Messages in this thread | | | Date | Mon, 21 May 2012 15:03:35 +0200 | From | Frederic Weisbecker <> | Subject | Re: [PATCH 02/17] perf: Add ability to attach registers dump to sample |
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On Wed, May 02, 2012 at 01:37:03PM +0200, Jiri Olsa wrote: > Introducing new sample_type bit PERF_SAMPLE_REGS. Once set, > the sample_regs value determines the kind of registers going > to be attached to the sample. > > Currently only user level registers are supported, specified by > PERF_SAMPLE_REGS_USER sample_regs value. Meaning the register > values of the user space context as it was before the user entered > the kernel for whatever reason (syscall, irq, exception, or a PMI > happening in userspace). > > When PERF_SAMPLE_REGS and PERF_SAMPLE_REGS_USER are set, the > sample_regs_user bitmap lets a user choose a set of registers > to dump for the sample. The layout of this bitmap is described > in asm/perf_regs.h for archs that support register dump. > > This is going to be useful to bring Dwarf CFI based stack > unwinding on top of samples. > > Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> > Signed-off-by: Jiri Olsa <jolsa@redhat.com> > --- > include/linux/perf_event.h | 25 ++++++++++- > kernel/events/core.c | 98 ++++++++++++++++++++++++++++++++++++++++++++ > 2 files changed, 121 insertions(+), 2 deletions(-) > > diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h > index ddbb6a9..6a8c974 100644 > --- a/include/linux/perf_event.h > +++ b/include/linux/perf_event.h > @@ -130,8 +130,9 @@ enum perf_event_sample_format { > PERF_SAMPLE_STREAM_ID = 1U << 9, > PERF_SAMPLE_RAW = 1U << 10, > PERF_SAMPLE_BRANCH_STACK = 1U << 11, > + PERF_SAMPLE_REGS = 1U << 12,
Given that we have to provide a reg mask anyway, is this sample type necessary? Zeroed mask means we don't want to record regs.
> > - PERF_SAMPLE_MAX = 1U << 12, /* non-ABI */ > + PERF_SAMPLE_MAX = 1U << 13, /* non-ABI */ > }; > > /* > @@ -163,6 +164,15 @@ enum perf_branch_sample_type { > PERF_SAMPLE_BRANCH_HV) > > /* > + * Values for sample_regs when PERF_SAMPLE_REGS is set. > + * Defines register set to be attached to the sample. > + */ > +enum perf_sample_regs { > + PERF_SAMPLE_REGS_USER = 1U << 0, /* user registers */ > + PERF_SAMPLE_REGS_MAX = 1U << 1, /* non-ABI */ > +};
If this is an enum, we won't be able to record multiple types of regs (eg: user regs and event live regs) in a single sample.
> + > +/* > * The format of the data returned by read() on a perf event fd, > * as specified by attr.read_format: > * > @@ -271,7 +281,16 @@ struct perf_event_attr { > __u64 bp_len; > __u64 config2; /* extension of config1 */ > }; > - __u64 branch_sample_type; /* enum branch_sample_type */ > + __u64 branch_sample_type; /* enum perf_branch_sample_type */ > + > + __u64 sample_regs; /* enum perf_sample_regs */ > + > + /* > + * Arch specific mask for PERF_SAMPLE_REGS_USER setup. > + * Defines set of user regs to dump on samples. > + * See asm/perf_regs.h for details. > + */ > + __u64 sample_regs_user;
We need to sort that out now. How do we handle normal/compat regs? Do we want sample_regs_user_64 and sample_regs_user_32? Or can we make it possible with a single field like above? Should we expect more modes than just a simple native and compat? I don't know much the world outside x86.
Would be nice to have the opinion of other people on this. Ingo, Peter, others?
Thanks.
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