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Diffstat (limited to 'kernel/tracepoint.c')
-rw-r--r--kernel/tracepoint.c91
1 files changed, 59 insertions, 32 deletions
diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index 7261fa0f5e3c..9f478d29b926 100644
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -53,6 +53,12 @@ struct tp_probes {
struct tracepoint_func probes[];
};
+/* Called in removal of a func but failed to allocate a new tp_funcs */
+static void tp_stub_func(void)
+{
+ return;
+}
+
static inline void *allocate_probes(int count)
{
struct tp_probes *p = kmalloc(struct_size(p, probes, count),
@@ -130,8 +136,9 @@ func_add(struct tracepoint_func **funcs, struct tracepoint_func *tp_func,
int prio)
{
struct tracepoint_func *old, *new;
- int nr_probes = 0;
- int pos = -1;
+ int iter_probes; /* Iterate over old probe array. */
+ int nr_probes = 0; /* Counter for probes */
+ int pos = -1; /* Insertion position into new array */
if (WARN_ON(!tp_func->func))
return ERR_PTR(-EINVAL);
@@ -140,13 +147,13 @@ func_add(struct tracepoint_func **funcs, struct tracepoint_func *tp_func,
old = *funcs;
if (old) {
/* (N -> N+1), (N != 0, 1) probes */
- for (nr_probes = 0; old[nr_probes].func; nr_probes++) {
- /* Insert before probes of lower priority */
- if (pos < 0 && old[nr_probes].prio < prio)
- pos = nr_probes;
- if (old[nr_probes].func == tp_func->func &&
- old[nr_probes].data == tp_func->data)
+ for (iter_probes = 0; old[iter_probes].func; iter_probes++) {
+ if (old[iter_probes].func == tp_stub_func)
+ continue; /* Skip stub functions. */
+ if (old[iter_probes].func == tp_func->func &&
+ old[iter_probes].data == tp_func->data)
return ERR_PTR(-EEXIST);
+ nr_probes++;
}
}
/* + 2 : one for new probe, one for NULL func */
@@ -154,20 +161,24 @@ func_add(struct tracepoint_func **funcs, struct tracepoint_func *tp_func,
if (new == NULL)
return ERR_PTR(-ENOMEM);
if (old) {
- if (pos < 0) {
- pos = nr_probes;
- memcpy(new, old, nr_probes * sizeof(struct tracepoint_func));
- } else {
- /* Copy higher priority probes ahead of the new probe */
- memcpy(new, old, pos * sizeof(struct tracepoint_func));
- /* Copy the rest after it. */
- memcpy(new + pos + 1, old + pos,
- (nr_probes - pos) * sizeof(struct tracepoint_func));
+ nr_probes = 0;
+ for (iter_probes = 0; old[iter_probes].func; iter_probes++) {
+ if (old[iter_probes].func == tp_stub_func)
+ continue;
+ /* Insert before probes of lower priority */
+ if (pos < 0 && old[iter_probes].prio < prio)
+ pos = nr_probes++;
+ new[nr_probes++] = old[iter_probes];
}
- } else
+ if (pos < 0)
+ pos = nr_probes++;
+ /* nr_probes now points to the end of the new array */
+ } else {
pos = 0;
+ nr_probes = 1; /* must point at end of array */
+ }
new[pos] = *tp_func;
- new[nr_probes + 1].func = NULL;
+ new[nr_probes].func = NULL;
*funcs = new;
debug_print_probes(*funcs);
return old;
@@ -188,8 +199,9 @@ static void *func_remove(struct tracepoint_func **funcs,
/* (N -> M), (N > 1, M >= 0) probes */
if (tp_func->func) {
for (nr_probes = 0; old[nr_probes].func; nr_probes++) {
- if (old[nr_probes].func == tp_func->func &&
- old[nr_probes].data == tp_func->data)
+ if ((old[nr_probes].func == tp_func->func &&
+ old[nr_probes].data == tp_func->data) ||
+ old[nr_probes].func == tp_stub_func)
nr_del++;
}
}
@@ -208,14 +220,27 @@ static void *func_remove(struct tracepoint_func **funcs,
/* N -> M, (N > 1, M > 0) */
/* + 1 for NULL */
new = allocate_probes(nr_probes - nr_del + 1);
- if (new == NULL)
- return ERR_PTR(-ENOMEM);
- for (i = 0; old[i].func; i++)
- if (old[i].func != tp_func->func
- || old[i].data != tp_func->data)
- new[j++] = old[i];
- new[nr_probes - nr_del].func = NULL;
- *funcs = new;
+ if (new) {
+ for (i = 0; old[i].func; i++) {
+ if ((old[i].func != tp_func->func ||
+ old[i].data != tp_func->data) &&
+ old[i].func != tp_stub_func)
+ new[j++] = old[i];
+ }
+ new[nr_probes - nr_del].func = NULL;
+ *funcs = new;
+ } else {
+ /*
+ * Failed to allocate, replace the old function
+ * with calls to tp_stub_func.
+ */
+ for (i = 0; old[i].func; i++) {
+ if (old[i].func == tp_func->func &&
+ old[i].data == tp_func->data)
+ WRITE_ONCE(old[i].func, tp_stub_func);
+ }
+ *funcs = old;
+ }
}
debug_print_probes(*funcs);
return old;
@@ -295,10 +320,12 @@ static int tracepoint_remove_func(struct tracepoint *tp,
tp_funcs = rcu_dereference_protected(tp->funcs,
lockdep_is_held(&tracepoints_mutex));
old = func_remove(&tp_funcs, func);
- if (IS_ERR(old)) {
- WARN_ON_ONCE(PTR_ERR(old) != -ENOMEM);
+ if (WARN_ON_ONCE(IS_ERR(old)))
return PTR_ERR(old);
- }
+
+ if (tp_funcs == old)
+ /* Failed allocating new tp_funcs, replaced func with stub */
+ return 0;
if (!tp_funcs) {
/* Removed last function */