linux-kernel - [PATCH v3 20/22] dyndbg: split multi-query strings with %

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Date: Sat, 23 Dec 2023 02:51:29 +0100
From: Łukasz Bartosik <lb@...ihalf.com>
To: Jason Baron <jbaron@...mai.com>,
	Jim Cromie <jim.cromie@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Kees Cook <keescook@...omium.org>,
	Douglas Anderson <dianders@...omium.org>
Cc: Guenter Roeck <groeck@...gle.com>,
	Yaniv Tzoreff <yanivt@...gle.com>,
	Benson Leung <bleung@...gle.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Vincent Whitchurch <vincent.whitchurch@...s.com>,
	Pekka Paalanen <ppaalanen@...il.com>,
	Sean Paul <seanpaul@...omium.org>,
	Daniel Vetter <daniel@...ll.ch>,
	Simon Ser <contact@...rsion.fr>,
	John Ogness <john.ogness@...utronix.de>,
	Petr Mladek <pmladek@...e.com>,
	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	linux-kernel@...r.kernel.org,
	upstream@...ihalf.com
Subject: [PATCH v3 20/22] dyndbg: split multi-query strings with %

From: Jim Cromie <jim.cromie@...il.com>

Multi-query strings have long allowed:

  modprobe drm dyndbg="class DRM_UT_CORE +p; class DRM_UT_KMS +p"
  modprobe drm dyndbg=<<EOX
     class DRM_UT_CORE +pmf
     class DRM_UT_KMS  +pmf
  EOX

More recently, the need for quoting was avoided by treating a comma
like a space/token-terminator:

  modprobe drm dyndbg=class,DRM_UT_CORE,+p\;class,DRM_UT_KMS,+p

But that leaves unfinished business; that semi-colon needs escaping,
and thats not robust to further string interpolation.  In particular,
it fails when passed to vng (virtme-ng).

So this patch adds '%' to the existing ';' and '\n' multi-cmd
separators, which is more shell-friendly, and avoids quoting and
escaping hassles.

  modprobe drm dyndbg=class,DRM_UT_CORE,+p%class,DRM_UT_KMS,+p

NOTE: it does alter/break this (ill conceived) search:

[root@v6 lx]# ddcmd format %s +p
[   38.170998] dyndbg: read 13 bytes from userspace
[   38.171542] dyndbg: query 0: <format > on module: <*>
[   38.172011] dyndbg: bad flag-op f, at start of format
[   38.172487] dyndbg: flags parse failed
[   38.172839] dyndbg: query 1: <s +p> on module: <*>
[   38.173285] dyndbg: expecting pairs of match-spec <value>
[   38.173791] dyndbg: query parse failed
[   38.174141] dyndbg: processed 2 queries, with 0 matches, 2 errs
bash: echo: write error: Invalid argument

In trade for that minor format selection limitation, we get to do:

  vng -v --user root -p 4 \
      -a dynamic_debug.verbose=3 \
      -a drm.debug=0x15 \
      -a i915.dyndbg=class,DRM_UT_CORE,+pfmlt_%class,DRM_UT_KMS,+pfml
  modprobe drm
  modprobe i915

NOTES/TLDR:

In this example, using both drm.debug & drm.dyndbg is mostly for
testing.  Using drm.debug is preferred, because the drivers all
explicitly depend on that input/control-point, so settings there are
propagated to drivers.

But more to the point, drm.dyndbg explicitly limits the query to drm.
In fact, you could pass a module wildcard in the above, and achieve
the same thing:

vng -v --user root -p 4 \
-a dynamic_debug.verbose=3 \
-a \*.dyndbg=class,DRM_UT_CORE,+pfmlt_%class,DRM_UT_KMS,+pfm%class, \
DRM_UT_ATOMIC,+pf

':' would be a more natural multi-cmd separator, but is reserved
for +T:<trace_buf> to designate separate tracebuf instances.

If '%' is distasteful, the backup plan is ",_,", since that would
never appear in a useful <format "$foo"> cmd.

Signed-off-by: Jim Cromie <jim.cromie@...il.com>
---
 lib/dynamic_debug.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index 48ce24c39457..453eab7092dc 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -963,7 +963,7 @@ static int ddebug_exec_queries(char *query, const char *modname)
 	int i, errs = 0, exitcode = 0, rc, nfound = 0;

 	for (i = 0; query; query = split) {
-		split = strpbrk(query, ";\n");
+		split = strpbrk(query, "%;\n");
 		if (split)
 			*split++ = '\0';

-- 
2.43.0.472.g3155946c3a-goog