text: // SPDX-License-Identifier: GPL-2.0-only
  /* Copyright (c) 2016 Facebook
   */
  #include <linux/bpf.h>
  #include <linux/jhash.h>
  #include <linux/filter.h>
  #include <linux/kernel.h>
  #include <linux/stacktrace.h>
  #include <linux/perf_event.h>
  #include <linux/elf.h>
  #include <linux/pagemap.h>
  #include <linux/irq_work.h>
  #include <linux/btf_ids.h>
  #include "percpu_freelist.h"
  
  #define STACK_CREATE_FLAG_MASK					\
  	(BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY |	\
  	 BPF_F_STACK_BUILD_ID)
  
  struct stack_map_bucket {
  	struct pcpu_freelist_node fnode;
  	u32 hash;
  	u32 nr;
  	u64 data[];
  };
  
  struct bpf_stack_map {
  	struct bpf_map map;
  	void *elems;
  	struct pcpu_freelist freelist;
  	u32 n_buckets;
  	struct stack_map_bucket *buckets[];
  };
  
  /* irq_work to run up_read() for build_id lookup in nmi context */
  struct stack_map_irq_work {
  	struct irq_work irq_work;
  	struct mm_struct *mm;
  };
  
  static void do_up_read(struct irq_work *entry)
  {
  	struct stack_map_irq_work *work;
  
  	if (WARN_ON_ONCE(IS_ENABLED(CONFIG_PREEMPT_RT)))
  		return;
  
  	work = container_of(entry, struct stack_map_irq_work, irq_work);
  	mmap_read_unlock_non_owner(work->mm);
  }
  
  static DEFINE_PER_CPU(struct stack_map_irq_work, up_read_work);
  
  static inline bool stack_map_use_build_id(struct bpf_map *map)
  {
  	return (map->map_flags & BPF_F_STACK_BUILD_ID);
  }
  
  static inline int stack_map_data_size(struct bpf_map *map)
  {
  	return stack_map_use_build_id(map) ?
  		sizeof(struct bpf_stack_build_id) : sizeof(u64);
  }
  
  static int prealloc_elems_and_freelist(struct bpf_stack_map *smap)
  {
  	u32 elem_size = sizeof(struct stack_map_bucket) + smap->map.value_size;
  	int err;
  
  	smap->elems = bpf_map_area_alloc(elem_size * smap->map.max_entries,
  					 smap->map.numa_node);
  	if (!smap->elems)
  		return -ENOMEM;
  
  	err = pcpu_freelist_init(&smap->freelist);
  	if (err)
  		goto free_elems;
  
  	pcpu_freelist_populate(&smap->freelist, smap->elems, elem_size,
  			       smap->map.max_entries);
  	return 0;
  
  free_elems:
  	bpf_map_area_free(smap->elems);
  	return err;
  }
  
  /* Called from syscall */
  static struct bpf_map *stack_map_alloc(union bpf_attr *attr)
  {
  	u32 value_size = attr->value_size;
  	struct bpf_stack_map *smap;
  	struct bpf_map_memory mem;
  	u64 cost, n_buckets;
  	int err;
  
  	if (!bpf_capable())
  		return ERR_PTR(-EPERM);
  
  	if (attr->map_flags & ~STACK_CREATE_FLAG_MASK)
  		return ERR_PTR(-EINVAL);
  
  	/* check sanity of attributes */
  	if (attr->max_entries == 0 || attr->key_size != 4 ||
  	    value_size < 8 || value_size % 8)
  		return ERR_PTR(-EINVAL);
  
  	BUILD_BUG_ON(sizeof(struct bpf_stack_build_id) % sizeof(u64));
  	if (attr->map_flags & BPF_F_STACK_BUILD_ID) {
  		if (value_size % sizeof(struct bpf_stack_build_id) ||
  		    value_size / sizeof(struct bpf_stack_build_id)
  		    > sysctl_perf_event_max_stack)
  			return ERR_PTR(-EINVAL);
  	} else if (value_size / 8 > sysctl_perf_event_max_stack)
  		return ERR_PTR(-EINVAL);
  
  	/* hash table size must be power of 2 */
  	n_buckets = roundup_pow_of_two(attr->max_entries);
  
  	cost = n_buckets * sizeof(struct stack_map_bucket *) + sizeof(*smap);
  	cost += n_buckets * (value_size + sizeof(struct stack_map_bucket));
  	err = bpf_map_charge_init(&mem, cost);
  	if (err)
  		return ERR_PTR(err);
  
  	smap = bpf_map_area_alloc(cost, bpf_map_attr_numa_node(attr));
  	if (!smap) {
  		bpf_map_charge_finish(&mem);
  		return ERR_PTR(-ENOMEM);
  	}
  
  	bpf_map_init_from_attr(&smap->map, attr);
  	smap->map.value_size = value_size;
  	smap->n_buckets = n_buckets;
  
  	err = get_callchain_buffers(sysctl_perf_event_max_stack);
  	if (err)
  		goto free_charge;
  
  	err = prealloc_elems_and_freelist(smap);
  	if (err)
  		goto put_buffers;
  
  	bpf_map_charge_move(&smap->map.memory, &mem);
  
  	return &smap->map;
  
  put_buffers:
  	put_callchain_buffers();
  free_charge:
  	bpf_map_charge_finish(&mem);
  	bpf_map_area_free(smap);
  	return ERR_PTR(err);
  }
  
  #define BPF_BUILD_ID 3
  /*
   * Parse build id from the note segment. This logic can be shared between
   * 32-bit and 64-bit system, because Elf32_Nhdr and Elf64_Nhdr are
   * identical.
   */
  static inline int stack_map_parse_build_id(void *page_addr,
  					   unsigned char *build_id,
  					   void *note_start,
  					   Elf32_Word note_size)
  {
  	Elf32_Word note_offs = 0, new_offs;
  
  	/* check for overflow */
  	if (note_start < page_addr || note_start + note_size < note_start)
  		return -EINVAL;
  
  	/* only supports note that fits in the first page */
  	if (note_start + note_size > page_addr + PAGE_SIZE)
  		return -EINVAL;
  
  	while (note_offs + sizeof(Elf32_Nhdr) < note_size) {
  		Elf32_Nhdr *nhdr = (Elf32_Nhdr *)(note_start + note_offs);
  
  		if (nhdr->n_type == BPF_BUILD_ID &&
  		    nhdr->n_namesz == sizeof("GNU") &&
  		    nhdr->n_descsz > 0 &&
  		    nhdr->n_descsz <= BPF_BUILD_ID_SIZE) {
  			memcpy(build_id,
  			       note_start + note_offs +
  			       ALIGN(sizeof("GNU"), 4) + sizeof(Elf32_Nhdr),
  			       nhdr->n_descsz);
  			memset(build_id + nhdr->n_descsz, 0,
  			       BPF_BUILD_ID_SIZE - nhdr->n_descsz);
  			return 0;
  		}
  		new_offs = note_offs + sizeof(Elf32_Nhdr) +
  			ALIGN(nhdr->n_namesz, 4) + ALIGN(nhdr->n_descsz, 4);
  		if (new_offs <= note_offs)  /* overflow */
  			break;
  		note_offs = new_offs;
  	}
  	return -EINVAL;
  }
  
  /* Parse build ID from 32-bit ELF */
  static int stack_map_get_build_id_32(void *page_addr,
  				     unsigned char *build_id)
  {
  	Elf32_Ehdr *ehdr = (Elf32_Ehdr *)page_addr;
  	Elf32_Phdr *phdr;
  	int i;
  
  	/* only supports phdr that fits in one page */
  	if (ehdr->e_phnum >
  	    (PAGE_SIZE - sizeof(Elf32_Ehdr)) / sizeof(Elf32_Phdr))
  		return -EINVAL;
  
  	phdr = (Elf32_Phdr *)(page_addr + sizeof(Elf32_Ehdr));
  
  	for (i = 0; i < ehdr->e_phnum; ++i) {
  		if (phdr[i].p_type == PT_NOTE &&
  		    !stack_map_parse_build_id(page_addr, build_id,
  					      page_addr + phdr[i].p_offset,
  					      phdr[i].p_filesz))
  			return 0;
  	}
  	return -EINVAL;
  }
  
  /* Parse build ID from 64-bit ELF */
  static int stack_map_get_build_id_64(void *page_addr,
  				     unsigned char *build_id)
  {
  	Elf64_Ehdr *ehdr = (Elf64_Ehdr *)page_addr;
  	Elf64_Phdr *phdr;
  	int i;
  
  	/* only supports phdr that fits in one page */
  	if (ehdr->e_phnum >
  	    (PAGE_SIZE - sizeof(Elf64_Ehdr)) / sizeof(Elf64_Phdr))
  		return -EINVAL;
  
  	phdr = (Elf64_Phdr *)(page_addr + sizeof(Elf64_Ehdr));
  
  	for (i = 0; i < ehdr->e_phnum; ++i) {
  		if (phdr[i].p_type == PT_NOTE &&
  		    !stack_map_parse_build_id(page_addr, build_id,
  					      page_addr + phdr[i].p_offset,
  					      phdr[i].p_filesz))
  			return 0;
  	}
  	return -EINVAL;
  }
  
  /* Parse build ID of ELF file mapped to vma */
  static int stack_map_get_build_id(struct vm_area_struct *vma,
  				  unsigned char *build_id)
  {
  	Elf32_Ehdr *ehdr;
  	struct page *page;
  	void *page_addr;
  	int ret;
  
  	/* only works for page backed storage  */
  	if (!vma->vm_file)
  		return -EINVAL;
  
  	page = find_get_page(vma->vm_file->f_mapping, 0);
  	if (!page)
  		return -EFAULT;	/* page not mapped */
  
  	ret = -EINVAL;
  	page_addr = kmap_atomic(page);
  	ehdr = (Elf32_Ehdr *)page_addr;
  
  	/* compare magic x7f "ELF" */
  	if (memcmp(ehdr->e_ident, ELFMAG, SELFMAG) != 0)
  		goto out;
  
  	/* only support executable file and shared object file */
  	if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN)
  		goto out;
  
  	if (ehdr->e_ident[EI_CLASS] == ELFCLASS32)
  		ret = stack_map_get_build_id_32(page_addr, build_id);
  	else if (ehdr->e_ident[EI_CLASS] == ELFCLASS64)
  		ret = stack_map_get_build_id_64(page_addr, build_id);
  out:
  	kunmap_atomic(page_addr);
  	put_page(page);
  	return ret;
  }
  
  static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
  					  u64 *ips, u32 trace_nr, bool user)
  {
  	int i;
  	struct vm_area_struct *vma;
  	bool irq_work_busy = false;
  	struct stack_map_irq_work *work = NULL;
  
  	if (irqs_disabled()) {
  		if (!IS_ENABLED(CONFIG_PREEMPT_RT)) {
  			work = this_cpu_ptr(&up_read_work);
  			if (atomic_read(&work->irq_work.flags) & IRQ_WORK_BUSY) {
  				/* cannot queue more up_read, fallback */
  				irq_work_busy = true;
  			}
  		} else {
  			/*
  			 * PREEMPT_RT does not allow to trylock mmap sem in
  			 * interrupt disabled context. Force the fallback code.
  			 */
  			irq_work_busy = true;
  		}
  	}
  
  	/*
  	 * We cannot do up_read() when the irq is disabled, because of
  	 * risk to deadlock with rq_lock. To do build_id lookup when the
  	 * irqs are disabled, we need to run up_read() in irq_work. We use
  	 * a percpu variable to do the irq_work. If the irq_work is
  	 * already used by another lookup, we fall back to report ips.
  	 *
  	 * Same fallback is used for kernel stack (!user) on a stackmap
  	 * with build_id.
  	 */
  	if (!user || !current || !current->mm || irq_work_busy ||
  	    !mmap_read_trylock_non_owner(current->mm)) {
  		/* cannot access current->mm, fall back to ips */
  		for (i = 0; i < trace_nr; i++) {
  			id_offs[i].status = BPF_STACK_BUILD_ID_IP;
  			id_offs[i].ip = ips[i];
  			memset(id_offs[i].build_id, 0, BPF_BUILD_ID_SIZE);
  		}
  		return;
  	}
  
  	for (i = 0; i < trace_nr; i++) {
  		vma = find_vma(current->mm, ips[i]);
  		if (!vma || stack_map_get_build_id(vma, id_offs[i].build_id)) {
  			/* per entry fall back to ips */
  			id_offs[i].status = BPF_STACK_BUILD_ID_IP;
  			id_offs[i].ip = ips[i];
  			memset(id_offs[i].build_id, 0, BPF_BUILD_ID_SIZE);
  			continue;
  		}
  		id_offs[i].offset = (vma->vm_pgoff << PAGE_SHIFT) + ips[i]
  			- vma->vm_start;
  		id_offs[i].status = BPF_STACK_BUILD_ID_VALID;
  	}
  
  	if (!work) {
  		mmap_read_unlock_non_owner(current->mm);
  	} else {
  		work->mm = current->mm;
  		irq_work_queue(&work->irq_work);
  	}
  }
  
  static struct perf_callchain_entry *
  get_callchain_entry_for_task(struct task_struct *task, u32 init_nr)
  {
  #ifdef CONFIG_STACKTRACE
  	struct perf_callchain_entry *entry;
  	int rctx;
  
  	entry = get_callchain_entry(&rctx);
  
  	if (!entry)
  		return NULL;
  
  	entry->nr = init_nr +
  		stack_trace_save_tsk(task, (unsigned long *)(entry->ip + init_nr),
  				     sysctl_perf_event_max_stack - init_nr, 0);
  
  	/* stack_trace_save_tsk() works on unsigned long array, while
  	 * perf_callchain_entry uses u64 array. For 32-bit systems, it is
  	 * necessary to fix this mismatch.
  	 */
  	if (__BITS_PER_LONG != 64) {
  		unsigned long *from = (unsigned long *) entry->ip;
  		u64 *to = entry->ip;
  		int i;
  
  		/* copy data from the end to avoid using extra buffer */
  		for (i = entry->nr - 1; i >= (int)init_nr; i--)
  			to[i] = (u64)(from[i]);
  	}
  
  	put_callchain_entry(rctx);
  
  	return entry;
  #else /* CONFIG_STACKTRACE */
  	return NULL;
  #endif
  }
  
  static long __bpf_get_stackid(struct bpf_map *map,
  			      struct perf_callchain_entry *trace, u64 flags)
  {
  	struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
  	struct stack_map_bucket *bucket, *new_bucket, *old_bucket;
  	u32 max_depth = map->value_size / stack_map_data_size(map);
  	/* stack_map_alloc() checks that max_depth <= sysctl_perf_event_max_stack */
  	u32 init_nr = sysctl_perf_event_max_stack - max_depth;
  	u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
  	u32 hash, id, trace_nr, trace_len;
  	bool user = flags & BPF_F_USER_STACK;
  	u64 *ips;
  	bool hash_matches;
  
  	/* get_perf_callchain() guarantees that trace->nr >= init_nr
  	 * and trace-nr <= sysctl_perf_event_max_stack, so trace_nr <= max_depth
  	 */
  	trace_nr = trace->nr - init_nr;
  
  	if (trace_nr <= skip)
  		/* skipping more than usable stack trace */
  		return -EFAULT;
  
  	trace_nr -= skip;
  	trace_len = trace_nr * sizeof(u64);
  	ips = trace->ip + skip + init_nr;
  	hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0);
  	id = hash & (smap->n_buckets - 1);
  	bucket = READ_ONCE(smap->buckets[id]);
  
  	hash_matches = bucket && bucket->hash == hash;
  	/* fast cmp */
  	if (hash_matches && flags & BPF_F_FAST_STACK_CMP)
  		return id;
  
  	if (stack_map_use_build_id(map)) {
  		/* for build_id+offset, pop a bucket before slow cmp */
  		new_bucket = (struct stack_map_bucket *)
  			pcpu_freelist_pop(&smap->freelist);
  		if (unlikely(!new_bucket))
  			return -ENOMEM;
  		new_bucket->nr = trace_nr;
  		stack_map_get_build_id_offset(
  			(struct bpf_stack_build_id *)new_bucket->data,
  			ips, trace_nr, user);
  		trace_len = trace_nr * sizeof(struct bpf_stack_build_id);
  		if (hash_matches && bucket->nr == trace_nr &&
  		    memcmp(bucket->data, new_bucket->data, trace_len) == 0) {
  			pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
  			return id;
  		}
  		if (bucket && !(flags & BPF_F_REUSE_STACKID)) {
  			pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
  			return -EEXIST;
  		}
  	} else {
  		if (hash_matches && bucket->nr == trace_nr &&
  		    memcmp(bucket->data, ips, trace_len) == 0)
  			return id;
  		if (bucket && !(flags & BPF_F_REUSE_STACKID))
  			return -EEXIST;
  
  		new_bucket = (struct stack_map_bucket *)
  			pcpu_freelist_pop(&smap->freelist);
  		if (unlikely(!new_bucket))
  			return -ENOMEM;
  		memcpy(new_bucket->data, ips, trace_len);
  	}
  
  	new_bucket->hash = hash;
  	new_bucket->nr = trace_nr;
  
  	old_bucket = xchg(&smap->buckets[id], new_bucket);
  	if (old_bucket)
  		pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
  	return id;
  }
  
  BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
  	   u64, flags)
  {
  	u32 max_depth = map->value_size / stack_map_data_size(map);
  	/* stack_map_alloc() checks that max_depth <= sysctl_perf_event_max_stack */
  	u32 init_nr = sysctl_perf_event_max_stack - max_depth;
  	bool user = flags & BPF_F_USER_STACK;
  	struct perf_callchain_entry *trace;
  	bool kernel = !user;
  
  	if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
  			       BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
  		return -EINVAL;
  
  	trace = get_perf_callchain(regs, init_nr, kernel, user,
  				   sysctl_perf_event_max_stack, false, false);
  
  	if (unlikely(!trace))
  		/* couldn't fetch the stack trace */
  		return -EFAULT;
  
  	return __bpf_get_stackid(map, trace, flags);
  }
  
  const struct bpf_func_proto bpf_get_stackid_proto = {
  	.func		= bpf_get_stackid,
  	.gpl_only	= true,
  	.ret_type	= RET_INTEGER,
  	.arg1_type	= ARG_PTR_TO_CTX,
  	.arg2_type	= ARG_CONST_MAP_PTR,
  	.arg3_type	= ARG_ANYTHING,
  };
  
  static __u64 count_kernel_ip(struct perf_callchain_entry *trace)
  {
  	__u64 nr_kernel = 0;
  
  	while (nr_kernel < trace->nr) {
  		if (trace->ip[nr_kernel] == PERF_CONTEXT_USER)
  			break;
  		nr_kernel++;
  	}
  	return nr_kernel;
  }
  
  BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx,
  	   struct bpf_map *, map, u64, flags)
  {
  	struct perf_event *event = ctx->event;
  	struct perf_callchain_entry *trace;
  	bool kernel, user;
  	__u64 nr_kernel;
  	int ret;
  
  	/* perf_sample_data doesn't have callchain, use bpf_get_stackid */
  	if (!(event->attr.sample_type & __PERF_SAMPLE_CALLCHAIN_EARLY))
  		return bpf_get_stackid((unsigned long)(ctx->regs),
  				       (unsigned long) map, flags, 0, 0);
  
  	if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
  			       BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
  		return -EINVAL;
  
  	user = flags & BPF_F_USER_STACK;
  	kernel = !user;
  
  	trace = ctx->data->callchain;
  	if (unlikely(!trace))
  		return -EFAULT;
  
  	nr_kernel = count_kernel_ip(trace);
  
  	if (kernel) {
  		__u64 nr = trace->nr;
  
  		trace->nr = nr_kernel;
  		ret = __bpf_get_stackid(map, trace, flags);
  
  		/* restore nr */
  		trace->nr = nr;
  	} else { /* user */
  		u64 skip = flags & BPF_F_SKIP_FIELD_MASK;
  
  		skip += nr_kernel;
  		if (skip > BPF_F_SKIP_FIELD_MASK)
  			return -EFAULT;
  
  		flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip;
  		ret = __bpf_get_stackid(map, trace, flags);
  	}
  	return ret;
  }
  
  const struct bpf_func_proto bpf_get_stackid_proto_pe = {
  	.func		= bpf_get_stackid_pe,
  	.gpl_only	= false,
  	.ret_type	= RET_INTEGER,
  	.arg1_type	= ARG_PTR_TO_CTX,
  	.arg2_type	= ARG_CONST_MAP_PTR,
  	.arg3_type	= ARG_ANYTHING,
  };
  
  static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,
  			    struct perf_callchain_entry *trace_in,
  			    void *buf, u32 size, u64 flags)
  {
  	u32 init_nr, trace_nr, copy_len, elem_size, num_elem;
  	bool user_build_id = flags & BPF_F_USER_BUILD_ID;
  	u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
  	bool user = flags & BPF_F_USER_STACK;
  	struct perf_callchain_entry *trace;
  	bool kernel = !user;
  	int err = -EINVAL;
  	u64 *ips;
  
  	if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
  			       BPF_F_USER_BUILD_ID)))
  		goto clear;
  	if (kernel && user_build_id)
  		goto clear;
  
  	elem_size = (user && user_build_id) ? sizeof(struct bpf_stack_build_id)
  					    : sizeof(u64);
  	if (unlikely(size % elem_size))
  		goto clear;
  
  	/* cannot get valid user stack for task without user_mode regs */
  	if (task && user && !user_mode(regs))
  		goto err_fault;
  
  	num_elem = size / elem_size;
  	if (sysctl_perf_event_max_stack < num_elem)
  		init_nr = 0;
  	else
  		init_nr = sysctl_perf_event_max_stack - num_elem;
  
  	if (trace_in)
  		trace = trace_in;
  	else if (kernel && task)
  		trace = get_callchain_entry_for_task(task, init_nr);
  	else
  		trace = get_perf_callchain(regs, init_nr, kernel, user,
  					   sysctl_perf_event_max_stack,
  					   false, false);
  	if (unlikely(!trace))
  		goto err_fault;
  
  	trace_nr = trace->nr - init_nr;
  	if (trace_nr < skip)
  		goto err_fault;
  
  	trace_nr -= skip;
  	trace_nr = (trace_nr <= num_elem) ? trace_nr : num_elem;
  	copy_len = trace_nr * elem_size;
  	ips = trace->ip + skip + init_nr;
  	if (user && user_build_id)
  		stack_map_get_build_id_offset(buf, ips, trace_nr, user);
  	else
  		memcpy(buf, ips, copy_len);
  
  	if (size > copy_len)
  		memset(buf + copy_len, 0, size - copy_len);
  	return copy_len;
  
  err_fault:
  	err = -EFAULT;
  clear:
  	memset(buf, 0, size);
  	return err;
  }
  
  BPF_CALL_4(bpf_get_stack, struct pt_regs *, regs, void *, buf, u32, size,
  	   u64, flags)
  {
  	return __bpf_get_stack(regs, NULL, NULL, buf, size, flags);
  }
  
  const struct bpf_func_proto bpf_get_stack_proto = {
  	.func		= bpf_get_stack,
  	.gpl_only	= true,
  	.ret_type	= RET_INTEGER,
  	.arg1_type	= ARG_PTR_TO_CTX,
  	.arg2_type	= ARG_PTR_TO_UNINIT_MEM,
  	.arg3_type	= ARG_CONST_SIZE_OR_ZERO,
  	.arg4_type	= ARG_ANYTHING,
  };
  
  BPF_CALL_4(bpf_get_task_stack, struct task_struct *, task, void *, buf,
  	   u32, size, u64, flags)
  {
  	struct pt_regs *regs = task_pt_regs(task);
  
  	return __bpf_get_stack(regs, task, NULL, buf, size, flags);
  }
  
  BTF_ID_LIST_SINGLE(bpf_get_task_stack_btf_ids, struct, task_struct)
  
  const struct bpf_func_proto bpf_get_task_stack_proto = {
  	.func		= bpf_get_task_stack,
  	.gpl_only	= false,
  	.ret_type	= RET_INTEGER,
  	.arg1_type	= ARG_PTR_TO_BTF_ID,
  	.arg1_btf_id	= &bpf_get_task_stack_btf_ids[0],
  	.arg2_type	= ARG_PTR_TO_UNINIT_MEM,
  	.arg3_type	= ARG_CONST_SIZE_OR_ZERO,
  	.arg4_type	= ARG_ANYTHING,
  };
  
  BPF_CALL_4(bpf_get_stack_pe, struct bpf_perf_event_data_kern *, ctx,
  	   void *, buf, u32, size, u64, flags)
  {
  	struct pt_regs *regs = (struct pt_regs *)(ctx->regs);
  	struct perf_event *event = ctx->event;
  	struct perf_callchain_entry *trace;
  	bool kernel, user;
  	int err = -EINVAL;
  	__u64 nr_kernel;
  
  	if (!(event->attr.sample_type & __PERF_SAMPLE_CALLCHAIN_EARLY))
  		return __bpf_get_stack(regs, NULL, NULL, buf, size, flags);
  
  	if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
  			       BPF_F_USER_BUILD_ID)))
  		goto clear;
  
  	user = flags & BPF_F_USER_STACK;
  	kernel = !user;
  
  	err = -EFAULT;
  	trace = ctx->data->callchain;
  	if (unlikely(!trace))
  		goto clear;
  
  	nr_kernel = count_kernel_ip(trace);
  
  	if (kernel) {
  		__u64 nr = trace->nr;
  
  		trace->nr = nr_kernel;
  		err = __bpf_get_stack(regs, NULL, trace, buf, size, flags);
  
  		/* restore nr */
  		trace->nr = nr;
  	} else { /* user */
  		u64 skip = flags & BPF_F_SKIP_FIELD_MASK;
  
  		skip += nr_kernel;
  		if (skip > BPF_F_SKIP_FIELD_MASK)
  			goto clear;
  
  		flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip;
  		err = __bpf_get_stack(regs, NULL, trace, buf, size, flags);
  	}
  	return err;
  
  clear:
  	memset(buf, 0, size);
  	return err;
  
  }
  
  const struct bpf_func_proto bpf_get_stack_proto_pe = {
  	.func		= bpf_get_stack_pe,
  	.gpl_only	= true,
  	.ret_type	= RET_INTEGER,
  	.arg1_type	= ARG_PTR_TO_CTX,
  	.arg2_type	= ARG_PTR_TO_UNINIT_MEM,
  	.arg3_type	= ARG_CONST_SIZE_OR_ZERO,
  	.arg4_type	= ARG_ANYTHING,
  };
  
  /* Called from eBPF program */
  static void *stack_map_lookup_elem(struct bpf_map *map, void *key)
  {
  	return ERR_PTR(-EOPNOTSUPP);
  }
  
  /* Called from syscall */
  int bpf_stackmap_copy(struct bpf_map *map, void *key, void *value)
  {
  	struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
  	struct stack_map_bucket *bucket, *old_bucket;
  	u32 id = *(u32 *)key, trace_len;
  
  	if (unlikely(id >= smap->n_buckets))
  		return -ENOENT;
  
  	bucket = xchg(&smap->buckets[id], NULL);
  	if (!bucket)
  		return -ENOENT;
  
  	trace_len = bucket->nr * stack_map_data_size(map);
  	memcpy(value, bucket->data, trace_len);
  	memset(value + trace_len, 0, map->value_size - trace_len);
  
  	old_bucket = xchg(&smap->buckets[id], bucket);
  	if (old_bucket)
  		pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
  	return 0;
  }
  
  static int stack_map_get_next_key(struct bpf_map *map, void *key,
  				  void *next_key)
  {
  	struct bpf_stack_map *smap = container_of(map,
  						  struct bpf_stack_map, map);
  	u32 id;
  
  	WARN_ON_ONCE(!rcu_read_lock_held());
  
  	if (!key) {
  		id = 0;
  	} else {
  		id = *(u32 *)key;
  		if (id >= smap->n_buckets || !smap->buckets[id])
  			id = 0;
  		else
  			id++;
  	}
  
  	while (id < smap->n_buckets && !smap->buckets[id])
  		id++;
  
  	if (id >= smap->n_buckets)
  		return -ENOENT;
  
  	*(u32 *)next_key = id;
  	return 0;
  }
  
  static int stack_map_update_elem(struct bpf_map *map, void *key, void *value,
  				 u64 map_flags)
  {
  	return -EINVAL;
  }
  
  /* Called from syscall or from eBPF program */
  static int stack_map_delete_elem(struct bpf_map *map, void *key)
  {
  	struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
  	struct stack_map_bucket *old_bucket;
  	u32 id = *(u32 *)key;
  
  	if (unlikely(id >= smap->n_buckets))
  		return -E2BIG;
  
  	old_bucket = xchg(&smap->buckets[id], NULL);
  	if (old_bucket) {
  		pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
  		return 0;
  	} else {
  		return -ENOENT;
  	}
  }
  
  /* Called when map->refcnt goes to zero, either from workqueue or from syscall */
  static void stack_map_free(struct bpf_map *map)
  {
  	struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
  
  	bpf_map_area_free(smap->elems);
  	pcpu_freelist_destroy(&smap->freelist);
  	bpf_map_area_free(smap);
  	put_callchain_buffers();
  }
  
  static int stack_trace_map_btf_id;
  const struct bpf_map_ops stack_trace_map_ops = {
  	.map_meta_equal = bpf_map_meta_equal,
  	.map_alloc = stack_map_alloc,
  	.map_free = stack_map_free,
  	.map_get_next_key = stack_map_get_next_key,
  	.map_lookup_elem = stack_map_lookup_elem,
  	.map_update_elem = stack_map_update_elem,
  	.map_delete_elem = stack_map_delete_elem,
  	.map_check_btf = map_check_no_btf,
  	.map_btf_name = "bpf_stack_map",
  	.map_btf_id = &stack_trace_map_btf_id,
  };
  
  static int __init stack_map_init(void)
  {
  	int cpu;
  	struct stack_map_irq_work *work;
  
  	for_each_possible_cpu(cpu) {
  		work = per_cpu_ptr(&up_read_work, cpu);
  		init_irq_work(&work->irq_work, do_up_read);
  	}
  	return 0;
  }
  subsys_initcall(stack_map_init);
  