tracing: provide trace_seq_reserve()
trace_seq_reserve() allows a caller to reserve space in a trace_seq and
write directly into it. This makes it easier to export binary data to
userspace via the tracing interface, by simply filling in a struct.
Signed-off-by: Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index 19261fd..6595074 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -167,6 +167,19 @@
return trace_seq_putmem(s, hex, j);
}
+void *trace_seq_reserve(struct trace_seq *s, size_t len)
+{
+ void *ret;
+
+ if (len > ((PAGE_SIZE - 1) - s->len))
+ return NULL;
+
+ ret = s->buffer + s->len;
+ s->len += len;
+
+ return ret;
+}
+
int trace_seq_path(struct trace_seq *s, struct path *path)
{
unsigned char *p;
diff --git a/kernel/trace/trace_output.h b/kernel/trace/trace_output.h
index 35c422f..0ae20b8 100644
--- a/kernel/trace/trace_output.h
+++ b/kernel/trace/trace_output.h
@@ -33,6 +33,7 @@
int trace_seq_putc(struct trace_seq *s, unsigned char c);
int trace_seq_putmem(struct trace_seq *s, void *mem, size_t len);
int trace_seq_putmem_hex(struct trace_seq *s, void *mem, size_t len);
+void *trace_seq_reserve(struct trace_seq *s, size_t len);
int trace_seq_path(struct trace_seq *s, struct path *path);
int seq_print_userip_objs(const struct userstack_entry *entry,
struct trace_seq *s, unsigned long sym_flags);
