From: Chris J Arges <chris.j.arges@canonical.com> To: Josh Poimboeuf <jpoimboe@redhat.com>, Miroslav Benes <mbenes@suse.cz> Cc: live-patching@vger.kernel.org, jeyu@redhat.com, Seth Jennings <sjenning@redhat.com>, Jiri Kosina <jikos@kernel.org>, Vojtech Pavlik <vojtech@suse.com>, linux-api@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] livepatch: old_name.number scheme in livepatch sysfs directory Date: Wed, 4 Nov 2015 10:17:52 -0600 [thread overview] Message-ID: <563A2FB0.60101@canonical.com> (raw) In-Reply-To: <20151104160354.GA29899@treble.redhat.com> On 11/04/2015 10:03 AM, Josh Poimboeuf wrote: > On Wed, Nov 04, 2015 at 10:52:52AM +0100, Miroslav Benes wrote: >> On Tue, 3 Nov 2015, Josh Poimboeuf wrote: >>>> Object entry would be empty for not loaded object. I would not >>>> dare to propose to remove such object entries. It would make things worse. >>> >>> Why would removing an empty object entry make things worse? >> >> I think it all comes down to a question whether the sysfs entries say what >> a patch is capable to patch or what this patch is currently patching in >> the system. I am inclined to the former so the removal would make me >> nervous. But I am not against the second approach. We are still in testing >> mode as far as sysfs is concerned so we can try even harsh changes and see >> how it's gonna go. > > I see your point. This approach only describes what is patched now, but > it doesn't describe what *will* be patched. Ideally we could find a way > to describe both. > > Speaking of harsh changes, here's an idea. > > What if we require the patch author to supply the value of 'n' instead > of supplying the symbol address? We could get rid of 'old_addr' as an > input in klp_func and and replace it with 'old_sympos' which has the > value of 'n'. Or alternatively we could require old_name to be of the > format "func,n". I like the idea of old_sympos better than modifying the string. In addition if no old_sympos is specified then it should default to 0, since this will probably be the more common case. > > That would uniquely identify each patched function, even _before_ the > object is loaded. > > It would also fix another big problem we have today, where there's no > way to disambiguate duplicate symbols in modules, for both function > addresses and for relocs. > > It would simplify the code in other places as well: no special handling > for kASLR, no need for klp_verify_vmlinux_symbol() vs > klp_find_object_symbol(). > > A drawback is that it requires the patch author to do a little more due > diligence when filling out klp_func. But we already require them to be > careful. > > Thoughts? > I'll hold off on my v3 for now. Very interesting discussion : ). --chris
WARNING: multiple messages have this Message-ID (diff)
From: Chris J Arges <chris.j.arges-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org> To: Josh Poimboeuf <jpoimboe-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Miroslav Benes <mbenes-AlSwsSmVLrQ@public.gmane.org> Cc: live-patching-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, jeyu-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, Seth Jennings <sjenning-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Jiri Kosina <jikos-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, Vojtech Pavlik <vojtech-IBi9RG/b67k@public.gmane.org>, linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org Subject: Re: [PATCH v2] livepatch: old_name.number scheme in livepatch sysfs directory Date: Wed, 4 Nov 2015 10:17:52 -0600 [thread overview] Message-ID: <563A2FB0.60101@canonical.com> (raw) In-Reply-To: <20151104160354.GA29899-8wJ5/zUtDR0XGNroddHbYwC/G2K4zDHf@public.gmane.org> On 11/04/2015 10:03 AM, Josh Poimboeuf wrote: > On Wed, Nov 04, 2015 at 10:52:52AM +0100, Miroslav Benes wrote: >> On Tue, 3 Nov 2015, Josh Poimboeuf wrote: >>>> Object entry would be empty for not loaded object. I would not >>>> dare to propose to remove such object entries. It would make things worse. >>> >>> Why would removing an empty object entry make things worse? >> >> I think it all comes down to a question whether the sysfs entries say what >> a patch is capable to patch or what this patch is currently patching in >> the system. I am inclined to the former so the removal would make me >> nervous. But I am not against the second approach. We are still in testing >> mode as far as sysfs is concerned so we can try even harsh changes and see >> how it's gonna go. > > I see your point. This approach only describes what is patched now, but > it doesn't describe what *will* be patched. Ideally we could find a way > to describe both. > > Speaking of harsh changes, here's an idea. > > What if we require the patch author to supply the value of 'n' instead > of supplying the symbol address? We could get rid of 'old_addr' as an > input in klp_func and and replace it with 'old_sympos' which has the > value of 'n'. Or alternatively we could require old_name to be of the > format "func,n". I like the idea of old_sympos better than modifying the string. In addition if no old_sympos is specified then it should default to 0, since this will probably be the more common case. > > That would uniquely identify each patched function, even _before_ the > object is loaded. > > It would also fix another big problem we have today, where there's no > way to disambiguate duplicate symbols in modules, for both function > addresses and for relocs. > > It would simplify the code in other places as well: no special handling > for kASLR, no need for klp_verify_vmlinux_symbol() vs > klp_find_object_symbol(). > > A drawback is that it requires the patch author to do a little more due > diligence when filling out klp_func. But we already require them to be > careful. > > Thoughts? > I'll hold off on my v3 for now. Very interesting discussion : ). --chris
next prev parent reply other threads:[~2015-11-04 16:18 UTC|newest] Thread overview: 104+ messages / expand[flat|nested] mbox.gz Atom feed top 2015-11-02 17:58 [PATCH] livepatch: old_name.number scheme in livepatch sysfs directory Chris J Arges 2015-11-02 17:58 ` Chris J Arges 2015-11-02 19:15 ` Jessica Yu 2015-11-02 19:52 ` [PATCH] " Josh Poimboeuf 2015-11-02 19:52 ` Josh Poimboeuf 2015-11-02 20:16 ` Chris J Arges 2015-11-02 20:32 ` Josh Poimboeuf 2015-11-02 22:59 ` [PATCH v2] " Chris J Arges 2015-11-02 22:59 ` Chris J Arges 2015-11-03 9:50 ` Miroslav Benes 2015-11-03 15:03 ` Josh Poimboeuf 2015-11-03 10:52 ` Miroslav Benes 2015-11-03 10:52 ` Miroslav Benes 2015-11-03 12:44 ` Petr Mladek 2015-11-03 12:44 ` Petr Mladek 2015-11-03 15:03 ` Josh Poimboeuf 2015-11-03 15:03 ` Josh Poimboeuf 2015-11-03 19:57 ` Jiri Kosina 2015-11-03 19:57 ` Jiri Kosina 2015-11-03 20:06 ` Josh Poimboeuf 2015-11-03 20:06 ` Josh Poimboeuf [not found] ` <1447259366-7055-1-git-send-email-chris.j.arges@canonical.com> 2015-11-11 16:28 ` [PATCH 1/3 v4] livepatch: add old_sympos as disambiguator field to klp_func Chris J Arges 2015-11-11 17:43 ` Josh Poimboeuf 2015-11-12 10:22 ` Miroslav Benes 2015-11-11 16:29 ` [PATCH 2/3 v4] livepatch: add old_sympos as disambiguator field to klp_reloc Chris J Arges 2015-11-11 16:39 ` Chris J Arges 2015-11-11 17:57 ` Josh Poimboeuf 2015-11-12 14:31 ` Petr Mladek 2015-11-12 19:19 ` Josh Poimboeuf 2015-11-13 13:54 ` Petr Mladek 2015-11-13 16:59 ` Josh Poimboeuf 2015-11-16 12:11 ` Petr Mladek 2015-11-12 10:23 ` Miroslav Benes 2015-11-11 16:29 ` [PATCH 3/3 v4] livepatch: old_name,number scheme in livepatch sysfs directory Chris J Arges 2015-11-11 18:01 ` Josh Poimboeuf 2015-11-11 18:01 ` Josh Poimboeuf [not found] ` <1447347595-30728-1-git-send-email-chris.j.arges@canonical.com> 2015-11-12 16:59 ` [PATCH 1/4 v5] livepatch: add old_sympos as disambiguator field to klp_func Chris J Arges 2015-11-12 19:45 ` Josh Poimboeuf 2015-11-13 9:56 ` Jiri Kosina 2015-11-13 10:14 ` Miroslav Benes 2015-11-13 16:27 ` Petr Mladek 2015-11-12 16:59 ` [PATCH 2/4 v5] livepatch: Simplify code for relocated external symbols Chris J Arges 2015-11-13 10:24 ` Miroslav Benes 2015-11-13 13:55 ` Petr Mladek 2015-11-12 16:59 ` [PATCH 3/4 v5] livepatch: add sympos as disambiguator field to klp_reloc Chris J Arges 2015-11-12 19:50 ` Josh Poimboeuf 2015-11-13 16:42 ` Petr Mladek 2015-11-12 16:59 ` [PATCH 4/4 v5] livepatch: function,sympos scheme in livepatch sysfs directory Chris J Arges [not found] ` <1447431804-18786-1-git-send-email-chris.j.arges@canonical.com> 2015-11-13 16:23 ` [PATCH 1/3 v6] livepatch: add old_sympos as disambiguator field to klp_func Chris J Arges 2015-11-13 16:23 ` [PATCH 2/3 v6] livepatch: add sympos as disambiguator field to klp_reloc Chris J Arges 2015-11-13 16:23 ` [PATCH 3/3 v6] livepatch: function,sympos scheme in livepatch sysfs directory Chris J Arges [not found] ` <1447693391-10065-1-git-send-email-chris.j.arges@canonical.com> 2015-11-16 17:03 ` [PATCH 1/3 v7] livepatch: add old_sympos as disambiguator field to klp_func Chris J Arges 2015-11-16 21:59 ` Jiri Kosina 2015-11-17 14:29 ` Chris J Arges 2015-11-19 10:02 ` Jiri Kosina 2015-11-16 17:03 ` [PATCH 2/3 v7] livepatch: add sympos as disambiguator field to klp_reloc Chris J Arges 2015-11-18 9:56 ` Miroslav Benes 2015-11-18 14:01 ` Josh Poimboeuf 2015-11-18 16:47 ` Petr Mladek 2015-11-18 16:37 ` Petr Mladek 2015-11-18 16:39 ` Chris J Arges 2015-11-18 16:55 ` Petr Mladek 2015-11-18 20:34 ` Jiri Kosina 2015-11-16 17:03 ` [PATCH 3/3 v7] livepatch: function,sympos scheme in livepatch sysfs directory Chris J Arges 2015-11-20 17:25 ` [PATCH 0/3 v8] livepatch: disambiguate symbols with the same name Chris J Arges 2015-11-20 17:25 ` [PATCH 1/3 v8] livepatch: add old_sympos as disambiguator field to klp_func Chris J Arges 2015-11-23 9:47 ` Miroslav Benes 2015-11-20 17:25 ` [PATCH 2/3 v8] livepatch: add sympos as disambiguator field to klp_reloc Chris J Arges 2015-11-23 9:52 ` Miroslav Benes 2015-11-30 20:46 ` Chris J Arges 2015-12-01 1:17 ` Josh Poimboeuf 2015-11-20 17:25 ` [PATCH 3/3 v8] livepatch: function,sympos scheme in livepatch sysfs directory Chris J Arges 2015-11-23 9:47 ` Miroslav Benes 2015-12-02 2:40 ` [PATCH 0/3 v9] livepatch: disambiguate symbols with the same name Chris J Arges 2015-12-02 2:40 ` [PATCH 1/3 v9] livepatch: add old_sympos as disambiguator field to klp_func Chris J Arges 2015-12-02 2:40 ` [PATCH 2/3 v9] livepatch: add sympos as disambiguator field to klp_reloc Chris J Arges 2015-12-14 12:45 ` Miroslav Benes 2015-12-02 2:40 ` [PATCH 3/3 v9] livepatch: function,sympos scheme in livepatch sysfs directory Chris J Arges 2015-12-02 15:28 ` [PATCH 0/3 v9] livepatch: disambiguate symbols with the same name Petr Mladek 2015-12-03 17:59 ` Josh Poimboeuf 2015-12-03 22:04 ` Jiri Kosina 2015-11-03 14:58 ` [PATCH v2] livepatch: old_name.number scheme in livepatch sysfs directory Josh Poimboeuf 2015-11-03 16:09 ` Miroslav Benes 2015-11-03 16:50 ` Josh Poimboeuf 2015-11-03 20:42 ` Chris J Arges 2015-11-03 20:42 ` Chris J Arges 2015-11-04 9:52 ` Miroslav Benes 2015-11-04 9:52 ` Miroslav Benes 2015-11-04 16:03 ` Josh Poimboeuf 2015-11-04 16:17 ` Chris J Arges [this message] 2015-11-04 16:17 ` Chris J Arges 2015-11-05 15:18 ` Miroslav Benes 2015-11-05 15:56 ` Josh Poimboeuf 2015-11-05 16:07 ` Chris J Arges 2015-11-09 16:16 ` [PATCH v3] livepatch: old_name,number " Chris J Arges 2015-11-09 16:16 ` Chris J Arges 2015-11-09 20:56 ` Josh Poimboeuf 2015-11-09 23:01 ` Chris J Arges 2015-11-09 23:01 ` Chris J Arges 2015-11-10 4:54 ` Josh Poimboeuf 2015-11-10 8:49 ` Miroslav Benes 2015-11-10 13:40 ` Josh Poimboeuf 2015-11-10 13:40 ` Josh Poimboeuf 2015-11-10 9:02 ` Miroslav Benes
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