Re: [Qemu-devel] [PATCH] tci: don't write zero for reloc in tci_out_label

[Stefan Weil]

Am 19.06.2012 04:31, schrieb Scott Wood:
> If tci_out_label is called in the context of tcg_gen_code_search_pc, we
> could be overwriting an already patched relocation with zero -- and not
> repatch it because the set_label is past search_pc, causing a QEMU crash
> when it tries to branch to a zero label.
>
> Not writing anything to the relocation area seems to be in line with what
> other backends do from the couple I looked at (x86, ppc).

Thanks, this might fix a crash which I have seen from time to time.
I'll run tests as soon as possible.

Could you please also look at the other backends?

I saw from git history that ppc once had the same bug.
The sparc backend (and maybe others) might still have it.

Regards,
Stefan W.

> Signed-off-by: Scott Wood<address@hidden>
> ---
>   tcg/tci/tcg-target.c |    2 +-
>   1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/tcg/tci/tcg-target.c b/tcg/tci/tcg-target.c
> index 453f187..3c6b0f5 100644
> --- a/tcg/tci/tcg-target.c
> +++ b/tcg/tci/tcg-target.c
> @@ -487,7 +487,7 @@ static void tci_out_label(TCGContext *s, TCGArg arg)
>           assert(label->u.value);
>       } else {
>           tcg_out_reloc(s, s->code_ptr, sizeof(tcg_target_ulong), arg, 0);
> -        tcg_out_i(s, 0);
> +        s->code_ptr += sizeof(tcg_target_ulong);
>       }
>   }