From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
To: Jan Beulich <JBeulich@suse.com>
Cc: keir@xen.org, ross.lagerwall@citrix.com,
andrew.cooper3@citrix.com, mpohlack@amazon.com,
sasha.levin@oracle.com, xen-devel@lists.xenproject.org
Subject: Re: [PATCH v8.1 17/27] xsplice: Add support for bug frames.
Date: Fri, 22 Apr 2016 06:10:32 -0400 [thread overview]
Message-ID: <20160422101032.GA11517@localhost.localdomain> (raw)
In-Reply-To: <5718940502000078000E4382@prv-mh.provo.novell.com>
On Thu, Apr 21, 2016 at 12:49:09AM -0600, Jan Beulich wrote:
> >>> On 21.04.16 at 02:29, <konrad.wilk@oracle.com> wrote:
> > On Tue, Apr 19, 2016 at 02:17:35PM -0600, Jan Beulich wrote:
> >> >>> Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> 04/14/16 12:02 AM >>>
> >> >+bool_t is_patch(const void *ptr)
> >> >+{
> >> >+ struct payload *data;
> >>
> >> You guess it: const.
> >>
> >> >+ /*
> >> >+ * No locking since this list is only ever changed during apply or revert
> >> >+ * context.
> >> >+ */
> >>
> >> What if you crash while applying or reverting a patch? Is the list update at
> >> least done such that the (then nested) traversal remains safe?
> >
> > Yes! We only add the struct payload to this applied_list _after_ the
> > patching has been done.` Hence if we crashed the list would not contain the
> > struct payload that was patching - but would be safe to traverse.
>
> Well, that only partly answers the question. Patch application to me
> means the entire process, i.e. up to and including adding the new
> patch to the list (read: the crash could also happen there). Hence
> I'd still like it to be made sure that even if the addition has got done
> only partially, the list remains traversable. Or IOW, I'm not sure the
> standard list macros make any guarantees like that.
It does. I've copied-n-pasted the list_add_tail hacking it have an
BUG_ON(1):
+static inline void __list_add_crash(struct list_head *new,
+ struct list_head *prev, /* applied list */
+ struct list_head *next /* applied_list */)
+{
+ next->prev = new; /* applied_list->prev = new */
+ new->next = next; /* new->next = applied_list */
+ new->prev = prev; /* new->prev = applied_list */
+ BUG_ON(1);
+ prev->next = new; /* applied_list->next=new */
+}
+static inline void list_add_tail_crash(struct list_head *new, struct
list_head *head)
+{
+ __list_add_crash(new, head->prev /* applied_list */, head /* applied_list */);
+}
static int apply_payload(struct payload *data)
{
unsigned int i;
@@ -967,7 +981,7 @@ static int apply_payload(struct payload *data)
arch_xsplice_patching_leave();
- list_add_tail(&data->applied_list, &applied_list);
+ list_add_tail_crash(&data->applied_list, &applied_list);
register_virtual_region(&data->region);
return 0;
And we get:
(XEN) xsplice: xen_hello_world: Applying 1 functions
(XEN) Xen BUG at xsplice.c:963
(XEN) *** DOUBLE FAULT ***
A bit more debugging shows that "is_patch" does not iterate over
the list - (which is inline with what I expected!) - so the insertion
is safe when crashing.
Now why I get a double fault.. will have to investigate that at some
point.
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next prev parent reply other threads:[~2016-04-22 10:10 UTC|newest]
Thread overview: 126+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-13 22:01 [PATCH v8.1] xSplice v1 design and implementation Konrad Rzeszutek Wilk
2016-04-13 22:01 ` [PATCH v8.1 01/27] Revert "libxc/libxl/python/xenstat/ocaml: Use new XEN_VERSION hypercall" Konrad Rzeszutek Wilk
2016-04-13 22:01 ` [PATCH v8.1 02/27] Revert "HYPERCALL_version_op. New hypercall mirroring XENVER_ but sane." Konrad Rzeszutek Wilk
2016-04-14 16:14 ` Jan Beulich
2016-04-13 22:01 ` [PATCH v8.1 03/27] xsplice: Design document Konrad Rzeszutek Wilk
2016-04-13 22:01 ` [PATCH v8.1 04/27] xen/xsplice: Hypervisor implementation of XEN_XSPLICE_op Konrad Rzeszutek Wilk
2016-04-14 16:36 ` Jan Beulich
2016-04-15 2:28 ` Konrad Rzeszutek Wilk
2016-04-17 8:05 ` Jan Beulich
2016-04-18 7:48 ` Konrad Rzeszutek Wilk
2016-04-18 16:33 ` Jan Beulich
2016-04-19 10:14 ` Konrad Rzeszutek Wilk
2016-04-13 22:01 ` [PATCH v8.1 05/27] libxc: Implementation of XEN_XSPLICE_op in libxc Konrad Rzeszutek Wilk
2016-04-13 22:01 ` [PATCH v8.1 06/27] xen-xsplice: Tool to manipulate xsplice payloads Konrad Rzeszutek Wilk
2016-04-13 22:01 ` [PATCH v8.1 07/27] arm/x86: Use struct virtual_region to do bug, symbol, and (x86) exception tables lookup Konrad Rzeszutek Wilk
2016-04-14 16:50 ` Jan Beulich
2016-04-13 22:01 ` [PATCH v8.1 08/27] arm/x86/vmap: Add vmalloc_xen, vfree_xen and vm_init_type Konrad Rzeszutek Wilk
2016-04-17 20:17 ` Jan Beulich
2016-04-13 22:01 ` [PATCH v8.1 09/27] x86/mm: Introduce modify_xen_mappings() Konrad Rzeszutek Wilk
2016-04-14 4:07 ` Jan Beulich
2016-04-14 13:34 ` Konrad Rzeszutek Wilk
2016-04-13 22:01 ` [PATCH v8.1 10/27] xsplice: Add helper elf routines Konrad Rzeszutek Wilk
2016-04-17 20:55 ` Jan Beulich
2016-04-18 5:53 ` Konrad Rzeszutek Wilk
2016-04-18 6:23 ` Jan Beulich
2016-04-20 16:07 ` Konrad Rzeszutek Wilk
2016-04-20 16:59 ` Jan Beulich
2016-04-13 22:01 ` [PATCH v8.1 11/27] xsplice: Implement payload loading Konrad Rzeszutek Wilk
2016-04-18 6:16 ` Jan Beulich
2016-04-20 15:59 ` Konrad Rzeszutek Wilk
2016-04-20 17:05 ` Jan Beulich
2016-04-20 17:36 ` Konrad Rzeszutek Wilk
2016-04-21 6:41 ` Jan Beulich
2016-04-21 15:15 ` Konrad Rzeszutek Wilk
2016-04-21 15:36 ` Jan Beulich
2016-04-21 16:47 ` Konrad Rzeszutek Wilk
2016-04-22 7:40 ` Jan Beulich
2016-04-13 22:01 ` [PATCH v8.1 12/27] xsplice: Implement support for applying/reverting/replacing patches Konrad Rzeszutek Wilk
2016-04-19 6:27 ` Jan Beulich
2016-04-21 0:28 ` Konrad Rzeszutek Wilk
2016-04-21 6:44 ` Jan Beulich
2016-04-21 20:27 ` Konrad Rzeszutek Wilk
2016-04-22 7:44 ` Jan Beulich
2016-04-22 10:51 ` Konrad Rzeszutek Wilk
2016-04-22 17:26 ` Konrad Rzeszutek Wilk
2016-04-25 7:55 ` Jan Beulich
2016-04-13 22:01 ` [PATCH v8.1 13/27] x86/xen_hello_world.xsplice: Test payload for patching 'xen_extra_version' Konrad Rzeszutek Wilk
2016-04-19 17:40 ` Jan Beulich
2016-04-20 16:10 ` Konrad Rzeszutek Wilk
2016-04-20 17:06 ` Jan Beulich
2016-04-13 22:01 ` [PATCH v8.1 14/27] xsplice, symbols: Implement symbol name resolution on address Konrad Rzeszutek Wilk
2016-04-19 19:31 ` Jan Beulich
2016-04-20 12:55 ` Ross Lagerwall
2016-04-21 0:26 ` Konrad Rzeszutek Wilk
2016-04-21 6:46 ` Jan Beulich
[not found] ` <CACJDEmrucgYZpCDv3EAkDJUOtdcP9P2T=Vine1o2pzUmwJDY1w@mail.gmail.com>
[not found] ` <CACJDEmrzieYh6__MHJH_okoZPk+RA56PuQKv-oid0j1t1po1oQ@mail.gmail.com>
[not found] ` <CACJDEmrdi3sTZjGowkvGP67-_DH3+TLvArC8qZfArsyPb6fpuA@mail.gmail.com>
[not found] ` <CACJDEmrQ6onv-xqYOi3nekioCSASb4c1eZHJ-rzMxU3Wa7SXTQ@mail.gmail.com>
2016-04-21 13:56 ` Konrad Rzeszutek Wilk
2016-04-21 14:25 ` Jan Beulich
2016-04-22 7:17 ` Ross Lagerwall
2016-04-22 7:51 ` Jan Beulich
2016-04-22 8:45 ` Ross Lagerwall
2016-04-22 10:08 ` Jan Beulich
2016-04-22 10:28 ` Konrad Rzeszutek Wilk
2016-04-22 10:50 ` Jan Beulich
2016-04-22 11:08 ` Konrad Rzeszutek Wilk
2016-04-22 11:18 ` Jan Beulich
2016-04-24 21:41 ` Konrad Rzeszutek Wilk
2016-04-25 8:02 ` Jan Beulich
2016-04-22 11:13 ` Ross Lagerwall
2016-04-22 11:24 ` Jan Beulich
2016-04-22 21:10 ` Konrad Rzeszutek Wilk
2016-04-25 6:41 ` Ross Lagerwall
2016-04-25 8:15 ` Jan Beulich
2016-04-22 14:17 ` Konrad Rzeszutek Wilk
2016-04-13 22:01 ` [PATCH v8.1 15/27] xsplice, symbols: Implement fast symbol names -> virtual addresses lookup Konrad Rzeszutek Wilk
2016-04-19 19:52 ` Jan Beulich
2016-04-22 15:21 ` Konrad Rzeszutek Wilk
2016-04-25 8:38 ` Jan Beulich
2016-04-25 14:12 ` Konrad Rzeszutek Wilk
2016-04-13 22:01 ` [PATCH v8.1 16/27] x86, xsplice: Print payload's symbol name and payload name in backtraces Konrad Rzeszutek Wilk
2016-04-19 20:09 ` Jan Beulich
2016-04-13 22:01 ` [PATCH v8.1 17/27] xsplice: Add support for bug frames Konrad Rzeszutek Wilk
2016-04-19 20:17 ` Jan Beulich
2016-04-21 0:29 ` Konrad Rzeszutek Wilk
2016-04-21 6:49 ` Jan Beulich
2016-04-22 10:10 ` Konrad Rzeszutek Wilk [this message]
2016-04-22 10:28 ` Jan Beulich
2016-04-22 10:54 ` Konrad Rzeszutek Wilk
2016-04-22 10:58 ` Jan Beulich
2016-04-22 11:10 ` Konrad Rzeszutek Wilk
2016-04-13 22:01 ` [PATCH v8.1 18/27] xsplice: Add support for exception tables Konrad Rzeszutek Wilk
2016-04-19 20:31 ` Jan Beulich
2016-04-13 22:02 ` [PATCH v8.1 19/27] xsplice: Add support for alternatives Konrad Rzeszutek Wilk
2016-04-20 6:28 ` Jan Beulich
2016-04-21 0:30 ` Konrad Rzeszutek Wilk
2016-04-21 6:55 ` Jan Beulich
2016-04-21 0:31 ` Konrad Rzeszutek Wilk
2016-04-21 6:56 ` Jan Beulich
2016-04-22 16:06 ` Konrad Rzeszutek Wilk
2016-04-13 22:02 ` [PATCH v8.1 20/27] build_id: Provide ld-embedded build-ids Konrad Rzeszutek Wilk
2016-04-20 7:14 ` Jan Beulich
2016-04-21 0:33 ` Konrad Rzeszutek Wilk
2016-04-21 6:59 ` Jan Beulich
2016-04-21 20:30 ` Konrad Rzeszutek Wilk
2016-04-22 16:16 ` Konrad Rzeszutek Wilk
2016-04-13 22:02 ` [PATCH v8.1 21/27] xsplice: Print build_id in keyhandler and on bootup Konrad Rzeszutek Wilk
2016-04-13 22:02 ` [PATCH v8.1 22/27] XENVER_build_id/libxc: Provide ld-embedded build-id Konrad Rzeszutek Wilk
2016-04-14 15:03 ` Wei Liu
2016-04-14 15:04 ` Daniel De Graaf
2016-04-20 7:19 ` Jan Beulich
2016-04-13 22:02 ` [PATCH v8.1 23/27] libxl: info: Display build_id of the hypervisor Konrad Rzeszutek Wilk
2016-04-14 15:06 ` Wei Liu
2016-04-13 22:02 ` [PATCH v8.1 24/27] xsplice: Stacking build-id dependency checking Konrad Rzeszutek Wilk
2016-04-20 7:49 ` Jan Beulich
2016-04-22 10:46 ` Konrad Rzeszutek Wilk
2016-04-22 10:55 ` Jan Beulich
2016-04-13 22:02 ` [PATCH v8.1 25/27] xsplice/xen_replace_world: Test-case for XSPLICE_ACTION_REPLACE Konrad Rzeszutek Wilk
2016-04-20 11:12 ` Jan Beulich
2016-04-13 22:02 ` [PATCH v8.1 26/27] xsplice: Prevent duplicate payloads from being loaded Konrad Rzeszutek Wilk
2016-04-20 11:16 ` Jan Beulich
2016-04-13 22:02 ` [PATCH v8.1 27/27] MAINTAINERS/xsplice: Add myself and Ross as the maintainers Konrad Rzeszutek Wilk
2016-04-14 14:26 ` [PATCH v8.1] xSplice v1 design and implementation Konrad Rzeszutek Wilk
2016-04-14 14:29 ` Julien Grall
2016-04-14 15:12 ` Andrew Cooper
2016-04-14 15:17 ` Jan Beulich
2016-04-15 0:55 ` Konrad Rzeszutek Wilk
2016-04-17 8:00 ` Jan Beulich
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