[jpoimboe:objtool-diff 2/2] kernel/fork.c:2815:9: warning: incompatible integer to pointer conversion assigning to 'int *' from 'int'

[jpoimboe:objtool-diff 2/2] kernel/fork.c:2815:9: warning: incompatible integer to pointer conversion assigning to 'int *' from 'int'

[kernel test robot]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/jpoimboe/linux.git objtool-diff
head:   745009dc796e56fc87e911138d801679ecd3576e
commit: 745009dc796e56fc87e911138d801679ecd3576e [2/2] test
config: arm-defconfig (https://download.01.org/0day-ci/archive/20240525/202405251037.WDBJpiSc-lkp@intel.com/config)
compiler: clang version 14.0.6 (https://github.com/llvm/llvm-project f28c006a5895fc0e329fe15fead81e37457cb1d1)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240525/202405251037.WDBJpiSc-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/202405251037.WDBJpiSc-lkp@intel.com/

All warnings (new ones prefixed by >>):

   kernel/fork.c:2815:11: error: implicit declaration of function 'klp_shadow_get_or_alloc' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
           newpid = klp_shadow_get_or_alloc(p, 0, sizeof(*newpid), GFP_KERNEL,
                    ^
>> kernel/fork.c:2815:9: warning: incompatible integer to pointer conversion assigning to 'int *' from 'int' [-Wint-conversion]
           newpid = klp_shadow_get_or_alloc(p, 0, sizeof(*newpid), GFP_KERNEL,
                  ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   1 warning and 1 error generated.
--
   fs/proc/array.c:408:11: error: implicit declaration of function 'klp_shadow_get' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
           newpid = klp_shadow_get(p, 0);
                    ^
>> fs/proc/array.c:408:9: warning: incompatible integer to pointer conversion assigning to 'int *' from 'int' [-Wint-conversion]
           newpid = klp_shadow_get(p, 0);
                  ^ ~~~~~~~~~~~~~~~~~~~~
   1 warning and 1 error generated.


vim +2815 kernel/fork.c

  2756	
  2757	/*
  2758	 *  Ok, this is the main fork-routine.
  2759	 *
  2760	 * It copies the process, and if successful kick-starts
  2761	 * it and waits for it to finish using the VM if required.
  2762	 *
  2763	 * args->exit_signal is expected to be checked for sanity by the caller.
  2764	 */
  2765	#include <linux/livepatch.h>
  2766	pid_t kernel_clone(struct kernel_clone_args *args)
  2767	{
  2768		u64 clone_flags = args->flags;
  2769		struct completion vfork;
  2770		struct pid *pid;
  2771		struct task_struct *p;
  2772		int trace = 0;
  2773		pid_t nr;
  2774		int *newpid;
  2775		static int ctr = 0;
  2776	
  2777		/*
  2778		 * For legacy clone() calls, CLONE_PIDFD uses the parent_tid argument
  2779		 * to return the pidfd. Hence, CLONE_PIDFD and CLONE_PARENT_SETTID are
  2780		 * mutually exclusive. With clone3() CLONE_PIDFD has grown a separate
  2781		 * field in struct clone_args and it still doesn't make sense to have
  2782		 * them both point at the same memory location. Performing this check
  2783		 * here has the advantage that we don't need to have a separate helper
  2784		 * to check for legacy clone().
  2785		 */
  2786		if ((clone_flags & CLONE_PIDFD) &&
  2787		    (clone_flags & CLONE_PARENT_SETTID) &&
  2788		    (args->pidfd == args->parent_tid))
  2789			return -EINVAL;
  2790	
  2791		/*
  2792		 * Determine whether and which event to report to ptracer.  When
  2793		 * called from kernel_thread or CLONE_UNTRACED is explicitly
  2794		 * requested, no event is reported; otherwise, report if the event
  2795		 * for the type of forking is enabled.
  2796		 */
  2797		if (!(clone_flags & CLONE_UNTRACED)) {
  2798			if (clone_flags & CLONE_VFORK)
  2799				trace = PTRACE_EVENT_VFORK;
  2800			else if (args->exit_signal != SIGCHLD)
  2801				trace = PTRACE_EVENT_CLONE;
  2802			else
  2803				trace = PTRACE_EVENT_FORK;
  2804	
  2805			if (likely(!ptrace_event_enabled(current, trace)))
  2806				trace = 0;
  2807		}
  2808	
  2809		p = copy_process(NULL, trace, NUMA_NO_NODE, args);
  2810		add_latent_entropy();
  2811	
  2812		if (IS_ERR(p))
  2813			return PTR_ERR(p);
  2814	
> 2815		newpid = klp_shadow_get_or_alloc(p, 0, sizeof(*newpid), GFP_KERNEL,
  2816						 NULL, NULL);
  2817		if (newpid)
  2818			*newpid = ctr++;
  2819	
  2820		/*
  2821		 * Do this prior waking up the new thread - the thread pointer
  2822		 * might get invalid after that point, if the thread exits quickly.
  2823		 */
  2824		trace_sched_process_fork(current, p);
  2825	
  2826		pid = get_task_pid(p, PIDTYPE_PID);
  2827		nr = pid_vnr(pid);
  2828	
  2829		if (clone_flags & CLONE_PARENT_SETTID)
  2830			put_user(nr, args->parent_tid);
  2831	
  2832		if (clone_flags & CLONE_VFORK) {
  2833			p->vfork_done = &vfork;
  2834			init_completion(&vfork);
  2835			get_task_struct(p);
  2836		}
  2837	
  2838		if (IS_ENABLED(CONFIG_LRU_GEN_WALKS_MMU) && !(clone_flags & CLONE_VM)) {
  2839			/* lock the task to synchronize with memcg migration */
  2840			task_lock(p);
  2841			lru_gen_add_mm(p->mm);
  2842			task_unlock(p);
  2843		}
  2844	
  2845		wake_up_new_task(p);
  2846	
  2847		/* forking complete and child started to run, tell ptracer */
  2848		if (unlikely(trace))
  2849			ptrace_event_pid(trace, pid);
  2850	
  2851		if (clone_flags & CLONE_VFORK) {
  2852			if (!wait_for_vfork_done(p, &vfork))
  2853				ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
  2854		}
  2855	
  2856		put_pid(pid);
  2857		return nr;
  2858	}
  2859	

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