lkml.org 
[lkml]   [2012]   [Jun]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 06/19] perf: Add ability to attach user stack dump to sample
Date
Introducing sample_stack_user value into the perf_event_attr
struct to define the size of the user stack dump to be attached
to the sample. The dump itself is triggered once the
sample_stack_user is not zero.

Beeing able to dump parts of the user stack, starting from the
stack pointer, will be useful to make a post mortem dwarf CFI
based stack unwinding.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Jiri Olsa <jolsa@redhat.com>
---
include/linux/perf_event.h | 5 +++
kernel/events/core.c | 66 ++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 71 insertions(+), 0 deletions(-)
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 8960968..8db1655 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -278,6 +278,11 @@ struct perf_event_attr {
* See asm/perf_regs.h for details.
*/
__u64 sample_regs_user;
+
+ /*
+ * Defines size of the user stack to dump on samples.
+ */
+ __u64 sample_stack_user;
};

/*
diff --git a/kernel/events/core.c b/kernel/events/core.c
index e4df59d..c1062a1 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3765,6 +3765,38 @@ perf_output_sample_regs(struct perf_output_handle *handle,
}
}

+static void
+perf_output_sample_ustack(struct perf_output_handle *handle, u64 dump_size,
+ struct pt_regs *regs)
+{
+ /* Case of a kernel thread, nothing to dump */
+ if (!regs) {
+ u64 size = 0;
+ perf_output_put(handle, size);
+ } else {
+ unsigned long sp;
+ unsigned int rem;
+ u64 dyn_size;
+
+ /*
+ * Static size: we always dump the size
+ * requested by the user because most of the
+ * time, the top of the user stack is not
+ * paged out.
+ */
+ perf_output_put(handle, dump_size);
+
+ sp = user_stack_pointer(regs);
+ rem = __output_copy_user(handle, (void *) sp, dump_size);
+ dyn_size = dump_size - rem;
+
+ perf_output_skip(handle, rem);
+
+ /* Dynamic size: whole dump - padding. */
+ perf_output_put(handle, dyn_size);
+ }
+}
+
static struct pt_regs *perf_sample_regs_user(struct pt_regs *regs)
{
if (!user_mode(regs)) {
@@ -4054,6 +4086,11 @@ void perf_output_sample(struct perf_output_handle *handle,
mask);
}
}
+
+ if (event->attr.sample_stack_user)
+ perf_output_sample_ustack(handle,
+ event->attr.sample_stack_user,
+ data->regs_user);
}

void perf_prepare_sample(struct perf_event_header *header,
@@ -4118,6 +4155,31 @@ void perf_prepare_sample(struct perf_event_header *header,

header->size += size;
}
+
+ if (event->attr.sample_stack_user) {
+ /*
+ * A first field that tells the _static_ size of the
+ * dump. 0 if there is nothing to dump (ie: we are in
+ * a kernel thread) otherwise the requested size.
+ */
+ int size = sizeof(u64);
+
+ if (!data->regs_user)
+ data->regs_user = perf_sample_regs_user(regs);
+
+ /*
+ * If there is something to dump, add space for the
+ * dump itself and for the field that tells the
+ * dynamic size, which is how many have been actually
+ * dumped.
+ */
+ if (data->regs_user) {
+ size += event->attr.sample_stack_user;
+ size += sizeof(u64);
+ }
+
+ header->size += size;
+ }
}

static void perf_event_output(struct perf_event *event,
@@ -6171,6 +6233,10 @@ static int perf_copy_attr(struct perf_event_attr __user *uattr,
if (attr->sample_regs_user)
ret = perf_reg_validate(attr->sample_regs_user);

+ if (attr->sample_stack_user)
+ attr->sample_stack_user = round_up(attr->sample_stack_user,
+ sizeof(u64));
+
out:
return ret;

--
1.7.7.6


\
 
 \ /
  Last update: 2012-06-11 16:24    [from the cache]
©2003-2014 Jasper Spaans. Advertise on this site