blob: 09a3fd97d329ea2b3ecdad1f1c5e85dbff0478ca [file] [log] [blame]
// 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/irq_work.h>
#include <linux/btf_ids.h>
#include <linux/buildid.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;
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);
if (!n_buckets)
return ERR_PTR(-E2BIG);
cost = n_buckets * sizeof(struct stack_map_bucket *) + sizeof(*smap);
cost += n_buckets * (value_size + sizeof(struct stack_map_bucket));
smap = bpf_map_area_alloc(cost, bpf_map_attr_numa_node(attr));
if (!smap)
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_smap;
err = prealloc_elems_and_freelist(smap);
if (err)
goto put_buffers;
return &smap->map;
put_buffers:
put_callchain_buffers();
free_smap:
bpf_map_area_free(smap);
return ERR_PTR(err);
}
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 (irq_work_is_busy(&work->irq_work)) {
/* 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(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, BUILD_ID_SIZE_MAX);
}
return;
}
for (i = 0; i < trace_nr; i++) {
vma = find_vma(current->mm, ips[i]);
if (!vma || build_id_parse(vma, id_offs[i].build_id, NULL)) {
/* 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, BUILD_ID_SIZE_MAX);
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(current->mm);
} else {
work->mm = current->mm;
/* The lock will be released once we're out of interrupt
* context. Tell lockdep that we've released it now so
* it doesn't complain that we forgot to release it.
*/
rwsem_release(&current->mm->mmap_lock.dep_map, _RET_IP_);
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;
long res;
if (!try_get_task_stack(task))
return -EFAULT;
regs = task_pt_regs(task);
res = __bpf_get_stack(regs, task, NULL, buf, size, flags);
put_task_stack(task);
return res;
}
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 = &btf_task_struct_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);