linux/kernel/bpf/stackmap.c
Lorenz Bauer 9436ef6e86 bpf: Allow specifying a BTF ID per argument in function protos
Function prototypes using ARG_PTR_TO_BTF_ID currently use two ways to signal
which BTF IDs are acceptable. First, bpf_func_proto.btf_id is an array of
IDs, one for each argument. This array is only accessed up to the highest
numbered argument that uses ARG_PTR_TO_BTF_ID and may therefore be less than
five arguments long. It usually points at a BTF_ID_LIST. Second, check_btf_id
is a function pointer that is called by the verifier if present. It gets the
actual BTF ID of the register, and the argument number we're currently checking.
It turns out that the only user check_arg_btf_id ignores the argument, and is
simply used to check whether the BTF ID has a struct sock_common at it's start.

Replace both of these mechanisms with an explicit BTF ID for each argument
in a function proto. Thanks to btf_struct_ids_match this is very flexible:
check_arg_btf_id can be replaced by requiring struct sock_common.

Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20200921121227.255763-5-lmb@cloudflare.com
2020-09-21 15:00:40 -07:00

865 lines
22 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/* Copyright (c) 2016 Facebook
*/
#include <linux/bpf.h>
#include <linux/jhash.h>
#include <linux/filter.h>
#include <linux/kernel.h>
#include <linux/stacktrace.h>
#include <linux/perf_event.h>
#include <linux/elf.h>
#include <linux/pagemap.h>
#include <linux/irq_work.h>
#include <linux/btf_ids.h>
#include "percpu_freelist.h"
#define STACK_CREATE_FLAG_MASK \
(BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY | \
BPF_F_STACK_BUILD_ID)
struct stack_map_bucket {
struct pcpu_freelist_node fnode;
u32 hash;
u32 nr;
u64 data[];
};
struct bpf_stack_map {
struct bpf_map map;
void *elems;
struct pcpu_freelist freelist;
u32 n_buckets;
struct stack_map_bucket *buckets[];
};
/* irq_work to run up_read() for build_id lookup in nmi context */
struct stack_map_irq_work {
struct irq_work irq_work;
struct mm_struct *mm;
};
static void do_up_read(struct irq_work *entry)
{
struct stack_map_irq_work *work;
if (WARN_ON_ONCE(IS_ENABLED(CONFIG_PREEMPT_RT)))
return;
work = container_of(entry, struct stack_map_irq_work, irq_work);
mmap_read_unlock_non_owner(work->mm);
}
static DEFINE_PER_CPU(struct stack_map_irq_work, up_read_work);
static inline bool stack_map_use_build_id(struct bpf_map *map)
{
return (map->map_flags & BPF_F_STACK_BUILD_ID);
}
static inline int stack_map_data_size(struct bpf_map *map)
{
return stack_map_use_build_id(map) ?
sizeof(struct bpf_stack_build_id) : sizeof(u64);
}
static int prealloc_elems_and_freelist(struct bpf_stack_map *smap)
{
u32 elem_size = sizeof(struct stack_map_bucket) + smap->map.value_size;
int err;
smap->elems = bpf_map_area_alloc(elem_size * smap->map.max_entries,
smap->map.numa_node);
if (!smap->elems)
return -ENOMEM;
err = pcpu_freelist_init(&smap->freelist);
if (err)
goto free_elems;
pcpu_freelist_populate(&smap->freelist, smap->elems, elem_size,
smap->map.max_entries);
return 0;
free_elems:
bpf_map_area_free(smap->elems);
return err;
}
/* Called from syscall */
static struct bpf_map *stack_map_alloc(union bpf_attr *attr)
{
u32 value_size = attr->value_size;
struct bpf_stack_map *smap;
struct bpf_map_memory mem;
u64 cost, n_buckets;
int err;
if (!bpf_capable())
return ERR_PTR(-EPERM);
if (attr->map_flags & ~STACK_CREATE_FLAG_MASK)
return ERR_PTR(-EINVAL);
/* check sanity of attributes */
if (attr->max_entries == 0 || attr->key_size != 4 ||
value_size < 8 || value_size % 8)
return ERR_PTR(-EINVAL);
BUILD_BUG_ON(sizeof(struct bpf_stack_build_id) % sizeof(u64));
if (attr->map_flags & BPF_F_STACK_BUILD_ID) {
if (value_size % sizeof(struct bpf_stack_build_id) ||
value_size / sizeof(struct bpf_stack_build_id)
> sysctl_perf_event_max_stack)
return ERR_PTR(-EINVAL);
} else if (value_size / 8 > sysctl_perf_event_max_stack)
return ERR_PTR(-EINVAL);
/* hash table size must be power of 2 */
n_buckets = roundup_pow_of_two(attr->max_entries);
cost = n_buckets * sizeof(struct stack_map_bucket *) + sizeof(*smap);
cost += n_buckets * (value_size + sizeof(struct stack_map_bucket));
err = bpf_map_charge_init(&mem, cost);
if (err)
return ERR_PTR(err);
smap = bpf_map_area_alloc(cost, bpf_map_attr_numa_node(attr));
if (!smap) {
bpf_map_charge_finish(&mem);
return ERR_PTR(-ENOMEM);
}
bpf_map_init_from_attr(&smap->map, attr);
smap->map.value_size = value_size;
smap->n_buckets = n_buckets;
err = get_callchain_buffers(sysctl_perf_event_max_stack);
if (err)
goto free_charge;
err = prealloc_elems_and_freelist(smap);
if (err)
goto put_buffers;
bpf_map_charge_move(&smap->map.memory, &mem);
return &smap->map;
put_buffers:
put_callchain_buffers();
free_charge:
bpf_map_charge_finish(&mem);
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 &&
!stack_map_parse_build_id(page_addr, build_id,
page_addr + phdr[i].p_offset,
phdr[i].p_filesz))
return 0;
}
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 &&
!stack_map_parse_build_id(page_addr, build_id,
page_addr + phdr[i].p_offset,
phdr[i].p_filesz))
return 0;
}
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()) {
if (!IS_ENABLED(CONFIG_PREEMPT_RT)) {
work = this_cpu_ptr(&up_read_work);
if (atomic_read(&work->irq_work.flags) & IRQ_WORK_BUSY) {
/* cannot queue more up_read, fallback */
irq_work_busy = true;
}
} else {
/*
* PREEMPT_RT does not allow to trylock mmap sem in
* interrupt disabled context. Force the fallback code.
*/
irq_work_busy = true;
}
}
/*
* We cannot do up_read() when the irq is disabled, because of
* risk to deadlock with rq_lock. To do build_id lookup when the
* irqs are disabled, we need to run up_read() in irq_work. We use
* a percpu variable to do the irq_work. If the irq_work is
* already used by another lookup, we fall back to report ips.
*
* Same fallback is used for kernel stack (!user) on a stackmap
* with build_id.
*/
if (!user || !current || !current->mm || irq_work_busy ||
!mmap_read_trylock_non_owner(current->mm)) {
/* cannot access current->mm, fall back to ips */
for (i = 0; i < trace_nr; i++) {
id_offs[i].status = BPF_STACK_BUILD_ID_IP;
id_offs[i].ip = ips[i];
memset(id_offs[i].build_id, 0, 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) {
mmap_read_unlock_non_owner(current->mm);
} else {
work->mm = current->mm;
irq_work_queue(&work->irq_work);
}
}
static struct perf_callchain_entry *
get_callchain_entry_for_task(struct task_struct *task, u32 init_nr)
{
#ifdef CONFIG_STACKTRACE
struct perf_callchain_entry *entry;
int rctx;
entry = get_callchain_entry(&rctx);
if (!entry)
return NULL;
entry->nr = init_nr +
stack_trace_save_tsk(task, (unsigned long *)(entry->ip + init_nr),
sysctl_perf_event_max_stack - init_nr, 0);
/* stack_trace_save_tsk() works on unsigned long array, while
* perf_callchain_entry uses u64 array. For 32-bit systems, it is
* necessary to fix this mismatch.
*/
if (__BITS_PER_LONG != 64) {
unsigned long *from = (unsigned long *) entry->ip;
u64 *to = entry->ip;
int i;
/* copy data from the end to avoid using extra buffer */
for (i = entry->nr - 1; i >= (int)init_nr; i--)
to[i] = (u64)(from[i]);
}
put_callchain_entry(rctx);
return entry;
#else /* CONFIG_STACKTRACE */
return NULL;
#endif
}
static long __bpf_get_stackid(struct bpf_map *map,
struct perf_callchain_entry *trace, u64 flags)
{
struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
struct stack_map_bucket *bucket, *new_bucket, *old_bucket;
u32 max_depth = map->value_size / stack_map_data_size(map);
/* stack_map_alloc() checks that max_depth <= sysctl_perf_event_max_stack */
u32 init_nr = sysctl_perf_event_max_stack - max_depth;
u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
u32 hash, id, trace_nr, trace_len;
bool user = flags & BPF_F_USER_STACK;
u64 *ips;
bool hash_matches;
/* get_perf_callchain() guarantees that trace->nr >= init_nr
* and trace-nr <= sysctl_perf_event_max_stack, so trace_nr <= max_depth
*/
trace_nr = trace->nr - init_nr;
if (trace_nr <= skip)
/* skipping more than usable stack trace */
return -EFAULT;
trace_nr -= skip;
trace_len = trace_nr * sizeof(u64);
ips = trace->ip + skip + init_nr;
hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0);
id = hash & (smap->n_buckets - 1);
bucket = READ_ONCE(smap->buckets[id]);
hash_matches = bucket && bucket->hash == hash;
/* fast cmp */
if (hash_matches && flags & BPF_F_FAST_STACK_CMP)
return id;
if (stack_map_use_build_id(map)) {
/* for build_id+offset, pop a bucket before slow cmp */
new_bucket = (struct stack_map_bucket *)
pcpu_freelist_pop(&smap->freelist);
if (unlikely(!new_bucket))
return -ENOMEM;
new_bucket->nr = trace_nr;
stack_map_get_build_id_offset(
(struct bpf_stack_build_id *)new_bucket->data,
ips, trace_nr, user);
trace_len = trace_nr * sizeof(struct bpf_stack_build_id);
if (hash_matches && bucket->nr == trace_nr &&
memcmp(bucket->data, new_bucket->data, trace_len) == 0) {
pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
return id;
}
if (bucket && !(flags & BPF_F_REUSE_STACKID)) {
pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
return -EEXIST;
}
} else {
if (hash_matches && bucket->nr == trace_nr &&
memcmp(bucket->data, ips, trace_len) == 0)
return id;
if (bucket && !(flags & BPF_F_REUSE_STACKID))
return -EEXIST;
new_bucket = (struct stack_map_bucket *)
pcpu_freelist_pop(&smap->freelist);
if (unlikely(!new_bucket))
return -ENOMEM;
memcpy(new_bucket->data, ips, trace_len);
}
new_bucket->hash = hash;
new_bucket->nr = trace_nr;
old_bucket = xchg(&smap->buckets[id], new_bucket);
if (old_bucket)
pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
return id;
}
BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
u64, flags)
{
u32 max_depth = map->value_size / stack_map_data_size(map);
/* stack_map_alloc() checks that max_depth <= sysctl_perf_event_max_stack */
u32 init_nr = sysctl_perf_event_max_stack - max_depth;
bool user = flags & BPF_F_USER_STACK;
struct perf_callchain_entry *trace;
bool kernel = !user;
if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
return -EINVAL;
trace = get_perf_callchain(regs, init_nr, kernel, user,
sysctl_perf_event_max_stack, false, false);
if (unlikely(!trace))
/* couldn't fetch the stack trace */
return -EFAULT;
return __bpf_get_stackid(map, trace, flags);
}
const struct bpf_func_proto bpf_get_stackid_proto = {
.func = bpf_get_stackid,
.gpl_only = true,
.ret_type = RET_INTEGER,
.arg1_type = ARG_PTR_TO_CTX,
.arg2_type = ARG_CONST_MAP_PTR,
.arg3_type = ARG_ANYTHING,
};
static __u64 count_kernel_ip(struct perf_callchain_entry *trace)
{
__u64 nr_kernel = 0;
while (nr_kernel < trace->nr) {
if (trace->ip[nr_kernel] == PERF_CONTEXT_USER)
break;
nr_kernel++;
}
return nr_kernel;
}
BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx,
struct bpf_map *, map, u64, flags)
{
struct perf_event *event = ctx->event;
struct perf_callchain_entry *trace;
bool kernel, user;
__u64 nr_kernel;
int ret;
/* perf_sample_data doesn't have callchain, use bpf_get_stackid */
if (!(event->attr.sample_type & __PERF_SAMPLE_CALLCHAIN_EARLY))
return bpf_get_stackid((unsigned long)(ctx->regs),
(unsigned long) map, flags, 0, 0);
if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
return -EINVAL;
user = flags & BPF_F_USER_STACK;
kernel = !user;
trace = ctx->data->callchain;
if (unlikely(!trace))
return -EFAULT;
nr_kernel = count_kernel_ip(trace);
if (kernel) {
__u64 nr = trace->nr;
trace->nr = nr_kernel;
ret = __bpf_get_stackid(map, trace, flags);
/* restore nr */
trace->nr = nr;
} else { /* user */
u64 skip = flags & BPF_F_SKIP_FIELD_MASK;
skip += nr_kernel;
if (skip > BPF_F_SKIP_FIELD_MASK)
return -EFAULT;
flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip;
ret = __bpf_get_stackid(map, trace, flags);
}
return ret;
}
const struct bpf_func_proto bpf_get_stackid_proto_pe = {
.func = bpf_get_stackid_pe,
.gpl_only = false,
.ret_type = RET_INTEGER,
.arg1_type = ARG_PTR_TO_CTX,
.arg2_type = ARG_CONST_MAP_PTR,
.arg3_type = ARG_ANYTHING,
};
static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,
struct perf_callchain_entry *trace_in,
void *buf, u32 size, u64 flags)
{
u32 init_nr, trace_nr, copy_len, elem_size, num_elem;
bool user_build_id = flags & BPF_F_USER_BUILD_ID;
u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
bool user = flags & BPF_F_USER_STACK;
struct perf_callchain_entry *trace;
bool kernel = !user;
int err = -EINVAL;
u64 *ips;
if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
BPF_F_USER_BUILD_ID)))
goto clear;
if (kernel && user_build_id)
goto clear;
elem_size = (user && user_build_id) ? sizeof(struct bpf_stack_build_id)
: sizeof(u64);
if (unlikely(size % elem_size))
goto clear;
/* cannot get valid user stack for task without user_mode regs */
if (task && user && !user_mode(regs))
goto err_fault;
num_elem = size / elem_size;
if (sysctl_perf_event_max_stack < num_elem)
init_nr = 0;
else
init_nr = sysctl_perf_event_max_stack - num_elem;
if (trace_in)
trace = trace_in;
else if (kernel && task)
trace = get_callchain_entry_for_task(task, init_nr);
else
trace = get_perf_callchain(regs, init_nr, kernel, user,
sysctl_perf_event_max_stack,
false, false);
if (unlikely(!trace))
goto err_fault;
trace_nr = trace->nr - init_nr;
if (trace_nr < skip)
goto err_fault;
trace_nr -= skip;
trace_nr = (trace_nr <= num_elem) ? trace_nr : num_elem;
copy_len = trace_nr * elem_size;
ips = trace->ip + skip + init_nr;
if (user && user_build_id)
stack_map_get_build_id_offset(buf, ips, trace_nr, user);
else
memcpy(buf, ips, copy_len);
if (size > copy_len)
memset(buf + copy_len, 0, size - copy_len);
return copy_len;
err_fault:
err = -EFAULT;
clear:
memset(buf, 0, size);
return err;
}
BPF_CALL_4(bpf_get_stack, struct pt_regs *, regs, void *, buf, u32, size,
u64, flags)
{
return __bpf_get_stack(regs, NULL, NULL, buf, size, flags);
}
const struct bpf_func_proto bpf_get_stack_proto = {
.func = bpf_get_stack,
.gpl_only = true,
.ret_type = RET_INTEGER,
.arg1_type = ARG_PTR_TO_CTX,
.arg2_type = ARG_PTR_TO_UNINIT_MEM,
.arg3_type = ARG_CONST_SIZE_OR_ZERO,
.arg4_type = ARG_ANYTHING,
};
BPF_CALL_4(bpf_get_task_stack, struct task_struct *, task, void *, buf,
u32, size, u64, flags)
{
struct pt_regs *regs = task_pt_regs(task);
return __bpf_get_stack(regs, task, NULL, buf, size, flags);
}
BTF_ID_LIST_SINGLE(bpf_get_task_stack_btf_ids, struct, task_struct)
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 = &bpf_get_task_stack_btf_ids[0],
.arg2_type = ARG_PTR_TO_UNINIT_MEM,
.arg3_type = ARG_CONST_SIZE_OR_ZERO,
.arg4_type = ARG_ANYTHING,
};
BPF_CALL_4(bpf_get_stack_pe, struct bpf_perf_event_data_kern *, ctx,
void *, buf, u32, size, u64, flags)
{
struct pt_regs *regs = (struct pt_regs *)(ctx->regs);
struct perf_event *event = ctx->event;
struct perf_callchain_entry *trace;
bool kernel, user;
int err = -EINVAL;
__u64 nr_kernel;
if (!(event->attr.sample_type & __PERF_SAMPLE_CALLCHAIN_EARLY))
return __bpf_get_stack(regs, NULL, NULL, buf, size, flags);
if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
BPF_F_USER_BUILD_ID)))
goto clear;
user = flags & BPF_F_USER_STACK;
kernel = !user;
err = -EFAULT;
trace = ctx->data->callchain;
if (unlikely(!trace))
goto clear;
nr_kernel = count_kernel_ip(trace);
if (kernel) {
__u64 nr = trace->nr;
trace->nr = nr_kernel;
err = __bpf_get_stack(regs, NULL, trace, buf, size, flags);
/* restore nr */
trace->nr = nr;
} else { /* user */
u64 skip = flags & BPF_F_SKIP_FIELD_MASK;
skip += nr_kernel;
if (skip > BPF_F_SKIP_FIELD_MASK)
goto clear;
flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip;
err = __bpf_get_stack(regs, NULL, trace, buf, size, flags);
}
return err;
clear:
memset(buf, 0, size);
return err;
}
const struct bpf_func_proto bpf_get_stack_proto_pe = {
.func = bpf_get_stack_pe,
.gpl_only = true,
.ret_type = RET_INTEGER,
.arg1_type = ARG_PTR_TO_CTX,
.arg2_type = ARG_PTR_TO_UNINIT_MEM,
.arg3_type = ARG_CONST_SIZE_OR_ZERO,
.arg4_type = ARG_ANYTHING,
};
/* Called from eBPF program */
static void *stack_map_lookup_elem(struct bpf_map *map, void *key)
{
return ERR_PTR(-EOPNOTSUPP);
}
/* Called from syscall */
int bpf_stackmap_copy(struct bpf_map *map, void *key, void *value)
{
struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
struct stack_map_bucket *bucket, *old_bucket;
u32 id = *(u32 *)key, trace_len;
if (unlikely(id >= smap->n_buckets))
return -ENOENT;
bucket = xchg(&smap->buckets[id], NULL);
if (!bucket)
return -ENOENT;
trace_len = bucket->nr * stack_map_data_size(map);
memcpy(value, bucket->data, trace_len);
memset(value + trace_len, 0, map->value_size - trace_len);
old_bucket = xchg(&smap->buckets[id], bucket);
if (old_bucket)
pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
return 0;
}
static int stack_map_get_next_key(struct bpf_map *map, void *key,
void *next_key)
{
struct bpf_stack_map *smap = container_of(map,
struct bpf_stack_map, map);
u32 id;
WARN_ON_ONCE(!rcu_read_lock_held());
if (!key) {
id = 0;
} else {
id = *(u32 *)key;
if (id >= smap->n_buckets || !smap->buckets[id])
id = 0;
else
id++;
}
while (id < smap->n_buckets && !smap->buckets[id])
id++;
if (id >= smap->n_buckets)
return -ENOENT;
*(u32 *)next_key = id;
return 0;
}
static int stack_map_update_elem(struct bpf_map *map, void *key, void *value,
u64 map_flags)
{
return -EINVAL;
}
/* Called from syscall or from eBPF program */
static int stack_map_delete_elem(struct bpf_map *map, void *key)
{
struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
struct stack_map_bucket *old_bucket;
u32 id = *(u32 *)key;
if (unlikely(id >= smap->n_buckets))
return -E2BIG;
old_bucket = xchg(&smap->buckets[id], NULL);
if (old_bucket) {
pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
return 0;
} else {
return -ENOENT;
}
}
/* Called when map->refcnt goes to zero, either from workqueue or from syscall */
static void stack_map_free(struct bpf_map *map)
{
struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
bpf_map_area_free(smap->elems);
pcpu_freelist_destroy(&smap->freelist);
bpf_map_area_free(smap);
put_callchain_buffers();
}
static int stack_trace_map_btf_id;
const struct bpf_map_ops stack_trace_map_ops = {
.map_meta_equal = bpf_map_meta_equal,
.map_alloc = stack_map_alloc,
.map_free = stack_map_free,
.map_get_next_key = stack_map_get_next_key,
.map_lookup_elem = stack_map_lookup_elem,
.map_update_elem = stack_map_update_elem,
.map_delete_elem = stack_map_delete_elem,
.map_check_btf = map_check_no_btf,
.map_btf_name = "bpf_stack_map",
.map_btf_id = &stack_trace_map_btf_id,
};
static int __init stack_map_init(void)
{
int cpu;
struct stack_map_irq_work *work;
for_each_possible_cpu(cpu) {
work = per_cpu_ptr(&up_read_work, cpu);
init_irq_work(&work->irq_work, do_up_read);
}
return 0;
}
subsys_initcall(stack_map_init);