[Crash-utility] [PATCH] Clear ununsed exception stack base

[Alexey Makhalov]

Hi Samuelliao,

I’ve sent similar patch some time ago:
https://www.redhat.com/archives/crash-utility/2020-November/msg00005.html
Review response was "it seems we should support this properly.”

Here is support for VC stack from me (not yet reviewed/merged)
https://www.redhat.com/archives/crash-utility/2020-November/msg00039.html

Regards,
—Alexey

> On Nov 22, 2020, at 11:00 PM, samuelliao(廖生苗) <samuelliao at tencent.com> wrote:
> 
> SEV-ES code may fill the 4th ist to VC_stack, but crash-util has no
> support for #VC frames. It break backtrace due the zero-size stack.
> So clear all unused stack base to workaround it.
> 
> Signed-off-by: samuelliao <samuelliao at samuelliao.com>
> ---
>  x86_64.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/x86_64.c b/x86_64.c
> index 939c8a9..382cff1 100644
> --- a/x86_64.c
> +++ b/x86_64.c
> @@ -1462,7 +1462,10 @@ x86_64_ist_init(void)
>  			for (i = 0; i < MAX_EXCEPTION_STACKS; i++) {
>  				if (ms->stkinfo.ebase[c][i] == 0) 
>  					continue;
> -				ms->stkinfo.ebase[c][i] -= ms->stkinfo.esize[i];
> +				if(ms->stkinfo.esize[i] == 0)
> +					ms->stkinfo.ebase[c][i] = 0;
> +				else
> +					ms->stkinfo.ebase[c][i] -= ms->stkinfo.esize[i];
>  			}
>  		}
>  
> -- 
> 2.18.4
> 
> 
> 
> 
> --
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