Re: [PATCH bpf-next v3 2/7] bpf: add two kfunc for TRACE_SESSION

[kernel test robot <lkp@intel.com>]

Hi Menglong,

kernel test robot noticed the following build warnings:

[auto build test WARNING on bpf-next/master]

url:    https://github.com/intel-lab-lkp/linux/commits/Menglong-Dong/bpf-add-tracing-session-support/20251026-110720
base:   https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git master
patch link:    https://lore.kernel.org/r/20251026030143.23807-3-dongml2%40chinatelecom.cn
patch subject: [PATCH bpf-next v3 2/7] bpf: add two kfunc for TRACE_SESSION
config: i386-buildonly-randconfig-003-20251026 (https://download.01.org/0day-ci/archive/20251026/202510261253.qRd57kJv-lkp@intel.com/config)
compiler: gcc-14 (Debian 14.2.0-19) 14.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251026/202510261253.qRd57kJv-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202510261253.qRd57kJv-lkp@intel.com/

All warnings (new ones prefixed by >>):

   kernel/trace/bpf_trace.c: In function '____bpf_trace_printk':
   kernel/trace/bpf_trace.c:377:9: warning: function '____bpf_trace_printk' might be a candidate for 'gnu_printf' format attribute [-Wsuggest-attribute=format]
     377 |         ret = bstr_printf(data.buf, MAX_BPRINTF_BUF, fmt, data.bin_args);
         |         ^~~
   kernel/trace/bpf_trace.c: In function '____bpf_trace_vprintk':
   kernel/trace/bpf_trace.c:433:9: warning: function '____bpf_trace_vprintk' might be a candidate for 'gnu_printf' format attribute [-Wsuggest-attribute=format]
     433 |         ret = bstr_printf(data.buf, MAX_BPRINTF_BUF, fmt, data.bin_args);
         |         ^~~
   kernel/trace/bpf_trace.c: In function '____bpf_seq_printf':
   kernel/trace/bpf_trace.c:475:9: warning: function '____bpf_seq_printf' might be a candidate for 'gnu_printf' format attribute [-Wsuggest-attribute=format]
     475 |         seq_bprintf(m, fmt, data.bin_args);
         |         ^~~~~~~~~~~
   kernel/trace/bpf_trace.c: In function 'bpf_fsession_cookie':
>> kernel/trace/bpf_trace.c:3379:16: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
    3379 |         return (u64 *)((u64 *)ctx)[nr_args + 2];
         |                ^

Kconfig warnings: (for reference only)
   WARNING: unmet direct dependencies detected for I2C_K1
   Depends on [n]: I2C [=y] && HAS_IOMEM [=y] && (ARCH_SPACEMIT || COMPILE_TEST [=y]) && OF [=n]
   Selected by [y]:
   - MFD_SPACEMIT_P1 [=y] && HAS_IOMEM [=y] && (ARCH_SPACEMIT || COMPILE_TEST [=y]) && I2C [=y]


vim +3379 kernel/trace/bpf_trace.c

  3372	
  3373	__bpf_kfunc u64 *bpf_fsession_cookie(void *ctx)
  3374	{
  3375		/* This helper call is inlined by verifier. */
  3376		u64 nr_args = ((u64 *)ctx)[-1];
  3377	
  3378		/* ctx[nr_args + 2] is the session cookie address */
> 3379		return (u64 *)((u64 *)ctx)[nr_args + 2];
  3380	}
  3381	

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