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

From: Madhavan Srinivasan <[email-masked]>
Date: Wed, 4 Nov 2015 11:15:18 +0530

On Tuesday 03 November 2015 02:46 PM, Michael Ellerman wrote:
> 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.

That won't work because we want to add more regs to the perf version but
not the ptrace version.

Maddy

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