Re: [syzbot] upstream test error: KASAN: invalid-access Read in __entry_tramp_text_end
flat view
From: Peter Zijlstra <peterz@infradead.org>
Date: 2021-09-29 10:02:06
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On Wed, Sep 29, 2021 at 09:50:45AM +0100, Mark Rutland wrote:
On Wed, Sep 29, 2021 at 09:39:47AM +0200, Peter Zijlstra wrote:quoted
On Tue, Sep 28, 2021 at 06:36:37PM -0700, Josh Poimboeuf wrote:
quoted
quoted
+ asm volatile("417: rdmsr\n" + : EAX_EDX_RET(val, low, high) + : "c" (msr)); + asm_volatile_goto(_ASM_EXTABLE(417b, %l[Efault]) :::: Efault);That's terrible :-) Could probably do with a comment, but might just work..The compiler is well within its rights to spill/restore/copy/shuffle registers or modify memory between the two asm blocks (which it's liable to do that when optimizing this after a few layers of inlining), and skipping that would cause all sorts of undefined behaviour.
Ah, but in this case it'll work irrespective of that (which is why we needs a comment!). This is because _ASM_EXTABLE only generates data for another section. There doesn't need to be code continuity between these two asm statements. As I said, this is terrible :-) _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel