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bpf: Refactor trampoline update code

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As we need to introduce a third type of attachment for trampolines, the
flattened signature of arch_prepare_bpf_trampoline gets even more
complicated.

Refactor the prog and count argument to arch_prepare_bpf_trampoline to
use bpf_tramp_progs to simplify the addition and accounting for new
attachment types.

Signed-off-by: KP Singh <kpsingh@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200304191853.1529-2-kpsingh@chromium.org
This commit is contained in:
KP Singh
2020-03-04 20:18:47 +01:00
committed by Alexei Starovoitov
parent cc6fa77102
commit 88fd9e5352
4 changed files with 71 additions and 45 deletions
Download Patch File Download Diff File Expand all files Collapse all files

10
kernel/bpf/bpf_struct_ops.c
View File

@@ -320,6 +320,7 @@ static int bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,
struct bpf_struct_ops_value *uvalue, *kvalue;
const struct btf_member *member;
const struct btf_type *t = st_ops->type;
struct bpf_tramp_progs *tprogs = NULL;
void *udata, *kdata;
int prog_fd, err = 0;
void *image;
@@ -343,6 +344,10 @@ static int bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,
if (uvalue->state || refcount_read(&uvalue->refcnt))
return -EINVAL;
tprogs = kcalloc(BPF_TRAMP_MAX, sizeof(*tprogs), GFP_KERNEL);
if (!tprogs)
return -ENOMEM;
uvalue = (struct bpf_struct_ops_value *)st_map->uvalue;
kvalue = (struct bpf_struct_ops_value *)&st_map->kvalue;
@@ -425,10 +430,12 @@ static int bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,
goto reset_unlock;
}
tprogs[BPF_TRAMP_FENTRY].progs[0] = prog;
tprogs[BPF_TRAMP_FENTRY].nr_progs = 1;
err = arch_prepare_bpf_trampoline(image,
st_map->image + PAGE_SIZE,
&st_ops->func_models[i], 0,
&prog, 1, NULL, 0, NULL);
tprogs, NULL);
if (err < 0)
goto reset_unlock;
@@ -469,6 +476,7 @@ reset_unlock:
memset(uvalue, 0, map->value_size);
memset(kvalue, 0, map->value_size);
unlock:
kfree(tprogs);
mutex_unlock(&st_map->lock);
return err;
}

62
kernel/bpf/trampoline.c
View File

@@ -190,40 +190,49 @@ static int register_fentry(struct bpf_trampoline *tr, void *new_addr)
return ret;
}
/* Each call __bpf_prog_enter + call bpf_func + call __bpf_prog_exit is ~50
* bytes on x86. Pick a number to fit into BPF_IMAGE_SIZE / 2
*/
#define BPF_MAX_TRAMP_PROGS 40
static struct bpf_tramp_progs *
bpf_trampoline_get_progs(const struct bpf_trampoline *tr, int *total)
{
const struct bpf_prog_aux *aux;
struct bpf_tramp_progs *tprogs;
struct bpf_prog **progs;
int kind;
*total = 0;
tprogs = kcalloc(BPF_TRAMP_MAX, sizeof(*tprogs), GFP_KERNEL);
if (!tprogs)
return ERR_PTR(-ENOMEM);
for (kind = 0; kind < BPF_TRAMP_MAX; kind++) {
tprogs[kind].nr_progs = tr->progs_cnt[kind];
*total += tr->progs_cnt[kind];
progs = tprogs[kind].progs;
hlist_for_each_entry(aux, &tr->progs_hlist[kind], tramp_hlist)
*progs++ = aux->prog;
}
return tprogs;
}
static int bpf_trampoline_update(struct bpf_trampoline *tr)
{
void *old_image = tr->image + ((tr->selector + 1) & 1) * BPF_IMAGE_SIZE/2;
void *new_image = tr->image + (tr->selector & 1) * BPF_IMAGE_SIZE/2;
struct bpf_prog *progs_to_run[BPF_MAX_TRAMP_PROGS];
int fentry_cnt = tr->progs_cnt[BPF_TRAMP_FENTRY];
int fexit_cnt = tr->progs_cnt[BPF_TRAMP_FEXIT];
struct bpf_prog **progs, **fentry, **fexit;
struct bpf_tramp_progs *tprogs;
u32 flags = BPF_TRAMP_F_RESTORE_REGS;
struct bpf_prog_aux *aux;
int err;
int err, total;
if (fentry_cnt + fexit_cnt == 0) {
tprogs = bpf_trampoline_get_progs(tr, &total);
if (IS_ERR(tprogs))
return PTR_ERR(tprogs);
if (total == 0) {
err = unregister_fentry(tr, old_image);
tr->selector = 0;
goto out;
}
/* populate fentry progs */
fentry = progs = progs_to_run;
hlist_for_each_entry(aux, &tr->progs_hlist[BPF_TRAMP_FENTRY], tramp_hlist)
*progs++ = aux->prog;
/* populate fexit progs */
fexit = progs;
hlist_for_each_entry(aux, &tr->progs_hlist[BPF_TRAMP_FEXIT], tramp_hlist)
*progs++ = aux->prog;
if (fexit_cnt)
if (tprogs[BPF_TRAMP_FEXIT].nr_progs)
flags = BPF_TRAMP_F_CALL_ORIG | BPF_TRAMP_F_SKIP_FRAME;
/* Though the second half of trampoline page is unused a task could be
@@ -232,12 +241,11 @@ static int bpf_trampoline_update(struct bpf_trampoline *tr)
* preempted task. Hence wait for tasks to voluntarily schedule or go
* to userspace.
*/
synchronize_rcu_tasks();
err = arch_prepare_bpf_trampoline(new_image, new_image + BPF_IMAGE_SIZE / 2,
&tr->func.model, flags,
fentry, fentry_cnt,
fexit, fexit_cnt,
&tr->func.model, flags, tprogs,
tr->func.addr);
if (err < 0)
goto out;
@@ -252,6 +260,7 @@ static int bpf_trampoline_update(struct bpf_trampoline *tr)
goto out;
tr->selector++;
out:
kfree(tprogs);
return err;
}
@@ -409,8 +418,7 @@ void notrace __bpf_prog_exit(struct bpf_prog *prog, u64 start)
int __weak
arch_prepare_bpf_trampoline(void *image, void *image_end,
const struct btf_func_model *m, u32 flags,
struct bpf_prog **fentry_progs, int fentry_cnt,
struct bpf_prog **fexit_progs, int fexit_cnt,
struct bpf_tramp_progs *tprogs,
void *orig_call)
{
return -ENOTSUPP;