From: Andy Lutomirski <luto@kernel.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Rich Felker <dalias@libc.org>, Jann Horn <jannh@google.com>,
"Andrew Lutomirski" <luto@kernel.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
"Christopherson, Sean J" <sean.j.christopherson@intel.com>,
Jethro Beekman <jethro@fortanix.com>,
Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
Florian Weimer <fweimer@redhat.com>,
Linux API <linux-api@vger.kernel.org>, X86 ML <x86@kernel.org>,
linux-arch <linux-arch@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>, <nhorman@redhat.com>,
<npmccallum@redhat.com>, "Ayoun, Serge" <serge.ayoun@intel.com>,
<shay.katz-zamir@intel.com>, <linux-sgx@vger.kernel.org>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"Carlos O'Donell" <carlos@redhat.com>,
<adhemerval.zanella@linaro.org>
Subject: Re: RFC: userspace exception fixups
Date: Thu, 1 Nov 2018 16:22:55 -0700 [thread overview]
Message-ID: <CALCETrWe4+apXJNswHAKVVqajGS3jTEKxdd2r3iu-MzGK1v0DA@mail.gmail.com> (raw)
In-Reply-To: <CAHk-=wiYSpmDOfpi9n7ETsxK2UrUKfT4kM=Y3yqRSaZuFFPY1A@mail.gmail.com>
On Thu, Nov 1, 2018 at 2:24 PM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> On Thu, Nov 1, 2018 at 12:31 PM Rich Felker <dalias@libc.org> wrote:
> >
> > See my other emails in this thread. You would register the *address*
> > (in TLS) of a function pointer object pointing to the handler, rather
> > than the function address of the handler. Then switching handler is
> > just a single store in userspace, no syscalls involved.
>
> Yes.
>
> And for just EENTER, maybe that's the right model.
>
> If we want to generalize it to other thread-synchronous faults, it
> needs way more information and a list of handlers, but if we limit the
> thing to _only_ EENTER getting an SGX fault, then a single "this is
> the fault handler" address is probably the right thing to do.
It sounds like you're saying that the kernel should know, *before*
running any user fixup code, whether the fault in question is one that
wants a fixup. Sounds reasonable.
I think it would be nice, but not absolutely necessary, if user code
didn't need to poke some value into TLS each time it ran a function
that had a fixup. With the poke-into-TLS approach, it looks a lot
like rseq, and rseq doesn't nest very nicely. I think we really want
this mechanism to Just Work. So we could maybe have a syscall that
associates a list of fixups with a given range of text addresses. We
might want the kernel to automatically zap the fixups when the text in
question is unmapped.
WARNING: multiple messages have this Message-ID (diff)
From: Andy Lutomirski <luto@kernel.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Rich Felker <dalias@libc.org>, Jann Horn <jannh@google.com>,
Andrew Lutomirski <luto@kernel.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
"Christopherson, Sean J" <sean.j.christopherson@intel.com>,
Jethro Beekman <jethro@fortanix.com>,
Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
Florian Weimer <fweimer@redhat.com>,
Linux API <linux-api@vger.kernel.org>, X86 ML <x86@kernel.org>,
linux-arch <linux-arch@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
nhorman@redhat.com, npmccallum@redhat.com, "Ayoun,
Serge" <serge.ayoun@intel.com>,
shay.katz-zamir@intel.com, linux-sgx@vger.kernel.org,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"Carlos O'Donell" <carlos@redhat.com>,
adhemerval.zanella@linaro.org
Subject: Re: RFC: userspace exception fixups
Date: Thu, 1 Nov 2018 16:22:55 -0700 [thread overview]
Message-ID: <CALCETrWe4+apXJNswHAKVVqajGS3jTEKxdd2r3iu-MzGK1v0DA@mail.gmail.com> (raw)
Message-ID: <20181101232255.S5_XmmTFTk29r4FUwOp4pFOPA18ko246gETGcs8TLt0@z> (raw)
In-Reply-To: <CAHk-=wiYSpmDOfpi9n7ETsxK2UrUKfT4kM=Y3yqRSaZuFFPY1A@mail.gmail.com>
On Thu, Nov 1, 2018 at 2:24 PM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> On Thu, Nov 1, 2018 at 12:31 PM Rich Felker <dalias@libc.org> wrote:
> >
> > See my other emails in this thread. You would register the *address*
> > (in TLS) of a function pointer object pointing to the handler, rather
> > than the function address of the handler. Then switching handler is
> > just a single store in userspace, no syscalls involved.
>
> Yes.
>
> And for just EENTER, maybe that's the right model.
>
> If we want to generalize it to other thread-synchronous faults, it
> needs way more information and a list of handlers, but if we limit the
> thing to _only_ EENTER getting an SGX fault, then a single "this is
> the fault handler" address is probably the right thing to do.
It sounds like you're saying that the kernel should know, *before*
running any user fixup code, whether the fault in question is one that
wants a fixup. Sounds reasonable.
I think it would be nice, but not absolutely necessary, if user code
didn't need to poke some value into TLS each time it ran a function
that had a fixup. With the poke-into-TLS approach, it looks a lot
like rseq, and rseq doesn't nest very nicely. I think we really want
this mechanism to Just Work. So we could maybe have a syscall that
associates a list of fixups with a given range of text addresses. We
might want the kernel to automatically zap the fixups when the text in
question is unmapped.
next prev parent reply other threads:[~2018-11-01 23:22 UTC|newest]
Thread overview: 163+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-01 17:53 RFC: userspace exception fixups Andy Lutomirski
2018-11-01 17:53 ` Andy Lutomirski
2018-11-01 18:09 ` Florian Weimer
2018-11-01 18:09 ` Florian Weimer
2018-11-01 18:30 ` Rich Felker
2018-11-01 18:30 ` Rich Felker
2018-11-01 19:00 ` Jarkko Sakkinen
2018-11-01 19:00 ` Jarkko Sakkinen
2018-11-01 18:27 ` Rich Felker
2018-11-01 18:27 ` Rich Felker
2018-11-01 18:33 ` Jann Horn
2018-11-01 18:33 ` Jann Horn
2018-11-01 18:52 ` Rich Felker
2018-11-01 18:52 ` Rich Felker
2018-11-01 19:10 ` Linus Torvalds
2018-11-01 19:10 ` Linus Torvalds
2018-11-01 19:31 ` Rich Felker
2018-11-01 19:31 ` Rich Felker
2018-11-01 21:24 ` Linus Torvalds
2018-11-01 21:24 ` Linus Torvalds
2018-11-01 23:22 ` Andy Lutomirski [this message]
2018-11-01 23:22 ` Andy Lutomirski
2018-11-02 16:30 ` Sean Christopherson
2018-11-02 16:30 ` Sean Christopherson
2018-11-02 16:37 ` Jethro Beekman
2018-11-02 16:37 ` Jethro Beekman
2018-11-02 16:52 ` Sean Christopherson
2018-11-02 16:52 ` Sean Christopherson
2018-11-02 16:56 ` Jethro Beekman
2018-11-02 16:56 ` Jethro Beekman
2018-11-02 17:01 ` Andy Lutomirski
2018-11-02 17:01 ` Andy Lutomirski
2018-11-02 17:05 ` Jethro Beekman
2018-11-02 17:05 ` Jethro Beekman
2018-11-02 17:16 ` Andy Lutomirski
2018-11-02 17:16 ` Andy Lutomirski
2018-11-02 17:32 ` Rich Felker
2018-11-02 17:32 ` Rich Felker
2018-11-02 17:12 ` Sean Christopherson
2018-11-02 17:12 ` Sean Christopherson
2018-11-02 22:42 ` Jarkko Sakkinen
2018-11-02 22:42 ` Jarkko Sakkinen
2018-11-02 16:56 ` Dave Hansen
2018-11-02 16:56 ` Dave Hansen
2018-11-02 17:06 ` Sean Christopherson
2018-11-02 17:06 ` Sean Christopherson
2018-11-02 17:13 ` Dave Hansen
2018-11-02 17:13 ` Dave Hansen
2018-11-02 17:33 ` Sean Christopherson
2018-11-02 17:33 ` Sean Christopherson
2018-11-02 17:48 ` Andy Lutomirski
2018-11-02 17:48 ` Andy Lutomirski
2018-11-02 18:27 ` Sean Christopherson
2018-11-02 18:27 ` Sean Christopherson
2018-11-02 19:02 ` Jann Horn
2018-11-02 19:02 ` Jann Horn
2018-11-02 22:04 ` Sean Christopherson
2018-11-02 22:04 ` Sean Christopherson
2018-11-02 23:27 ` Jann Horn
2018-11-02 23:27 ` Jann Horn
2018-11-02 23:32 ` Andy Lutomirski
2018-11-02 23:32 ` Andy Lutomirski
2018-11-02 23:36 ` Jann Horn
2018-11-02 23:36 ` Jann Horn
2018-11-06 15:37 ` Sean Christopherson
2018-11-06 15:37 ` Sean Christopherson
2018-11-06 16:57 ` Andy Lutomirski
2018-11-06 16:57 ` Andy Lutomirski
2018-11-06 17:03 ` Dave Hansen
2018-11-06 17:03 ` Dave Hansen
2018-11-06 17:19 ` Sean Christopherson
2018-11-06 17:19 ` Sean Christopherson
2018-11-06 18:20 ` Andy Lutomirski
2018-11-06 18:20 ` Andy Lutomirski
2018-11-06 18:41 ` Dave Hansen
2018-11-06 18:41 ` Dave Hansen
2018-11-06 19:02 ` Andy Lutomirski
2018-11-06 19:02 ` Andy Lutomirski
2018-11-06 19:22 ` Dave Hansen
2018-11-06 19:22 ` Dave Hansen
2018-11-06 20:12 ` Andy Lutomirski
2018-11-06 20:12 ` Andy Lutomirski
2018-11-06 21:00 ` Dave Hansen
2018-11-06 21:00 ` Dave Hansen
2018-11-06 21:07 ` Andy Lutomirski
2018-11-06 21:07 ` Andy Lutomirski
2018-11-06 21:41 ` Andy Lutomirski
2018-11-06 21:41 ` Andy Lutomirski
2018-11-06 21:59 ` Sean Christopherson
2018-11-06 21:59 ` Sean Christopherson
2018-11-06 23:00 ` Andy Lutomirski
2018-11-06 23:00 ` Andy Lutomirski
2018-11-06 23:35 ` Sean Christopherson
2018-11-06 23:35 ` Sean Christopherson
2018-11-06 23:39 ` Andy Lutomirski
2018-11-06 23:39 ` Andy Lutomirski
2018-11-07 0:02 ` Sean Christopherson
2018-11-07 0:02 ` Sean Christopherson
2018-11-07 1:17 ` Andy Lutomirski
2018-11-07 1:17 ` Andy Lutomirski
2018-11-07 6:47 ` Jethro Beekman
2018-11-07 6:47 ` Jethro Beekman
2018-11-07 15:34 ` Sean Christopherson
2018-11-07 15:34 ` Sean Christopherson
2018-11-07 19:01 ` Sean Christopherson
2018-11-07 19:01 ` Sean Christopherson
2018-11-07 20:56 ` Dave Hansen
2018-11-07 20:56 ` Dave Hansen
2018-11-08 15:04 ` Jarkko Sakkinen
2018-11-08 15:04 ` Jarkko Sakkinen
2018-11-08 19:54 ` Sean Christopherson
2018-11-08 19:54 ` Sean Christopherson
2018-11-08 20:05 ` Andy Lutomirski
2018-11-08 20:05 ` Andy Lutomirski
2018-11-08 20:10 ` Dave Hansen
2018-11-08 20:10 ` Dave Hansen
2018-11-08 21:16 ` Sean Christopherson
2018-11-08 21:16 ` Sean Christopherson
2018-11-08 21:50 ` Dave Hansen
2018-11-08 21:50 ` Dave Hansen
2018-11-08 22:04 ` Sean Christopherson
2018-11-08 22:04 ` Sean Christopherson
2018-11-09 7:12 ` Christoph Hellwig
2018-11-09 7:12 ` Christoph Hellwig
2018-11-06 23:17 ` Rich Felker
2018-11-06 23:17 ` Rich Felker
2018-11-06 23:26 ` Sean Christopherson
2018-11-06 23:26 ` Sean Christopherson
2018-11-07 21:27 ` Rich Felker
2018-11-07 21:27 ` Rich Felker
2018-11-07 21:33 ` Andy Lutomirski
2018-11-07 21:33 ` Andy Lutomirski
2018-11-07 21:40 ` Sean Christopherson
2018-11-07 21:40 ` Sean Christopherson
2018-11-08 15:11 ` Jarkko Sakkinen
2018-11-08 15:11 ` Jarkko Sakkinen
2018-11-06 17:00 ` Dave Hansen
2018-11-06 17:00 ` Dave Hansen
2018-11-02 22:37 ` Jarkko Sakkinen
2018-11-02 22:37 ` Jarkko Sakkinen
2018-11-01 19:06 ` Linus Torvalds
2018-11-01 19:06 ` Linus Torvalds
2018-11-02 22:07 ` Jarkko Sakkinen
2018-11-02 22:07 ` Jarkko Sakkinen
2018-11-18 7:15 ` Jarkko Sakkinen
2018-11-18 7:18 ` Jarkko Sakkinen
2018-11-18 13:02 ` Jarkko Sakkinen
2018-11-19 5:17 ` Jethro Beekman
2018-11-19 14:05 ` Jarkko Sakkinen
2018-11-19 14:59 ` Jarkko Sakkinen
2018-11-19 15:29 ` Andy Lutomirski
2018-11-19 16:02 ` Jarkko Sakkinen
2018-11-19 17:00 ` Andy Lutomirski
2018-11-20 10:11 ` Jarkko Sakkinen
2018-11-20 15:19 ` Andy Lutomirski
2018-11-20 22:55 ` Jarkko Sakkinen
2018-11-21 5:17 ` Jethro Beekman
2018-11-21 15:17 ` Jarkko Sakkinen
2018-11-24 17:07 ` Jarkko Sakkinen
2018-11-26 14:35 ` Sean Christopherson
2018-11-26 22:06 ` Jarkko Sakkinen
2018-11-20 18:09 ` Sean Christopherson
2018-11-20 22:46 ` Jarkko Sakkinen
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