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From: Richard Henderson <richard.henderson@linaro.org>
To: Peter Maydell <peter.maydell@linaro.org>
Cc: qemu-devel@nongnu.org, qemu-arm@nongnu.org
Subject: Re: [PATCH 2/2] target/arm: Look up ARMCPRegInfo at runtime
Date: Mon, 23 Jan 2023 14:20:11 -1000	[thread overview]
Message-ID: <3443cf40-4013-6ac6-895d-08f86c229809@linaro.org> (raw)
In-Reply-To: <CAFEAcA9mh+eS8rHwqmyjOAmcnPDJ7K54QbJPd7itKZskQeox5g@mail.gmail.com>

On 1/23/23 02:53, Peter Maydell wrote:
> On Fri, 6 Jan 2023 at 19:45, Richard Henderson
> <richard.henderson@linaro.org> wrote:
>>
>> Do not encode the pointer as a constant in the opcode stream.
>> This pointer is specific to the cpu that first generated the
>> translation, which runs into problems with both hot-pluggable
>> cpus and user-only threads, as cpus are removed.
>>
>> Perform the lookup in either helper_access_check_cp_reg,
>> or a new helper_lookup_cp_reg.
> 
> As well as the use-after-free, this is also a correctness
> bug, isn't it? If we hardwire in the cpregs pointer for
> CPU 0 into the TB, and then CPU 1 with a slightly different
> config executes the TB, it will get the cpregs of CPU 0,
> not its own, so it might see a register it should not or
> vice-versa.

Existing assumption was that each cpu configuration would have its own cluster_index, 
which gets encoded into cpu->tcg_cflags, which is part of the comparison used when hashing 
TBs.

But including this patch allows relaxation of what constitutes a "cpu configuration".


r~


  reply	other threads:[~2023-01-24  0:21 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-01-06 19:44 [PATCH 0/2] target/arm: Look up ARMCPRegInfo at runtime Richard Henderson
2023-01-06 19:44 ` [PATCH 1/2] target/arm: Reorg do_coproc_insn Richard Henderson
2023-01-17 15:42   ` Alex Bennée
2023-01-06 19:44 ` [PATCH 2/2] target/arm: Look up ARMCPRegInfo at runtime Richard Henderson
2023-01-23 12:53   ` Peter Maydell
2023-01-24  0:20     ` Richard Henderson [this message]
2023-01-24  9:48       ` Peter Maydell
2023-01-24 10:39       ` Alex Bennée
2023-01-16 20:16 ` [PATCH 0/2] " Richard Henderson
2023-01-17 10:28   ` Peter Maydell
2023-01-17 15:20     ` Richard Henderson
2023-01-23 12:55 ` Peter Maydell

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