "paravirt_patch_default")))
> > +             return TRUE;
> > +
> > +     if (symbol_exists("xen_start_info") &&
> > +         readmem(symbol_value("xen_start_info"), KVADDR, &addr,
> > +         sizeof(void *), "xen_start_info", RETURN_ON_ERROR) &&
> > +         addr != 0)
> > +             return TRUE;
> > +
> > +     return FALSE;
> > +}
> > +
> >   /*
> >    *  Get the kernel's xtime timespec from its relevant location.
> >    */
> >
> >
> > --
> > Crash-utility mailing list
> > Crash-utility at redhat.com
> > https://listman.redhat.com/mailman/listinfo/crash-utility
>