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https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-23 09:19:51 +00:00
![Alexei Starovoitov](/assets/img/avatar_default.png)
Lockdep warns about false positive:
[ 11.211460] ------------[ cut here ]------------
[ 11.211936] DEBUG_LOCKS_WARN_ON(depth <= 0)
[ 11.211985] WARNING: CPU: 0 PID: 141 at ../kernel/locking/lockdep.c:3592 lock_release+0x1ad/0x280
[ 11.213134] Modules linked in:
[ 11.214954] RIP: 0010:lock_release+0x1ad/0x280
[ 11.223508] Call Trace:
[ 11.223705] <IRQ>
[ 11.223874] ? __local_bh_enable+0x7a/0x80
[ 11.224199] up_read+0x1c/0xa0
[ 11.224446] do_up_read+0x12/0x20
[ 11.224713] irq_work_run_list+0x43/0x70
[ 11.225030] irq_work_run+0x26/0x50
[ 11.225310] smp_irq_work_interrupt+0x57/0x1f0
[ 11.225662] irq_work_interrupt+0xf/0x20
since rw_semaphore is released in a different task vs task that locked the sema.
It is expected behavior.
Fix the warning with up_read_non_owner() and rwsem_release() annotation.
Fixes: bae77c5eb5
("bpf: enable stackmap with build_id in nmi context")
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
636 lines
17 KiB
C
636 lines
17 KiB
C
/* Copyright (c) 2016 Facebook
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of version 2 of the GNU General Public
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* License as published by the Free Software Foundation.
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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/stacktrace.h>
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#include <linux/perf_event.h>
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#include <linux/elf.h>
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#include <linux/pagemap.h>
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#include <linux/irq_work.h>
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#include "percpu_freelist.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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/* irq_work to run up_read() for build_id lookup in nmi context */
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struct stack_map_irq_work {
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struct irq_work irq_work;
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struct rw_semaphore *sem;
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};
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static void do_up_read(struct irq_work *entry)
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{
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struct stack_map_irq_work *work;
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work = container_of(entry, struct stack_map_irq_work, irq_work);
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up_read_non_owner(work->sem);
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work->sem = NULL;
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}
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static DEFINE_PER_CPU(struct stack_map_irq_work, up_read_work);
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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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u32 elem_size = sizeof(struct stack_map_bucket) + 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 (!capable(CAP_SYS_ADMIN))
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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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cost = n_buckets * sizeof(struct stack_map_bucket *) + sizeof(*smap);
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if (cost >= U32_MAX - PAGE_SIZE)
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return ERR_PTR(-E2BIG);
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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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err = -E2BIG;
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cost += n_buckets * (value_size + sizeof(struct stack_map_bucket));
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if (cost >= U32_MAX - PAGE_SIZE)
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goto free_smap;
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bpf_map_init_from_attr(&smap->map, attr);
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smap->map.value_size = value_size;
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smap->n_buckets = n_buckets;
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smap->map.pages = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT;
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err = bpf_map_precharge_memlock(smap->map.pages);
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if (err)
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goto free_smap;
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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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#define BPF_BUILD_ID 3
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/*
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* Parse build id from the note segment. This logic can be shared between
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* 32-bit and 64-bit system, because Elf32_Nhdr and Elf64_Nhdr are
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* identical.
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*/
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static inline int stack_map_parse_build_id(void *page_addr,
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unsigned char *build_id,
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void *note_start,
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Elf32_Word note_size)
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{
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Elf32_Word note_offs = 0, new_offs;
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/* check for overflow */
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if (note_start < page_addr || note_start + note_size < note_start)
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return -EINVAL;
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/* only supports note that fits in the first page */
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if (note_start + note_size > page_addr + PAGE_SIZE)
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return -EINVAL;
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while (note_offs + sizeof(Elf32_Nhdr) < note_size) {
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Elf32_Nhdr *nhdr = (Elf32_Nhdr *)(note_start + note_offs);
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if (nhdr->n_type == BPF_BUILD_ID &&
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nhdr->n_namesz == sizeof("GNU") &&
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nhdr->n_descsz > 0 &&
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nhdr->n_descsz <= BPF_BUILD_ID_SIZE) {
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memcpy(build_id,
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note_start + note_offs +
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ALIGN(sizeof("GNU"), 4) + sizeof(Elf32_Nhdr),
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nhdr->n_descsz);
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memset(build_id + nhdr->n_descsz, 0,
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BPF_BUILD_ID_SIZE - nhdr->n_descsz);
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return 0;
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}
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new_offs = note_offs + sizeof(Elf32_Nhdr) +
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ALIGN(nhdr->n_namesz, 4) + ALIGN(nhdr->n_descsz, 4);
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if (new_offs <= note_offs) /* overflow */
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break;
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note_offs = new_offs;
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}
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return -EINVAL;
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}
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/* Parse build ID from 32-bit ELF */
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static int stack_map_get_build_id_32(void *page_addr,
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unsigned char *build_id)
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{
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Elf32_Ehdr *ehdr = (Elf32_Ehdr *)page_addr;
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Elf32_Phdr *phdr;
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int i;
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/* only supports phdr that fits in one page */
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if (ehdr->e_phnum >
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(PAGE_SIZE - sizeof(Elf32_Ehdr)) / sizeof(Elf32_Phdr))
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return -EINVAL;
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phdr = (Elf32_Phdr *)(page_addr + sizeof(Elf32_Ehdr));
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for (i = 0; i < ehdr->e_phnum; ++i)
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if (phdr[i].p_type == PT_NOTE)
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return stack_map_parse_build_id(page_addr, build_id,
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page_addr + phdr[i].p_offset,
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phdr[i].p_filesz);
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return -EINVAL;
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}
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/* Parse build ID from 64-bit ELF */
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static int stack_map_get_build_id_64(void *page_addr,
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unsigned char *build_id)
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{
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Elf64_Ehdr *ehdr = (Elf64_Ehdr *)page_addr;
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Elf64_Phdr *phdr;
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int i;
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/* only supports phdr that fits in one page */
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if (ehdr->e_phnum >
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(PAGE_SIZE - sizeof(Elf64_Ehdr)) / sizeof(Elf64_Phdr))
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return -EINVAL;
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phdr = (Elf64_Phdr *)(page_addr + sizeof(Elf64_Ehdr));
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for (i = 0; i < ehdr->e_phnum; ++i)
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if (phdr[i].p_type == PT_NOTE)
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return stack_map_parse_build_id(page_addr, build_id,
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page_addr + phdr[i].p_offset,
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phdr[i].p_filesz);
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return -EINVAL;
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}
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/* Parse build ID of ELF file mapped to vma */
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static int stack_map_get_build_id(struct vm_area_struct *vma,
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unsigned char *build_id)
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{
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Elf32_Ehdr *ehdr;
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struct page *page;
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void *page_addr;
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int ret;
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/* only works for page backed storage */
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if (!vma->vm_file)
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return -EINVAL;
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page = find_get_page(vma->vm_file->f_mapping, 0);
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if (!page)
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return -EFAULT; /* page not mapped */
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ret = -EINVAL;
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page_addr = kmap_atomic(page);
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ehdr = (Elf32_Ehdr *)page_addr;
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/* compare magic x7f "ELF" */
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if (memcmp(ehdr->e_ident, ELFMAG, SELFMAG) != 0)
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goto out;
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/* only support executable file and shared object file */
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if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN)
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goto out;
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if (ehdr->e_ident[EI_CLASS] == ELFCLASS32)
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ret = stack_map_get_build_id_32(page_addr, build_id);
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else if (ehdr->e_ident[EI_CLASS] == ELFCLASS64)
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ret = stack_map_get_build_id_64(page_addr, build_id);
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out:
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kunmap_atomic(page_addr);
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put_page(page);
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return ret;
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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 vm_area_struct *vma;
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bool irq_work_busy = false;
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struct stack_map_irq_work *work = NULL;
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if (in_nmi()) {
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work = this_cpu_ptr(&up_read_work);
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if (work->irq_work.flags & IRQ_WORK_BUSY)
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/* cannot queue more up_read, fallback */
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irq_work_busy = true;
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}
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/*
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* We cannot do up_read() in nmi context. To do build_id lookup
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* in nmi context, we need to run up_read() in irq_work. We use
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* a percpu variable to do the irq_work. If the irq_work is
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* already used by another lookup, we fall back to report ips.
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*
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* Same fallback is used for kernel stack (!user) on a stackmap
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* with build_id.
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*/
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if (!user || !current || !current->mm || irq_work_busy ||
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down_read_trylock(¤t->mm->mmap_sem) == 0) {
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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, BPF_BUILD_ID_SIZE);
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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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vma = find_vma(current->mm, ips[i]);
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if (!vma || stack_map_get_build_id(vma, id_offs[i].build_id)) {
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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, BPF_BUILD_ID_SIZE);
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continue;
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}
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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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}
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if (!work) {
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up_read(¤t->mm->mmap_sem);
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} else {
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work->sem = ¤t->mm->mmap_sem;
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irq_work_queue(&work->irq_work);
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/*
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* The irq_work will release the mmap_sem with
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* up_read_non_owner(). The rwsem_release() is called
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* here to release the lock from lockdep's perspective.
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*/
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rwsem_release(¤t->mm->mmap_sem.dep_map, 1, _RET_IP_);
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}
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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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struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
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struct perf_callchain_entry *trace;
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struct stack_map_bucket *bucket, *new_bucket, *old_bucket;
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u32 max_depth = map->value_size / stack_map_data_size(map);
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/* stack_map_alloc() checks that max_depth <= sysctl_perf_event_max_stack */
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u32 init_nr = sysctl_perf_event_max_stack - max_depth;
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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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bool kernel = !user;
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u64 *ips;
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bool hash_matches;
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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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trace = get_perf_callchain(regs, init_nr, kernel, user,
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sysctl_perf_event_max_stack, 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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/* get_perf_callchain() guarantees that trace->nr >= init_nr
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* and trace-nr <= sysctl_perf_event_max_stack, so trace_nr <= max_depth
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*/
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trace_nr = trace->nr - init_nr;
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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 -= skip;
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trace_len = trace_nr * sizeof(u64);
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ips = trace->ip + skip + init_nr;
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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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const struct bpf_func_proto bpf_get_stackid_proto = {
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.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);
|