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From: Peter Zijlstra <peterz@infradead.org>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>,
	linux-kernel@vger.kernel.org, x86@kernel.org, dvyukov@google.com,
	elver@google.com, andreyknvl@google.com, Mark.Rutland@arm.com,
	mhelsley@vmware.com, rostedt@goodmis.org, jthierry@redhat.com,
	mbenes@suse.cz
Subject: Re: [PATCH 1/7] x86/entry: Fix #UD vs WARN more
Date: Thu, 18 Jun 2020 17:50:17 +0200	[thread overview]
Message-ID: <20200618155017.GK576905@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <70455B9B-0952-4E03-B2CE-EEAE1E110C5B@amacapital.net>

On Thu, Jun 18, 2020 at 07:57:35AM -0700, Andy Lutomirski wrote:
> 
> 
> > On Jun 18, 2020, at 7:50 AM, Peter Zijlstra <peterz@infradead.org> wrote:
> > 
> > vmlinux.o: warning: objtool: exc_invalid_op()+0x47: call to probe_kernel_read() leaves .noinstr.text section
> > 
> > Since we use UD2 as a short-cut for 'CALL __WARN', treat it as such.
> > Have the bare exception handler do the report_bug() thing.
> 
> I think you should consider inlining or noinstr-ifying report_bug()
> too if you want to make this more bulletproof. I admit the scenario
> where someone instruments it and it goes wrong is farfetched.

How far down that rabbit hole do we go? Because then we need to noinstr
printk, the console drivers, those will very quickly pull in lovely bits
like PCI, USB, DRM :/

At some point we have to just give up.

  reply	other threads:[~2020-06-18 15:50 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-18 14:44 [PATCH 0/7] x86/entry: noinstr fixes Peter Zijlstra
2020-06-18 14:44 ` [PATCH 1/7] x86/entry: Fix #UD vs WARN more Peter Zijlstra
2020-06-18 14:57   ` Andy Lutomirski
2020-06-18 15:50     ` Peter Zijlstra [this message]
2020-06-18 18:36       ` Andy Lutomirski
2020-06-18 19:02         ` Peter Zijlstra
2020-06-18 19:29           ` Andy Lutomirski
2020-06-18 21:18             ` Peter Zijlstra
2020-06-22 11:47               ` Peter Zijlstra
2020-06-24 22:37                 ` Andy Lutomirski
2020-06-25 11:53                 ` [tip: x86/entry] " tip-bot2 for Peter Zijlstra
2020-06-18 14:44 ` [PATCH 2/7] objtool: Dont consider vmlinux a C-file Peter Zijlstra
2020-06-25 11:53   ` [tip: x86/entry] objtool: Don't " tip-bot2 for Peter Zijlstra
2020-06-18 14:44 ` [PATCH 3/7] x86/entry: Fixup bad_iret vs noinstr Peter Zijlstra
2020-06-18 15:13   ` Marco Elver
2020-06-25 11:53   ` [tip: x86/entry] " tip-bot2 for Peter Zijlstra
2020-06-18 14:44 ` [PATCH 4/7] x86/entry: Increase entry_stack size to a full page Peter Zijlstra
2020-06-18 15:06   ` Marco Elver
2020-06-19  3:10   ` Lai Jiangshan
2020-06-25 11:53   ` [tip: x86/entry] " tip-bot2 for Peter Zijlstra
2020-06-18 14:44 ` [PATCH 5/7] objtool: Clean up elf_write() condition Peter Zijlstra
2020-06-18 14:44 ` [PATCH 6/7] objtool: Provide elf_write_{insn,reloc}() Peter Zijlstra
2020-06-18 14:44 ` [PATCH 7/7] objtool: Fix noinstr vs KCOV Peter Zijlstra

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