[PATCH sched_ext/for-7.2] sched_ext: Add __printf format attributes to scx_vexit() and bstr formatters

[Tejun Heo <tj@kernel.org>]

scx_vexit() forwards (fmt, args) to vscnprintf(); bstr_format() and
__bstr_format() forward fmt to bstr_printf(); the BPF kfunc wrappers
scx_bpf_exit_bstr(), scx_bpf_error_bstr() and scx_bpf_dump_bstr() in
turn forward fmt to those formatters. None of them have __printf(),
so clang -Wmissing-format-attribute fires on the forwarded calls and
C-side callers don't get format-string checking.

Annotate the six functions with __printf(N, 0) matching the fmt
parameter position in each.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/all/202605041112.Y6OG7v9r-lkp@intel.com/
Signed-off-by: Tejun Heo <tj@kernel.org>
---
 kernel/sched/ext.c          | 5 +++++
 kernel/sched/ext_internal.h | 5 +++--
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 966a846c213c..7ac7d10a41be 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -9338,6 +9338,7 @@ __bpf_kfunc void scx_bpf_reenqueue_local___v2(const struct bpf_prog_aux *aux)

 __bpf_kfunc_end_defs();

+__printf(5, 0)
 static s32 __bstr_format(struct scx_sched *sch, u64 *data_buf, char *line_buf,
 			 size_t line_size, char *fmt, unsigned long long *data,
 			 u32 data__sz)
@@ -9375,6 +9376,7 @@ static s32 __bstr_format(struct scx_sched *sch, u64 *data_buf, char *line_buf,
 	return ret;
 }

+__printf(3, 0)
 static s32 bstr_format(struct scx_sched *sch, struct scx_bstr_buf *buf,
 		       char *fmt, unsigned long long *data, u32 data__sz)
 {
@@ -9395,6 +9397,7 @@ __bpf_kfunc_start_defs();
  * Indicate that the BPF scheduler wants to exit gracefully, and initiate ops
  * disabling.
  */
+__printf(2, 0)
 __bpf_kfunc void scx_bpf_exit_bstr(s64 exit_code, char *fmt,
 				   unsigned long long *data, u32 data__sz,
 				   const struct bpf_prog_aux *aux)
@@ -9420,6 +9423,7 @@ __bpf_kfunc void scx_bpf_exit_bstr(s64 exit_code, char *fmt,
  * Indicate that the BPF scheduler encountered a fatal error and initiate ops
  * disabling.
  */
+__printf(1, 0)
 __bpf_kfunc void scx_bpf_error_bstr(char *fmt, unsigned long long *data,
 				    u32 data__sz, const struct bpf_prog_aux *aux)
 {
@@ -9447,6 +9451,7 @@ __bpf_kfunc void scx_bpf_error_bstr(char *fmt, unsigned long long *data,
  * The extra dump may be multiple lines. A single line may be split over
  * multiple calls. The last line is automatically terminated.
  */
+__printf(1, 0)
 __bpf_kfunc void scx_bpf_dump_bstr(char *fmt, unsigned long long *data,
 				   u32 data__sz, const struct bpf_prog_aux *aux)
 {
diff --git a/kernel/sched/ext_internal.h b/kernel/sched/ext_internal.h
index b4f5dd28855e..0ed79bd891c7 100644
--- a/kernel/sched/ext_internal.h
+++ b/kernel/sched/ext_internal.h
@@ -1477,8 +1477,9 @@ int scx_kfunc_context_filter(const struct bpf_prog *prog, u32 kfunc_id);

 bool scx_cpu_valid(struct scx_sched *sch, s32 cpu, const char *where);

-bool scx_vexit(struct scx_sched *sch, enum scx_exit_kind kind, s64 exit_code,
-	       s32 exit_cpu, const char *fmt, va_list args);
+__printf(5, 0) bool scx_vexit(struct scx_sched *sch, enum scx_exit_kind kind,
+			      s64 exit_code, s32 exit_cpu, const char *fmt,
+			      va_list args);
 __printf(5, 6) bool __scx_exit(struct scx_sched *sch, enum scx_exit_kind kind,
 			       s64 exit_code, s32 exit_cpu, const char *fmt, ...);

--
2.47.0