Re: [RFC bpf-next 4/4] bpf: Runtime part of fast-path termination approach

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

Hi Raj,

[This is a private test report for your RFC patch.]
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/Raj-Sahu/bpf-Introduce-new-structs-and-struct-fields/20250420-185825
base:   https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git master
patch link:    https://lore.kernel.org/r/20250420105524.2115690-5-rjsu26%40gmail.com
patch subject: [RFC bpf-next 4/4] bpf: Runtime part of fast-path termination approach
config: arc-randconfig-002-20250420 (https://download.01.org/0day-ci/archive/20250420/202504202116.gfxIZI0c-lkp@intel.com/config)
compiler: arc-linux-gcc (GCC) 12.4.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250420/202504202116.gfxIZI0c-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/202504202116.gfxIZI0c-lkp@intel.com/

All warnings (new ones prefixed by >>):

   kernel/bpf/syscall.c: In function 'bpf_prog_load':
   kernel/bpf/syscall.c:2981:14: warning: variable 'have_termination_prog' set but not used [-Wunused-but-set-variable]
    2981 |         bool have_termination_prog = false;
         |              ^~~~~~~~~~~~~~~~~~~~~
   kernel/bpf/syscall.c: In function 'bpf_die':
   kernel/bpf/syscall.c:6077:29: error: storage size of 'state' isn't known
    6077 |         struct unwind_state state;
         |                             ^~~~~
   kernel/bpf/syscall.c:6094:9: error: implicit declaration of function 'unwind_start' [-Werror=implicit-function-declaration]
    6094 |         unwind_start(&state, current, regs, NULL);
         |         ^~~~~~~~~~~~
   kernel/bpf/syscall.c:6095:16: error: implicit declaration of function 'unwind_get_return_address'; did you mean 'ftrace_return_address'? [-Werror=implicit-function-declaration]
    6095 |         addr = unwind_get_return_address(&state);
         |                ^~~~~~~~~~~~~~~~~~~~~~~~~
         |                ftrace_return_address
   kernel/bpf/syscall.c:6104:23: error: 'struct pt_regs' has no member named 'ip'; did you mean 'fp'?
    6104 |                 regs->ip = new_addr;
         |                       ^~
         |                       fp
   kernel/bpf/syscall.c:6132:17: error: implicit declaration of function 'unwind_next_frame' [-Werror=implicit-function-declaration]
    6132 |                 unwind_next_frame(&state);
         |                 ^~~~~~~~~~~~~~~~~
>> kernel/bpf/syscall.c:6077:29: warning: unused variable 'state' [-Wunused-variable]
    6077 |         struct unwind_state state;
         |                             ^~~~~
   cc1: some warnings being treated as errors


vim +/state +6077 kernel/bpf/syscall.c

  6073	
  6074	
  6075	void bpf_die(void *data)
  6076	{
> 6077		struct unwind_state state;
  6078		struct bpf_prog *prog, *patch_prog;
  6079		struct pt_regs *regs;
  6080		char str[KSYM_SYMBOL_LEN];
  6081		unsigned long addr, new_addr, bpf_loop_addr, bpf_loop_term_addr;
  6082		int cpu_id = raw_smp_processor_id();
  6083	
  6084		prog = (struct bpf_prog *)data;
  6085		patch_prog = prog->termination_states->patch_prog;
  6086	
  6087		if(!per_cpu_flag_is_true(prog->termination_states, cpu_id))
  6088			return;
  6089	
  6090		regs = &prog->termination_states->pre_execution_state[cpu_id];
  6091		bpf_loop_addr = (unsigned long)bpf_loop_proto.func;
  6092		bpf_loop_term_addr = (unsigned long)bpf_loop_termination_proto.func;
  6093	
  6094		unwind_start(&state, current, regs, NULL);
  6095		addr = unwind_get_return_address(&state);
  6096	
  6097		/* BPF programs RIP is in bpf program context when termination
  6098		 * signal raises an IPI
  6099		 */
  6100		if (is_bpf_address(prog, addr)) {
  6101			new_addr = find_offset_in_patch_prog(patch_prog, prog, addr);
  6102			if (new_addr < 0)
  6103				return;
  6104			regs->ip = new_addr;
  6105		}
  6106	
  6107		unsigned long stack_addr = regs->sp;
  6108		while (addr) {
  6109			if (is_bpf_address(prog, addr)) {
  6110				while (*(unsigned long *)stack_addr != addr) {
  6111					stack_addr += 1;
  6112				}
  6113				new_addr = find_offset_in_patch_prog(patch_prog, prog, addr);
  6114				if (new_addr < 0)
  6115					return;
  6116				*(unsigned long *)stack_addr = new_addr;
  6117			} else {
  6118				/* Handles termination non-inline bpf_loop scenario.
  6119				 * Could be modular and later extended to other iterators.
  6120				 */
  6121				const char *name = kallsyms_lookup(addr, NULL, NULL, NULL, str);
  6122				if (name) {
  6123					unsigned long lookup_addr = kallsyms_lookup_name(name);
  6124					if (lookup_addr && lookup_addr == bpf_loop_addr) {
  6125						while (*(unsigned long *)stack_addr != addr) {
  6126							stack_addr += 1;
  6127						}
  6128						*(unsigned long *)stack_addr = bpf_loop_term_addr;
  6129					}
  6130				}
  6131			}
  6132			unwind_next_frame(&state);
  6133			addr = unwind_get_return_address(&state);
  6134		}
  6135	
  6136		atomic64_dec(&prog->aux->refcnt);
  6137	
  6138		return;
  6139	}
  6140	

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