[linux-block.git] / kernel / bpf / stackmap.c

// 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/stacktrace.h>
#include <linux/perf_event.h>
#include <linux/elf.h>
#include <linux/pagemap.h>
#include <linux/irq_work.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 rw_semaphore *sem;
};

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);
	up_read_non_owner(work->sem);
	work->sem = NULL;
}

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 (!capable(CAP_SYS_ADMIN))
		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)
			return stack_map_parse_build_id(page_addr, build_id,
					page_addr + phdr[i].p_offset,
					phdr[i].p_filesz);
	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)
			return stack_map_parse_build_id(page_addr, build_id,
					page_addr + phdr[i].p_offset,
					phdr[i].p_filesz);
	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 ||
	    down_read_trylock(&current->mm->mmap_sem) == 0) {
		/* 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) {
		up_read(&current->mm->mmap_sem);
	} else {
		work->sem = &current->mm->mmap_sem;
		irq_work_queue(&work->irq_work);
		/*
		 * The irq_work will release the mmap_sem with
		 * up_read_non_owner(). The rwsem_release() is called
		 * here to release the lock from lockdep's perspective.
		 */
		rwsem_release(&current->mm->mmap_sem.dep_map, _RET_IP_);
	}
}

BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
	   u64, flags)
{
	struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
	struct perf_callchain_entry *trace;
	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;
	bool kernel = !user;
	u64 *ips;
	bool hash_matches;

	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;

	/* 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;
}

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,
};

BPF_CALL_4(bpf_get_stack, struct pt_regs *, regs, 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;

	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;
	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;
}

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,
};

/* 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);

	/* wait for bpf programs to complete before freeing stack map */
	synchronize_rcu();

	bpf_map_area_free(smap->elems);
	pcpu_freelist_destroy(&smap->freelist);
	bpf_map_area_free(smap);
	put_callchain_buffers();
}

const struct bpf_map_ops stack_trace_map_ops = {
	.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,
};

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);
Commit	Line	Data
25763b3c	1	// SPDX-License-Identifier: GPL-2.0-only
d5a3b1f6	2	/* Copyright (c) 2016 Facebook
d5a3b1f6 AS	3	*/
	4	#include <linux/bpf.h>
	5	#include <linux/jhash.h>
	6	#include <linux/filter.h>
d5a3b1f6 AS	7	#include <linux/stacktrace.h>
d5a3b1f6 AS	8	#include <linux/perf_event.h>
615755a7 SL	9	#include <linux/elf.h>
615755a7 SL	10	#include <linux/pagemap.h>
bae77c5e	11	#include <linux/irq_work.h>
557c0c6e	12	#include "percpu_freelist.h"
d5a3b1f6	13
615755a7 SL	14	#define STACK_CREATE_FLAG_MASK \
	15	(BPF_F_NUMA_NODE \| BPF_F_RDONLY \| BPF_F_WRONLY \| \
	16	BPF_F_STACK_BUILD_ID)
6e71b04a	17
d5a3b1f6	18	struct stack_map_bucket {
557c0c6e	19	struct pcpu_freelist_node fnode;
d5a3b1f6 AS	20	u32 hash;
d5a3b1f6 AS	21	u32 nr;
615755a7	22	u64 data[];
d5a3b1f6 AS	23	};
	24
	25	struct bpf_stack_map {
	26	struct bpf_map map;
557c0c6e AS	27	void *elems;
557c0c6e AS	28	struct pcpu_freelist freelist;
d5a3b1f6	29	u32 n_buckets;
557c0c6e	30	struct stack_map_bucket *buckets[];
d5a3b1f6 AS	31	};
d5a3b1f6 AS	32
bae77c5e SL	33	/* irq_work to run up_read() for build_id lookup in nmi context */
	34	struct stack_map_irq_work {
	35	struct irq_work irq_work;
	36	struct rw_semaphore *sem;
	37	};
	38
	39	static void do_up_read(struct irq_work *entry)
	40	{
	41	struct stack_map_irq_work *work;
	42
099bfaa7 DM	43	if (WARN_ON_ONCE(IS_ENABLED(CONFIG_PREEMPT_RT)))
	44	return;
	45
bae77c5e	46	work = container_of(entry, struct stack_map_irq_work, irq_work);
3defaf2f	47	up_read_non_owner(work->sem);
bae77c5e SL	48	work->sem = NULL;
	49	}
	50
	51	static DEFINE_PER_CPU(struct stack_map_irq_work, up_read_work);
	52
615755a7 SL	53	static inline bool stack_map_use_build_id(struct bpf_map *map)
	54	{
	55	return (map->map_flags & BPF_F_STACK_BUILD_ID);
	56	}
	57
	58	static inline int stack_map_data_size(struct bpf_map *map)
	59	{
	60	return stack_map_use_build_id(map) ?
	61	sizeof(struct bpf_stack_build_id) : sizeof(u64);
	62	}
	63
557c0c6e AS	64	static int prealloc_elems_and_freelist(struct bpf_stack_map *smap)
	65	{
	66	u32 elem_size = sizeof(struct stack_map_bucket) + smap->map.value_size;
	67	int err;
	68
96eabe7a MKL	69	smap->elems = bpf_map_area_alloc(elem_size * smap->map.max_entries,
96eabe7a MKL	70	smap->map.numa_node);
557c0c6e AS	71	if (!smap->elems)
	72	return -ENOMEM;
	73
	74	err = pcpu_freelist_init(&smap->freelist);
	75	if (err)
	76	goto free_elems;
	77
	78	pcpu_freelist_populate(&smap->freelist, smap->elems, elem_size,
	79	smap->map.max_entries);
	80	return 0;
	81
	82	free_elems:
d407bd25	83	bpf_map_area_free(smap->elems);
557c0c6e AS	84	return err;
	85	}
	86
d5a3b1f6 AS	87	/* Called from syscall */
	88	static struct bpf_map stack_map_alloc(union bpf_attr attr)
	89	{
	90	u32 value_size = attr->value_size;
	91	struct bpf_stack_map *smap;
b936ca64	92	struct bpf_map_memory mem;
d5a3b1f6 AS	93	u64 cost, n_buckets;
	94	int err;
	95
	96	if (!capable(CAP_SYS_ADMIN))
	97	return ERR_PTR(-EPERM);
	98
6e71b04a	99	if (attr->map_flags & ~STACK_CREATE_FLAG_MASK)
823707b6 AS	100	return ERR_PTR(-EINVAL);
823707b6 AS	101
d5a3b1f6 AS	102	/* check sanity of attributes */
d5a3b1f6 AS	103	if (attr->max_entries == 0 \|\| attr->key_size != 4 \|\|
615755a7 SL	104	value_size < 8 \|\| value_size % 8)
	105	return ERR_PTR(-EINVAL);
	106
	107	BUILD_BUG_ON(sizeof(struct bpf_stack_build_id) % sizeof(u64));
	108	if (attr->map_flags & BPF_F_STACK_BUILD_ID) {
	109	if (value_size % sizeof(struct bpf_stack_build_id) \|\|
	110	value_size / sizeof(struct bpf_stack_build_id)
	111	> sysctl_perf_event_max_stack)
	112	return ERR_PTR(-EINVAL);
	113	} else if (value_size / 8 > sysctl_perf_event_max_stack)
d5a3b1f6 AS	114	return ERR_PTR(-EINVAL);
	115
	116	/* hash table size must be power of 2 */
	117	n_buckets = roundup_pow_of_two(attr->max_entries);
	118
	119	cost = n_buckets * sizeof(struct stack_map_bucket ) + sizeof(smap);
b936ca64	120	cost += n_buckets * (value_size + sizeof(struct stack_map_bucket));
c85d6913	121	err = bpf_map_charge_init(&mem, cost);
b936ca64 RG	122	if (err)
	123	return ERR_PTR(err);
	124
96eabe7a	125	smap = bpf_map_area_alloc(cost, bpf_map_attr_numa_node(attr));
b936ca64 RG	126	if (!smap) {
b936ca64 RG	127	bpf_map_charge_finish(&mem);
d407bd25	128	return ERR_PTR(-ENOMEM);
b936ca64	129	}
d5a3b1f6	130
bd475643	131	bpf_map_init_from_attr(&smap->map, attr);
d5a3b1f6	132	smap->map.value_size = value_size;
d5a3b1f6	133	smap->n_buckets = n_buckets;
557c0c6e	134
97c79a38	135	err = get_callchain_buffers(sysctl_perf_event_max_stack);
d5a3b1f6	136	if (err)
b936ca64	137	goto free_charge;
d5a3b1f6	138
557c0c6e AS	139	err = prealloc_elems_and_freelist(smap);
	140	if (err)
	141	goto put_buffers;
	142
b936ca64 RG	143	bpf_map_charge_move(&smap->map.memory, &mem);
b936ca64 RG	144
d5a3b1f6 AS	145	return &smap->map;
d5a3b1f6 AS	146
557c0c6e AS	147	put_buffers:
557c0c6e AS	148	put_callchain_buffers();
b936ca64 RG	149	free_charge:
b936ca64 RG	150	bpf_map_charge_finish(&mem);
d407bd25	151	bpf_map_area_free(smap);
d5a3b1f6 AS	152	return ERR_PTR(err);
	153	}
	154
615755a7 SL	155	#define BPF_BUILD_ID 3
	156	/*
	157	* Parse build id from the note segment. This logic can be shared between
	158	* 32-bit and 64-bit system, because Elf32_Nhdr and Elf64_Nhdr are
	159	* identical.
	160	*/
	161	static inline int stack_map_parse_build_id(void *page_addr,
	162	unsigned char *build_id,
	163	void *note_start,
	164	Elf32_Word note_size)
	165	{
	166	Elf32_Word note_offs = 0, new_offs;
	167
	168	/* check for overflow */
	169	if (note_start < page_addr \|\| note_start + note_size < note_start)
	170	return -EINVAL;
	171
	172	/* only supports note that fits in the first page */
	173	if (note_start + note_size > page_addr + PAGE_SIZE)
	174	return -EINVAL;
	175
	176	while (note_offs + sizeof(Elf32_Nhdr) < note_size) {
	177	Elf32_Nhdr nhdr = (Elf32_Nhdr )(note_start + note_offs);
	178
	179	if (nhdr->n_type == BPF_BUILD_ID &&
	180	nhdr->n_namesz == sizeof("GNU") &&
0b698005 SF	181	nhdr->n_descsz > 0 &&
0b698005 SF	182	nhdr->n_descsz <= BPF_BUILD_ID_SIZE) {
615755a7 SL	183	memcpy(build_id,
	184	note_start + note_offs +
	185	ALIGN(sizeof("GNU"), 4) + sizeof(Elf32_Nhdr),
0b698005 SF	186	nhdr->n_descsz);
	187	memset(build_id + nhdr->n_descsz, 0,
	188	BPF_BUILD_ID_SIZE - nhdr->n_descsz);
615755a7 SL	189	return 0;
	190	}
	191	new_offs = note_offs + sizeof(Elf32_Nhdr) +
	192	ALIGN(nhdr->n_namesz, 4) + ALIGN(nhdr->n_descsz, 4);
	193	if (new_offs <= note_offs) /* overflow */
	194	break;
	195	note_offs = new_offs;
	196	}
	197	return -EINVAL;
	198	}
	199
	200	/* Parse build ID from 32-bit ELF */
	201	static int stack_map_get_build_id_32(void *page_addr,
	202	unsigned char *build_id)
	203	{
	204	Elf32_Ehdr ehdr = (Elf32_Ehdr )page_addr;
	205	Elf32_Phdr *phdr;
	206	int i;
	207
	208	/* only supports phdr that fits in one page */
	209	if (ehdr->e_phnum >
	210	(PAGE_SIZE - sizeof(Elf32_Ehdr)) / sizeof(Elf32_Phdr))
	211	return -EINVAL;
	212
	213	phdr = (Elf32_Phdr *)(page_addr + sizeof(Elf32_Ehdr));
	214
	215	for (i = 0; i < ehdr->e_phnum; ++i)
	216	if (phdr[i].p_type == PT_NOTE)
	217	return stack_map_parse_build_id(page_addr, build_id,
	218	page_addr + phdr[i].p_offset,
	219	phdr[i].p_filesz);
	220	return -EINVAL;
	221	}
	222
	223	/* Parse build ID from 64-bit ELF */
	224	static int stack_map_get_build_id_64(void *page_addr,
	225	unsigned char *build_id)
	226	{
	227	Elf64_Ehdr ehdr = (Elf64_Ehdr )page_addr;
	228	Elf64_Phdr *phdr;
	229	int i;
	230
	231	/* only supports phdr that fits in one page */
	232	if (ehdr->e_phnum >
	233	(PAGE_SIZE - sizeof(Elf64_Ehdr)) / sizeof(Elf64_Phdr))
	234	return -EINVAL;
	235
	236	phdr = (Elf64_Phdr *)(page_addr + sizeof(Elf64_Ehdr));
	237
	238	for (i = 0; i < ehdr->e_phnum; ++i)
	239	if (phdr[i].p_type == PT_NOTE)
	240	return stack_map_parse_build_id(page_addr, build_id,
	241	page_addr + phdr[i].p_offset,
	242	phdr[i].p_filesz);
	243	return -EINVAL;
	244	}
	245
	246	/* Parse build ID of ELF file mapped to vma */
	247	static int stack_map_get_build_id(struct vm_area_struct *vma,
	248	unsigned char *build_id)
	249	{
	250	Elf32_Ehdr *ehdr;
	251	struct page *page;
	252	void *page_addr;
253	int ret;
254
255	/* only works for page backed storage */
256	if (!vma->vm_file)
257	return -EINVAL;
258
259	page = find_get_page(vma->vm_file->f_mapping, 0);
260	if (!page)
261	return -EFAULT; /* page not mapped */
262
263	ret = -EINVAL;
beaf3d19	264	page_addr = kmap_atomic(page);
615755a7 SL	265	ehdr = (Elf32_Ehdr *)page_addr;
	266
	267	/* compare magic x7f "ELF" */
	268	if (memcmp(ehdr->e_ident, ELFMAG, SELFMAG) != 0)
	269	goto out;
	270
	271	/* only support executable file and shared object file */
	272	if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN)
	273	goto out;
	274
	275	if (ehdr->e_ident[EI_CLASS] == ELFCLASS32)
	276	ret = stack_map_get_build_id_32(page_addr, build_id);
	277	else if (ehdr->e_ident[EI_CLASS] == ELFCLASS64)
	278	ret = stack_map_get_build_id_64(page_addr, build_id);
	279	out:
beaf3d19	280	kunmap_atomic(page_addr);
615755a7 SL	281	put_page(page);
	282	return ret;
	283	}
	284
5f412632	285	static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
615755a7 SL	286	u64 *ips, u32 trace_nr, bool user)
	287	{
	288	int i;
	289	struct vm_area_struct *vma;
bae77c5e	290	bool irq_work_busy = false;
dc3b8ae9	291	struct stack_map_irq_work *work = NULL;
bae77c5e	292
eac9153f	293	if (irqs_disabled()) {
099bfaa7 DM	294	if (!IS_ENABLED(CONFIG_PREEMPT_RT)) {
	295	work = this_cpu_ptr(&up_read_work);
	296	if (atomic_read(&work->irq_work.flags) & IRQ_WORK_BUSY) {
	297	/* cannot queue more up_read, fallback */
	298	irq_work_busy = true;
	299	}
	300	} else {
	301	/*
	302	* PREEMPT_RT does not allow to trylock mmap sem in
	303	* interrupt disabled context. Force the fallback code.
	304	*/
bae77c5e	305	irq_work_busy = true;
099bfaa7	306	}
bae77c5e	307	}
615755a7 SL	308
615755a7 SL	309	/*
eac9153f SL	310	* We cannot do up_read() when the irq is disabled, because of
	311	* risk to deadlock with rq_lock. To do build_id lookup when the
	312	* irqs are disabled, we need to run up_read() in irq_work. We use
bae77c5e SL	313	* a percpu variable to do the irq_work. If the irq_work is
bae77c5e SL	314	* already used by another lookup, we fall back to report ips.
615755a7 SL	315	*
	316	* Same fallback is used for kernel stack (!user) on a stackmap
	317	* with build_id.
	318	*/
bae77c5e	319	if (!user \|\| !current \|\| !current->mm \|\| irq_work_busy \|\|
615755a7 SL	320	down_read_trylock(&current->mm->mmap_sem) == 0) {
	321	/* cannot access current->mm, fall back to ips */
	322	for (i = 0; i < trace_nr; i++) {
	323	id_offs[i].status = BPF_STACK_BUILD_ID_IP;
	324	id_offs[i].ip = ips[i];
4af396ae	325	memset(id_offs[i].build_id, 0, BPF_BUILD_ID_SIZE);
615755a7 SL	326	}
	327	return;
	328	}
	329
	330	for (i = 0; i < trace_nr; i++) {
	331	vma = find_vma(current->mm, ips[i]);
	332	if (!vma \|\| stack_map_get_build_id(vma, id_offs[i].build_id)) {
	333	/* per entry fall back to ips */
	334	id_offs[i].status = BPF_STACK_BUILD_ID_IP;
	335	id_offs[i].ip = ips[i];
4af396ae	336	memset(id_offs[i].build_id, 0, BPF_BUILD_ID_SIZE);
615755a7 SL	337	continue;
	338	}
	339	id_offs[i].offset = (vma->vm_pgoff << PAGE_SHIFT) + ips[i]
	340	- vma->vm_start;
	341	id_offs[i].status = BPF_STACK_BUILD_ID_VALID;
	342	}
bae77c5e	343
dc3b8ae9	344	if (!work) {
bae77c5e SL	345	up_read(&current->mm->mmap_sem);
	346	} else {
	347	work->sem = &current->mm->mmap_sem;
	348	irq_work_queue(&work->irq_work);
3defaf2f AS	349	/*
	350	* The irq_work will release the mmap_sem with
	351	* up_read_non_owner(). The rwsem_release() is called
	352	* here to release the lock from lockdep's perspective.
	353	*/
5facae4f	354	rwsem_release(&current->mm->mmap_sem.dep_map, _RET_IP_);
bae77c5e	355	}
615755a7 SL	356	}
615755a7 SL	357
f3694e00 DB	358	BPF_CALL_3(bpf_get_stackid, struct pt_regs , regs, struct bpf_map , map,
f3694e00 DB	359	u64, flags)
d5a3b1f6	360	{
d5a3b1f6 AS	361	struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
	362	struct perf_callchain_entry *trace;
	363	struct stack_map_bucket bucket, new_bucket, *old_bucket;
615755a7	364	u32 max_depth = map->value_size / stack_map_data_size(map);
c5dfd78e ACM	365	/* stack_map_alloc() checks that max_depth <= sysctl_perf_event_max_stack */
c5dfd78e ACM	366	u32 init_nr = sysctl_perf_event_max_stack - max_depth;
d5a3b1f6 AS	367	u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
	368	u32 hash, id, trace_nr, trace_len;
	369	bool user = flags & BPF_F_USER_STACK;
	370	bool kernel = !user;
	371	u64 *ips;
615755a7	372	bool hash_matches;
d5a3b1f6 AS	373
	374	if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK \| BPF_F_USER_STACK \|
	375	BPF_F_FAST_STACK_CMP \| BPF_F_REUSE_STACKID)))
	376	return -EINVAL;
	377
cfbcf468 ACM	378	trace = get_perf_callchain(regs, init_nr, kernel, user,
cfbcf468 ACM	379	sysctl_perf_event_max_stack, false, false);
d5a3b1f6 AS	380
	381	if (unlikely(!trace))
	382	/* couldn't fetch the stack trace */
	383	return -EFAULT;
	384
	385	/* get_perf_callchain() guarantees that trace->nr >= init_nr
c5dfd78e	386	* and trace-nr <= sysctl_perf_event_max_stack, so trace_nr <= max_depth
d5a3b1f6 AS	387	*/
	388	trace_nr = trace->nr - init_nr;
	389
	390	if (trace_nr <= skip)
	391	/* skipping more than usable stack trace */
	392	return -EFAULT;
	393
	394	trace_nr -= skip;
	395	trace_len = trace_nr * sizeof(u64);
	396	ips = trace->ip + skip + init_nr;
	397	hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0);
	398	id = hash & (smap->n_buckets - 1);
557c0c6e	399	bucket = READ_ONCE(smap->buckets[id]);
d5a3b1f6	400
615755a7 SL	401	hash_matches = bucket && bucket->hash == hash;
	402	/* fast cmp */
	403	if (hash_matches && flags & BPF_F_FAST_STACK_CMP)
	404	return id;
	405
	406	if (stack_map_use_build_id(map)) {
	407	/* for build_id+offset, pop a bucket before slow cmp */
	408	new_bucket = (struct stack_map_bucket *)
	409	pcpu_freelist_pop(&smap->freelist);
	410	if (unlikely(!new_bucket))
	411	return -ENOMEM;
5f412632 YS	412	new_bucket->nr = trace_nr;
	413	stack_map_get_build_id_offset(
	414	(struct bpf_stack_build_id *)new_bucket->data,
	415	ips, trace_nr, user);
615755a7 SL	416	trace_len = trace_nr * sizeof(struct bpf_stack_build_id);
	417	if (hash_matches && bucket->nr == trace_nr &&
	418	memcmp(bucket->data, new_bucket->data, trace_len) == 0) {
	419	pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
d5a3b1f6	420	return id;
615755a7 SL	421	}
	422	if (bucket && !(flags & BPF_F_REUSE_STACKID)) {
	423	pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
	424	return -EEXIST;
	425	}
	426	} else {
	427	if (hash_matches && bucket->nr == trace_nr &&
	428	memcmp(bucket->data, ips, trace_len) == 0)
d5a3b1f6	429	return id;
615755a7 SL	430	if (bucket && !(flags & BPF_F_REUSE_STACKID))
	431	return -EEXIST;
	432
	433	new_bucket = (struct stack_map_bucket *)
	434	pcpu_freelist_pop(&smap->freelist);
	435	if (unlikely(!new_bucket))
	436	return -ENOMEM;
	437	memcpy(new_bucket->data, ips, trace_len);
d5a3b1f6 AS	438	}
d5a3b1f6 AS	439
d5a3b1f6 AS	440	new_bucket->hash = hash;
	441	new_bucket->nr = trace_nr;
	442
	443	old_bucket = xchg(&smap->buckets[id], new_bucket);
	444	if (old_bucket)
557c0c6e	445	pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
d5a3b1f6 AS	446	return id;
	447	}
	448
	449	const struct bpf_func_proto bpf_get_stackid_proto = {
	450	.func = bpf_get_stackid,
	451	.gpl_only = true,
	452	.ret_type = RET_INTEGER,
	453	.arg1_type = ARG_PTR_TO_CTX,
	454	.arg2_type = ARG_CONST_MAP_PTR,
	455	.arg3_type = ARG_ANYTHING,
	456	};
	457
c195651e YS	458	BPF_CALL_4(bpf_get_stack, struct pt_regs , regs, void , buf, u32, size,
	459	u64, flags)
	460	{
	461	u32 init_nr, trace_nr, copy_len, elem_size, num_elem;
	462	bool user_build_id = flags & BPF_F_USER_BUILD_ID;
	463	u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
	464	bool user = flags & BPF_F_USER_STACK;
	465	struct perf_callchain_entry *trace;
	466	bool kernel = !user;
	467	int err = -EINVAL;
	468	u64 *ips;
	469
	470	if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK \| BPF_F_USER_STACK \|
	471	BPF_F_USER_BUILD_ID)))
	472	goto clear;
	473	if (kernel && user_build_id)
	474	goto clear;
	475
	476	elem_size = (user && user_build_id) ? sizeof(struct bpf_stack_build_id)
	477	: sizeof(u64);
	478	if (unlikely(size % elem_size))
	479	goto clear;
	480
	481	num_elem = size / elem_size;
	482	if (sysctl_perf_event_max_stack < num_elem)
	483	init_nr = 0;
	484	else
	485	init_nr = sysctl_perf_event_max_stack - num_elem;
	486	trace = get_perf_callchain(regs, init_nr, kernel, user,
	487	sysctl_perf_event_max_stack, false, false);
	488	if (unlikely(!trace))
	489	goto err_fault;
	490
	491	trace_nr = trace->nr - init_nr;
	492	if (trace_nr < skip)
	493	goto err_fault;
	494
	495	trace_nr -= skip;
	496	trace_nr = (trace_nr <= num_elem) ? trace_nr : num_elem;
	497	copy_len = trace_nr * elem_size;
	498	ips = trace->ip + skip + init_nr;
	499	if (user && user_build_id)
	500	stack_map_get_build_id_offset(buf, ips, trace_nr, user);
	501	else
	502	memcpy(buf, ips, copy_len);
	503
	504	if (size > copy_len)
	505	memset(buf + copy_len, 0, size - copy_len);
	506	return copy_len;
	507
	508	err_fault:
	509	err = -EFAULT;
	510	clear:
	511	memset(buf, 0, size);
	512	return err;
	513	}
	514
	515	const struct bpf_func_proto bpf_get_stack_proto = {
	516	.func = bpf_get_stack,
	517	.gpl_only = true,
	518	.ret_type = RET_INTEGER,
	519	.arg1_type = ARG_PTR_TO_CTX,
	520	.arg2_type = ARG_PTR_TO_UNINIT_MEM,
	521	.arg3_type = ARG_CONST_SIZE_OR_ZERO,
522	.arg4_type = ARG_ANYTHING,
523	};
524
557c0c6e	525	/* Called from eBPF program */
d5a3b1f6	526	static void stack_map_lookup_elem(struct bpf_map map, void *key)
557c0c6e	527	{
3b4a63f6	528	return ERR_PTR(-EOPNOTSUPP);
557c0c6e AS	529	}
	530
	531	/* Called from syscall */
	532	int bpf_stackmap_copy(struct bpf_map map, void key, void *value)
d5a3b1f6 AS	533	{
d5a3b1f6 AS	534	struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
557c0c6e AS	535	struct stack_map_bucket bucket, old_bucket;
557c0c6e AS	536	u32 id = (u32 )key, trace_len;
d5a3b1f6 AS	537
d5a3b1f6 AS	538	if (unlikely(id >= smap->n_buckets))
557c0c6e AS	539	return -ENOENT;
	540
	541	bucket = xchg(&smap->buckets[id], NULL);
	542	if (!bucket)
	543	return -ENOENT;
	544
615755a7 SL	545	trace_len = bucket->nr * stack_map_data_size(map);
615755a7 SL	546	memcpy(value, bucket->data, trace_len);
557c0c6e AS	547	memset(value + trace_len, 0, map->value_size - trace_len);
	548
	549	old_bucket = xchg(&smap->buckets[id], bucket);
	550	if (old_bucket)
	551	pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
	552	return 0;
d5a3b1f6 AS	553	}
d5a3b1f6 AS	554
16f07c55 YS	555	static int stack_map_get_next_key(struct bpf_map map, void key,
16f07c55 YS	556	void *next_key)
d5a3b1f6	557	{
16f07c55 YS	558	struct bpf_stack_map *smap = container_of(map,
	559	struct bpf_stack_map, map);
	560	u32 id;
	561
	562	WARN_ON_ONCE(!rcu_read_lock_held());
	563
	564	if (!key) {
	565	id = 0;
	566	} else {
	567	id = (u32 )key;
	568	if (id >= smap->n_buckets \|\| !smap->buckets[id])
	569	id = 0;
	570	else
	571	id++;
	572	}
	573
	574	while (id < smap->n_buckets && !smap->buckets[id])
	575	id++;
	576
	577	if (id >= smap->n_buckets)
	578	return -ENOENT;
	579
	580	(u32 )next_key = id;
	581	return 0;
d5a3b1f6 AS	582	}
	583
	584	static int stack_map_update_elem(struct bpf_map map, void key, void *value,
	585	u64 map_flags)
	586	{
	587	return -EINVAL;
	588	}
	589
	590	/* Called from syscall or from eBPF program */
	591	static int stack_map_delete_elem(struct bpf_map map, void key)
	592	{
	593	struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
	594	struct stack_map_bucket *old_bucket;
	595	u32 id = (u32 )key;
	596
	597	if (unlikely(id >= smap->n_buckets))
	598	return -E2BIG;
	599
	600	old_bucket = xchg(&smap->buckets[id], NULL);
	601	if (old_bucket) {
557c0c6e	602	pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
d5a3b1f6 AS	603	return 0;
	604	} else {
	605	return -ENOENT;
	606	}
	607	}
	608
	609	/* Called when map->refcnt goes to zero, either from workqueue or from syscall */
	610	static void stack_map_free(struct bpf_map *map)
	611	{
	612	struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
d5a3b1f6	613
557c0c6e	614	/* wait for bpf programs to complete before freeing stack map */
d5a3b1f6 AS	615	synchronize_rcu();
d5a3b1f6 AS	616
d407bd25	617	bpf_map_area_free(smap->elems);
557c0c6e	618	pcpu_freelist_destroy(&smap->freelist);
d407bd25	619	bpf_map_area_free(smap);
d5a3b1f6 AS	620	put_callchain_buffers();
	621	}
	622
14499160	623	const struct bpf_map_ops stack_trace_map_ops = {
d5a3b1f6 AS	624	.map_alloc = stack_map_alloc,
	625	.map_free = stack_map_free,
	626	.map_get_next_key = stack_map_get_next_key,
	627	.map_lookup_elem = stack_map_lookup_elem,
	628	.map_update_elem = stack_map_update_elem,
	629	.map_delete_elem = stack_map_delete_elem,
e8d2bec0	630	.map_check_btf = map_check_no_btf,
d5a3b1f6	631	};
bae77c5e SL	632
	633	static int __init stack_map_init(void)
	634	{
	635	int cpu;
	636	struct stack_map_irq_work *work;
	637
	638	for_each_possible_cpu(cpu) {
	639	work = per_cpu_ptr(&up_read_work, cpu);
	640	init_irq_work(&work->irq_work, do_up_read);
	641	}
	642	return 0;
	643	}
	644	subsys_initcall(stack_map_init);