Re: [PATCH 4/5] tracing/probes: Extend max length of argument string
From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Date: 2026-07-13 02:16:27
Also in:
linux-kselftest, lkml
On Mon, 13 Jul 2026 00:06:42 +0900 "Masami Hiramatsu (Google)" [off-list ref] wrote:
From: Masami Hiramatsu <mhiramat@kernel.org> 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 256. 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@kernel.org>
Sashiko asked to extend other macros,
Does this code also need to increase MAX_BTF_ARGS_LEN and MAX_DENTRY_ARGS_LEN?
I don't agree this. MAX_BTF_ARGS_LEN is only for expanding "$args" into each parameter names. The other arguments are kept on the same memory. MAX_DENTRY_ARGS_LEN is already 256, so I think if that is too long, it should be rejected. (But MAX_ARGSTR_LEN should be 255.) BTW, both macro names are a bit complicated because those are just buffer size, not max length of something. Thank you,
quoted hunk ↗ jump to hunk
--- 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..e6aee800a7d9 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 256 +#define MAX_COMMON_HEAD_LEN 63 #define MAX_ARRAY_LEN 64 #define MAX_ARG_NAME_LEN 32 #define MAX_BTF_ARGS_LEN 128diff --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_BODYdiff --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_BODYdiff --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)
-- Masami Hiramatsu (Google) [off-list ref]