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bpf: Convert bpf_prog refcnt to atomic64_t

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Similarly to bpf_map's refcnt/usercnt, convert bpf_prog's refcnt to atomic64
and remove artificial 32k limit. This allows to make bpf_prog's refcounting
non-failing, simplifying logic of users of bpf_prog_add/bpf_prog_inc.

Validated compilation by running allyesconfig kernel build.

Suggested-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20191117172806.2195367-3-andriin@fb.com
This commit is contained in:
Andrii Nakryiko
2019-11-17 09:28:03 -08:00
committed by Daniel Borkmann
parent 1e0bd5a091
commit 85192dbf4d
11 changed files with 40 additions and 97 deletions
Download Patch File Download Diff File Expand all files Collapse all files

5
kernel/bpf/inode.c
View File

@@ -31,7 +31,7 @@ static void *bpf_any_get(void *raw, enum bpf_type type)
{
switch (type) {
case BPF_TYPE_PROG:
raw = bpf_prog_inc(raw);
bpf_prog_inc(raw);
break;
case BPF_TYPE_MAP:
bpf_map_inc_with_uref(raw);
@@ -534,7 +534,8 @@ static struct bpf_prog *__get_prog_inode(struct inode *inode, enum bpf_prog_type
if (!bpf_prog_get_ok(prog, &type, false))
return ERR_PTR(-EINVAL);
return bpf_prog_inc(prog);
bpf_prog_inc(prog);
return prog;
}
struct bpf_prog *bpf_prog_get_type_path(const char *name, enum bpf_prog_type type)

30
kernel/bpf/syscall.c
View File

@@ -1339,7 +1339,7 @@ static void __bpf_prog_put_noref(struct bpf_prog *prog, bool deferred)
static void __bpf_prog_put(struct bpf_prog *prog, bool do_idr_lock)
{
if (atomic_dec_and_test(&prog->aux->refcnt)) {
if (atomic64_dec_and_test(&prog->aux->refcnt)) {
perf_event_bpf_event(prog, PERF_BPF_EVENT_PROG_UNLOAD, 0);
/* bpf_prog_free_id() must be called first */
bpf_prog_free_id(prog, do_idr_lock);
@@ -1445,16 +1445,9 @@ static struct bpf_prog *____bpf_prog_get(struct fd f)
return f.file->private_data;
}
/* prog's refcnt limit */
#define BPF_MAX_REFCNT 32768
struct bpf_prog *bpf_prog_add(struct bpf_prog *prog, int i)
void bpf_prog_add(struct bpf_prog *prog, int i)
{
if (atomic_add_return(i, &prog->aux->refcnt) > BPF_MAX_REFCNT) {
atomic_sub(i, &prog->aux->refcnt);
return ERR_PTR(-EBUSY);
}
return prog;
atomic64_add(i, &prog->aux->refcnt);
}
EXPORT_SYMBOL_GPL(bpf_prog_add);
@@ -1465,13 +1458,13 @@ void bpf_prog_sub(struct bpf_prog *prog, int i)
* path holds a reference to the program, thus atomic_sub() can
* be safely used in such cases!
*/
WARN_ON(atomic_sub_return(i, &prog->aux->refcnt) == 0);
WARN_ON(atomic64_sub_return(i, &prog->aux->refcnt) == 0);
}
EXPORT_SYMBOL_GPL(bpf_prog_sub);
struct bpf_prog *bpf_prog_inc(struct bpf_prog *prog)
void bpf_prog_inc(struct bpf_prog *prog)
{
return bpf_prog_add(prog, 1);
atomic64_inc(&prog->aux->refcnt);
}
EXPORT_SYMBOL_GPL(bpf_prog_inc);
@@ -1480,12 +1473,7 @@ struct bpf_prog *bpf_prog_inc_not_zero(struct bpf_prog *prog)
{
int refold;
refold = atomic_fetch_add_unless(&prog->aux->refcnt, 1, 0);
if (refold >= BPF_MAX_REFCNT) {
__bpf_prog_put(prog, false);
return ERR_PTR(-EBUSY);
}
refold = atomic64_fetch_add_unless(&prog->aux->refcnt, 1, 0);
if (!refold)
return ERR_PTR(-ENOENT);
@@ -1523,7 +1511,7 @@ static struct bpf_prog *__bpf_prog_get(u32 ufd, enum bpf_prog_type *attach_type,
goto out;
}
prog = bpf_prog_inc(prog);
bpf_prog_inc(prog);
out:
fdput(f);
return prog;
@@ -1714,7 +1702,7 @@ static int bpf_prog_load(union bpf_attr *attr, union bpf_attr __user *uattr)
prog->orig_prog = NULL;
prog->jited = 0;
atomic_set(&prog->aux->refcnt, 1);
atomic64_set(&prog->aux->refcnt, 1);
prog->gpl_compatible = is_gpl ? 1 : 0;
if (bpf_prog_is_dev_bound(prog->aux)) {

7
kernel/events/core.c
View File

@@ -10477,12 +10477,9 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
context = parent_event->overflow_handler_context;
#if defined(CONFIG_BPF_SYSCALL) && defined(CONFIG_EVENT_TRACING)
if (overflow_handler == bpf_overflow_handler) {
struct bpf_prog *prog = bpf_prog_inc(parent_event->prog);
struct bpf_prog *prog = parent_event->prog;
if (IS_ERR(prog)) {
err = PTR_ERR(prog);
goto err_ns;
}
bpf_prog_inc(prog);
event->prog = prog;
event->orig_overflow_handler =
parent_event->orig_overflow_handler;