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Subject[PATCH 14/16] dyndbg: add inverted-flags, implement filtering on flags
Date
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@gmail.com>
---
.../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
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