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mm/damon: hide kernel pointer from tracepoint event 

DAMON's virtual address spaces monitoring primitive uses 'struct pid *'
of the target process as its monitoring target id.  The kernel address
is exposed as-is to the user space via the DAMON tracepoint,
'damon_aggregated'.

Though primarily only privileged users are allowed to access that, it
would be better to avoid unnecessarily exposing kernel pointers so.
Because the trace result is only required to be able to distinguish each
target, we aren't need to use the pointer as-is.

This makes the tracepoint to use the index of the target in the
context's targets list as its id in the tracepoint, to hide the kernel
space address.

Link: https://lkml.kernel.org/r/20211229131016.23641-5-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
SeongJae Park 2022-01-14 14:10:50 -08:00 committed by Linus Torvalds
parent 962fe7a6b1
commit 76fd0285b4
2 changed files with 7 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
include/trace/events/damon.h
View File

@ -11,10 +11,10 @@
TRACE_EVENT(damon_aggregated,
TP_PROTO(struct damon_target *t, struct damon_region *r,
unsigned int nr_regions),
TP_PROTO(struct damon_target *t, unsigned int target_id,
struct damon_region *r, unsigned int nr_regions),
TP_ARGS(t, r, nr_regions),
TP_ARGS(t, target_id, r, nr_regions),
TP_STRUCT__entry(
__field(unsigned long, target_id)
@ -26,7 +26,7 @@ TRACE_EVENT(damon_aggregated,
),
TP_fast_assign(
__entry->target_id = t->id;
__entry->target_id = target_id;
__entry->nr_regions = nr_regions;
__entry->start = r->ar.start;
__entry->end = r->ar.end;

4
mm/damon/core.c
View File

@ -514,15 +514,17 @@ static bool kdamond_aggregate_interval_passed(struct damon_ctx *ctx)
static void kdamond_reset_aggregated(struct damon_ctx *c)
{
struct damon_target *t;
unsigned int ti = 0; /* target's index */
damon_for_each_target(t, c) {
struct damon_region *r;
damon_for_each_region(r, t) {
trace_damon_aggregated(t, r, damon_nr_regions(t));
trace_damon_aggregated(t, ti, r, damon_nr_regions(t));
r->last_nr_accesses = r->nr_accesses;
r->nr_accesses = 0;
}
ti++;
}
}