From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org,
Ard Biesheuvel <ard.biesheuvel@linaro.org>,
Andy Lutomirski <luto@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Ingo Molnar <mingo@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Linus Torvalds <torvalds@linux-foundation.org>,
Masami Hiramatsu <mhiramat@kernel.org>,
Jason Baron <jbaron@akamai.com>, Jiri Kosina <jkosina@suse.cz>,
David Laight <David.Laight@ACULAB.COM>,
Borislav Petkov <bp@alien8.de>, Julia Cartwright <julia@ni.com>,
Jessica Yu <jeyu@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [PATCH v2 4/4] x86/static_call: Add inline static call implementation for x86-64
Date: Mon, 26 Nov 2018 11:10:36 -0600 [thread overview]
Message-ID: <20181126171036.chcbmb35ygpxziub@treble> (raw)
In-Reply-To: <20181126160217.GR2113@hirez.programming.kicks-ass.net>
On Mon, Nov 26, 2018 at 05:02:17PM +0100, Peter Zijlstra wrote:
> On Mon, Nov 26, 2018 at 07:55:00AM -0600, Josh Poimboeuf wrote:
> > diff --git a/arch/x86/kernel/static_call.c b/arch/x86/kernel/static_call.c
> > index 8026d176f25c..d3869295b88d 100644
> > --- a/arch/x86/kernel/static_call.c
> > +++ b/arch/x86/kernel/static_call.c
> > @@ -9,13 +9,21 @@
> >
> > void static_call_bp_handler(void);
> > void *bp_handler_dest;
> > +void *bp_handler_continue;
> >
> > asm(".pushsection .text, \"ax\" \n"
> > ".globl static_call_bp_handler \n"
> > ".type static_call_bp_handler, @function \n"
> > "static_call_bp_handler: \n"
> > - "ANNOTATE_RETPOLINE_SAFE \n"
> > +#ifdef CONFIG_HAVE_STATIC_CALL_INLINE
> > + ANNOTATE_RETPOLINE_SAFE
> > + "call *bp_handler_dest \n"
> > + ANNOTATE_RETPOLINE_SAFE
> > + "jmp *bp_handler_continue \n"
> > +#else /* !CONFIG_HAVE_STATIC_CALL_INLINE */
> > + ANNOTATE_RETPOLINE_SAFE
> > "jmp *bp_handler_dest \n"
> > +#endif
> > ".popsection \n");
> >
> > void arch_static_call_transform(void *site, void *tramp, void *func)
> > @@ -25,7 +33,10 @@ void arch_static_call_transform(void *site, void *tramp, void *func)
> > unsigned char insn_opcode;
> > unsigned char opcodes[CALL_INSN_SIZE];
> >
> > - insn = (unsigned long)tramp;
> > + if (IS_ENABLED(CONFIG_HAVE_STATIC_CALL_INLINE))
> > + insn = (unsigned long)site;
> > + else
> > + insn = (unsigned long)tramp;
> >
> > mutex_lock(&text_mutex);
> >
> > @@ -41,8 +52,10 @@ void arch_static_call_transform(void *site, void *tramp, void *func)
> > opcodes[0] = insn_opcode;
> > memcpy(&opcodes[1], &dest_relative, CALL_INSN_SIZE - 1);
> >
> > - /* Set up the variable for the breakpoint handler: */
> > + /* Set up the variables for the breakpoint handler: */
> > bp_handler_dest = func;
> > + if (IS_ENABLED(CONFIG_HAVE_STATIC_CALL_INLINE))
> > + bp_handler_continue = (void *)(insn + CALL_INSN_SIZE);
> >
> > /* Patch the call site: */
> > text_poke_bp((void *)insn, opcodes, CALL_INSN_SIZE,
>
> OK, so this is where that static_call_bp_handler comes from; you need
> that CALL to frob the stack.
>
> But I still think it is broken; consider:
>
> CPU0 CPU1
>
> bp_handler = ponies;
>
> text_poke_bp(, &static_call_bp_handler)
> text_poke(&int3);
> on_each_cpu(sync)
> <IPI>
> ...
> </IPI>
>
> text_poke(/* all but first bytes */)
> on_each_cpu(sync)
> <IPI>
> ...
> </IPI>
>
> <int3>
> pt_regs->ip = &static_call_bp_handler
> </int3>
>
> // VCPU takes a nap...
> text_poke(/* first byte */)
> on_each_cpu(sync)
> <IPI>
> ...
> </IPI>
>
> // VCPU sleeps more
> bp_handler = unicorn;
>
> CALL unicorn
>
> *whoops*
>
> Now, granted, that is all rather 'unlikely', but that never stopped
> Murphy.
Good find, thanks Peter.
As we discussed on IRC, we'll need to fix this from within the int3
exception handler by faking the call: putting a fake return address on
the stack (pointing to right after the call) and setting regs->ip to the
called function.
And for the out-of-line case we can just jump straight to the function,
so the function itself will be the text_poke_bp() "handler".
So the static_call_bp_handler() trampoline will go away.
--
Josh
next prev parent reply other threads:[~2018-11-26 17:10 UTC|newest]
Thread overview: 120+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-26 13:54 [PATCH v2 0/4] Static calls Josh Poimboeuf
2018-11-26 13:54 ` [PATCH v2 1/4] compiler.h: Make __ADDRESSABLE() symbol truly unique Josh Poimboeuf
2018-11-27 8:49 ` Ard Biesheuvel
2018-11-26 13:54 ` [PATCH v2 2/4] static_call: Add static call infrastructure Josh Poimboeuf
2018-11-26 13:54 ` [PATCH v2 3/4] x86/static_call: Add out-of-line static call implementation Josh Poimboeuf
2018-11-26 15:43 ` Peter Zijlstra
2018-11-26 16:19 ` Steven Rostedt
2018-11-26 13:55 ` [PATCH v2 4/4] x86/static_call: Add inline static call implementation for x86-64 Josh Poimboeuf
2018-11-26 16:02 ` Peter Zijlstra
2018-11-26 17:10 ` Josh Poimboeuf [this message]
2018-11-26 17:56 ` Josh Poimboeuf
2018-11-26 20:00 ` Peter Zijlstra
2018-11-26 20:08 ` Peter Zijlstra
2018-11-26 21:26 ` Josh Poimboeuf
2018-11-27 8:43 ` Peter Zijlstra
2018-11-27 8:50 ` Peter Zijlstra
2018-11-29 6:05 ` Andy Lutomirski
2018-11-29 9:42 ` Peter Zijlstra
2018-11-29 13:11 ` Josh Poimboeuf
2018-11-29 13:37 ` Andy Lutomirski
2018-11-29 14:38 ` Peter Zijlstra
2018-11-29 14:42 ` Jiri Kosina
2018-11-29 16:33 ` Josh Poimboeuf
2018-11-29 16:49 ` Peter Zijlstra
2018-11-29 16:59 ` Andy Lutomirski
2018-11-29 17:10 ` Josh Poimboeuf
2018-11-29 22:01 ` Peter Zijlstra
2018-11-29 22:14 ` Josh Poimboeuf
2018-11-29 22:22 ` Peter Zijlstra
2018-11-29 22:25 ` Andy Lutomirski
2018-11-29 22:30 ` Josh Poimboeuf
2018-11-29 17:15 ` Peter Zijlstra
2018-11-29 17:20 ` Steven Rostedt
2018-11-29 17:21 ` Steven Rostedt
2018-11-29 17:41 ` Andy Lutomirski
2018-11-29 17:45 ` Josh Poimboeuf
2018-11-29 17:52 ` Andy Lutomirski
2018-11-29 17:49 ` Steven Rostedt
2018-11-29 18:37 ` Josh Poimboeuf
2018-11-29 16:50 ` Linus Torvalds
2018-11-29 16:55 ` Steven Rostedt
2018-11-29 17:02 ` Andy Lutomirski
2018-11-29 17:07 ` Peter Zijlstra
2018-11-29 17:31 ` Andy Lutomirski
2018-11-29 17:35 ` Jiri Kosina
2018-11-29 17:13 ` Steven Rostedt
2018-11-29 17:35 ` Linus Torvalds
2018-11-29 17:44 ` Steven Rostedt
2018-11-29 17:50 ` Linus Torvalds
2018-11-29 17:54 ` Linus Torvalds
2018-11-29 17:58 ` Steven Rostedt
2018-11-29 18:23 ` Linus Torvalds
2018-11-29 18:47 ` Steven Rostedt
2018-11-29 18:58 ` Linus Torvalds
2018-11-29 19:08 ` Linus Torvalds
2018-11-29 19:11 ` Linus Torvalds
2018-12-10 23:58 ` Pavel Machek
2018-12-11 1:43 ` Linus Torvalds
2018-11-29 19:12 ` Steven Rostedt
2018-11-29 19:27 ` Andy Lutomirski
2018-11-29 20:24 ` Josh Poimboeuf
2018-11-29 22:17 ` Josh Poimboeuf
2018-11-29 23:04 ` Linus Torvalds
2018-11-30 16:27 ` Josh Poimboeuf
2018-12-11 9:41 ` David Laight
2018-12-11 17:19 ` Josh Poimboeuf
2018-12-12 18:29 ` Josh Poimboeuf
2018-11-30 16:42 ` Andy Lutomirski
2018-11-30 18:39 ` Josh Poimboeuf
2018-11-30 19:45 ` Linus Torvalds
2018-11-30 20:18 ` Andy Lutomirski
2018-11-30 20:28 ` Steven Rostedt
2018-11-30 20:59 ` Andy Lutomirski
2018-11-30 21:01 ` Steven Rostedt
2018-11-30 21:13 ` Jiri Kosina
2018-11-30 21:10 ` Josh Poimboeuf
2018-11-29 19:16 ` Steven Rostedt
2018-11-29 19:22 ` Josh Poimboeuf
2018-11-29 19:27 ` Steven Rostedt
2018-11-30 22:16 ` Rasmus Villemoes
2018-11-30 22:24 ` Josh Poimboeuf
2018-11-29 19:24 ` Linus Torvalds
2018-11-29 19:28 ` Andy Lutomirski
2018-11-29 19:31 ` Steven Rostedt
2018-11-29 20:12 ` Josh Poimboeuf
2018-11-29 18:00 ` Andy Lutomirski
2018-11-29 18:42 ` Linus Torvalds
2018-11-29 18:55 ` Steven Rostedt
2018-11-29 17:29 ` Linus Torvalds
2018-11-29 17:35 ` Andy Lutomirski
2018-11-26 18:28 ` Andy Lutomirski
2018-11-26 20:14 ` Josh Poimboeuf
2018-11-27 8:46 ` Peter Zijlstra
2018-11-26 16:08 ` Peter Zijlstra
2018-11-26 16:11 ` Ard Biesheuvel
2018-11-26 16:33 ` Andy Lutomirski
2018-11-26 16:39 ` Peter Zijlstra
2018-11-26 16:44 ` Josh Poimboeuf
2018-11-26 14:01 ` [PATCH v2 0/4] Static calls Josh Poimboeuf
2018-11-26 20:54 ` Steven Rostedt
2018-11-26 22:24 ` Josh Poimboeuf
2018-11-26 22:53 ` Steven Rostedt
2018-12-04 23:08 ` Steven Rostedt
2018-12-04 23:41 ` Andy Lutomirski
2018-12-05 15:04 ` Josh Poimboeuf
2018-12-05 23:36 ` Andy Lutomirski
2018-12-07 16:06 ` Edward Cree
2018-12-07 16:49 ` Edward Cree
2018-12-11 18:05 ` Josh Poimboeuf
2018-12-12 5:59 ` Nadav Amit
2018-12-12 17:11 ` Edward Cree
2018-12-12 17:47 ` [RFC/WIP PATCH 0/2] dynamic calls Edward Cree
2018-12-12 17:50 ` [RFC PATCH 1/2] static_call: fix out-of-line static call implementation Edward Cree
2018-12-12 17:52 ` [RFC PATCH 2/2] net: core: rather hacky PoC implementation of dynamic calls Edward Cree
2018-12-12 18:14 ` [PATCH v2 0/4] Static calls Nadav Amit
2018-12-12 18:33 ` Edward Cree
2018-12-12 21:15 ` Nadav Amit
2018-12-12 21:36 ` Edward Cree
2018-12-12 21:45 ` Nadav Amit
2018-12-10 23:57 ` Pavel Machek
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