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.thomp...@linaro.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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