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core.c
2299 lines (2012 loc) · 58.9 KB
/
core.c
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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Linux Socket Filter - Kernel level socket filtering
*
* Based on the design of the Berkeley Packet Filter. The new
* internal format has been designed by PLUMgrid:
*
* Copyright (c) 2011 - 2014 PLUMgrid, http://plumgrid.com
*
* Authors:
*
* Jay Schulist <jschlst@samba.org>
* Alexei Starovoitov <ast@plumgrid.com>
* Daniel Borkmann <dborkman@redhat.com>
*
* Andi Kleen - Fix a few bad bugs and races.
* Kris Katterjohn - Added many additional checks in bpf_check_classic()
*/
#include <uapi/linux/btf.h>
#include <linux/filter.h>
#include <linux/skbuff.h>
#include <linux/vmalloc.h>
#include <linux/random.h>
#include <linux/moduleloader.h>
#include <linux/bpf.h>
#include <linux/btf.h>
#include <linux/frame.h>
#include <linux/rbtree_latch.h>
#include <linux/kallsyms.h>
#include <linux/rcupdate.h>
#include <linux/perf_event.h>
#include <linux/extable.h>
#include <linux/log2.h>
#include <asm/unaligned.h>
/* Registers */
#define BPF_R0 regs[BPF_REG_0]
#define BPF_R1 regs[BPF_REG_1]
#define BPF_R2 regs[BPF_REG_2]
#define BPF_R3 regs[BPF_REG_3]
#define BPF_R4 regs[BPF_REG_4]
#define BPF_R5 regs[BPF_REG_5]
#define BPF_R6 regs[BPF_REG_6]
#define BPF_R7 regs[BPF_REG_7]
#define BPF_R8 regs[BPF_REG_8]
#define BPF_R9 regs[BPF_REG_9]
#define BPF_R10 regs[BPF_REG_10]
/* Named registers */
#define DST regs[insn->dst_reg]
#define SRC regs[insn->src_reg]
#define FP regs[BPF_REG_FP]
#define AX regs[BPF_REG_AX]
#define ARG1 regs[BPF_REG_ARG1]
#define CTX regs[BPF_REG_CTX]
#define IMM insn->imm
/* No hurry in this branch
*
* Exported for the bpf jit load helper.
*/
void *bpf_internal_load_pointer_neg_helper(const struct sk_buff *skb, int k, unsigned int size)
{
u8 *ptr = NULL;
if (k >= SKF_NET_OFF)
ptr = skb_network_header(skb) + k - SKF_NET_OFF;
else if (k >= SKF_LL_OFF)
ptr = skb_mac_header(skb) + k - SKF_LL_OFF;
if (ptr >= skb->head && ptr + size <= skb_tail_pointer(skb))
return ptr;
return NULL;
}
struct bpf_prog *bpf_prog_alloc_no_stats(unsigned int size, gfp_t gfp_extra_flags)
{
gfp_t gfp_flags = GFP_KERNEL | __GFP_ZERO | gfp_extra_flags;
struct bpf_prog_aux *aux;
struct bpf_prog *fp;
size = round_up(size, PAGE_SIZE);
fp = __vmalloc(size, gfp_flags);
if (fp == NULL)
return NULL;
aux = kzalloc(sizeof(*aux), GFP_KERNEL | gfp_extra_flags);
if (aux == NULL) {
vfree(fp);
return NULL;
}
fp->pages = size / PAGE_SIZE;
fp->aux = aux;
fp->aux->prog = fp;
fp->jit_requested = ebpf_jit_enabled();
INIT_LIST_HEAD_RCU(&fp->aux->ksym.lnode);
return fp;
}
struct bpf_prog *bpf_prog_alloc(unsigned int size, gfp_t gfp_extra_flags)
{
gfp_t gfp_flags = GFP_KERNEL | __GFP_ZERO | gfp_extra_flags;
struct bpf_prog *prog;
int cpu;
prog = bpf_prog_alloc_no_stats(size, gfp_extra_flags);
if (!prog)
return NULL;
prog->aux->stats = alloc_percpu_gfp(struct bpf_prog_stats, gfp_flags);
if (!prog->aux->stats) {
kfree(prog->aux);
vfree(prog);
return NULL;
}
for_each_possible_cpu(cpu) {
struct bpf_prog_stats *pstats;
pstats = per_cpu_ptr(prog->aux->stats, cpu);
u64_stats_init(&pstats->syncp);
}
return prog;
}
EXPORT_SYMBOL_GPL(bpf_prog_alloc);
int bpf_prog_alloc_jited_linfo(struct bpf_prog *prog)
{
if (!prog->aux->nr_linfo || !prog->jit_requested)
return 0;
prog->aux->jited_linfo = kcalloc(prog->aux->nr_linfo,
sizeof(*prog->aux->jited_linfo),
GFP_KERNEL | __GFP_NOWARN);
if (!prog->aux->jited_linfo)
return -ENOMEM;
return 0;
}
void bpf_prog_free_jited_linfo(struct bpf_prog *prog)
{
kfree(prog->aux->jited_linfo);
prog->aux->jited_linfo = NULL;
}
void bpf_prog_free_unused_jited_linfo(struct bpf_prog *prog)
{
if (prog->aux->jited_linfo && !prog->aux->jited_linfo[0])
bpf_prog_free_jited_linfo(prog);
}
/* The jit engine is responsible to provide an array
* for insn_off to the jited_off mapping (insn_to_jit_off).
*
* The idx to this array is the insn_off. Hence, the insn_off
* here is relative to the prog itself instead of the main prog.
* This array has one entry for each xlated bpf insn.
*
* jited_off is the byte off to the last byte of the jited insn.
*
* Hence, with
* insn_start:
* The first bpf insn off of the prog. The insn off
* here is relative to the main prog.
* e.g. if prog is a subprog, insn_start > 0
* linfo_idx:
* The prog's idx to prog->aux->linfo and jited_linfo
*
* jited_linfo[linfo_idx] = prog->bpf_func
*
* For i > linfo_idx,
*
* jited_linfo[i] = prog->bpf_func +
* insn_to_jit_off[linfo[i].insn_off - insn_start - 1]
*/
void bpf_prog_fill_jited_linfo(struct bpf_prog *prog,
const u32 *insn_to_jit_off)
{
u32 linfo_idx, insn_start, insn_end, nr_linfo, i;
const struct bpf_line_info *linfo;
void **jited_linfo;
if (!prog->aux->jited_linfo)
/* Userspace did not provide linfo */
return;
linfo_idx = prog->aux->linfo_idx;
linfo = &prog->aux->linfo[linfo_idx];
insn_start = linfo[0].insn_off;
insn_end = insn_start + prog->len;
jited_linfo = &prog->aux->jited_linfo[linfo_idx];
jited_linfo[0] = prog->bpf_func;
nr_linfo = prog->aux->nr_linfo - linfo_idx;
for (i = 1; i < nr_linfo && linfo[i].insn_off < insn_end; i++)
/* The verifier ensures that linfo[i].insn_off is
* strictly increasing
*/
jited_linfo[i] = prog->bpf_func +
insn_to_jit_off[linfo[i].insn_off - insn_start - 1];
}
void bpf_prog_free_linfo(struct bpf_prog *prog)
{
bpf_prog_free_jited_linfo(prog);
kvfree(prog->aux->linfo);
}
struct bpf_prog *bpf_prog_realloc(struct bpf_prog *fp_old, unsigned int size,
gfp_t gfp_extra_flags)
{
gfp_t gfp_flags = GFP_KERNEL | __GFP_ZERO | gfp_extra_flags;
struct bpf_prog *fp;
u32 pages, delta;
int ret;
size = round_up(size, PAGE_SIZE);
pages = size / PAGE_SIZE;
if (pages <= fp_old->pages)
return fp_old;
delta = pages - fp_old->pages;
ret = __bpf_prog_charge(fp_old->aux->user, delta);
if (ret)
return NULL;
fp = __vmalloc(size, gfp_flags);
if (fp == NULL) {
__bpf_prog_uncharge(fp_old->aux->user, delta);
} else {
memcpy(fp, fp_old, fp_old->pages * PAGE_SIZE);
fp->pages = pages;
fp->aux->prog = fp;
/* We keep fp->aux from fp_old around in the new
* reallocated structure.
*/
fp_old->aux = NULL;
__bpf_prog_free(fp_old);
}
return fp;
}
void __bpf_prog_free(struct bpf_prog *fp)
{
if (fp->aux) {
free_percpu(fp->aux->stats);
kfree(fp->aux->poke_tab);
kfree(fp->aux);
}
vfree(fp);
}
int bpf_prog_calc_tag(struct bpf_prog *fp)
{
const u32 bits_offset = SHA1_BLOCK_SIZE - sizeof(__be64);
u32 raw_size = bpf_prog_tag_scratch_size(fp);
u32 digest[SHA1_DIGEST_WORDS];
u32 ws[SHA1_WORKSPACE_WORDS];
u32 i, bsize, psize, blocks;
struct bpf_insn *dst;
bool was_ld_map;
u8 *raw, *todo;
__be32 *result;
__be64 *bits;
raw = vmalloc(raw_size);
if (!raw)
return -ENOMEM;
sha1_init(digest);
memset(ws, 0, sizeof(ws));
/* We need to take out the map fd for the digest calculation
* since they are unstable from user space side.
*/
dst = (void *)raw;
for (i = 0, was_ld_map = false; i < fp->len; i++) {
dst[i] = fp->insnsi[i];
if (!was_ld_map &&
dst[i].code == (BPF_LD | BPF_IMM | BPF_DW) &&
(dst[i].src_reg == BPF_PSEUDO_MAP_FD ||
dst[i].src_reg == BPF_PSEUDO_MAP_VALUE)) {
was_ld_map = true;
dst[i].imm = 0;
} else if (was_ld_map &&
dst[i].code == 0 &&
dst[i].dst_reg == 0 &&
dst[i].src_reg == 0 &&
dst[i].off == 0) {
was_ld_map = false;
dst[i].imm = 0;
} else {
was_ld_map = false;
}
}
psize = bpf_prog_insn_size(fp);
memset(&raw[psize], 0, raw_size - psize);
raw[psize++] = 0x80;
bsize = round_up(psize, SHA1_BLOCK_SIZE);
blocks = bsize / SHA1_BLOCK_SIZE;
todo = raw;
if (bsize - psize >= sizeof(__be64)) {
bits = (__be64 *)(todo + bsize - sizeof(__be64));
} else {
bits = (__be64 *)(todo + bsize + bits_offset);
blocks++;
}
*bits = cpu_to_be64((psize - 1) << 3);
while (blocks--) {
sha1_transform(digest, todo, ws);
todo += SHA1_BLOCK_SIZE;
}
result = (__force __be32 *)digest;
for (i = 0; i < SHA1_DIGEST_WORDS; i++)
result[i] = cpu_to_be32(digest[i]);
memcpy(fp->tag, result, sizeof(fp->tag));
vfree(raw);
return 0;
}
static int bpf_adj_delta_to_imm(struct bpf_insn *insn, u32 pos, s32 end_old,
s32 end_new, s32 curr, const bool probe_pass)
{
const s64 imm_min = S32_MIN, imm_max = S32_MAX;
s32 delta = end_new - end_old;
s64 imm = insn->imm;
if (curr < pos && curr + imm + 1 >= end_old)
imm += delta;
else if (curr >= end_new && curr + imm + 1 < end_new)
imm -= delta;
if (imm < imm_min || imm > imm_max)
return -ERANGE;
if (!probe_pass)
insn->imm = imm;
return 0;
}
static int bpf_adj_delta_to_off(struct bpf_insn *insn, u32 pos, s32 end_old,
s32 end_new, s32 curr, const bool probe_pass)
{
const s32 off_min = S16_MIN, off_max = S16_MAX;
s32 delta = end_new - end_old;
s32 off = insn->off;
if (curr < pos && curr + off + 1 >= end_old)
off += delta;
else if (curr >= end_new && curr + off + 1 < end_new)
off -= delta;
if (off < off_min || off > off_max)
return -ERANGE;
if (!probe_pass)
insn->off = off;
return 0;
}
static int bpf_adj_branches(struct bpf_prog *prog, u32 pos, s32 end_old,
s32 end_new, const bool probe_pass)
{
u32 i, insn_cnt = prog->len + (probe_pass ? end_new - end_old : 0);
struct bpf_insn *insn = prog->insnsi;
int ret = 0;
for (i = 0; i < insn_cnt; i++, insn++) {
u8 code;
/* In the probing pass we still operate on the original,
* unpatched image in order to check overflows before we
* do any other adjustments. Therefore skip the patchlet.
*/
if (probe_pass && i == pos) {
i = end_new;
insn = prog->insnsi + end_old;
}
code = insn->code;
if ((BPF_CLASS(code) != BPF_JMP &&
BPF_CLASS(code) != BPF_JMP32) ||
BPF_OP(code) == BPF_EXIT)
continue;
/* Adjust offset of jmps if we cross patch boundaries. */
if (BPF_OP(code) == BPF_CALL) {
if (insn->src_reg != BPF_PSEUDO_CALL)
continue;
ret = bpf_adj_delta_to_imm(insn, pos, end_old,
end_new, i, probe_pass);
} else {
ret = bpf_adj_delta_to_off(insn, pos, end_old,
end_new, i, probe_pass);
}
if (ret)
break;
}
return ret;
}
static void bpf_adj_linfo(struct bpf_prog *prog, u32 off, u32 delta)
{
struct bpf_line_info *linfo;
u32 i, nr_linfo;
nr_linfo = prog->aux->nr_linfo;
if (!nr_linfo || !delta)
return;
linfo = prog->aux->linfo;
for (i = 0; i < nr_linfo; i++)
if (off < linfo[i].insn_off)
break;
/* Push all off < linfo[i].insn_off by delta */
for (; i < nr_linfo; i++)
linfo[i].insn_off += delta;
}
struct bpf_prog *bpf_patch_insn_single(struct bpf_prog *prog, u32 off,
const struct bpf_insn *patch, u32 len)
{
u32 insn_adj_cnt, insn_rest, insn_delta = len - 1;
const u32 cnt_max = S16_MAX;
struct bpf_prog *prog_adj;
int err;
/* Since our patchlet doesn't expand the image, we're done. */
if (insn_delta == 0) {
memcpy(prog->insnsi + off, patch, sizeof(*patch));
return prog;
}
insn_adj_cnt = prog->len + insn_delta;
/* Reject anything that would potentially let the insn->off
* target overflow when we have excessive program expansions.
* We need to probe here before we do any reallocation where
* we afterwards may not fail anymore.
*/
if (insn_adj_cnt > cnt_max &&
(err = bpf_adj_branches(prog, off, off + 1, off + len, true)))
return ERR_PTR(err);
/* Several new instructions need to be inserted. Make room
* for them. Likely, there's no need for a new allocation as
* last page could have large enough tailroom.
*/
prog_adj = bpf_prog_realloc(prog, bpf_prog_size(insn_adj_cnt),
GFP_USER);
if (!prog_adj)
return ERR_PTR(-ENOMEM);
prog_adj->len = insn_adj_cnt;
/* Patching happens in 3 steps:
*
* 1) Move over tail of insnsi from next instruction onwards,
* so we can patch the single target insn with one or more
* new ones (patching is always from 1 to n insns, n > 0).
* 2) Inject new instructions at the target location.
* 3) Adjust branch offsets if necessary.
*/
insn_rest = insn_adj_cnt - off - len;
memmove(prog_adj->insnsi + off + len, prog_adj->insnsi + off + 1,
sizeof(*patch) * insn_rest);
memcpy(prog_adj->insnsi + off, patch, sizeof(*patch) * len);
/* We are guaranteed to not fail at this point, otherwise
* the ship has sailed to reverse to the original state. An
* overflow cannot happen at this point.
*/
BUG_ON(bpf_adj_branches(prog_adj, off, off + 1, off + len, false));
bpf_adj_linfo(prog_adj, off, insn_delta);
return prog_adj;
}
int bpf_remove_insns(struct bpf_prog *prog, u32 off, u32 cnt)
{
/* Branch offsets can't overflow when program is shrinking, no need
* to call bpf_adj_branches(..., true) here
*/
memmove(prog->insnsi + off, prog->insnsi + off + cnt,
sizeof(struct bpf_insn) * (prog->len - off - cnt));
prog->len -= cnt;
return WARN_ON_ONCE(bpf_adj_branches(prog, off, off + cnt, off, false));
}
static void bpf_prog_kallsyms_del_subprogs(struct bpf_prog *fp)
{
int i;
for (i = 0; i < fp->aux->func_cnt; i++)
bpf_prog_kallsyms_del(fp->aux->func[i]);
}
void bpf_prog_kallsyms_del_all(struct bpf_prog *fp)
{
bpf_prog_kallsyms_del_subprogs(fp);
bpf_prog_kallsyms_del(fp);
}
#ifdef CONFIG_BPF_JIT
/* All BPF JIT sysctl knobs here. */
int bpf_jit_enable __read_mostly = IS_BUILTIN(CONFIG_BPF_JIT_DEFAULT_ON);
int bpf_jit_kallsyms __read_mostly = IS_BUILTIN(CONFIG_BPF_JIT_DEFAULT_ON);
int bpf_jit_harden __read_mostly;
long bpf_jit_limit __read_mostly;
static void
bpf_prog_ksym_set_addr(struct bpf_prog *prog)
{
const struct bpf_binary_header *hdr = bpf_jit_binary_hdr(prog);
unsigned long addr = (unsigned long)hdr;
WARN_ON_ONCE(!bpf_prog_ebpf_jited(prog));
prog->aux->ksym.start = (unsigned long) prog->bpf_func;
prog->aux->ksym.end = addr + hdr->pages * PAGE_SIZE;
}
static void
bpf_prog_ksym_set_name(struct bpf_prog *prog)
{
char *sym = prog->aux->ksym.name;
const char *end = sym + KSYM_NAME_LEN;
const struct btf_type *type;
const char *func_name;
BUILD_BUG_ON(sizeof("bpf_prog_") +
sizeof(prog->tag) * 2 +
/* name has been null terminated.
* We should need +1 for the '_' preceding
* the name. However, the null character
* is double counted between the name and the
* sizeof("bpf_prog_") above, so we omit
* the +1 here.
*/
sizeof(prog->aux->name) > KSYM_NAME_LEN);
sym += snprintf(sym, KSYM_NAME_LEN, "bpf_prog_");
sym = bin2hex(sym, prog->tag, sizeof(prog->tag));
/* prog->aux->name will be ignored if full btf name is available */
if (prog->aux->func_info_cnt) {
type = btf_type_by_id(prog->aux->btf,
prog->aux->func_info[prog->aux->func_idx].type_id);
func_name = btf_name_by_offset(prog->aux->btf, type->name_off);
snprintf(sym, (size_t)(end - sym), "_%s", func_name);
return;
}
if (prog->aux->name[0])
snprintf(sym, (size_t)(end - sym), "_%s", prog->aux->name);
else
*sym = 0;
}
static unsigned long bpf_get_ksym_start(struct latch_tree_node *n)
{
return container_of(n, struct bpf_ksym, tnode)->start;
}
static __always_inline bool bpf_tree_less(struct latch_tree_node *a,
struct latch_tree_node *b)
{
return bpf_get_ksym_start(a) < bpf_get_ksym_start(b);
}
static __always_inline int bpf_tree_comp(void *key, struct latch_tree_node *n)
{
unsigned long val = (unsigned long)key;
const struct bpf_ksym *ksym;
ksym = container_of(n, struct bpf_ksym, tnode);
if (val < ksym->start)
return -1;
if (val >= ksym->end)
return 1;
return 0;
}
static const struct latch_tree_ops bpf_tree_ops = {
.less = bpf_tree_less,
.comp = bpf_tree_comp,
};
static DEFINE_SPINLOCK(bpf_lock);
static LIST_HEAD(bpf_kallsyms);
static struct latch_tree_root bpf_tree __cacheline_aligned;
void bpf_ksym_add(struct bpf_ksym *ksym)
{
spin_lock_bh(&bpf_lock);
WARN_ON_ONCE(!list_empty(&ksym->lnode));
list_add_tail_rcu(&ksym->lnode, &bpf_kallsyms);
latch_tree_insert(&ksym->tnode, &bpf_tree, &bpf_tree_ops);
spin_unlock_bh(&bpf_lock);
}
static void __bpf_ksym_del(struct bpf_ksym *ksym)
{
if (list_empty(&ksym->lnode))
return;
latch_tree_erase(&ksym->tnode, &bpf_tree, &bpf_tree_ops);
list_del_rcu(&ksym->lnode);
}
void bpf_ksym_del(struct bpf_ksym *ksym)
{
spin_lock_bh(&bpf_lock);
__bpf_ksym_del(ksym);
spin_unlock_bh(&bpf_lock);
}
static bool bpf_prog_kallsyms_candidate(const struct bpf_prog *fp)
{
return fp->jited && !bpf_prog_was_classic(fp);
}
static bool bpf_prog_kallsyms_verify_off(const struct bpf_prog *fp)
{
return list_empty(&fp->aux->ksym.lnode) ||
fp->aux->ksym.lnode.prev == LIST_POISON2;
}
void bpf_prog_kallsyms_add(struct bpf_prog *fp)
{
if (!bpf_prog_kallsyms_candidate(fp) ||
!bpf_capable())
return;
bpf_prog_ksym_set_addr(fp);
bpf_prog_ksym_set_name(fp);
fp->aux->ksym.prog = true;
bpf_ksym_add(&fp->aux->ksym);
}
void bpf_prog_kallsyms_del(struct bpf_prog *fp)
{
if (!bpf_prog_kallsyms_candidate(fp))
return;
bpf_ksym_del(&fp->aux->ksym);
}
static struct bpf_ksym *bpf_ksym_find(unsigned long addr)
{
struct latch_tree_node *n;
n = latch_tree_find((void *)addr, &bpf_tree, &bpf_tree_ops);
return n ? container_of(n, struct bpf_ksym, tnode) : NULL;
}
const char *__bpf_address_lookup(unsigned long addr, unsigned long *size,
unsigned long *off, char *sym)
{
struct bpf_ksym *ksym;
char *ret = NULL;
rcu_read_lock();
ksym = bpf_ksym_find(addr);
if (ksym) {
unsigned long symbol_start = ksym->start;
unsigned long symbol_end = ksym->end;
strncpy(sym, ksym->name, KSYM_NAME_LEN);
ret = sym;
if (size)
*size = symbol_end - symbol_start;
if (off)
*off = addr - symbol_start;
}
rcu_read_unlock();
return ret;
}
bool is_bpf_text_address(unsigned long addr)
{
bool ret;
rcu_read_lock();
ret = bpf_ksym_find(addr) != NULL;
rcu_read_unlock();
return ret;
}
static struct bpf_prog *bpf_prog_ksym_find(unsigned long addr)
{
struct bpf_ksym *ksym = bpf_ksym_find(addr);
return ksym && ksym->prog ?
container_of(ksym, struct bpf_prog_aux, ksym)->prog :
NULL;
}
const struct exception_table_entry *search_bpf_extables(unsigned long addr)
{
const struct exception_table_entry *e = NULL;
struct bpf_prog *prog;
rcu_read_lock();
prog = bpf_prog_ksym_find(addr);
if (!prog)
goto out;
if (!prog->aux->num_exentries)
goto out;
e = search_extable(prog->aux->extable, prog->aux->num_exentries, addr);
out:
rcu_read_unlock();
return e;
}
int bpf_get_kallsym(unsigned int symnum, unsigned long *value, char *type,
char *sym)
{
struct bpf_ksym *ksym;
unsigned int it = 0;
int ret = -ERANGE;
if (!bpf_jit_kallsyms_enabled())
return ret;
rcu_read_lock();
list_for_each_entry_rcu(ksym, &bpf_kallsyms, lnode) {
if (it++ != symnum)
continue;
strncpy(sym, ksym->name, KSYM_NAME_LEN);
*value = ksym->start;
*type = BPF_SYM_ELF_TYPE;
ret = 0;
break;
}
rcu_read_unlock();
return ret;
}
int bpf_jit_add_poke_descriptor(struct bpf_prog *prog,
struct bpf_jit_poke_descriptor *poke)
{
struct bpf_jit_poke_descriptor *tab = prog->aux->poke_tab;
static const u32 poke_tab_max = 1024;
u32 slot = prog->aux->size_poke_tab;
u32 size = slot + 1;
if (size > poke_tab_max)
return -ENOSPC;
if (poke->ip || poke->ip_stable || poke->adj_off)
return -EINVAL;
switch (poke->reason) {
case BPF_POKE_REASON_TAIL_CALL:
if (!poke->tail_call.map)
return -EINVAL;
break;
default:
return -EINVAL;
}
tab = krealloc(tab, size * sizeof(*poke), GFP_KERNEL);
if (!tab)
return -ENOMEM;
memcpy(&tab[slot], poke, sizeof(*poke));
prog->aux->size_poke_tab = size;
prog->aux->poke_tab = tab;
return slot;
}
static atomic_long_t bpf_jit_current;
/* Can be overridden by an arch's JIT compiler if it has a custom,
* dedicated BPF backend memory area, or if neither of the two
* below apply.
*/
u64 __weak bpf_jit_alloc_exec_limit(void)
{
#if defined(MODULES_VADDR)
return MODULES_END - MODULES_VADDR;
#else
return VMALLOC_END - VMALLOC_START;
#endif
}
static int __init bpf_jit_charge_init(void)
{
/* Only used as heuristic here to derive limit. */
bpf_jit_limit = min_t(u64, round_up(bpf_jit_alloc_exec_limit() >> 2,
PAGE_SIZE), LONG_MAX);
return 0;
}
pure_initcall(bpf_jit_charge_init);
static int bpf_jit_charge_modmem(u32 pages)
{
if (atomic_long_add_return(pages, &bpf_jit_current) >
(bpf_jit_limit >> PAGE_SHIFT)) {
if (!capable(CAP_SYS_ADMIN)) {
atomic_long_sub(pages, &bpf_jit_current);
return -EPERM;
}
}
return 0;
}
static void bpf_jit_uncharge_modmem(u32 pages)
{
atomic_long_sub(pages, &bpf_jit_current);
}
void *__weak bpf_jit_alloc_exec(unsigned long size)
{
return module_alloc(size);
}
void __weak bpf_jit_free_exec(void *addr)
{
module_memfree(addr);
}
struct bpf_binary_header *
bpf_jit_binary_alloc(unsigned int proglen, u8 **image_ptr,
unsigned int alignment,
bpf_jit_fill_hole_t bpf_fill_ill_insns)
{
struct bpf_binary_header *hdr;
u32 size, hole, start, pages;
WARN_ON_ONCE(!is_power_of_2(alignment) ||
alignment > BPF_IMAGE_ALIGNMENT);
/* Most of BPF filters are really small, but if some of them
* fill a page, allow at least 128 extra bytes to insert a
* random section of illegal instructions.
*/
size = round_up(proglen + sizeof(*hdr) + 128, PAGE_SIZE);
pages = size / PAGE_SIZE;
if (bpf_jit_charge_modmem(pages))
return NULL;
hdr = bpf_jit_alloc_exec(size);
if (!hdr) {
bpf_jit_uncharge_modmem(pages);
return NULL;
}
/* Fill space with illegal/arch-dep instructions. */
bpf_fill_ill_insns(hdr, size);
hdr->pages = pages;
hole = min_t(unsigned int, size - (proglen + sizeof(*hdr)),
PAGE_SIZE - sizeof(*hdr));
start = (get_random_int() % hole) & ~(alignment - 1);
/* Leave a random number of instructions before BPF code. */
*image_ptr = &hdr->image[start];
return hdr;
}
void bpf_jit_binary_free(struct bpf_binary_header *hdr)
{
u32 pages = hdr->pages;
bpf_jit_free_exec(hdr);
bpf_jit_uncharge_modmem(pages);
}
/* This symbol is only overridden by archs that have different
* requirements than the usual eBPF JITs, f.e. when they only
* implement cBPF JIT, do not set images read-only, etc.
*/
void __weak bpf_jit_free(struct bpf_prog *fp)
{
if (fp->jited) {
struct bpf_binary_header *hdr = bpf_jit_binary_hdr(fp);
bpf_jit_binary_free(hdr);
WARN_ON_ONCE(!bpf_prog_kallsyms_verify_off(fp));
}
bpf_prog_unlock_free(fp);
}
int bpf_jit_get_func_addr(const struct bpf_prog *prog,
const struct bpf_insn *insn, bool extra_pass,
u64 *func_addr, bool *func_addr_fixed)
{
s16 off = insn->off;
s32 imm = insn->imm;
u8 *addr;
*func_addr_fixed = insn->src_reg != BPF_PSEUDO_CALL;
if (!*func_addr_fixed) {
/* Place-holder address till the last pass has collected
* all addresses for JITed subprograms in which case we
* can pick them up from prog->aux.
*/
if (!extra_pass)
addr = NULL;
else if (prog->aux->func &&
off >= 0 && off < prog->aux->func_cnt)
addr = (u8 *)prog->aux->func[off]->bpf_func;
else
return -EINVAL;
} else {
/* Address of a BPF helper call. Since part of the core
* kernel, it's always at a fixed location. __bpf_call_base
* and the helper with imm relative to it are both in core
* kernel.
*/
addr = (u8 *)__bpf_call_base + imm;
}
*func_addr = (unsigned long)addr;
return 0;
}
static int bpf_jit_blind_insn(const struct bpf_insn *from,
const struct bpf_insn *aux,
struct bpf_insn *to_buff,
bool emit_zext)
{
struct bpf_insn *to = to_buff;
u32 imm_rnd = get_random_int();
s16 off;
BUILD_BUG_ON(BPF_REG_AX + 1 != MAX_BPF_JIT_REG);
BUILD_BUG_ON(MAX_BPF_REG + 1 != MAX_BPF_JIT_REG);
/* Constraints on AX register:
*
* AX register is inaccessible from user space. It is mapped in
* all JITs, and used here for constant blinding rewrites. It is
* typically "stateless" meaning its contents are only valid within
* the executed instruction, but not across several instructions.
* There are a few exceptions however which are further detailed
* below.
*
* Constant blinding is only used by JITs, not in the interpreter.
* The interpreter uses AX in some occasions as a local temporary
* register e.g. in DIV or MOD instructions.
*
* In restricted circumstances, the verifier can also use the AX
* register for rewrites as long as they do not interfere with
* the above cases!
*/
if (from->dst_reg == BPF_REG_AX || from->src_reg == BPF_REG_AX)
goto out;
if (from->imm == 0 &&
(from->code == (BPF_ALU | BPF_MOV | BPF_K) ||
from->code == (BPF_ALU64 | BPF_MOV | BPF_K))) {
*to++ = BPF_ALU64_REG(BPF_XOR, from->dst_reg, from->dst_reg);
goto out;
}
switch (from->code) {
case BPF_ALU | BPF_ADD | BPF_K:
case BPF_ALU | BPF_SUB | BPF_K:
case BPF_ALU | BPF_AND | BPF_K:
case BPF_ALU | BPF_OR | BPF_K:
case BPF_ALU | BPF_XOR | BPF_K:
case BPF_ALU | BPF_MUL | BPF_K:
case BPF_ALU | BPF_MOV | BPF_K:
case BPF_ALU | BPF_DIV | BPF_K:
case BPF_ALU | BPF_MOD | BPF_K:
*to++ = BPF_ALU32_IMM(BPF_MOV, BPF_REG_AX, imm_rnd ^ from->imm);
*to++ = BPF_ALU32_IMM(BPF_XOR, BPF_REG_AX, imm_rnd);