[PATCH v3 3/3] kdb: Implement seq_file command

[Daniel Thompson <daniel.thompson@linaro.org>]

Combining the kdb seq_file infrastructure with its symbolic lookups allows
a good sub-set of files held in pseudo filesystems to be displayed by
kdb. The seq_file command does exactly this and allows a significant
subset of pseudo files to be safely examined whilst debugging (and in
the hands of a brave expert an even bigger subset can be unsafely
examined).

Good arguments to try with this command include: cpuinfo_op,
gpiolib_seq_ops and vmalloc_op.

Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
---
 kernel/debug/kdb/kdb_main.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c
index 379650b..f11db91 100644
--- a/kernel/debug/kdb/kdb_main.c
+++ b/kernel/debug/kdb/kdb_main.c
@@ -1734,6 +1734,32 @@ static int kdb_mm(int argc, const char **argv)
 }
 
 /*
+ * kdb_seq_file - This function implements the 'seq_file' command.
+ *	seq_file address-expression
+ */
+static int kdb_seq_file(int argc, const char **argv)
+{
+	int diag;
+	unsigned long addr;
+	int nextarg;
+	long offset;
+	char *name;
+	const struct seq_operations *ops;
+
+	nextarg = 1;
+	diag = kdbgetaddrarg(argc, argv, &nextarg, &addr, &offset, &name);
+	if (diag)
+		return diag;
+
+	if (nextarg != argc+1)
+		return KDB_ARGCOUNT;
+
+	ops = (const struct seq_operations *) (addr + offset);
+	kdb_printf("Using sequence_ops at 0x%p (%s)\n", ops, name);
+	return kdb_print_seq_file(ops);
+}
+
+/*
  * kdb_go - This function implements the 'go' command.
  *	go [address-expression]
  */
@@ -2838,6 +2864,8 @@ static void __init kdb_inittab(void)
 	  "Display per_cpu variables", 3, KDB_REPEAT_NONE);
 	kdb_register_repeat("grephelp", kdb_grep_help, "",
 	  "Display help on | grep", 0, KDB_REPEAT_NONE);
+	kdb_register_repeat("seq_file", kdb_seq_file, "",
+	  "Show a seq_file using struct seq_operations", 3, KDB_REPEAT_NONE);
 }
 
 /* Execute any commands defined in kdb_cmds.  */
-- 
1.9.3