[PATCH 4/5] tracing/probes: Extend max length of argument string
From: Masami Hiramatsu (Google)
Date: Mon Jul 13 2026 - 03:33:33 EST
From: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
To support BTF argument parsing (such as accessing fields within nested
structures via typecasting), the maximum argument string length needs
to be extended. Extend MAX_ARGSTR_LEN from 63 to 255.
Since MAX_ARGSTR_LEN was previously reused to format command heads in
trace_*probe_match_command_head() functions, introduce a dedicated
MAX_COMMON_HEAD_LEN (63) macro for matching command heads and switch
these functions to use the new macro.
Assisted-by: Antigravity:gemini-3.5-flash
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
---
Changes in v2:
- Make the MAX_ARGSTR_LEN to 255 instead of 256.
---
kernel/trace/trace_fprobe.c | 2 +-
kernel/trace/trace_kprobe.c | 2 +-
kernel/trace/trace_probe.h | 3 ++-
kernel/trace/trace_uprobe.c | 2 +-
.../ftrace/test.d/dynevent/fprobe_syntax_errors.tc | 2 +-
.../ftrace/test.d/dynevent/tprobe_syntax_errors.tc | 2 +-
.../ftrace/test.d/kprobe/kprobe_syntax_errors.tc | 2 +-
7 files changed, 8 insertions(+), 7 deletions(-)
diff --git a/kernel/trace/trace_fprobe.c b/kernel/trace/trace_fprobe.c
index 536781cd4c47..5638a90e61cc 100644
--- a/kernel/trace/trace_fprobe.c
+++ b/kernel/trace/trace_fprobe.c
@@ -238,7 +238,7 @@ static bool trace_fprobe_is_busy(struct dyn_event *ev)
static bool trace_fprobe_match_command_head(struct trace_fprobe *tf,
int argc, const char **argv)
{
- char buf[MAX_ARGSTR_LEN + 1];
+ char buf[MAX_COMMON_HEAD_LEN + 1];
if (!argc)
return true;
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index cfa807d8e760..cc24e992732c 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -149,7 +149,7 @@ static bool trace_kprobe_is_busy(struct dyn_event *ev)
static bool trace_kprobe_match_command_head(struct trace_kprobe *tk,
int argc, const char **argv)
{
- char buf[MAX_ARGSTR_LEN + 1];
+ char buf[MAX_COMMON_HEAD_LEN + 1];
if (!argc)
return true;
diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h
index e64e323244a5..e6d427910c4f 100644
--- a/kernel/trace/trace_probe.h
+++ b/kernel/trace/trace_probe.h
@@ -32,7 +32,8 @@
#include "trace_output.h"
#define MAX_TRACE_ARGS 128
-#define MAX_ARGSTR_LEN 63
+#define MAX_ARGSTR_LEN 255
+#define MAX_COMMON_HEAD_LEN 63
#define MAX_ARRAY_LEN 64
#define MAX_ARG_NAME_LEN 32
#define MAX_BTF_ARGS_LEN 128
diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
index b2e264a4b96c..67bd8fd91e3e 100644
--- a/kernel/trace/trace_uprobe.c
+++ b/kernel/trace/trace_uprobe.c
@@ -281,7 +281,7 @@ static bool trace_uprobe_is_busy(struct dyn_event *ev)
static bool trace_uprobe_match_command_head(struct trace_uprobe *tu,
int argc, const char **argv)
{
- char buf[MAX_ARGSTR_LEN + 1];
+ char buf[MAX_COMMON_HEAD_LEN + 1];
int len;
if (!argc)
diff --git a/tools/testing/selftests/ftrace/test.d/dynevent/fprobe_syntax_errors.tc b/tools/testing/selftests/ftrace/test.d/dynevent/fprobe_syntax_errors.tc
index e9d7e6919c7f..984ab94df213 100644
--- a/tools/testing/selftests/ftrace/test.d/dynevent/fprobe_syntax_errors.tc
+++ b/tools/testing/selftests/ftrace/test.d/dynevent/fprobe_syntax_errors.tc
@@ -75,7 +75,7 @@ check_error 'f vfs_read ^arg123456789012345678901234567890=@11' # ARG_NAME_TOO_L
check_error 'f vfs_read ^=@11' # NO_ARG_NAME
check_error 'f vfs_read ^var.1=@11' # BAD_ARG_NAME
check_error 'f vfs_read var1=@11 ^var1=@12' # USED_ARG_NAME
-check_error 'f vfs_read ^+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(@1234))))))' # ARG_TOO_LONG
+check_error 'f vfs_read ^+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(@1234))))))))))))))))))))))))))' # ARG_TOO_LONG
check_error 'f vfs_read arg1=^' # NO_ARG_BODY
diff --git a/tools/testing/selftests/ftrace/test.d/dynevent/tprobe_syntax_errors.tc b/tools/testing/selftests/ftrace/test.d/dynevent/tprobe_syntax_errors.tc
index ffe8ffef4027..2d0905b2c8b7 100644
--- a/tools/testing/selftests/ftrace/test.d/dynevent/tprobe_syntax_errors.tc
+++ b/tools/testing/selftests/ftrace/test.d/dynevent/tprobe_syntax_errors.tc
@@ -61,7 +61,7 @@ check_error 't kfree ^arg123456789012345678901234567890=@11' # ARG_NAME_TOO_LOG
check_error 't kfree ^=@11' # NO_ARG_NAME
check_error 't kfree ^var.1=@11' # BAD_ARG_NAME
check_error 't kfree var1=@11 ^var1=@12' # USED_ARG_NAME
-check_error 't kfree ^+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(@1234))))))' # ARG_TOO_LONG
+check_error 't kfree ^+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(@1234))))))))))))))))))))))))))' # ARG_TOO_LONG
check_error 't kfree arg1=^' # NO_ARG_BODY
diff --git a/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_syntax_errors.tc b/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_syntax_errors.tc
index 21ce8414459f..d28f63b7e8a9 100644
--- a/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_syntax_errors.tc
+++ b/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_syntax_errors.tc
@@ -71,7 +71,7 @@ check_error 'p vfs_read ^arg123456789012345678901234567890=@11' # ARG_NAME_TOO_L
check_error 'p vfs_read ^=@11' # NO_ARG_NAME
check_error 'p vfs_read ^var.1=@11' # BAD_ARG_NAME
check_error 'p vfs_read var1=@11 ^var1=@12' # USED_ARG_NAME
-check_error 'p vfs_read ^+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(@1234))))))' # ARG_TOO_LONG
+check_error 'p vfs_read ^+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(+1234567(@1234))))))))))))))))))))))))))' # ARG_TOO_LONG
check_error 'p vfs_read arg1=^' # NO_ARG_BODY
# instruction boundary check is valid on x86 (at this moment)