From: Paolo Bonzini <pbonzini@redhat.com>
To: Michael Walle <michael@walle.cc>
Cc: "Paolo Bonzini" <paolo.bonzini@gmail.com>,
qemu-devel@nongnu.org, "Radim Krčmář" <rkrcmar@redhat.com>
Subject: Re: [Qemu-devel] [PATCH 2/2] milkymist-pfpu: fix GCC 5.0.0 aggressive-loop-optimizations warning
Date: Fri, 20 Feb 2015 15:55:58 +0100 [thread overview]
Message-ID: <54E74AFE.6030004@redhat.com> (raw)
In-Reply-To: <31761482c674426717c95680d6e1ba02@walle.cc>
On 20/02/2015 15:52, Michael Walle wrote:
>>>
>>> - i = 0;
>>> - while (pfpu_decode_insn(s)) {
>>> - /* decode at most MICROCODE_WORDS instructions */
>>> - if (i++ >= MICROCODE_WORDS) {
>>
>> Isn't the fix just to say "++i" instead of "i++"?
>
> In the first run, s->regs[R_PC] may have any value, therefore the "insn
> = s->microcode[pc]" from above may access out of bounds.
Then should pfpu_decode_insn access s->microcode[pc & (MICROCODE_WORDS -
1)]? That's likely what happens in hardware, and the purpose of the
error is just to avoid an infinite loop in device code.
Paolo
next prev parent reply other threads:[~2015-02-20 14:56 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-02-20 14:18 [Qemu-devel] [PATCH 0/2] Fix GCC 5.0.0 build errors Radim Krčmář
2015-02-20 14:18 ` [Qemu-devel] [PATCH 1/2] fix GCC 5.0.0 logical-not-parentheses warnings Radim Krčmář
2015-02-20 14:38 ` Paolo Bonzini
2015-02-20 15:43 ` Radim Krčmář
2015-02-20 14:18 ` [Qemu-devel] [PATCH 2/2] milkymist-pfpu: fix GCC 5.0.0 aggressive-loop-optimizations warning Radim Krčmář
2015-02-20 14:24 ` Radim Krčmář
2015-02-20 14:36 ` Paolo Bonzini
2015-02-20 14:52 ` Michael Walle
2015-02-20 14:55 ` Paolo Bonzini [this message]
2015-02-20 15:48 ` Radim Krčmář
2015-02-20 14:40 ` Peter Maydell
2015-02-20 15:37 ` Radim Krčmář
2015-02-20 16:10 ` Michael Walle
-- strict thread matches above, loose matches on Subject: below --
2015-02-20 16:06 [Qemu-devel] [PATCH 0/2] Fix GCC 5.0.0 build errors Radim Krčmář
2015-02-20 16:06 ` [Qemu-devel] [PATCH 2/2] milkymist-pfpu: fix GCC 5.0.0 aggressive-loop-optimizations warning Radim Krčmář
2015-02-23 17:32 ` Michael Walle
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