[Crash-utility] [PATCH] x86_64: Fix check for __per_cpu_offset initialisation

[HAGIO KAZUHITO(萩尾 一仁)]

-----Original Message-----
> Since at least kernel v2.6.30 the __per_cpu_offset gets initialized to
> __per_cpu_load. So first check if the __per_cpu_offset was set to a
> proper value before reading any per cpu variable to prevent potential
> bugs.
> 
> Signed-off-by: Philipp Rudo <prudo at redhat.com>

Thanks for the fix.
 
Acked-by: Kazuhito Hagio <k-hagio-ab at nec.com>

Kazu

> ---
>  x86_64.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/x86_64.c b/x86_64.c
> index 6eb7d67..0bb8705 100644
> --- a/x86_64.c
> +++ b/x86_64.c
> @@ -1327,6 +1327,8 @@ x86_64_per_cpu_init(void)
>  		ms->stkinfo.isize = 16384;
> 
>  	for (i = cpus = 0; i < NR_CPUS; i++) {
> +		if (kt->__per_cpu_offset[i] == symbol_value("__per_cpu_load"))
> +			break;
>  		if (!readmem(cpu_sp->value + kt->__per_cpu_offset[i],
>  		    KVADDR, &cpunumber, sizeof(int),
>  		    "cpu number (per_cpu)", QUIET|RETURN_ON_ERROR))
> @@ -5602,7 +5604,7 @@ x86_64_get_smp_cpus(void)
>  			return 1;
> 
>  		for (i = cpus = 0; i < NR_CPUS; i++) {
> -			if (kt->__per_cpu_offset[i] == 0)
> +			if (kt->__per_cpu_offset[i] == symbol_value("__per_cpu_load"))
>  				break;
>  			if (!readmem(sp->value + kt->__per_cpu_offset[i],
>  			    KVADDR, &cpunumber, sizeof(int),
> --
> 2.31.1
> 
> --
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