Re: [Qemu-devel] [PATCH for-2.11?] target/arm: Generate UNDEF for 32-bit Thumb2 insns

[Richard Henderson]

On 12/11/2017 07:42 AM, Peter Maydell wrote:
> The refactoring of commit 296e5a0a6c3935 has a nasty bug:
> it accidentally dropped the generation of code to raise
> the UNDEF exception when disas_thumb2_insn() returns nonzero.
> This means that 32-bit Thumb2 instruction patterns that
> ought to UNDEF just act like nops instead. This is likely
> to break any number of things, including the kernel's "disable
> the FPU and use the UNDEF exception to identify when to turn
> it back on again" trick.
> 
> Signed-off-by: Peter Maydell <address@hidden>
> ---
> This is the smallest possible fix that will correct the
> bug, for possible inclusion in 2.11; for 2.12 we should
> fix the asymmetry where disas_thumb() generates its own
> exception-raising code but disas_thumb2() wants the caller
> to do it. (This asymmetry is why we didn't notice the
> problem in code review.)
> 
> I'm not sure whether this should go into 2.11 or not --
> this time last week it would have been an easy "yes".

Reviewed-by: Richard Henderson <address@hidden>


r~