[PATCH 14/16] dyndbg: add inverted-flags, implement filtering on flags

[Jim Cromie]

1. Add 3 user-flags [xyz] which work like original [pfmlt] flags, but
have no effect on callsite behavior; they allow marking of arbitrary
sets of callsites.  Just adding the flag defs themselves is enough,
they inherit the existing flags mechanics.

2. Add [PFMLT],[XYZ] flags, which invert their counterparts; P===!p etc.
And in ddebug_read_flags():
   current code does:	[pfmlt_xyz] -> flags
   copy it to:		[PFMLT_XYZ] -> mask
also disallow both of a pair: ie no 'xX', no true & false.

3. Add filtering ops into ddebug_change(), right after all the
callsite-property selections are complete.  These test the callsite's
current flagstate before applying modflags.

Why ?

The 3 new/user flags facilitate batching of changes.  By marking
individual callsites with 'xyz', user can compose an arbitrary set of
changes, then activate them together by selecting on 'xyz':

  #> echo 'file foo.c +xyz; file bar.c +xyz' > control
  #> echo 'xyz+p' > control

These user flags aren't strictly needed, but with them you can avoid
using [fmlt] flags for marking, which would alter logging.

Signed-off-by: Jim Cromie <jim.cromie@xxxxxxxxx>
---
 .../admin-guide/dynamic-debug-howto.rst       | 28 ++++++++++++++--
 include/linux/dynamic_debug.h                 |  3 ++
 lib/dynamic_debug.c                           | 33 ++++++++++++++-----
 3 files changed, 54 insertions(+), 10 deletions(-)

diff --git a/Documentation/admin-guide/dynamic-debug-howto.rst b/Documentation/admin-guide/dynamic-debug-howto.rst
index cdc45dcb3e0c..5404e23eeac8 100644
--- a/Documentation/admin-guide/dynamic-debug-howto.rst
+++ b/Documentation/admin-guide/dynamic-debug-howto.rst
@@ -231,9 +231,33 @@ The flags are::
   m    Include module name in the printed message
   t    Include thread ID in messages not generated from interrupt context
   _    No flags are set. (Or'd with others on input)
+  x    user flag, to mark callsites into a group
+  y    user flag, ...
+  z    user flag, ...
 
-For ``print_hex_dump_debug()`` and ``print_hex_dump_bytes()``, only ``p`` flag
-have meaning, other flags ignored.
+Additionally, the flags above have upper-case versions, which invert
+their respective meanings.  Their use follows.
+
+Using Filters::
+
+Filter-flags specify an optional additional selector on pr_debug
+callsites; with them you can compose an arbitrary set of callsites, by
+iteratively marking them with ``+xyz``, then enabling them all with
+``xyz+p``.
+
+Filters can also contain upper-case flags, like ``XY``, which select
+only callsites with x&y cleared.
+
+Flagsets cannot contain ``xX`` etc, a flag cannot be true and false.
+
+modflags containing upper-case flags is reserved/undefined for now.
+inverted-flags are currently ignored, usage gets trickier if given
+``-pXy``, it should leave x set.
+
+Notes::
+
+For ``print_hex_dump_debug()`` and ``print_hex_dump_bytes()``, only
+``p`` flag has meaning, other flags are ignored.
 
 For display, the flags are preceded by ``=``
 (mnemonic: what the flags are currently equal to).
diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h
index 802480ea8708..0d7c9a3538b6 100644
--- a/include/linux/dynamic_debug.h
+++ b/include/linux/dynamic_debug.h
@@ -32,6 +32,9 @@ struct _ddebug {
 #define _DPRINTK_FLAGS_INCL_FUNCNAME	(1<<2)
 #define _DPRINTK_FLAGS_INCL_LINENO	(1<<3)
 #define _DPRINTK_FLAGS_INCL_TID		(1<<4)
+#define _DPRINTK_FLAGS_USR_X		(1<<5)
+#define _DPRINTK_FLAGS_USR_Y		(1<<6)
+#define _DPRINTK_FLAGS_USR_Z		(1<<7)
 #if defined DEBUG
 #define _DPRINTK_FLAGS_DEFAULT _DPRINTK_FLAGS_PRINT
 #else
diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index 26432f88b329..b2630df0c3a5 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -85,13 +85,16 @@ static inline const char *trim_prefix(const char *path)
 	return path + skip;
 }
 
-static struct { unsigned flag:8; char opt_char; } opt_array[] = {
-	{ _DPRINTK_FLAGS_PRINT, 'p' },
-	{ _DPRINTK_FLAGS_INCL_MODNAME, 'm' },
-	{ _DPRINTK_FLAGS_INCL_FUNCNAME, 'f' },
-	{ _DPRINTK_FLAGS_INCL_LINENO, 'l' },
-	{ _DPRINTK_FLAGS_INCL_TID, 't' },
-	{ _DPRINTK_FLAGS_NONE, '_' },
+static struct { unsigned flag:8; char opt_char, not_char; } opt_array[] = {
+	{ _DPRINTK_FLAGS_PRINT,		'p', 'P' },
+	{ _DPRINTK_FLAGS_INCL_MODNAME,	'm', 'M' },
+	{ _DPRINTK_FLAGS_INCL_FUNCNAME,	'f', 'F' },
+	{ _DPRINTK_FLAGS_INCL_LINENO,	'l', 'L' },
+	{ _DPRINTK_FLAGS_INCL_TID,	't', 'T' },
+	{ _DPRINTK_FLAGS_NONE,		'_', '_' },
+	{ _DPRINTK_FLAGS_USR_X,		'x', 'X' },
+	{ _DPRINTK_FLAGS_USR_Y,		'y', 'Y' },
+	{ _DPRINTK_FLAGS_USR_Z,		'z', 'Z' },
 };
 
 /* format a string into buf[] which describes the _ddebug's flags */
@@ -195,6 +198,13 @@ static int ddebug_change(const struct ddebug_query *query,
 			    dp->lineno > query->last_lineno)
 				continue;
 
+			/* filter for required flags */
+			if ((dp->flags & filter->flags) != filter->flags)
+				continue;
+			/* filter on prohibited bits */
+			if ((~dp->flags & filter->mask) != filter->mask)
+				continue;
+
 			nfound++;
 
 			newflags = (dp->flags & mods->mask) | mods->flags;
@@ -428,10 +438,17 @@ static int ddebug_read_flags(const char *str, struct flagsettings *f)
 			if (*str == opt_array[i].opt_char) {
 				f->flags |= opt_array[i].flag;
 				break;
+			} else if (*str == opt_array[i].not_char) {
+				f->mask |= opt_array[i].flag;
+				break;
 			}
 		}
 		if (i < 0) {
-			pr_err("unknown flag '%c' in \"%s\"\n", *str, str);
+			pr_err("unknown flag '%c'", *str);
+			return -EINVAL;
+		}
+		if (f->flags & f->mask) {
+			pr_err("flag '%c' conflicts with earlier one\n", *str);
 			return -EINVAL;
 		}
 	}
-- 
2.23.0