1 files changed, 164 insertions, 0 deletions
diff --git a/kernel/trace/trace_kdb.c b/kernel/trace/trace_kdb.c
new file mode 100644
index 000000000..59857a1ee
--- /dev/null
+++ b/kernel/trace/trace_kdb.c
@@ -0,0 +1,164 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * kdb helper for dumping the ftrace buffer
+ *
+ * Copyright (C) 2010 Jason Wessel <jason.wessel@windriver.com>
+ *
+ * ftrace_dump_buf based on ftrace_dump:
+ * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
+ * Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>
+ *
+ */
+#include <linux/init.h>
+#include <linux/kgdb.h>
+#include <linux/kdb.h>
+#include <linux/ftrace.h>
+
+#include "trace.h"
+#include "trace_output.h"
+
+static struct trace_iterator iter;
+static struct ring_buffer_iter *buffer_iter[CONFIG_NR_CPUS];
+
+static void ftrace_dump_buf(int skip_entries, long cpu_file)
+{
+	struct trace_array *tr;
+	unsigned int old_userobj;
+	int cnt = 0, cpu;
+
+	tr = iter.tr;
+
+	old_userobj = tr->trace_flags;
+
+	/* don't look at user memory in panic mode */
+	tr->trace_flags &= ~TRACE_ITER_SYM_USEROBJ;
+
+	kdb_printf("Dumping ftrace buffer:\n");
+	if (skip_entries)
+		kdb_printf("(skipping %d entries)\n", skip_entries);
+
+	trace_iterator_reset(&iter);
+	iter.iter_flags |= TRACE_FILE_LAT_FMT;
+
+	if (cpu_file == RING_BUFFER_ALL_CPUS) {
+		for_each_tracing_cpu(cpu) {
+			iter.buffer_iter[cpu] =
+			ring_buffer_read_prepare(iter.array_buffer->buffer,
+						 cpu, GFP_ATOMIC);
+			ring_buffer_read_start(iter.buffer_iter[cpu]);
+			tracing_iter_reset(&iter, cpu);
+		}
+	} else {
+		iter.cpu_file = cpu_file;
+		iter.buffer_iter[cpu_file] =
+			ring_buffer_read_prepare(iter.array_buffer->buffer,
+						 cpu_file, GFP_ATOMIC);
+		ring_buffer_read_start(iter.buffer_iter[cpu_file]);
+		tracing_iter_reset(&iter, cpu_file);
+	}
+
+	while (trace_find_next_entry_inc(&iter)) {
+		if (!cnt)
+			kdb_printf("---------------------------------\n");
+		cnt++;
+
+		if (!skip_entries) {
+			print_trace_line(&iter);
+			trace_printk_seq(&iter.seq);
+		} else {
+			skip_entries--;
+		}
+
+		if (KDB_FLAG(CMD_INTERRUPT))
+			goto out;
+	}
+
+	if (!cnt)
+		kdb_printf("   (ftrace buffer empty)\n");
+	else
+		kdb_printf("---------------------------------\n");
+
+out:
+	tr->trace_flags = old_userobj;
+
+	for_each_tracing_cpu(cpu) {
+		if (iter.buffer_iter[cpu]) {
+			ring_buffer_read_finish(iter.buffer_iter[cpu]);
+			iter.buffer_iter[cpu] = NULL;
+		}
+	}
+}
+
+/*
+ * kdb_ftdump - Dump the ftrace log buffer
+ */
+static int kdb_ftdump(int argc, const char **argv)
+{
+	int skip_entries = 0;
+	long cpu_file;
+	char *cp;
+	int cnt;
+	int cpu;
+
+	if (argc > 2)
+		return KDB_ARGCOUNT;
+
+	if (argc) {
+		skip_entries = simple_strtol(argv[1], &cp, 0);
+		if (*cp)
+			skip_entries = 0;
+	}
+
+	if (argc == 2) {
+		cpu_file = simple_strtol(argv[2], &cp, 0);
+		if (*cp || cpu_file >= NR_CPUS || cpu_file < 0 ||
+		    !cpu_online(cpu_file))
+			return KDB_BADINT;
+	} else {
+		cpu_file = RING_BUFFER_ALL_CPUS;
+	}
+
+	kdb_trap_printk++;
+
+	trace_init_global_iter(&iter);
+	iter.buffer_iter = buffer_iter;
+
+	for_each_tracing_cpu(cpu) {
+		atomic_inc(&per_cpu_ptr(iter.array_buffer->data, cpu)->disabled);
+	}
+
+	/* A negative skip_entries means skip all but the last entries */
+	if (skip_entries < 0) {
+		if (cpu_file == RING_BUFFER_ALL_CPUS)
+			cnt = trace_total_entries(NULL);
+		else
+			cnt = trace_total_entries_cpu(NULL, cpu_file);
+		skip_entries = max(cnt + skip_entries, 0);
+	}
+
+	ftrace_dump_buf(skip_entries, cpu_file);
+
+	for_each_tracing_cpu(cpu) {
+		atomic_dec(&per_cpu_ptr(iter.array_buffer->data, cpu)->disabled);
+	}
+
+	kdb_trap_printk--;
+
+	return 0;
+}
+
+static kdbtab_t ftdump_cmd = {
+	.name = "ftdump",
+	.func = kdb_ftdump,
+	.usage = "[skip_#entries] [cpu]",
+	.help = "Dump ftrace log; -skip dumps last #entries",
+	.flags = KDB_ENABLE_ALWAYS_SAFE,
+};
+
+static __init int kdb_ftrace_register(void)
+{
+	kdb_register(&ftdump_cmd);
+	return 0;
+}
+
+late_initcall(kdb_ftrace_register);