linux-kernel - [PATCH 3/3] kdb: Implement seq

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Message-Id: <1398872427-18435-4-git-send-email-daniel.thompson@linaro.org>
Date:	Wed, 30 Apr 2014 16:40:27 +0100
From:	Daniel Thompson <daniel.thompson@...aro.org>
To:	kgdb-bugreport@...ts.sourceforge.net,
	Jason Wessel <jason.wessel@...driver.com>
Cc:	patches@...aro.org, linaro-kernel@...ts.linaro.org,
	Daniel Thompson <daniel.thompson@...aro.org>,
	linux-kernel@...r.kernel.org,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mike Travis <travis@....com>,
	Dimitri Sivanich <sivanich@....com>,
	Hedi Berriche <hedi@....com>,
	John Stultz <john.stultz@...aro.org>,
	Anton Vorontsov <anton.vorontsov@...aro.org>,
	Colin Cross <ccross@...roid.com>, kernel-team@...roid.com
Subject: [PATCH 3/3] kdb: Implement seq_file command

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@...aro.org>
---
 kernel/debug/kdb/kdb_io.c   |  6 ++++--
 kernel/debug/kdb/kdb_main.c | 28 ++++++++++++++++++++++++++++
 2 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/kernel/debug/kdb/kdb_io.c b/kernel/debug/kdb/kdb_io.c
index c68c223..5863180 100644
--- a/kernel/debug/kdb/kdb_io.c
+++ b/kernel/debug/kdb/kdb_io.c
@@ -878,8 +878,10 @@ int kdb_print_seq_file(const struct seq_operations *ops)
 	struct seq_file m = {
 		.buf = seq_buf,
 		.size = sizeof(seq_buf),
-		/* .lock is deliberately uninitialized to help reveal
-		 * unsupportable show methods
+		/* .lock is deliberately left uninitialized because it is
+		 * used by seq_file read/lseek wrapper functions. It cannot be
+		 * used from any of the seq_operations (assuming the ops are
+		 * deadlock free with the normal interface).
 		 */
 		.op = ops,
 	};
diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c
index 0b097c8..d87731c 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.  */
-- 
1.9.0

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