text: /*
  Copyright (C) 2021 The Falco Authors.
  
  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
  You may obtain a copy of the License at
  
      http://www.apache.org/licenses/LICENSE-2.0
  
  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License.
  */
  
  #ifndef _SCAP_BPF_H
  #define _SCAP_BPF_H
  
  #include "compat/perf_event.h"
  
  struct perf_event_sample {
  	struct perf_event_header header;
  	uint32_t size;
  	char data[];
  };
  
  struct perf_lost_sample {
  	struct perf_event_header header;
  	uint64_t id;
  	uint64_t lost;
  };
  
  int32_t scap_bpf_load(scap_t *handle, const char *bpf_probe);
  int32_t scap_bpf_start_capture(scap_t *handle);
  int32_t scap_bpf_stop_capture(scap_t *handle);
  int32_t scap_bpf_close(scap_t *handle);
  int32_t scap_bpf_set_snaplen(scap_t* handle, uint32_t snaplen);
  int32_t scap_bpf_set_fullcapture_port_range(scap_t* handle, uint16_t range_start, uint16_t range_end);
  int32_t scap_bpf_set_statsd_port(scap_t* handle, uint16_t port);
  int32_t scap_bpf_enable_dynamic_snaplen(scap_t* handle);
  int32_t scap_bpf_disable_dynamic_snaplen(scap_t* handle);
  int32_t scap_bpf_enable_page_faults(scap_t* handle);
  int32_t scap_bpf_start_dropping_mode(scap_t* handle, uint32_t sampling_ratio);
  int32_t scap_bpf_stop_dropping_mode(scap_t* handle);
  int32_t scap_bpf_enable_tracers_capture(scap_t* handle);
  int32_t scap_bpf_get_stats(scap_t* handle, OUT scap_stats* stats);
  int32_t scap_bpf_get_n_tracepoint_hit(scap_t* handle, long* ret);
  int32_t scap_bpf_set_simple_mode(scap_t* handle);
  int32_t scap_bpf_handle_event_mask(scap_t *handle, uint32_t op, uint32_t event_id);
  
  static inline scap_evt *scap_bpf_evt_from_perf_sample(void *evt)
  {
  	struct perf_event_sample *perf_evt = (struct perf_event_sample *) evt;
  	ASSERT(perf_evt->header.type == PERF_RECORD_SAMPLE);
  	return (scap_evt *) perf_evt->data;
  }
  
  static inline void scap_bpf_get_buf_pointers(char *buf, uint64_t *phead, uint64_t *ptail, uint64_t *pread_size)
  {
  	struct perf_event_mmap_page *header;
  	uint64_t begin;
  	uint64_t end;
  
  	header = (struct perf_event_mmap_page *) buf;
  
  	*phead = header->data_head;
  	*ptail = header->data_tail;
  
  	// clang-format off
  	asm volatile("" ::: "memory");
  	// clang-format on
  
  	begin = *ptail % header->data_size;
  	end = *phead % header->data_size;
  
  	if(begin > end)
  	{
  		*pread_size = header->data_size - begin + end;
  	}
  	else
  	{
  		*pread_size = end - begin;
  	}
  }
  
  static inline int32_t scap_bpf_advance_to_evt(scap_t *handle, uint16_t cpuid, bool skip_current,
  					      char *cur_evt, char **next_evt, uint32_t *len)
  {
  	struct scap_device *dev;
  	void *base;
  	void *begin;
  
  	dev = &handle->m_devs[cpuid];
  
  	struct perf_event_mmap_page *header = (struct perf_event_mmap_page *) dev->m_buffer;
  
  	base = ((char *) header) + header->data_offset;
  	begin = cur_evt;
  
  	while(*len)
  	{
  		struct perf_event_header *e = begin;
  
  		ASSERT(*len >= sizeof(*e));
  		ASSERT(*len >= e->size);
  		if(e->type == PERF_RECORD_SAMPLE)
  		{
  #ifdef _DEBUG
  			struct perf_event_sample *sample = (struct perf_event_sample *) e;
  #endif
  			ASSERT(*len >= sizeof(*sample));
  			ASSERT(*len >= sample->size);
  			ASSERT(e->size == sizeof(*e) + sizeof(sample->size) + sample->size);
  			ASSERT(((scap_evt *) sample->data)->len <= sample->size);
  
  			if(skip_current)
  			{
  				skip_current = false;
  			}
  			else
  			{
  				*next_evt = (char *) e;
  				break;
  			}
  		}
  		else if(e->type != PERF_RECORD_LOST)
  		{
  			printf("Unknown event type=%d size=%d\n",
  			       e->type, e->size);
  			ASSERT(false);
  		}
  
  		if(begin + e->size > base + header->data_size)
  		{
  			begin = begin + e->size - header->data_size;
  		}
  		else if(begin + e->size == base + header->data_size)
  		{
  			begin = base;
  		}
  		else
  		{
  			begin += e->size;
  		}
  
  		*len -= e->size;
  	}
  
  	return SCAP_SUCCESS;
  }
  
  static inline void scap_bpf_advance_tail(scap_t *handle, uint32_t cpuid)
  {
  	struct perf_event_mmap_page *header;
  	struct scap_device *dev;
  
  	dev = &handle->m_devs[cpuid];
  	header = (struct perf_event_mmap_page *)dev->m_buffer;
  
  	// clang-format off
  	asm volatile("" ::: "memory");
  	// clang-format on
  
  	ASSERT(dev->m_lastreadsize > 0);
  	header->data_tail += dev->m_lastreadsize;
  	dev->m_lastreadsize = 0;
  }
  
  static inline int32_t scap_bpf_readbuf(scap_t *handle, uint32_t cpuid, char **buf, uint32_t *len)
  {
  	struct perf_event_mmap_page *header;
  	struct scap_device *dev;
  	uint64_t tail;
  	uint64_t head;
  	uint64_t read_size;
  	char *p;
  
  	dev = &handle->m_devs[cpuid];
  	header = (struct perf_event_mmap_page *) dev->m_buffer;
  
  	ASSERT(dev->m_lastreadsize == 0);
  	scap_bpf_get_buf_pointers((char *) header, &head, &tail, &read_size);
  
  	dev->m_lastreadsize = read_size;
  	p = ((char *) header) + header->data_offset + tail % header->data_size;
  	*len = read_size;
  
  	return scap_bpf_advance_to_evt(handle, cpuid, false, p, buf, len);
  }
  
  #endif
  