linux-kernel - Re: [PATCH V3 2/3] perf/powerpc :add support for sampling intr machine state

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Date:	Tue, 03 Nov 2015 20:16:35 +1100
From:	Michael Ellerman <mpe@...erman.id.au>
To:	Anju T <anju@...ux.vnet.ibm.com>, linuxppc-dev@...ts.ozlabs.org,
	linux-kernel@...r.kernel.org
Cc:	maddy@...ux.vnet.ibm.com, khandual@...ux.vnet.ibm.com,
	sukadev@...ux.vnet.ibm.com, acme@...hat.com, dsahern@...il.com,
	jolsa@...hat.com, hemant@...ux.vnet.ibm.com,
	naveen.n.rao@...ux.vnet.ibm.com
Subject: Re: [PATCH V3 2/3] perf/powerpc :add support for sampling intr
 machine state

On Tue, 2015-11-03 at 11:40 +0530, Anju T wrote:

> The perf infrastructure uses a bit mask to find out
> valid registers to display. Define a register mask
> for supported registers defined in asm/perf_regs.h.
> The bit positions also correspond to register IDs
> which is used by perf infrastructure to fetch the register
> values.CONFIG_HAVE_PERF_REGS enables
> sampling of the interrupted machine state.

> diff --git a/arch/powerpc/perf/perf_regs.c b/arch/powerpc/perf/perf_regs.c
> new file mode 100644
> index 0000000..0520492
> --- /dev/null
> +++ b/arch/powerpc/perf/perf_regs.c
> @@ -0,0 +1,92 @@
> +#include <linux/errno.h>
> +#include <linux/kernel.h>
> +#include <linux/sched.h>
> +#include <linux/perf_event.h>
> +#include <linux/bug.h>
> +#include <linux/stddef.h>
> +#include <asm/ptrace.h>
> +#include <asm/perf_regs.h>
> +
> +#define PT_REGS_OFFSET(id, r) [id] = offsetof(struct pt_regs, r)
> +
> +#define REG_RESERVED (~((1ULL << PERF_REG_POWERPC_MAX) - 1))
> +
> +static unsigned int pt_regs_offset[PERF_REG_POWERPC_MAX] = {
> +	PT_REGS_OFFSET(PERF_REG_POWERPC_GPR0, gpr[0]),
> +	PT_REGS_OFFSET(PERF_REG_POWERPC_GPR1, gpr[1]),
> +	PT_REGS_OFFSET(PERF_REG_POWERPC_GPR2, gpr[2]),

<snip>

I realise you're following the example of other architectures, but we have
almost this exact same structure in ptrace.c, see regoffset_table.

It would be really nice if we could share them between ptrace and perf.

cheers

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