From: Miroslav Benes <mbenes@suse.cz>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Joe Lawrence <joe.lawrence@redhat.com>,
Jessica Yu <jeyu@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
x86@kernel.org, linux-kernel@vger.kernel.org,
mhiramat@kernel.org, bristot@redhat.com, jbaron@akamai.com,
torvalds@linux-foundation.org, tglx@linutronix.de,
mingo@kernel.org, namit@vmware.com, hpa@zytor.com,
luto@kernel.org, ard.biesheuvel@linaro.org, jpoimboe@redhat.com,
live-patching@vger.kernel.org
Subject: Re: [PATCH v3 5/6] x86/ftrace: Use text_poke()
Date: Tue, 22 Oct 2019 10:45:23 +0200 (CEST) [thread overview]
Message-ID: <alpine.LSU.2.21.1910221034450.28918@pobox.suse.cz> (raw)
In-Reply-To: <20191016123906.GR2328@hirez.programming.kicks-ass.net>
On Wed, 16 Oct 2019, Peter Zijlstra wrote:
> On Wed, Oct 16, 2019 at 08:51:27AM +0200, Miroslav Benes wrote:
> > On Tue, 15 Oct 2019, Joe Lawrence wrote:
> >
> > > On 10/15/19 10:13 AM, Miroslav Benes wrote:
> > > > Yes, it does. klp_module_coming() calls module_disable_ro() on all
> > > > patching modules which patch the coming module in order to call
> > > > apply_relocate_add(). New (patching) code for a module can be relocated
> > > > only when the relevant module is loaded.
> > >
> > > FWIW, would the LPC blue-sky2 model (ie, Steve's suggestion @ plumber's where
> > > livepatches only patch a single object and updates are kept on disk to handle
> > > coming module updates as they are loaded) eliminate those outstanding
> > > relocations and the need to perform this late permission flipping?
> >
> > Yes, it should, but we don't have to wait for it. PeterZ proposed a
> > different solution to this specific issue in
> > https://lore.kernel.org/lkml/20191015141111.GP2359@hirez.programming.kicks-ass.net/
> >
> > It should not be a problem to create a live patch module like that and the
> > code in kernel/livepatch/ is almost ready. Something like
> > module_section_disable_ro(mod, section) (and similar for X protection)
> > should be enough. Module reloads would still require juggling with the
> > protections, but I think it is all feasible.
>
> Something a little like so.. completely fresh of the keyboard.
Yes, but I noticed you found different and better way through text_poke()
(I was not aware that text_poke() works around the protections).
Miroslav
> ---
> --- a/include/linux/module.h
> +++ b/include/linux/module.h
> @@ -853,6 +853,18 @@ static inline void module_enable_ro(cons
> static inline void module_disable_ro(const struct module *mod) { }
> #endif
>
> +#if defined(CONFIG_STRICT_MODULE_RWX) && defined(CONFIG_LIVEPATCH)
> +extern void module_section_disable_ro(struct module *mod, const char *sec);
> +extern void module_section_enable_ro(struct module *mod, const char *sec);
> +extern void module_section_disable_x(struct module *mod, const char *sec);
> +extern void module_section_enable_x(struct module *mod, const char *sec);
> +#else
> +static inline void module_section_disable_ro(struct module *mod, const char *sec) { }
> +static inline void module_section_enable_ro(struct module *mod, const char *sec) { }
> +static inline void module_section_disable_x(struct module *mod, const char *sec) { }
> +static inline void module_section_enable_x(struct module *mod, const char *sec) { }
> +#endif
> +
> #ifdef CONFIG_GENERIC_BUG
> void module_bug_finalize(const Elf_Ehdr *, const Elf_Shdr *,
> struct module *);
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -2107,6 +2107,54 @@ static void free_module_elf(struct modul
> kfree(mod->klp_info->secstrings);
> kfree(mod->klp_info);
> }
> +
> +#ifdef CONFIG_STRICT_MODULE_RWX
> +
> +static void __frob_section(struct Elf_Shdr *sec, int (*set_memory)(unsigned long start, int num_pages))
> +{
> + BUG_ON((unsigned long)sec->sh_addr & (PAGE_SIZE-1));
> + BUG_ON((unsigned long)sec->sh_size & (PAGE_SIZE-1));
> + set_memory((unsigned long)sec->sh_addr, sec->sh_size >> PAGE_SHIFT);
> +}
> +
> +static void frob_section(struct module *mod, const char *section,
> + int (*set_memory)(unsigned long start, int num_pages))
> +{
> + struct klp_modinfo *info = mod->klp_info;
> + const char *secname;
> + Elf_Shdr *s;
> +
> + for (s = info->sechdrs; s < info->sechdrs + info->hdr.e_shnum; s++) {
> + secname = mod->klp_info->secstrings + s->sh_name;
> + if (strcmp(secname, section))
> + continue;
> +
> + __frob_section(s, set_memory);
> + }
> +}
> +
> +void module_section_disable_ro(struct module *mod, const char *section)
> +{
> + frob_section(mod, section, set_memory_rw);
> +}
> +
> +void module_section_enable_ro(struct module *mod, const char *section)
> +{
> + frob_section(mod, section, set_memory_ro);
> +}
> +
> +void module_section_disable_x(struct module *mod, const char *section)
> +{
> + frob_section(mod, section, set_memory_nx);
> +}
> +
> +void module_section_enable_x(struct module *mod, const char *section)
> +{
> + frob_section(mod, section, set_memory_x);
> +}
> +
> +#endif /* ONFIG_STRICT_MODULE_RWX */
> +
> #else /* !CONFIG_LIVEPATCH */
> static int copy_module_elf(struct module *mod, struct load_info *info)
> {
>
prev parent reply other threads:[~2019-10-22 8:45 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20191007081945.10951536.8@infradead.org>
[not found] ` <20191008104335.6fcd78c9@gandalf.local.home>
[not found] ` <20191009224135.2dcf7767@oasis.local.home>
[not found] ` <20191010092054.GR2311@hirez.programming.kicks-ass.net>
[not found] ` <20191010091956.48fbcf42@gandalf.local.home>
[not found] ` <20191010140513.GT2311@hirez.programming.kicks-ass.net>
[not found] ` <20191010115449.22044b53@gandalf.local.home>
[not found] ` <20191010172819.GS2328@hirez.programming.kicks-ass.net>
[not found] ` <20191011125903.GN2359@hirez.programming.kicks-ass.net>
[not found] ` <20191015130739.GA23565@linux-8ccs>
[not found] ` <20191015135634.GK2328@hirez.programming.kicks-ass.net>
2019-10-15 14:13 ` [PATCH v3 5/6] x86/ftrace: Use text_poke() Miroslav Benes
2019-10-15 15:06 ` Joe Lawrence
2019-10-15 15:31 ` Jessica Yu
2019-10-15 22:17 ` Joe Lawrence
2019-10-15 22:27 ` Steven Rostedt
2019-10-16 7:42 ` Peter Zijlstra
2019-10-16 10:15 ` Miroslav Benes
2019-10-21 15:05 ` Josh Poimboeuf
2020-01-20 16:50 ` Josh Poimboeuf
2020-01-21 8:35 ` Miroslav Benes
2020-01-21 16:10 ` Josh Poimboeuf
2020-01-22 10:09 ` Miroslav Benes
2020-01-22 21:42 ` Josh Poimboeuf
2020-01-28 9:28 ` Miroslav Benes
2020-01-28 15:00 ` Josh Poimboeuf
2020-01-28 15:40 ` Petr Mladek
2020-01-28 17:02 ` Josh Poimboeuf
2020-01-29 0:46 ` Jiri Kosina
2020-01-29 2:17 ` Josh Poimboeuf
2020-01-29 3:14 ` Jiri Kosina
2020-01-29 12:28 ` Miroslav Benes
2020-01-29 15:59 ` Josh Poimboeuf
2020-01-30 9:53 ` Petr Mladek
2020-01-30 14:17 ` Josh Poimboeuf
2020-01-31 7:17 ` Petr Mladek
2020-01-22 12:15 ` Miroslav Benes
2020-01-22 15:05 ` Miroslav Benes
2020-01-22 22:03 ` Josh Poimboeuf
2020-01-23 10:19 ` Martin Jambor
2019-10-16 7:49 ` Peter Zijlstra
2019-10-16 10:20 ` Miroslav Benes
2019-10-16 13:29 ` Miroslav Benes
2019-10-18 13:03 ` Jessica Yu
2019-10-18 13:40 ` Petr Mladek
2019-10-21 14:14 ` Jessica Yu
2019-10-21 15:31 ` Josh Poimboeuf
2019-10-22 8:27 ` Miroslav Benes
2019-10-22 14:31 ` Josh Poimboeuf
2019-10-23 9:04 ` Miroslav Benes
2019-10-16 6:51 ` Miroslav Benes
2019-10-16 9:23 ` Peter Zijlstra
2019-10-16 9:36 ` Jessica Yu
2019-10-16 9:51 ` Peter Zijlstra
2019-10-16 12:39 ` Peter Zijlstra
2019-10-22 8:45 ` Miroslav Benes [this message]
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