Since commit
85f7f6c0edb8 ("dynamic_debug: process multiple debug-queries on a line")

Multi-query commands have been allowed:

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

That works, but it needs the escaped semicolon, which is a shell
special-char (one of the bash control operators), so it is brittle
when passed in/down/around scripts.  In particular, it fails when
passed to vng (virtme-ng).

So this patch adds '%' to the existing ';' and '\n' multi-command
separators, which is more shell-friendly, so you can more fully avoid
quoting and escaping hassles.

NOTE: it does break format matching on '%' patterns:

bash-5.2# ddcmd 'format "find-me: %foo" +p'
[  203.900581] dyndbg: read 26 bytes from userspace
[  203.900883] dyndbg: query 0: "format "find-me: " mod:*
[  203.901118] dyndbg: unclosed quote: find-me:
[  203.901355] dyndbg: tokenize failed
[  203.901529] dyndbg: query 1: "foo" +p" mod:*
[  203.901957] dyndbg: split into words: "foo"" "+p"
[  203.902243] dyndbg: op='+' flags=0x1 maskp=0xffffffff
[  203.902458] dyndbg: expecting pairs of match-spec <value>
[  203.902703] dyndbg: query parse failed
[  203.902871] dyndbg: processed 2 queries, with 0 matches, 2 errs
bash: echo: write error: Invalid argument

The '%' splits the input into 2 queries, and both fail.  Given the
limited utility of matching against the working parts of a format
string "foo: %d bar %s", nothing is actually lost here.

selftests-dyndbg: test_percent_splitting

This does basic testing of classmaps using '%' separated
multi-queries.  It modprobes test_dynamic_debug with several classes
enabled, and counts to verify that the expected sites show the
enablement in the control file.

Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
Reviewed-by: Louis Chauvet <louis.chauvet@bootlin.com>
---
-v3 squash feature, test, doc together
    gate new test, which needs test-dynamic-debug.ko

test-percent-escape
---
 .../admin-guide/dynamic-debug-howto.rst       |  8 ++++---
 lib/dynamic_debug.c                           |  2 +-
 .../dynamic_debug/dyndbg_selftest.sh          | 24 +++++++++++++++++++
 3 files changed, 30 insertions(+), 4 deletions(-)

diff --git a/Documentation/admin-guide/dynamic-debug-howto.rst b/Documentation/admin-guide/dynamic-debug-howto.rst
index e2dbb5d9b314..1ceadf4f28f9 100644
--- a/Documentation/admin-guide/dynamic-debug-howto.rst
+++ b/Documentation/admin-guide/dynamic-debug-howto.rst
@@ -85,10 +85,12 @@ by spaces, tabs, or commas.  So these are all equivalent::
   :#> ddcmd '  file   svcsock.c     line  1603 +p  '
   :#> ddcmd file,svcsock.c,line,1603,+p
 
-Command submissions are bounded by a write() system call.
-Multiple commands can be written together, separated by ``;`` or ``\n``::
+Command submissions are bounded by a write() system call.  Multiple
+commands can be written together, separated by ``%``, ``;`` or ``\n``::
 
-  :#> ddcmd "func pnpacpi_get_resources +p; func pnp_assign_mem +p"
+  :#> ddcmd func foo +p % func bar +p
+  :#> ddcmd func foo +p \; func bar +p
+  :#> ddcmd "func foo +p ; func bar +p"
   :#> ddcmd <<"EOC"
   func pnpacpi_get_resources +p
   func pnp_assign_mem +p
diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index 5737f1b4eba8..7a60088a1b5c 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -605,7 +605,7 @@ 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';
 
diff --git a/tools/testing/selftests/dynamic_debug/dyndbg_selftest.sh b/tools/testing/selftests/dynamic_debug/dyndbg_selftest.sh
index c7bf521f36ee..513f6cb1db1d 100755
--- a/tools/testing/selftests/dynamic_debug/dyndbg_selftest.sh
+++ b/tools/testing/selftests/dynamic_debug/dyndbg_selftest.sh
@@ -256,9 +256,33 @@ function comma_terminator_tests {
     ddcmd =_
 }
 
+function test_percent_splitting {
+    echo -e "${GREEN}# TEST_PERCENT_SPLITTING - multi-command splitting on % ${NC}"
+    if [ $LACK_TMOD -eq 1 ]; then
+	echo "SKIP - test requires test-dynamic-debug.ko"
+	return
+    fi
+    ifrmmod test_dynamic_debug_submod
+    ifrmmod test_dynamic_debug
+    ddcmd =_
+    modprobe test_dynamic_debug dyndbg=class,D2_CORE,+pf%class,D2_KMS,+pt%class,D2_ATOMIC,+pm
+    check_match_ct =pf 1
+    check_match_ct =pt 1
+    check_match_ct =pm 1
+    check_match_ct test_dynamic_debug 23 -r
+    # add flags to those callsites
+    ddcmd class,D2_CORE,+mf%class,D2_KMS,+lt%class,D2_ATOMIC,+ml
+    check_match_ct =pmf 1
+    check_match_ct =plt 1
+    check_match_ct =pml 1
+    check_match_ct test_dynamic_debug 23 -r
+    ifrmmod test_dynamic_debug
+}
+
 tests_list=(
     basic_tests
     comma_terminator_tests
+    test_percent_splitting
 )
 
 # Run tests
-- 
2.49.0