From: mbenes@suse.cz (Miroslav Benes)
To: linux-arm-kernel@lists.infradead.org
Subject: arm64: implement live patching
Date: Tue, 12 Jul 2016 11:47:41 +0200 (CEST) [thread overview]
Message-ID: <alpine.LNX.2.00.1607121141480.16277@pobox.suse.cz> (raw)
In-Reply-To: <20160711215807.GA23097@packer-debian-8-amd64.digitalocean.com>
On Mon, 11 Jul 2016, Jessica Yu wrote:
> +++ Miroslav Benes [11/07/16 16:03 +0200]:
> > On Mon, 27 Jun 2016, Torsten Duwe wrote:
> >
> > > diff --git a/arch/arm64/include/asm/livepatch.h
> > > b/arch/arm64/include/asm/livepatch.h
> > > new file mode 100644
> > > index 0000000..6b9a3d1
> > > --- /dev/null
> > > +++ b/arch/arm64/include/asm/livepatch.h
> > > @@ -0,0 +1,37 @@
> > > +/*
> > > + * livepatch.h - arm64-specific Kernel Live Patching Core
> > > + *
> > > + * Copyright (C) 2016 SUSE
> > > + *
> > > + * This program is free software; you can redistribute it and/or
> > > + * modify it under the terms of the GNU General Public License
> > > + * as published by the Free Software Foundation; either version 2
> > > + * of the License, or (at your option) any later version.
> > > + *
> > > + * This program is distributed in the hope that it will be useful,
> > > + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> > > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> > > + * GNU General Public License for more details.
> > > + *
> > > + * You should have received a copy of the GNU General Public License
> > > + * along with this program; if not, see <http://www.gnu.org/licenses/>.
> > > + */
> > > +#ifndef _ASM_ARM64_LIVEPATCH_H
> > > +#define _ASM_ARM64_LIVEPATCH_H
> > > +
> > > +#include <linux/module.h>
> > > +#include <linux/ftrace.h>
> > > +
> > > +#ifdef CONFIG_LIVEPATCH
> >
> > A nit but we removed such guards in the other header files.
> >
> > > +static inline int klp_check_compiler_support(void)
> > > +{
> > > + return 0;
> > > +}
> > > +
> > > +static inline void klp_arch_set_pc(struct pt_regs *regs, unsigned long
> > > ip)
> > > +{
> > > + regs->pc = ip;
> > > +}
> > > +#endif /* CONFIG_LIVEPATCH */
> >
> > I also checked mod_arch_specific structure because of the way we deal
> > with relocations. It is defined only if CONFIG_ARM64_MODULE_PLTS is
> > enabled and there is a pointer to 'struct elf64_shdr' called plt. It is
> > used indirectly in apply_relocate_add() so we need it to stay. However it
> > points to an existing Elf section and SHF_ALLOC is added to its sh_flags
> > in module_frob_arch_sections() (arch/arm64/kernel/module-plts.c).
> > Therefore we should be ok.
> >
> > Jessica, could you check it as well, please?
>
> That sounds right, the plt will remain in module core memory, so we
> are fine there.
>
> However I think the plt->sh_size calculation will be incorrect for
> livepatch modules. In calculating mod->arch.plt_max_entries (see:
> module-plts.c), count_plts() is called for every rela section.
> For livepatch modules, this means count_plts() will also be called for
> our .klp.rela sections, which is correct behavior. However,
> count_plts() only considers relas referring to SHN_UNDEF symbols, and
> since every rela in a klp rela section refers to a SHN_LIVEPATCH
> symbol, these are all ignored. So count_plts() may return an incorrect
> value for a klp rela section.
You're right. During the patch module creation we basically transform all
SHN_UNDEF relas to SHN_LIVEPATCH, right? We must take it into account
here.
> Miroslav, can you confirm the issue? I think the fix would be easy
> though; we can just add an additional check for SHN_LIVEPATCH in
> count_plts().
Yes, such a check should be sufficient.
Thanks for looking into it.
Miroslav
next prev parent reply other threads:[~2016-07-12 9:47 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-27 15:15 [PATCH v2 0/2] arm64 live patching Torsten Duwe
2016-06-27 15:17 ` [PATCH v2 1/2] arm64: implement FTRACE_WITH_REGS Torsten Duwe
2016-07-01 12:53 ` Josh Poimboeuf
2016-07-04 9:18 ` Torsten Duwe
2016-07-03 5:17 ` kbuild test robot
2016-07-08 14:58 ` Petr Mladek
2016-07-08 15:07 ` Torsten Duwe
2016-07-08 15:24 ` Petr Mladek
2016-07-08 15:48 ` Josh Poimboeuf
2016-07-08 15:57 ` Steven Rostedt
2016-07-08 20:24 ` Torsten Duwe
2016-07-08 21:08 ` Steven Rostedt
2016-07-09 9:06 ` Torsten Duwe
2016-07-15 18:36 ` Steven Rostedt
2016-07-08 15:49 ` Steven Rostedt
2016-06-27 15:17 ` [PATCH v2 2/2] arm64: implement live patching Torsten Duwe
2016-07-11 14:03 ` Miroslav Benes
2016-07-11 21:58 ` Jessica Yu
2016-07-12 9:47 ` Miroslav Benes [this message]
2016-07-13 0:11 ` [PATCH] arm64: take SHN_LIVEPATCH syms into account when calculating plt_max_entries Jessica Yu
2016-08-17 9:38 ` Miroslav Benes
2016-08-11 16:46 ` [PATCH v2 2/2] arm64: implement live patching Torsten Duwe
2016-07-15 16:03 ` Paul Gortmaker
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