Re: [PATCH 3/5] bpf: Add bpf_user_ringbuf_drain() helper

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

Hi David,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on bpf-next/master]
[also build test WARNING on bpf/master linus/master next-20220808]
[cannot apply to v5.19]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/David-Vernet/bpf-Clear-callee-saved-regs-after-updating-REG0/20220808-235558
base:   https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git master
config: arc-allyesconfig (https://download.01.org/0day-ci/archive/20220809/202208090505.me3WqXOM-lkp@intel.com/config)
compiler: arceb-elf-gcc (GCC) 12.1.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/intel-lab-lkp/linux/commit/70db51b231aeddaa6eecd19afeeebef610ae2686
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review David-Vernet/bpf-Clear-callee-saved-regs-after-updating-REG0/20220808-235558
        git checkout 70db51b231aeddaa6eecd19afeeebef610ae2686
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=arc SHELL=/bin/bash kernel/bpf/

If you fix the issue, kindly add following tag where applicable
Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

   kernel/bpf/ringbuf.c: In function '__bpf_user_ringbuf_poll':
>> kernel/bpf/ringbuf.c:653:15: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
     653 |         hdr = (u32 *)((uintptr_t)rb->data + (cons_pos & rb->mask));
         |               ^
   kernel/bpf/ringbuf.c:682:19: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
     682 |         *sample = (void *)((uintptr_t)rb->data +
         |                   ^
   kernel/bpf/ringbuf.c: In function '____bpf_user_ringbuf_drain':
>> kernel/bpf/ringbuf.c:736:40: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
     736 |                         ret = callback((u64)&dynptr,
         |                                        ^


vim +653 kernel/bpf/ringbuf.c

   626	
   627	static int __bpf_user_ringbuf_poll(struct bpf_ringbuf *rb, void **sample,
   628					   u32 *size)
   629	{
   630		unsigned long cons_pos, prod_pos;
   631		u32 sample_len, total_len;
   632		u32 *hdr;
   633		int err;
   634		int busy = 0;
   635	
   636		/* If another consumer is already consuming a sample, wait for them to
   637		 * finish.
   638		 */
   639		if (!atomic_try_cmpxchg(&rb->busy, &busy, 1))
   640			return -EBUSY;
   641	
   642		/* Synchronizes with smp_store_release() in user-space. */
   643		prod_pos = smp_load_acquire(&rb->producer_pos);
   644		/* Synchronizes with smp_store_release() in
   645		 * __bpf_user_ringbuf_sample_release().
   646		 */
   647		cons_pos = smp_load_acquire(&rb->consumer_pos);
   648		if (cons_pos >= prod_pos) {
   649			atomic_set(&rb->busy, 0);
   650			return -ENODATA;
   651		}
   652	
 > 653		hdr = (u32 *)((uintptr_t)rb->data + (cons_pos & rb->mask));
   654		sample_len = *hdr;
   655	
   656		/* Check that the sample can fit into a dynptr. */
   657		err = bpf_dynptr_check_size(sample_len);
   658		if (err) {
   659			atomic_set(&rb->busy, 0);
   660			return err;
   661		}
   662	
   663		/* Check that the sample fits within the region advertised by the
   664		 * consumer position.
   665		 */
   666		total_len = sample_len + BPF_RINGBUF_HDR_SZ;
   667		if (total_len > prod_pos - cons_pos) {
   668			atomic_set(&rb->busy, 0);
   669			return -E2BIG;
   670		}
   671	
   672		/* Check that the sample fits within the data region of the ring buffer.
   673		 */
   674		if (total_len > rb->mask + 1) {
   675			atomic_set(&rb->busy, 0);
   676			return -E2BIG;
   677		}
   678	
   679		/* consumer_pos is updated when the sample is released.
   680		 */
   681	
   682		*sample = (void *)((uintptr_t)rb->data +
   683				   ((cons_pos + BPF_RINGBUF_HDR_SZ) & rb->mask));
   684		*size = sample_len;
   685	
   686		return 0;
   687	}
   688	
   689	static void
   690	__bpf_user_ringbuf_sample_release(struct bpf_ringbuf *rb, size_t size,
   691					  u64 flags)
   692	{
   693	
   694	
   695		/* To release the ringbuffer, just increment the producer position to
   696		 * signal that a new sample can be consumed. The busy bit is cleared by
   697		 * userspace when posting a new sample to the ringbuffer.
   698		 */
   699		smp_store_release(&rb->consumer_pos, rb->consumer_pos + size +
   700				  BPF_RINGBUF_HDR_SZ);
   701	
   702		if (flags & BPF_RB_FORCE_WAKEUP || !(flags & BPF_RB_NO_WAKEUP))
   703			irq_work_queue(&rb->work);
   704	
   705		atomic_set(&rb->busy, 0);
   706	}
   707	
   708	BPF_CALL_4(bpf_user_ringbuf_drain, struct bpf_map *, map,
   709		   void *, callback_fn, void *, callback_ctx, u64, flags)
   710	{
   711		struct bpf_ringbuf *rb;
   712		long num_samples = 0, ret = 0;
   713		int err;
   714		bpf_callback_t callback = (bpf_callback_t)callback_fn;
   715		u64 wakeup_flags = BPF_RB_NO_WAKEUP | BPF_RB_FORCE_WAKEUP;
   716	
   717		if (unlikely(flags & ~wakeup_flags))
   718			return -EINVAL;
   719	
   720		/* The two wakeup flags are mutually exclusive. */
   721		if (unlikely((flags & wakeup_flags) == wakeup_flags))
   722			return -EINVAL;
   723	
   724		rb = container_of(map, struct bpf_ringbuf_map, map)->rb;
   725		do {
   726			u32 size;
   727			void *sample;
   728	
   729			err = __bpf_user_ringbuf_poll(rb, &sample, &size);
   730	
   731			if (!err) {
   732				struct bpf_dynptr_kern dynptr;
   733	
   734				bpf_dynptr_init(&dynptr, sample, BPF_DYNPTR_TYPE_LOCAL,
   735						0, size);
 > 736				ret = callback((u64)&dynptr,
   737						(u64)(uintptr_t)callback_ctx, 0, 0, 0);
   738	
   739				__bpf_user_ringbuf_sample_release(rb, size, flags);
   740				num_samples++;
   741			}
   742		} while (err == 0 && num_samples < 4096 && ret == 0);
   743	
   744		return num_samples;
   745	}
   746	

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