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![Namhyung Kim](/assets/img/avatar_default.png)
If the perf_event has PERF_SAMPLE_CALLCHAIN, BPF can use it for stack trace. The problematic cases like PEBS and IBS already handled in the PMU driver and they filled the callchain info in the sample data. For others, we can call perf_callchain() before the BPF handler. Signed-off-by: Namhyung Kim <namhyung@kernel.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lore.kernel.org/r/20220908214104.3851807-2-namhyung@kernel.org
668 lines
17 KiB
C
668 lines
17 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/* Copyright (c) 2016 Facebook
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*/
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#include <linux/bpf.h>
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#include <linux/jhash.h>
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#include <linux/filter.h>
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#include <linux/kernel.h>
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#include <linux/stacktrace.h>
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#include <linux/perf_event.h>
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#include <linux/btf_ids.h>
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#include <linux/buildid.h>
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#include "percpu_freelist.h"
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#include "mmap_unlock_work.h"
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#define STACK_CREATE_FLAG_MASK \
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(BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY | \
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BPF_F_STACK_BUILD_ID)
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struct stack_map_bucket {
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struct pcpu_freelist_node fnode;
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u32 hash;
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u32 nr;
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u64 data[];
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};
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struct bpf_stack_map {
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struct bpf_map map;
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void *elems;
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struct pcpu_freelist freelist;
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u32 n_buckets;
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struct stack_map_bucket *buckets[];
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};
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static inline bool stack_map_use_build_id(struct bpf_map *map)
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{
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return (map->map_flags & BPF_F_STACK_BUILD_ID);
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}
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static inline int stack_map_data_size(struct bpf_map *map)
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{
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return stack_map_use_build_id(map) ?
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sizeof(struct bpf_stack_build_id) : sizeof(u64);
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}
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static int prealloc_elems_and_freelist(struct bpf_stack_map *smap)
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{
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u64 elem_size = sizeof(struct stack_map_bucket) +
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(u64)smap->map.value_size;
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int err;
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smap->elems = bpf_map_area_alloc(elem_size * smap->map.max_entries,
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smap->map.numa_node);
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if (!smap->elems)
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return -ENOMEM;
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err = pcpu_freelist_init(&smap->freelist);
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if (err)
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goto free_elems;
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pcpu_freelist_populate(&smap->freelist, smap->elems, elem_size,
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smap->map.max_entries);
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return 0;
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free_elems:
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bpf_map_area_free(smap->elems);
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return err;
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}
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/* Called from syscall */
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static struct bpf_map *stack_map_alloc(union bpf_attr *attr)
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{
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u32 value_size = attr->value_size;
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struct bpf_stack_map *smap;
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u64 cost, n_buckets;
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int err;
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if (!bpf_capable())
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return ERR_PTR(-EPERM);
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if (attr->map_flags & ~STACK_CREATE_FLAG_MASK)
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return ERR_PTR(-EINVAL);
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/* check sanity of attributes */
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if (attr->max_entries == 0 || attr->key_size != 4 ||
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value_size < 8 || value_size % 8)
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return ERR_PTR(-EINVAL);
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BUILD_BUG_ON(sizeof(struct bpf_stack_build_id) % sizeof(u64));
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if (attr->map_flags & BPF_F_STACK_BUILD_ID) {
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if (value_size % sizeof(struct bpf_stack_build_id) ||
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value_size / sizeof(struct bpf_stack_build_id)
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> sysctl_perf_event_max_stack)
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return ERR_PTR(-EINVAL);
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} else if (value_size / 8 > sysctl_perf_event_max_stack)
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return ERR_PTR(-EINVAL);
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/* hash table size must be power of 2 */
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n_buckets = roundup_pow_of_two(attr->max_entries);
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if (!n_buckets)
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return ERR_PTR(-E2BIG);
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cost = n_buckets * sizeof(struct stack_map_bucket *) + sizeof(*smap);
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smap = bpf_map_area_alloc(cost, bpf_map_attr_numa_node(attr));
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if (!smap)
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return ERR_PTR(-ENOMEM);
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bpf_map_init_from_attr(&smap->map, attr);
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smap->n_buckets = n_buckets;
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err = get_callchain_buffers(sysctl_perf_event_max_stack);
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if (err)
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goto free_smap;
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err = prealloc_elems_and_freelist(smap);
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if (err)
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goto put_buffers;
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return &smap->map;
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put_buffers:
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put_callchain_buffers();
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free_smap:
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bpf_map_area_free(smap);
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return ERR_PTR(err);
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}
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static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
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u64 *ips, u32 trace_nr, bool user)
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{
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int i;
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struct mmap_unlock_irq_work *work = NULL;
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bool irq_work_busy = bpf_mmap_unlock_get_irq_work(&work);
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struct vm_area_struct *vma, *prev_vma = NULL;
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const char *prev_build_id;
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/* If the irq_work is in use, fall back to report ips. Same
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* fallback is used for kernel stack (!user) on a stackmap with
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* build_id.
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*/
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if (!user || !current || !current->mm || irq_work_busy ||
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!mmap_read_trylock(current->mm)) {
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/* cannot access current->mm, fall back to ips */
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for (i = 0; i < trace_nr; i++) {
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id_offs[i].status = BPF_STACK_BUILD_ID_IP;
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id_offs[i].ip = ips[i];
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memset(id_offs[i].build_id, 0, BUILD_ID_SIZE_MAX);
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}
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return;
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}
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for (i = 0; i < trace_nr; i++) {
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if (range_in_vma(prev_vma, ips[i], ips[i])) {
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vma = prev_vma;
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memcpy(id_offs[i].build_id, prev_build_id,
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BUILD_ID_SIZE_MAX);
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goto build_id_valid;
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}
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vma = find_vma(current->mm, ips[i]);
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if (!vma || build_id_parse(vma, id_offs[i].build_id, NULL)) {
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/* per entry fall back to ips */
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id_offs[i].status = BPF_STACK_BUILD_ID_IP;
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id_offs[i].ip = ips[i];
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memset(id_offs[i].build_id, 0, BUILD_ID_SIZE_MAX);
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continue;
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}
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build_id_valid:
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id_offs[i].offset = (vma->vm_pgoff << PAGE_SHIFT) + ips[i]
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- vma->vm_start;
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id_offs[i].status = BPF_STACK_BUILD_ID_VALID;
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prev_vma = vma;
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prev_build_id = id_offs[i].build_id;
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}
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bpf_mmap_unlock_mm(work, current->mm);
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}
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static struct perf_callchain_entry *
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get_callchain_entry_for_task(struct task_struct *task, u32 max_depth)
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{
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#ifdef CONFIG_STACKTRACE
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struct perf_callchain_entry *entry;
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int rctx;
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entry = get_callchain_entry(&rctx);
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if (!entry)
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return NULL;
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entry->nr = stack_trace_save_tsk(task, (unsigned long *)entry->ip,
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max_depth, 0);
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/* stack_trace_save_tsk() works on unsigned long array, while
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* perf_callchain_entry uses u64 array. For 32-bit systems, it is
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* necessary to fix this mismatch.
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*/
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if (__BITS_PER_LONG != 64) {
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unsigned long *from = (unsigned long *) entry->ip;
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u64 *to = entry->ip;
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int i;
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/* copy data from the end to avoid using extra buffer */
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for (i = entry->nr - 1; i >= 0; i--)
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to[i] = (u64)(from[i]);
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}
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put_callchain_entry(rctx);
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return entry;
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#else /* CONFIG_STACKTRACE */
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return NULL;
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#endif
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}
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static long __bpf_get_stackid(struct bpf_map *map,
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struct perf_callchain_entry *trace, u64 flags)
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{
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struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
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struct stack_map_bucket *bucket, *new_bucket, *old_bucket;
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u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
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u32 hash, id, trace_nr, trace_len;
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bool user = flags & BPF_F_USER_STACK;
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u64 *ips;
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bool hash_matches;
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if (trace->nr <= skip)
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/* skipping more than usable stack trace */
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return -EFAULT;
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trace_nr = trace->nr - skip;
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trace_len = trace_nr * sizeof(u64);
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ips = trace->ip + skip;
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hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0);
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id = hash & (smap->n_buckets - 1);
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bucket = READ_ONCE(smap->buckets[id]);
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hash_matches = bucket && bucket->hash == hash;
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/* fast cmp */
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if (hash_matches && flags & BPF_F_FAST_STACK_CMP)
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return id;
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if (stack_map_use_build_id(map)) {
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/* for build_id+offset, pop a bucket before slow cmp */
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new_bucket = (struct stack_map_bucket *)
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pcpu_freelist_pop(&smap->freelist);
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if (unlikely(!new_bucket))
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return -ENOMEM;
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new_bucket->nr = trace_nr;
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stack_map_get_build_id_offset(
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(struct bpf_stack_build_id *)new_bucket->data,
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ips, trace_nr, user);
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trace_len = trace_nr * sizeof(struct bpf_stack_build_id);
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if (hash_matches && bucket->nr == trace_nr &&
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memcmp(bucket->data, new_bucket->data, trace_len) == 0) {
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pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
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return id;
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}
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if (bucket && !(flags & BPF_F_REUSE_STACKID)) {
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pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
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return -EEXIST;
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}
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} else {
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if (hash_matches && bucket->nr == trace_nr &&
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memcmp(bucket->data, ips, trace_len) == 0)
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return id;
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if (bucket && !(flags & BPF_F_REUSE_STACKID))
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return -EEXIST;
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new_bucket = (struct stack_map_bucket *)
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pcpu_freelist_pop(&smap->freelist);
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if (unlikely(!new_bucket))
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return -ENOMEM;
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memcpy(new_bucket->data, ips, trace_len);
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}
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new_bucket->hash = hash;
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new_bucket->nr = trace_nr;
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old_bucket = xchg(&smap->buckets[id], new_bucket);
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if (old_bucket)
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pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
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return id;
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}
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BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
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u64, flags)
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{
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u32 max_depth = map->value_size / stack_map_data_size(map);
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u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
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bool user = flags & BPF_F_USER_STACK;
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struct perf_callchain_entry *trace;
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bool kernel = !user;
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if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
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BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
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return -EINVAL;
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max_depth += skip;
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if (max_depth > sysctl_perf_event_max_stack)
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max_depth = sysctl_perf_event_max_stack;
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trace = get_perf_callchain(regs, 0, kernel, user, max_depth,
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false, false);
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if (unlikely(!trace))
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/* couldn't fetch the stack trace */
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return -EFAULT;
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return __bpf_get_stackid(map, trace, flags);
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}
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const struct bpf_func_proto bpf_get_stackid_proto = {
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.func = bpf_get_stackid,
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.gpl_only = true,
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.ret_type = RET_INTEGER,
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.arg1_type = ARG_PTR_TO_CTX,
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.arg2_type = ARG_CONST_MAP_PTR,
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.arg3_type = ARG_ANYTHING,
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};
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static __u64 count_kernel_ip(struct perf_callchain_entry *trace)
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{
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__u64 nr_kernel = 0;
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while (nr_kernel < trace->nr) {
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if (trace->ip[nr_kernel] == PERF_CONTEXT_USER)
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break;
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nr_kernel++;
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}
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return nr_kernel;
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}
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BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx,
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struct bpf_map *, map, u64, flags)
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{
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struct perf_event *event = ctx->event;
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struct perf_callchain_entry *trace;
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bool kernel, user;
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__u64 nr_kernel;
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int ret;
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/* perf_sample_data doesn't have callchain, use bpf_get_stackid */
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if (!(event->attr.sample_type & PERF_SAMPLE_CALLCHAIN))
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return bpf_get_stackid((unsigned long)(ctx->regs),
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(unsigned long) map, flags, 0, 0);
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if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
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BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
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return -EINVAL;
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user = flags & BPF_F_USER_STACK;
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kernel = !user;
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trace = ctx->data->callchain;
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if (unlikely(!trace))
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return -EFAULT;
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nr_kernel = count_kernel_ip(trace);
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if (kernel) {
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__u64 nr = trace->nr;
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trace->nr = nr_kernel;
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ret = __bpf_get_stackid(map, trace, flags);
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/* restore nr */
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trace->nr = nr;
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} else { /* user */
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u64 skip = flags & BPF_F_SKIP_FIELD_MASK;
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skip += nr_kernel;
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if (skip > BPF_F_SKIP_FIELD_MASK)
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return -EFAULT;
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flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip;
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ret = __bpf_get_stackid(map, trace, flags);
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}
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return ret;
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}
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const struct bpf_func_proto bpf_get_stackid_proto_pe = {
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.func = bpf_get_stackid_pe,
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.gpl_only = false,
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.ret_type = RET_INTEGER,
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.arg1_type = ARG_PTR_TO_CTX,
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.arg2_type = ARG_CONST_MAP_PTR,
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.arg3_type = ARG_ANYTHING,
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};
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static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,
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struct perf_callchain_entry *trace_in,
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void *buf, u32 size, u64 flags)
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{
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u32 trace_nr, copy_len, elem_size, num_elem, max_depth;
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bool user_build_id = flags & BPF_F_USER_BUILD_ID;
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u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
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bool user = flags & BPF_F_USER_STACK;
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struct perf_callchain_entry *trace;
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bool kernel = !user;
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int err = -EINVAL;
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u64 *ips;
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if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
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BPF_F_USER_BUILD_ID)))
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goto clear;
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if (kernel && user_build_id)
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goto clear;
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elem_size = (user && user_build_id) ? sizeof(struct bpf_stack_build_id)
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: sizeof(u64);
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if (unlikely(size % elem_size))
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goto clear;
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/* cannot get valid user stack for task without user_mode regs */
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if (task && user && !user_mode(regs))
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goto err_fault;
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num_elem = size / elem_size;
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max_depth = num_elem + skip;
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if (sysctl_perf_event_max_stack < max_depth)
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max_depth = sysctl_perf_event_max_stack;
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if (trace_in)
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trace = trace_in;
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else if (kernel && task)
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trace = get_callchain_entry_for_task(task, max_depth);
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else
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trace = get_perf_callchain(regs, 0, kernel, user, max_depth,
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false, false);
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if (unlikely(!trace))
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goto err_fault;
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if (trace->nr < skip)
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goto err_fault;
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trace_nr = trace->nr - skip;
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trace_nr = (trace_nr <= num_elem) ? trace_nr : num_elem;
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copy_len = trace_nr * elem_size;
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ips = trace->ip + skip;
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if (user && user_build_id)
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stack_map_get_build_id_offset(buf, ips, trace_nr, user);
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else
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memcpy(buf, ips, copy_len);
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if (size > copy_len)
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memset(buf + copy_len, 0, size - copy_len);
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return copy_len;
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err_fault:
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err = -EFAULT;
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clear:
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memset(buf, 0, size);
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return err;
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}
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BPF_CALL_4(bpf_get_stack, struct pt_regs *, regs, void *, buf, u32, size,
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u64, flags)
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{
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return __bpf_get_stack(regs, NULL, NULL, buf, size, flags);
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}
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const struct bpf_func_proto bpf_get_stack_proto = {
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.func = bpf_get_stack,
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.gpl_only = true,
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.ret_type = RET_INTEGER,
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.arg1_type = ARG_PTR_TO_CTX,
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.arg2_type = ARG_PTR_TO_UNINIT_MEM,
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.arg3_type = ARG_CONST_SIZE_OR_ZERO,
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.arg4_type = ARG_ANYTHING,
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};
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BPF_CALL_4(bpf_get_task_stack, struct task_struct *, task, void *, buf,
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u32, size, u64, flags)
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|
{
|
|
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],
|
|
};
|