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- // 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/btf_ids.h>
- #include <linux/buildid.h>
- #include "percpu_freelist.h"
- #include "mmap_unlock_work.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[];
- };
- 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)
- {
- u64 elem_size = sizeof(struct stack_map_bucket) +
- (u64)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);
- 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->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 mmap_unlock_irq_work *work = NULL;
- bool irq_work_busy = bpf_mmap_unlock_get_irq_work(&work);
- struct vm_area_struct *vma, *prev_vma = NULL;
- const char *prev_build_id;
- /* If the irq_work is in use, 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++) {
- if (range_in_vma(prev_vma, ips[i], ips[i])) {
- vma = prev_vma;
- memcpy(id_offs[i].build_id, prev_build_id,
- BUILD_ID_SIZE_MAX);
- goto build_id_valid;
- }
- 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;
- }
- build_id_valid:
- id_offs[i].offset = (vma->vm_pgoff << PAGE_SHIFT) + ips[i]
- - vma->vm_start;
- id_offs[i].status = BPF_STACK_BUILD_ID_VALID;
- prev_vma = vma;
- prev_build_id = id_offs[i].build_id;
- }
- bpf_mmap_unlock_mm(work, current->mm);
- }
- static struct perf_callchain_entry *
- get_callchain_entry_for_task(struct task_struct *task, u32 max_depth)
- {
- #ifdef CONFIG_STACKTRACE
- struct perf_callchain_entry *entry;
- int rctx;
- entry = get_callchain_entry(&rctx);
- if (!entry)
- return NULL;
- entry->nr = stack_trace_save_tsk(task, (unsigned long *)entry->ip,
- max_depth, 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 >= 0; 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 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;
- if (trace->nr <= skip)
- /* skipping more than usable stack trace */
- return -EFAULT;
- trace_nr = trace->nr - skip;
- trace_len = trace_nr * sizeof(u64);
- ips = trace->ip + skip;
- 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);
- u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
- 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;
- max_depth += skip;
- if (max_depth > sysctl_perf_event_max_stack)
- max_depth = sysctl_perf_event_max_stack;
- trace = get_perf_callchain(regs, 0, kernel, user, max_depth,
- 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))
- 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 trace_nr, copy_len, elem_size, num_elem, max_depth;
- 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;
- max_depth = num_elem + skip;
- if (sysctl_perf_event_max_stack < max_depth)
- max_depth = sysctl_perf_event_max_stack;
- if (trace_in)
- trace = trace_in;
- else if (kernel && task)
- trace = get_callchain_entry_for_task(task, max_depth);
- else
- trace = get_perf_callchain(regs, 0, kernel, user, max_depth,
- false, false);
- if (unlikely(!trace))
- goto err_fault;
- if (trace->nr < skip)
- goto err_fault;
- trace_nr = trace->nr - skip;
- trace_nr = (trace_nr <= num_elem) ? trace_nr : num_elem;
- copy_len = trace_nr * elem_size;
- ips = trace->ip + skip;
- 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 = -EINVAL;
- if (!try_get_task_stack(task))
- return -EFAULT;
- regs = task_pt_regs(task);
- if (regs)
- 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_tracing_ids[BTF_TRACING_TYPE_TASK],
- .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))
- 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();
- }
- BTF_ID_LIST_SINGLE(stack_trace_map_btf_ids, struct, bpf_stack_map)
- 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_id = &stack_trace_map_btf_ids[0],
- };
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