tracing: Add trace_seq_pop() and seq_buf_pop()

In order to allow an interface to remove an added character from the
trace_seq and seq_buf descriptors, add helper functions trace_seq_pop()
and seq_buf_pop().

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Takaya Saeki <takayas@google.com>
Cc: Tom Zanussi <zanussi@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ian Rogers <irogers@google.com>
Cc: Douglas Raillard <douglas.raillard@arm.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Link: https://lore.kernel.org/20251028231148.594898736@kernel.org
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/include/linux/seq_buf.h b/include/linux/seq_buf.h
index 52791e0705063ec646c51824a2bbb2408b093fde..9f2839e73f8a1dc69cd2a6bc43e79e1628dce5a4 100644 (file)
--- a/include/linux/seq_buf.h
+++ b/include/linux/seq_buf.h
@@ -149,6 +149,23 @@ static inline void seq_buf_commit(struct seq_buf *s, int num)
        }
 }
 
+/**
+ * seq_buf_pop - pop off the last written character
+ * @s: the seq_buf handle
+ *
+ * Removes the last written character to the seq_buf @s.
+ *
+ * Returns the last character or -1 if it is empty.
+ */
+static inline int seq_buf_pop(struct seq_buf *s)
+{
+       if (!s->len)
+               return -1;
+
+       s->len--;
+       return (unsigned int)s->buffer[s->len];
+}
+
 extern __printf(2, 3)
 int seq_buf_printf(struct seq_buf *s, const char *fmt, ...);
 extern __printf(2, 0)

diff --git a/include/linux/trace_seq.h b/include/linux/trace_seq.h
index 557780fe1c775a7ebd53331f4cdbe80d3485f863..4a0b8c172d274fa54c2a3604ae9693edd1b245c8 100644 (file)
--- a/include/linux/trace_seq.h
+++ b/include/linux/trace_seq.h
@@ -80,6 +80,19 @@ static inline bool trace_seq_has_overflowed(struct trace_seq *s)
        return s->full || seq_buf_has_overflowed(&s->seq);
 }
 
+/**
+ * trace_seq_pop - pop off the last written character
+ * @s: trace sequence descriptor
+ *
+ * Removes the last written character to the trace_seq @s.
+ *
+ * Returns the last character or -1 if it is empty.
+ */
+static inline int trace_seq_pop(struct trace_seq *s)
+{
+       return seq_buf_pop(&s->seq);
+}
+
 /*
  * Currently only defined when tracing is enabled.
  */