Re: [PATCH 1/2] perf/x86: Disable non generic regs for software/probe events

From: Ingo Molnar
Date: Sat May 25 2019 - 04:51:48 EST



* kan.liang@xxxxxxxxxxxxxxx <kan.liang@xxxxxxxxxxxxxxx> wrote:

> @@ -57,6 +57,11 @@ static unsigned int pt_regs_offset[PERF_REG_X86_MAX] = {
> #endif
> };
>
> +u64 non_generic_regs_mask(void)
> +{
> + return (~((1ULL << PERF_REG_X86_XMM0) - 1));
> +}
> +
> u64 perf_reg_value(struct pt_regs *regs, int idx)
> {
> struct x86_perf_regs *perf_regs;
> diff --git a/include/linux/perf_regs.h b/include/linux/perf_regs.h
> index 4767474..c1c3454 100644
> --- a/include/linux/perf_regs.h
> +++ b/include/linux/perf_regs.h
> @@ -9,6 +9,8 @@ struct perf_regs {
> struct pt_regs *regs;
> };
>
> +u64 non_generic_regs_mask(void);

This is a *constant* value, why is it in a separate function, not an
inline?

Or rather, since it's obviously a constant, name it in such a way.
(PERF_REG_X86_NON_GENERIC_MASK or so.)

To the generic code define it as 0 if arch headers haven't overriden it.

> +u64 __weak non_generic_regs_mask(void)
> +{
> + return 0;
> +}
> +
> +static inline bool has_non_generic_regs(struct perf_event *event)
> +{
> + u64 mask = non_generic_regs_mask();
> +
> + return ((event->attr.sample_regs_user & mask) ||
> + (event->attr.sample_regs_intr & mask));

'return' is not a function ...

> + /* only support generic regs */
> + if (has_non_generic_regs(event))
> + return -EOPNOTSUPP;

In human readable comments please use complete sentences with no
unnecessary abbreviations, i.e. "Only support generic registers".

Thanks,

Ingo