Re: [v3 12/15] powerpc/perf: Add support for outputting extended regs in perf intr_regs

[Ravi Bangoria <ravi.bangoria@linux.ibm.com>]

Hi Athira,

> +/* Function to return the extended register values */
> +static u64 get_ext_regs_value(int idx)
> +{
> +	switch (idx) {
> +	case PERF_REG_POWERPC_MMCR0:
> +		return mfspr(SPRN_MMCR0);
> +	case PERF_REG_POWERPC_MMCR1:
> +		return mfspr(SPRN_MMCR1);
> +	case PERF_REG_POWERPC_MMCR2:
> +		return mfspr(SPRN_MMCR2);
> +	default: return 0;
> +	}
> +}
> +
>   u64 perf_reg_value(struct pt_regs *regs, int idx)
>   {
> -	if (WARN_ON_ONCE(idx >= PERF_REG_POWERPC_MAX))
> -		return 0;
> +	u64 PERF_REG_EXTENDED_MAX;

PERF_REG_EXTENDED_MAX should be initialized. otherwise ...

> +
> +	if (cpu_has_feature(CPU_FTR_ARCH_300))
> +		PERF_REG_EXTENDED_MAX = PERF_REG_MAX_ISA_300;
>   
>   	if (idx == PERF_REG_POWERPC_SIER &&
>   	   (IS_ENABLED(CONFIG_FSL_EMB_PERF_EVENT) ||
> @@ -85,6 +103,16 @@ u64 perf_reg_value(struct pt_regs *regs, int idx)
>   	    IS_ENABLED(CONFIG_PPC32)))
>   		return 0;
>   
> +	if (idx >= PERF_REG_POWERPC_MAX && idx < PERF_REG_EXTENDED_MAX)
> +		return get_ext_regs_value(idx);

On non p9/p10 machine, PERF_REG_EXTENDED_MAX may contain random value which will
allow user to pass this if condition unintentionally.

Neat: PERF_REG_EXTENDED_MAX is a local variable so it should be in lowercase.
Any specific reason to define it in capital?

Ravi