Re: [PATCH v2] ARM:unwind:fix unwind abort for uleb128 case

[Alexandre Mergnat]

On 13/04/2023 09:39, Linus Walleij wrote:
> On Thu, Apr 13, 2023 at 9:34 AM Haibo Li<haibo.li@xxxxxxxxxxxx>  wrote:
>
> > When unwind instruction is 0xb2,the subsequent instructions
> > are uleb128 bytes.
> > For now,it uses only the first uleb128 byte in code.
> >
> > For vsp increments of 0x204~0x400,use one uleb128 byte like below:
> > 0xc06a00e4 <unwind_test_work>: 0x80b27fac
> >    Compact model index: 0
> >    0xb2 0x7f vsp = vsp + 1024
> >    0xac      pop {r4, r5, r6, r7, r8, r14}
> >
> > For vsp increments larger than 0x400,use two uleb128 bytes like below:
> > 0xc06a00e4 <unwind_test_work>: @0xc0cc9e0c
> >    Compact model index: 1
> >    0xb2 0x81 0x01 vsp = vsp + 1032
> >    0xac      pop {r4, r5, r6, r7, r8, r14}
> > The unwind works well since the decoded uleb128 byte is also 0x81.
> >
> > For vsp increments larger than 0x600,use two uleb128 bytes like below:
> > 0xc06a00e4 <unwind_test_work>: @0xc0cc9e0c
> >    Compact model index: 1
> >    0xb2 0x81 0x02 vsp = vsp + 1544
> >    0xac      pop {r4, r5, r6, r7, r8, r14}
> > In this case,the decoded uleb128 result is 0x101(vsp=0x204+(0x101<<2)).
> > While the uleb128 used in code is 0x81(vsp=0x204+(0x81<<2)).
> > The unwind aborts at this frame since it gets incorrect vsp.
> >
> > To fix this,add uleb128 decode to cover all the above case.
> >
> > Signed-off-by: Haibo Li<haibo.li@xxxxxxxxxxxx>
> Thanks Haibo,
> Reviewed-by: Linus Walleij<linus.walleij@xxxxxxxxxx>

Reviewed-by: Alexandre Mergnat <amergnat@xxxxxxxxxxxx>


Regards,
Alexandre