1 files changed, 50 insertions, 38 deletions

diff --git a/kernel/trace/trace_kdb.c b/kernel/trace/trace_kdb.c
index 57149bce6aad..b30795f34079 100644
--- a/kernel/trace/trace_kdb.c
+++ b/kernel/trace/trace_kdb.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * kdb helper for dumping the ftrace buffer
  *
@@ -16,49 +17,41 @@
 #include "trace.h"
 #include "trace_output.h"
 
-static void ftrace_dump_buf(int skip_lines, long cpu_file)
+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)
 {
-	/* use static because iter can be a bit big for the stack */
-	static struct trace_iterator iter;
-	static struct ring_buffer_iter *buffer_iter[CONFIG_NR_CPUS];
 	struct trace_array *tr;
 	unsigned int old_userobj;
 	int cnt = 0, cpu;
 
-	trace_init_global_iter(&iter);
-	iter.buffer_iter = buffer_iter;
 	tr = iter.tr;
 
-	for_each_tracing_cpu(cpu) {
-		atomic_inc(&per_cpu_ptr(iter.trace_buffer->data, cpu)->disabled);
-	}
-
 	old_userobj = tr->trace_flags;
 
 	/* don't look at user memory in panic mode */
-	tr->trace_flags &= ~TRACE_ITER_SYM_USEROBJ;
+	tr->trace_flags &= ~TRACE_ITER(SYM_USEROBJ);
 
 	kdb_printf("Dumping ftrace buffer:\n");
+	if (skip_entries)
+		kdb_printf("(skipping %d entries)\n", skip_entries);
 
-	/* reset all but tr, trace, and overruns */
-	memset(&iter.seq, 0,
-		   sizeof(struct trace_iterator) -
-		   offsetof(struct trace_iterator, seq));
+	trace_iterator_reset(&iter);
 	iter.iter_flags |= TRACE_FILE_LAT_FMT;
-	iter.pos = -1;
 
 	if (cpu_file == RING_BUFFER_ALL_CPUS) {
 		for_each_tracing_cpu(cpu) {
 			iter.buffer_iter[cpu] =
-			ring_buffer_read_prepare(iter.trace_buffer->buffer, cpu);
-			ring_buffer_read_start(iter.buffer_iter[cpu]);
+			ring_buffer_read_start(iter.array_buffer->buffer,
+					       cpu, GFP_ATOMIC);
 			tracing_iter_reset(&iter, cpu);
 		}
 	} else {
 		iter.cpu_file = cpu_file;
 		iter.buffer_iter[cpu_file] =
-			ring_buffer_read_prepare(iter.trace_buffer->buffer, cpu_file);
-		ring_buffer_read_start(iter.buffer_iter[cpu_file]);
+			ring_buffer_read_start(iter.array_buffer->buffer,
+						 cpu_file, GFP_ATOMIC);
 		tracing_iter_reset(&iter, cpu_file);
 	}
 
@@ -67,11 +60,11 @@ static void ftrace_dump_buf(int skip_lines, long cpu_file)
 			kdb_printf("---------------------------------\n");
 		cnt++;
 
-		if (!skip_lines) {
+		if (!skip_entries) {
 			print_trace_line(&iter);
 			trace_printk_seq(&iter.seq);
 		} else {
-			skip_lines--;
+			skip_entries--;
 		}
 
 		if (KDB_FLAG(CMD_INTERRUPT))
@@ -87,10 +80,6 @@ out:
 	tr->trace_flags = old_userobj;
 
 	for_each_tracing_cpu(cpu) {
-		atomic_dec(&per_cpu_ptr(iter.trace_buffer->data, cpu)->disabled);
-	}
-
-	for_each_tracing_cpu(cpu) {
 		if (iter.buffer_iter[cpu]) {
 			ring_buffer_read_finish(iter.buffer_iter[cpu]);
 			iter.buffer_iter[cpu] = NULL;
@@ -103,22 +92,20 @@ out:
  */
 static int kdb_ftdump(int argc, const char **argv)
 {
-	int skip_lines = 0;
+	int skip_entries = 0;
 	long cpu_file;
-	char *cp;
+	int err;
+	int cnt;
 
 	if (argc > 2)
 		return KDB_ARGCOUNT;
 
-	if (argc) {
-		skip_lines = simple_strtol(argv[1], &cp, 0);
-		if (*cp)
-			skip_lines = 0;
-	}
+	if (argc && kstrtoint(argv[1], 0, &skip_entries))
+		return KDB_BADINT;
 
 	if (argc == 2) {
-		cpu_file = simple_strtol(argv[2], &cp, 0);
-		if (*cp || cpu_file >= NR_CPUS || cpu_file < 0 ||
+		err = kstrtol(argv[2], 0, &cpu_file);
+		if (err || cpu_file >= NR_CPUS || cpu_file < 0 ||
 		    !cpu_online(cpu_file))
 			return KDB_BADINT;
 	} else {
@@ -126,16 +113,41 @@ static int kdb_ftdump(int argc, const char **argv)
 	}
 
 	kdb_trap_printk++;
-	ftrace_dump_buf(skip_lines, cpu_file);
+
+	trace_init_global_iter(&iter);
+	iter.buffer_iter = buffer_iter;
+
+	tracer_tracing_disable(iter.tr);
+
+	/* 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);
+
+	tracer_tracing_enable(iter.tr);
+
 	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_flags("ftdump", kdb_ftdump, "[skip_#lines] [cpu]",
-			    "Dump ftrace log", 0, KDB_ENABLE_ALWAYS_SAFE);
+	kdb_register(&ftdump_cmd);
 	return 0;
 }