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-rw-r--r--kernel/bpf/stackmap.c640
1 files changed, 640 insertions, 0 deletions
diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
new file mode 100644
index 000000000..92310b07c
--- /dev/null
+++ b/kernel/bpf/stackmap.c
@@ -0,0 +1,640 @@
+/* Copyright (c) 2016 Facebook
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ */
+#include <linux/bpf.h>
+#include <linux/jhash.h>
+#include <linux/filter.h>
+#include <linux/stacktrace.h>
+#include <linux/perf_event.h>
+#include <linux/elf.h>
+#include <linux/pagemap.h>
+#include <linux/irq_work.h>
+#include "percpu_freelist.h"
+
+#define STACK_CREATE_FLAG_MASK \
+ (BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY | \
+ BPF_F_STACK_BUILD_ID)
+
+struct stack_map_bucket {
+ struct pcpu_freelist_node fnode;
+ u32 hash;
+ u32 nr;
+ u64 data[];
+};
+
+struct bpf_stack_map {
+ struct bpf_map map;
+ void *elems;
+ struct pcpu_freelist freelist;
+ u32 n_buckets;
+ struct stack_map_bucket *buckets[];
+};
+
+/* irq_work to run up_read() for build_id lookup in nmi context */
+struct stack_map_irq_work {
+ struct irq_work irq_work;
+ struct rw_semaphore *sem;
+};
+
+static void do_up_read(struct irq_work *entry)
+{
+ struct stack_map_irq_work *work;
+
+ work = container_of(entry, struct stack_map_irq_work, irq_work);
+ up_read_non_owner(work->sem);
+ work->sem = NULL;
+}
+
+static DEFINE_PER_CPU(struct stack_map_irq_work, up_read_work);
+
+static inline bool stack_map_use_build_id(struct bpf_map *map)
+{
+ return (map->map_flags & BPF_F_STACK_BUILD_ID);
+}
+
+static inline int stack_map_data_size(struct bpf_map *map)
+{
+ return stack_map_use_build_id(map) ?
+ sizeof(struct bpf_stack_build_id) : sizeof(u64);
+}
+
+static int prealloc_elems_and_freelist(struct bpf_stack_map *smap)
+{
+ 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 (!capable(CAP_SYS_ADMIN))
+ return ERR_PTR(-EPERM);
+
+ if (attr->map_flags & ~STACK_CREATE_FLAG_MASK)
+ return ERR_PTR(-EINVAL);
+
+ /* check sanity of attributes */
+ if (attr->max_entries == 0 || attr->key_size != 4 ||
+ value_size < 8 || value_size % 8)
+ return ERR_PTR(-EINVAL);
+
+ BUILD_BUG_ON(sizeof(struct bpf_stack_build_id) % sizeof(u64));
+ if (attr->map_flags & BPF_F_STACK_BUILD_ID) {
+ if (value_size % sizeof(struct bpf_stack_build_id) ||
+ value_size / sizeof(struct bpf_stack_build_id)
+ > sysctl_perf_event_max_stack)
+ return ERR_PTR(-EINVAL);
+ } else if (value_size / 8 > sysctl_perf_event_max_stack)
+ return ERR_PTR(-EINVAL);
+
+ /* hash table size must be power of 2 */
+ n_buckets = roundup_pow_of_two(attr->max_entries);
+ if (!n_buckets)
+ return ERR_PTR(-E2BIG);
+
+ cost = n_buckets * sizeof(struct stack_map_bucket *) + sizeof(*smap);
+ if (cost >= U32_MAX - PAGE_SIZE)
+ return ERR_PTR(-E2BIG);
+
+ smap = bpf_map_area_alloc(cost, bpf_map_attr_numa_node(attr));
+ if (!smap)
+ return ERR_PTR(-ENOMEM);
+
+ err = -E2BIG;
+ cost += n_buckets * (value_size + sizeof(struct stack_map_bucket));
+ if (cost >= U32_MAX - PAGE_SIZE)
+ goto free_smap;
+
+ bpf_map_init_from_attr(&smap->map, attr);
+ smap->map.value_size = value_size;
+ smap->n_buckets = n_buckets;
+ smap->map.pages = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT;
+
+ err = bpf_map_precharge_memlock(smap->map.pages);
+ if (err)
+ goto free_smap;
+
+ 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);
+}
+
+#define BPF_BUILD_ID 3
+/*
+ * Parse build id from the note segment. This logic can be shared between
+ * 32-bit and 64-bit system, because Elf32_Nhdr and Elf64_Nhdr are
+ * identical.
+ */
+static inline int stack_map_parse_build_id(void *page_addr,
+ unsigned char *build_id,
+ void *note_start,
+ Elf32_Word note_size)
+{
+ Elf32_Word note_offs = 0, new_offs;
+
+ /* check for overflow */
+ if (note_start < page_addr || note_start + note_size < note_start)
+ return -EINVAL;
+
+ /* only supports note that fits in the first page */
+ if (note_start + note_size > page_addr + PAGE_SIZE)
+ return -EINVAL;
+
+ while (note_offs + sizeof(Elf32_Nhdr) < note_size) {
+ Elf32_Nhdr *nhdr = (Elf32_Nhdr *)(note_start + note_offs);
+
+ if (nhdr->n_type == BPF_BUILD_ID &&
+ nhdr->n_namesz == sizeof("GNU") &&
+ nhdr->n_descsz > 0 &&
+ nhdr->n_descsz <= BPF_BUILD_ID_SIZE) {
+ memcpy(build_id,
+ note_start + note_offs +
+ ALIGN(sizeof("GNU"), 4) + sizeof(Elf32_Nhdr),
+ nhdr->n_descsz);
+ memset(build_id + nhdr->n_descsz, 0,
+ BPF_BUILD_ID_SIZE - nhdr->n_descsz);
+ return 0;
+ }
+ new_offs = note_offs + sizeof(Elf32_Nhdr) +
+ ALIGN(nhdr->n_namesz, 4) + ALIGN(nhdr->n_descsz, 4);
+ if (new_offs <= note_offs) /* overflow */
+ break;
+ note_offs = new_offs;
+ }
+ return -EINVAL;
+}
+
+/* Parse build ID from 32-bit ELF */
+static int stack_map_get_build_id_32(void *page_addr,
+ unsigned char *build_id)
+{
+ Elf32_Ehdr *ehdr = (Elf32_Ehdr *)page_addr;
+ Elf32_Phdr *phdr;
+ int i;
+
+ /* only supports phdr that fits in one page */
+ if (ehdr->e_phnum >
+ (PAGE_SIZE - sizeof(Elf32_Ehdr)) / sizeof(Elf32_Phdr))
+ return -EINVAL;
+
+ phdr = (Elf32_Phdr *)(page_addr + sizeof(Elf32_Ehdr));
+
+ for (i = 0; i < ehdr->e_phnum; ++i)
+ if (phdr[i].p_type == PT_NOTE)
+ return stack_map_parse_build_id(page_addr, build_id,
+ page_addr + phdr[i].p_offset,
+ phdr[i].p_filesz);
+ return -EINVAL;
+}
+
+/* Parse build ID from 64-bit ELF */
+static int stack_map_get_build_id_64(void *page_addr,
+ unsigned char *build_id)
+{
+ Elf64_Ehdr *ehdr = (Elf64_Ehdr *)page_addr;
+ Elf64_Phdr *phdr;
+ int i;
+
+ /* only supports phdr that fits in one page */
+ if (ehdr->e_phnum >
+ (PAGE_SIZE - sizeof(Elf64_Ehdr)) / sizeof(Elf64_Phdr))
+ return -EINVAL;
+
+ phdr = (Elf64_Phdr *)(page_addr + sizeof(Elf64_Ehdr));
+
+ for (i = 0; i < ehdr->e_phnum; ++i)
+ if (phdr[i].p_type == PT_NOTE)
+ return stack_map_parse_build_id(page_addr, build_id,
+ page_addr + phdr[i].p_offset,
+ phdr[i].p_filesz);
+ return -EINVAL;
+}
+
+/* Parse build ID of ELF file mapped to vma */
+static int stack_map_get_build_id(struct vm_area_struct *vma,
+ unsigned char *build_id)
+{
+ Elf32_Ehdr *ehdr;
+ struct page *page;
+ void *page_addr;
+ int ret;
+
+ /* only works for page backed storage */
+ if (!vma->vm_file)
+ return -EINVAL;
+
+ page = find_get_page(vma->vm_file->f_mapping, 0);
+ if (!page)
+ return -EFAULT; /* page not mapped */
+
+ ret = -EINVAL;
+ page_addr = kmap_atomic(page);
+ ehdr = (Elf32_Ehdr *)page_addr;
+
+ /* compare magic x7f "ELF" */
+ if (memcmp(ehdr->e_ident, ELFMAG, SELFMAG) != 0)
+ goto out;
+
+ /* only support executable file and shared object file */
+ if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN)
+ goto out;
+
+ if (ehdr->e_ident[EI_CLASS] == ELFCLASS32)
+ ret = stack_map_get_build_id_32(page_addr, build_id);
+ else if (ehdr->e_ident[EI_CLASS] == ELFCLASS64)
+ ret = stack_map_get_build_id_64(page_addr, build_id);
+out:
+ kunmap_atomic(page_addr);
+ put_page(page);
+ return ret;
+}
+
+static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
+ u64 *ips, u32 trace_nr, bool user)
+{
+ int i;
+ struct vm_area_struct *vma;
+ bool irq_work_busy = false;
+ struct stack_map_irq_work *work = NULL;
+
+ if (irqs_disabled()) {
+ work = this_cpu_ptr(&up_read_work);
+ if (work->irq_work.flags & IRQ_WORK_BUSY)
+ /* cannot queue more up_read, fallback */
+ irq_work_busy = true;
+ }
+
+ /*
+ * We cannot do up_read() when the irq is disabled, because of
+ * risk to deadlock with rq_lock. To do build_id lookup when the
+ * irqs are disabled, we need to run up_read() in irq_work. We use
+ * a percpu variable to do the irq_work. If the irq_work is
+ * already used by another lookup, we fall back to report ips.
+ *
+ * Same fallback is used for kernel stack (!user) on a stackmap
+ * with build_id.
+ */
+ if (!user || !current || !current->mm || irq_work_busy ||
+ down_read_trylock(&current->mm->mmap_sem) == 0) {
+ /* cannot access current->mm, fall back to ips */
+ for (i = 0; i < trace_nr; i++) {
+ id_offs[i].status = BPF_STACK_BUILD_ID_IP;
+ id_offs[i].ip = ips[i];
+ memset(id_offs[i].build_id, 0, BPF_BUILD_ID_SIZE);
+ }
+ return;
+ }
+
+ for (i = 0; i < trace_nr; i++) {
+ vma = find_vma(current->mm, ips[i]);
+ if (!vma || stack_map_get_build_id(vma, id_offs[i].build_id)) {
+ /* per entry fall back to ips */
+ id_offs[i].status = BPF_STACK_BUILD_ID_IP;
+ id_offs[i].ip = ips[i];
+ memset(id_offs[i].build_id, 0, BPF_BUILD_ID_SIZE);
+ continue;
+ }
+ id_offs[i].offset = (vma->vm_pgoff << PAGE_SHIFT) + ips[i]
+ - vma->vm_start;
+ id_offs[i].status = BPF_STACK_BUILD_ID_VALID;
+ }
+
+ if (!work) {
+ up_read(&current->mm->mmap_sem);
+ } else {
+ work->sem = &current->mm->mmap_sem;
+ irq_work_queue(&work->irq_work);
+ /*
+ * The irq_work will release the mmap_sem with
+ * up_read_non_owner(). The rwsem_release() is called
+ * here to release the lock from lockdep's perspective.
+ */
+ rwsem_release(&current->mm->mmap_sem.dep_map, 1, _RET_IP_);
+ }
+}
+
+BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
+ u64, flags)
+{
+ struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
+ struct perf_callchain_entry *trace;
+ struct stack_map_bucket *bucket, *new_bucket, *old_bucket;
+ u32 max_depth = map->value_size / stack_map_data_size(map);
+ /* stack_map_alloc() checks that max_depth <= sysctl_perf_event_max_stack */
+ u32 init_nr = sysctl_perf_event_max_stack - max_depth;
+ u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
+ u32 hash, id, trace_nr, trace_len;
+ bool user = flags & BPF_F_USER_STACK;
+ bool kernel = !user;
+ u64 *ips;
+ bool hash_matches;
+
+ if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
+ BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
+ return -EINVAL;
+
+ trace = get_perf_callchain(regs, init_nr, kernel, user,
+ sysctl_perf_event_max_stack, false, false);
+
+ if (unlikely(!trace))
+ /* couldn't fetch the stack trace */
+ return -EFAULT;
+
+ /* get_perf_callchain() guarantees that trace->nr >= init_nr
+ * and trace-nr <= sysctl_perf_event_max_stack, so trace_nr <= max_depth
+ */
+ trace_nr = trace->nr - init_nr;
+
+ if (trace_nr <= skip)
+ /* skipping more than usable stack trace */
+ return -EFAULT;
+
+ trace_nr -= skip;
+ trace_len = trace_nr * sizeof(u64);
+ ips = trace->ip + skip + init_nr;
+ hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0);
+ id = hash & (smap->n_buckets - 1);
+ bucket = READ_ONCE(smap->buckets[id]);
+
+ hash_matches = bucket && bucket->hash == hash;
+ /* fast cmp */
+ if (hash_matches && flags & BPF_F_FAST_STACK_CMP)
+ return id;
+
+ if (stack_map_use_build_id(map)) {
+ /* for build_id+offset, pop a bucket before slow cmp */
+ new_bucket = (struct stack_map_bucket *)
+ pcpu_freelist_pop(&smap->freelist);
+ if (unlikely(!new_bucket))
+ return -ENOMEM;
+ new_bucket->nr = trace_nr;
+ stack_map_get_build_id_offset(
+ (struct bpf_stack_build_id *)new_bucket->data,
+ ips, trace_nr, user);
+ trace_len = trace_nr * sizeof(struct bpf_stack_build_id);
+ if (hash_matches && bucket->nr == trace_nr &&
+ memcmp(bucket->data, new_bucket->data, trace_len) == 0) {
+ pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
+ return id;
+ }
+ if (bucket && !(flags & BPF_F_REUSE_STACKID)) {
+ pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
+ return -EEXIST;
+ }
+ } else {
+ if (hash_matches && bucket->nr == trace_nr &&
+ memcmp(bucket->data, ips, trace_len) == 0)
+ return id;
+ if (bucket && !(flags & BPF_F_REUSE_STACKID))
+ return -EEXIST;
+
+ new_bucket = (struct stack_map_bucket *)
+ pcpu_freelist_pop(&smap->freelist);
+ if (unlikely(!new_bucket))
+ return -ENOMEM;
+ memcpy(new_bucket->data, ips, trace_len);
+ }
+
+ new_bucket->hash = hash;
+ new_bucket->nr = trace_nr;
+
+ old_bucket = xchg(&smap->buckets[id], new_bucket);
+ if (old_bucket)
+ pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
+ return id;
+}
+
+const struct bpf_func_proto bpf_get_stackid_proto = {
+ .func = bpf_get_stackid,
+ .gpl_only = true,
+ .ret_type = RET_INTEGER,
+ .arg1_type = ARG_PTR_TO_CTX,
+ .arg2_type = ARG_CONST_MAP_PTR,
+ .arg3_type = ARG_ANYTHING,
+};
+
+BPF_CALL_4(bpf_get_stack, struct pt_regs *, regs, void *, buf, u32, size,
+ u64, flags)
+{
+ u32 init_nr, trace_nr, copy_len, elem_size, num_elem;
+ bool user_build_id = flags & BPF_F_USER_BUILD_ID;
+ u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
+ bool user = flags & BPF_F_USER_STACK;
+ struct perf_callchain_entry *trace;
+ bool kernel = !user;
+ int err = -EINVAL;
+ u64 *ips;
+
+ if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
+ BPF_F_USER_BUILD_ID)))
+ goto clear;
+ if (kernel && user_build_id)
+ goto clear;
+
+ elem_size = (user && user_build_id) ? sizeof(struct bpf_stack_build_id)
+ : sizeof(u64);
+ if (unlikely(size % elem_size))
+ goto clear;
+
+ num_elem = size / elem_size;
+ if (sysctl_perf_event_max_stack < num_elem)
+ init_nr = 0;
+ else
+ init_nr = sysctl_perf_event_max_stack - num_elem;
+ trace = get_perf_callchain(regs, init_nr, kernel, user,
+ sysctl_perf_event_max_stack, false, false);
+ if (unlikely(!trace))
+ goto err_fault;
+
+ trace_nr = trace->nr - init_nr;
+ if (trace_nr < skip)
+ goto err_fault;
+
+ trace_nr -= skip;
+ trace_nr = (trace_nr <= num_elem) ? trace_nr : num_elem;
+ copy_len = trace_nr * elem_size;
+ ips = trace->ip + skip + init_nr;
+ if (user && user_build_id)
+ stack_map_get_build_id_offset(buf, ips, trace_nr, user);
+ else
+ memcpy(buf, ips, copy_len);
+
+ if (size > copy_len)
+ memset(buf + copy_len, 0, size - copy_len);
+ return copy_len;
+
+err_fault:
+ err = -EFAULT;
+clear:
+ memset(buf, 0, size);
+ return err;
+}
+
+const struct bpf_func_proto bpf_get_stack_proto = {
+ .func = bpf_get_stack,
+ .gpl_only = true,
+ .ret_type = RET_INTEGER,
+ .arg1_type = ARG_PTR_TO_CTX,
+ .arg2_type = ARG_PTR_TO_UNINIT_MEM,
+ .arg3_type = ARG_CONST_SIZE_OR_ZERO,
+ .arg4_type = ARG_ANYTHING,
+};
+
+/* Called from eBPF program */
+static void *stack_map_lookup_elem(struct bpf_map *map, void *key)
+{
+ return NULL;
+}
+
+/* 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_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);
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-13 02:00:11 +0000