Thank you for helping with the test, David.
On Wed, Oct 5, 2022 at 7:01 PM David Wysochanski <dwyso...@redhat.com>
wrote:
> On Tue, Oct 4, 2022 at 10:22 PM Lianbo Jiang <liji...@redhat.com> wrote:
> >
> > Currently crash will fail and then exit, if the initialization of
> > the emergency stacks information fails. In real customer environments,
> > sometimes, a vmcore may be partially damaged, although such vmcores
> > are rare. For example:
> >
> > # ./crash ../3.10.0-1127.18.2.el7.ppc64le/vmcore
> ../3.10.0-1127.18.2.el7.ppc64le/vmlinux -s
> > crash: invalid kernel virtual address: 38 type: "paca->emergency_sp"
> > #
> >
> > Lets try to keep loading vmcore if such issues happen, so call
> > the readmem() with the RETURN_ON_ERROR instead of FAULT_ON_ERROR,
> > which allows the crash move on.
> >
> > Reported-by: Dave Wysochanski <dwyso...@redhat.com>
> > Signed-off-by: Lianbo Jiang <liji...@redhat.com>
> > ---
> > ppc64.c | 12 ++++++------
> > 1 file changed, 6 insertions(+), 6 deletions(-)
> >
> > diff --git a/ppc64.c b/ppc64.c
> > index 4ea1f7c0c6f8..f94b402ec64d 100644
> > --- a/ppc64.c
> > +++ b/ppc64.c
> > @@ -1224,13 +1224,13 @@ ppc64_init_paca_info(void)
> > ulong paca_loc;
> >
> > readmem(symbol_value("paca_ptrs"), KVADDR, &paca_loc,
> sizeof(void *),
> > - "paca double pointer", FAULT_ON_ERROR);
> > + "paca double pointer", RETURN_ON_ERROR);
> > readmem(paca_loc, KVADDR, paca_ptr, sizeof(void *) *
> kt->cpus,
> > - "paca pointers", FAULT_ON_ERROR);
> > + "paca pointers", RETURN_ON_ERROR);
> > } else if (symbol_exists("paca") &&
> > (get_symbol_type("paca", NULL, NULL) ==
> TYPE_CODE_PTR)) {
> > readmem(symbol_value("paca"), KVADDR, paca_ptr,
> sizeof(void *) * kt->cpus,
> > - "paca pointers", FAULT_ON_ERROR);
> > + "paca pointers", RETURN_ON_ERROR);
> > } else {
> > free(paca_ptr);
> > return;
> > @@ -1245,7 +1245,7 @@ ppc64_init_paca_info(void)
> > for (i = 0; i < kt->cpus; i++)
> > readmem(paca_ptr[i] + offset, KVADDR,
> &ms->emergency_sp[i],
> > sizeof(void *), "paca->emergency_sp",
> > - FAULT_ON_ERROR);
> > + RETURN_ON_ERROR);
> > }
> >
> > if (MEMBER_EXISTS("paca_struct", "nmi_emergency_sp")) {
> > @@ -1256,7 +1256,7 @@ ppc64_init_paca_info(void)
> > for (i = 0; i < kt->cpus; i++)
> > readmem(paca_ptr[i] + offset, KVADDR,
> &ms->nmi_emergency_sp[i],
> > sizeof(void *), "paca->nmi_emergency_sp",
> > - FAULT_ON_ERROR);
> > + RETURN_ON_ERROR);
> > }
> >
> > if (MEMBER_EXISTS("paca_struct", "mc_emergency_sp")) {
> > @@ -1267,7 +1267,7 @@ ppc64_init_paca_info(void)
> > for (i = 0; i < kt->cpus; i++)
> > readmem(paca_ptr[i] + offset, KVADDR,
> &ms->mc_emergency_sp[i],
> > sizeof(void *), "paca->mc_emergency_sp",
> > - FAULT_ON_ERROR);
> > + RETURN_ON_ERROR);
> > }
> >
> > free(paca_ptr);
> > --
> > 2.37.1
> >
>
> Consider adding a 'Fixes' tag for the patch that introduced this
> problem, per the bisect
> in https://bugzilla.redhat.com/show_bug.cgi?id=2127525
> Fixes: cdd57e8b16ab ("ppc64: handle backtrace when CPU is in an
> emergency stack")
>
>
Agree. It should be good to add the 'Fixes' tag.
Thank you for pointing out this issue.
Lianbo
Other than that, I tested this and now on the vmcore in question,
> crash loads ok.
> I get a lot of the below "invalid kernel virtual address", but I think
> it is fine:
> ...
> crash: invalid kernel virtual address: 2d0 type: "paca->mc_emergency_sp"
> crash> quit
>
> Tested-and-Reviewed-by: Dave Wysochanski <dwyso...@redhat.com>
>
> Good job Lianbo!
>
>
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