| Message ID | 9d4f76f3a0bffe93a6d5146c9b53ee7b985f22da.1499416107.git.panand@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Fri, Jul 07, 2017 at 05:33:57PM +0530, Pratyush Anand wrote: > Architecture like ARM64 currently allows to use default hw breakpoint > single step handler only to perf. However, some other users like few > systemtap tests or kernel test in > samples/hw_breakpoint/data_breakpoint.c can also work with default step > handler implementation. At the same time, some other like GDB/ptrace may > implement their own step handler. > > Therefore, this patch introduces a new perf_event_attr bit field, so > that arch specific code(specially on arm64) can make a decision to > enable single stepping. > > Any architecture which is not using this field will not have any > side effect. > > Signed-off-by: Pratyush Anand <panand@redhat.com> > --- > include/linux/hw_breakpoint.h | 6 ++++++ > include/uapi/linux/perf_event.h | 3 ++- > kernel/events/core.c | 2 ++ > tools/include/uapi/linux/perf_event.h | 3 ++- > 4 files changed, 12 insertions(+), 2 deletions(-) > > diff --git a/include/linux/hw_breakpoint.h b/include/linux/hw_breakpoint.h > index 0464c85e63fd..6173ae048cbc 100644 > --- a/include/linux/hw_breakpoint.h > +++ b/include/linux/hw_breakpoint.h > @@ -38,6 +38,12 @@ static inline int hw_breakpoint_type(struct perf_event *bp) > return bp->attr.bp_type; > } > > +static inline bool > +hw_breakpoint_needs_single_step(struct perf_event *bp) > +{ > + return bp->attr.step_needed; > +} > + > static inline unsigned long hw_breakpoint_len(struct perf_event *bp) > { > return bp->attr.bp_len; > diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h > index b1c0b187acfe..00935808de0d 100644 > --- a/include/uapi/linux/perf_event.h > +++ b/include/uapi/linux/perf_event.h > @@ -345,7 +345,8 @@ struct perf_event_attr { > context_switch : 1, /* context switch data */ > write_backward : 1, /* Write ring buffer from end to beginning */ > namespaces : 1, /* include namespaces data */ > - __reserved_1 : 35; > + step_needed : 1, /* Use arch step handler */ > + __reserved_1 : 34; This needs documenting properly, as I really have no idea how userspace is going to use it sensibley, especially as you silently overwrite it in some cases below. Will > > union { > __u32 wakeup_events; /* wakeup every n events */ > diff --git a/kernel/events/core.c b/kernel/events/core.c > index 6c4e523dc1e2..220e26941475 100644 > --- a/kernel/events/core.c > +++ b/kernel/events/core.c > @@ -9444,9 +9444,11 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu, > } else if (is_write_backward(event)){ > event->overflow_handler = perf_event_output_backward; > event->overflow_handler_context = NULL; > + event->attr.step_needed = 1; > } else { > event->overflow_handler = perf_event_output_forward; > event->overflow_handler_context = NULL; > + event->attr.step_needed = 1; > } > > perf_event__state_init(event); > diff --git a/tools/include/uapi/linux/perf_event.h b/tools/include/uapi/linux/perf_event.h > index b1c0b187acfe..00935808de0d 100644 > --- a/tools/include/uapi/linux/perf_event.h > +++ b/tools/include/uapi/linux/perf_event.h > @@ -345,7 +345,8 @@ struct perf_event_attr { > context_switch : 1, /* context switch data */ > write_backward : 1, /* Write ring buffer from end to beginning */ > namespaces : 1, /* include namespaces data */ > - __reserved_1 : 35; > + step_needed : 1, /* Use arch step handler */ > + __reserved_1 : 34; > > union { > __u32 wakeup_events; /* wakeup every n events */ > -- > 2.9.3 >
On Tue, Jul 25, 2017 at 02:27:38PM +0100, Will Deacon wrote: > On Fri, Jul 07, 2017 at 05:33:57PM +0530, Pratyush Anand wrote: > > Architecture like ARM64 currently allows to use default hw breakpoint > > single step handler only to perf. However, some other users like few > > systemtap tests or kernel test in > > samples/hw_breakpoint/data_breakpoint.c can also work with default step > > handler implementation. At the same time, some other like GDB/ptrace may > > implement their own step handler. > > > > Therefore, this patch introduces a new perf_event_attr bit field, so > > that arch specific code(specially on arm64) can make a decision to > > enable single stepping. > > > > Any architecture which is not using this field will not have any > > side effect. > > diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h > > index b1c0b187acfe..00935808de0d 100644 > > --- a/include/uapi/linux/perf_event.h > > +++ b/include/uapi/linux/perf_event.h > > @@ -345,7 +345,8 @@ struct perf_event_attr { > > context_switch : 1, /* context switch data */ > > write_backward : 1, /* Write ring buffer from end to beginning */ > > namespaces : 1, /* include namespaces data */ > > - __reserved_1 : 35; > > + step_needed : 1, /* Use arch step handler */ > > + __reserved_1 : 34; > > This needs documenting properly, as I really have no idea how userspace is > going to use it sensibley, especially as you silently overwrite it in some > cases below. This is not something userspace _can_ use sensibly afaict. Therefore it should probably not live here.
On Tue, Jul 25, 2017 at 04:14:23PM +0200, Peter Zijlstra wrote: > On Tue, Jul 25, 2017 at 02:27:38PM +0100, Will Deacon wrote: > > On Fri, Jul 07, 2017 at 05:33:57PM +0530, Pratyush Anand wrote: > > > Architecture like ARM64 currently allows to use default hw breakpoint > > > single step handler only to perf. However, some other users like few > > > systemtap tests or kernel test in > > > samples/hw_breakpoint/data_breakpoint.c can also work with default step > > > handler implementation. At the same time, some other like GDB/ptrace may > > > implement their own step handler. > > > > > > Therefore, this patch introduces a new perf_event_attr bit field, so > > > that arch specific code(specially on arm64) can make a decision to > > > enable single stepping. > > > > > > Any architecture which is not using this field will not have any > > > side effect. > > > > diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h > > > index b1c0b187acfe..00935808de0d 100644 > > > --- a/include/uapi/linux/perf_event.h > > > +++ b/include/uapi/linux/perf_event.h > > > @@ -345,7 +345,8 @@ struct perf_event_attr { > > > context_switch : 1, /* context switch data */ > > > write_backward : 1, /* Write ring buffer from end to beginning */ > > > namespaces : 1, /* include namespaces data */ > > > - __reserved_1 : 35; > > > + step_needed : 1, /* Use arch step handler */ > > > + __reserved_1 : 34; > > > > This needs documenting properly, as I really have no idea how userspace is > > going to use it sensibley, especially as you silently overwrite it in some > > cases below. > > This is not something userspace _can_ use sensibly afaict. Therefore it > should probably not live here. Indeed. When I suggested this, I meant that it would be a kernel-internal flag, and not UAPI. Thanks, Mark.
On Tuesday 25 July 2017 06:57 PM, Will Deacon wrote: > On Fri, Jul 07, 2017 at 05:33:57PM +0530, Pratyush Anand wrote: >> Architecture like ARM64 currently allows to use default hw breakpoint >> single step handler only to perf. However, some other users like few >> systemtap tests or kernel test in >> samples/hw_breakpoint/data_breakpoint.c can also work with default step >> handler implementation. At the same time, some other like GDB/ptrace may >> implement their own step handler. >> >> Therefore, this patch introduces a new perf_event_attr bit field, so >> that arch specific code(specially on arm64) can make a decision to >> enable single stepping. >> >> Any architecture which is not using this field will not have any >> side effect. >> >> Signed-off-by: Pratyush Anand <panand@redhat.com> >> --- >> include/linux/hw_breakpoint.h | 6 ++++++ >> include/uapi/linux/perf_event.h | 3 ++- >> kernel/events/core.c | 2 ++ >> tools/include/uapi/linux/perf_event.h | 3 ++- >> 4 files changed, 12 insertions(+), 2 deletions(-) >> >> diff --git a/include/linux/hw_breakpoint.h b/include/linux/hw_breakpoint.h >> index 0464c85e63fd..6173ae048cbc 100644 >> --- a/include/linux/hw_breakpoint.h >> +++ b/include/linux/hw_breakpoint.h >> @@ -38,6 +38,12 @@ static inline int hw_breakpoint_type(struct perf_event *bp) >> return bp->attr.bp_type; >> } >> >> +static inline bool >> +hw_breakpoint_needs_single_step(struct perf_event *bp) >> +{ >> + return bp->attr.step_needed; >> +} >> + >> static inline unsigned long hw_breakpoint_len(struct perf_event *bp) >> { >> return bp->attr.bp_len; >> diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h >> index b1c0b187acfe..00935808de0d 100644 >> --- a/include/uapi/linux/perf_event.h >> +++ b/include/uapi/linux/perf_event.h >> @@ -345,7 +345,8 @@ struct perf_event_attr { >> context_switch : 1, /* context switch data */ >> write_backward : 1, /* Write ring buffer from end to beginning */ >> namespaces : 1, /* include namespaces data */ >> - __reserved_1 : 35; >> + step_needed : 1, /* Use arch step handler */ >> + __reserved_1 : 34; > > This needs documenting properly, as I really have no idea how userspace is > going to use it sensibley, especially as you silently overwrite it in some > cases below. I too had thought to put it under include/linux/perf_event.h : struct perf_event. But, see hw_break_module_init() which does not have knowledge of this structure, and we need to have some way so that none-perf kernel module implementation can tell that it needs default arch step handler. Do you see any alternative?
On Wed, Jul 26, 2017 at 11:12:03AM +0530, Pratyush Anand wrote: > I too had thought to put it under include/linux/perf_event.h : struct > perf_event. But, see hw_break_module_init() which does not have knowledge of > this structure, and we need to have some way so that none-perf kernel module > implementation can tell that it needs default arch step handler. > > Do you see any alternative? Fix the hw_breakpoint interface?
diff --git a/include/linux/hw_breakpoint.h b/include/linux/hw_breakpoint.h index 0464c85e63fd..6173ae048cbc 100644 --- a/include/linux/hw_breakpoint.h +++ b/include/linux/hw_breakpoint.h @@ -38,6 +38,12 @@ static inline int hw_breakpoint_type(struct perf_event *bp) return bp->attr.bp_type; } +static inline bool +hw_breakpoint_needs_single_step(struct perf_event *bp) +{ + return bp->attr.step_needed; +} + static inline unsigned long hw_breakpoint_len(struct perf_event *bp) { return bp->attr.bp_len; diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h index b1c0b187acfe..00935808de0d 100644 --- a/include/uapi/linux/perf_event.h +++ b/include/uapi/linux/perf_event.h @@ -345,7 +345,8 @@ struct perf_event_attr { context_switch : 1, /* context switch data */ write_backward : 1, /* Write ring buffer from end to beginning */ namespaces : 1, /* include namespaces data */ - __reserved_1 : 35; + step_needed : 1, /* Use arch step handler */ + __reserved_1 : 34; union { __u32 wakeup_events; /* wakeup every n events */ diff --git a/kernel/events/core.c b/kernel/events/core.c index 6c4e523dc1e2..220e26941475 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -9444,9 +9444,11 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu, } else if (is_write_backward(event)){ event->overflow_handler = perf_event_output_backward; event->overflow_handler_context = NULL; + event->attr.step_needed = 1; } else { event->overflow_handler = perf_event_output_forward; event->overflow_handler_context = NULL; + event->attr.step_needed = 1; } perf_event__state_init(event); diff --git a/tools/include/uapi/linux/perf_event.h b/tools/include/uapi/linux/perf_event.h index b1c0b187acfe..00935808de0d 100644 --- a/tools/include/uapi/linux/perf_event.h +++ b/tools/include/uapi/linux/perf_event.h @@ -345,7 +345,8 @@ struct perf_event_attr { context_switch : 1, /* context switch data */ write_backward : 1, /* Write ring buffer from end to beginning */ namespaces : 1, /* include namespaces data */ - __reserved_1 : 35; + step_needed : 1, /* Use arch step handler */ + __reserved_1 : 34; union { __u32 wakeup_events; /* wakeup every n events */
Architecture like ARM64 currently allows to use default hw breakpoint single step handler only to perf. However, some other users like few systemtap tests or kernel test in samples/hw_breakpoint/data_breakpoint.c can also work with default step handler implementation. At the same time, some other like GDB/ptrace may implement their own step handler. Therefore, this patch introduces a new perf_event_attr bit field, so that arch specific code(specially on arm64) can make a decision to enable single stepping. Any architecture which is not using this field will not have any side effect. Signed-off-by: Pratyush Anand <panand@redhat.com> --- include/linux/hw_breakpoint.h | 6 ++++++ include/uapi/linux/perf_event.h | 3 ++- kernel/events/core.c | 2 ++ tools/include/uapi/linux/perf_event.h | 3 ++- 4 files changed, 12 insertions(+), 2 deletions(-)