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    SubjectRe: [RFC][PATCH 07/11] perf: Provide PERF_SAMPLE_REGS
    On Wed, Mar 03, 2010 at 05:39:43PM +0100, Peter Zijlstra wrote:
    > Simply copy out the provided pt_regs in a u64 aligned fashion.
    >
    > XXX: do task_pt_regs() and get_irq_regs() always clear everything or
    > are we now leaking data?


    It looks like there is a leak in case of non trace syscalls.
    where we don't appear to save r12-15.

    Then task_pt_regs() may leak the top of a process stack...?


    >
    > Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
    > ---
    > include/linux/perf_event.h | 5 ++++-
    > kernel/perf_event.c | 17 +++++++++++++++++
    > 2 files changed, 21 insertions(+), 1 deletion(-)
    >
    > Index: linux-2.6/include/linux/perf_event.h
    > ===================================================================
    > --- linux-2.6.orig/include/linux/perf_event.h
    > +++ linux-2.6/include/linux/perf_event.h
    > @@ -125,8 +125,9 @@ enum perf_event_sample_format {
    > PERF_SAMPLE_PERIOD = 1U << 8,
    > PERF_SAMPLE_STREAM_ID = 1U << 9,
    > PERF_SAMPLE_RAW = 1U << 10,
    > + PERF_SAMPLE_REGS = 1U << 11,
    >
    > - PERF_SAMPLE_MAX = 1U << 11, /* non-ABI */
    > + PERF_SAMPLE_MAX = 1U << 12, /* non-ABI */
    > };
    >
    > /*
    > @@ -392,6 +393,7 @@ enum perf_event_type {
    > * { u64 period; } && PERF_SAMPLE_PERIOD
    > *
    > * { struct read_format values; } && PERF_SAMPLE_READ
    > + * { struct pt_regs regs; } && PERF_SAMPLE_REGS
    > *
    > * { u64 nr,
    > * u64 ips[nr]; } && PERF_SAMPLE_CALLCHAIN
    > @@ -800,6 +802,7 @@ struct perf_sample_data {
    > u64 period;
    > struct perf_callchain_entry *callchain;
    > struct perf_raw_record *raw;
    > + struct pt_regs *regs;
    > };
    >
    > static inline
    > Index: linux-2.6/kernel/perf_event.c
    > ===================================================================
    > --- linux-2.6.orig/kernel/perf_event.c
    > +++ linux-2.6/kernel/perf_event.c
    > @@ -3176,6 +3176,17 @@ void perf_output_sample(struct perf_outp
    > if (sample_type & PERF_SAMPLE_READ)
    > perf_output_read(handle, event);
    >
    > + if (sample_type & PERF_SAMPLE_REGS) {
    > + int size = DIV_ROUND_UP(sizeof(struct pt_regs), sizeof(u64)) -
    > + sizeof(struct pt_regs);
    > +
    > + perf_output_put(handle, *data->regs);
    > + if (size) {
    > + u64 zero = 0;
    > + perf_output_copy(handle, &zero, size);
    > + }
    > + }
    > +
    > if (sample_type & PERF_SAMPLE_CALLCHAIN) {
    > if (data->callchain) {
    > int size = 1;
    > @@ -3273,6 +3284,12 @@ void perf_prepare_sample(struct perf_eve
    > if (sample_type & PERF_SAMPLE_READ)
    > header->size += perf_event_read_size(event);
    >
    > + if (sample_type & PERF_SAMPLE_REGS) {
    > + data->regs = regs;
    > + header->size += DIV_ROUND_UP(sizeof(struct pt_regs),
    > + sizeof(u64));
    > + }
    > +
    > if (sample_type & PERF_SAMPLE_CALLCHAIN) {
    > int size = 1;
    >
    >
    > --
    >



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