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BACKPORT: bpf: Simplify __bpf_arch_text_poke poke type handling

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Given that we have BPF_MOD_NOP_TO_{CALL,JUMP}, BPF_MOD_{CALL,JUMP}_TO_NOP
and BPF_MOD_{CALL,JUMP}_TO_{CALL,JUMP} poke types and that we also pass in
old_addr as well as new_addr, it's a bit redundant and unnecessarily
complicates __bpf_arch_text_poke() itself since we can derive the same from
the *_addr that were passed in. Hence simplify and use BPF_MOD_{CALL,JUMP}
as types which also allows to clean up call-sites.

In addition to that, __bpf_arch_text_poke() currently verifies that text
matches expected old_insn before we invoke text_poke_bp(). Also add a check
on new_insn and skip rewrite if it already matches. Reason why this is rather
useful is that it avoids making any special casing in prog_array_map_poke_run()
when old and new prog were NULL and has the benefit that also for this case
we perform a check on text whether it really matches our expectations.

Suggested-by: Andrii Nakryiko <andriin@fb.com>
Change-Id: I4a6eead6f3d99c7932dfa9549dd090978b194cad
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/fcb00a2b0b288d6c73de4ef58116a821c8fe8f2f.1574555798.git.daniel@iogearbox.net
This commit is contained in:
Daniel Borkmann 2019-11-24 01:39:42 +01:00 • committed by basamaryan
commit 840e01a0c6
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GPG key ID: 210D5384FB2A5885
3 changed files with 7 additions and 23 deletions
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10
include/linux/bpf.h
View file

@ -1351,14 +1351,8 @@ static inline u32 bpf_xdp_sock_convert_ctx_access(enum bpf_access_type type,
#endif /* CONFIG_INET */
enum bpf_text_poke_type {
/* All call-related pokes. */
BPF_MOD_NOP_TO_CALL,
BPF_MOD_CALL_TO_CALL,
BPF_MOD_CALL_TO_NOP,
/* All jump-related pokes. */
BPF_MOD_NOP_TO_JUMP,
BPF_MOD_JUMP_TO_JUMP,
BPF_MOD_JUMP_TO_NOP,
BPF_MOD_CALL,
BPF_MOD_JUMP,
};
int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,

12
kernel/bpf/arraymap.c
View file

@ -749,19 +749,9 @@ static void prog_array_map_poke_run(struct bpf_map *map, u32 key,
struct bpf_prog *old,
struct bpf_prog *new)
{
enum bpf_text_poke_type type;
struct prog_poke_elem *elem;
struct bpf_array_aux *aux;
if (!old && new)
type = BPF_MOD_NOP_TO_JUMP;
else if (old && !new)
type = BPF_MOD_JUMP_TO_NOP;
else if (old && new)
type = BPF_MOD_JUMP_TO_JUMP;
else
return;
aux = container_of(map, struct bpf_array, map)->aux;
WARN_ON_ONCE(!mutex_is_locked(&aux->poke_mutex));
@ -809,7 +799,7 @@ static void prog_array_map_poke_run(struct bpf_map *map, u32 key,
poke->tail_call.key != key)
continue;
ret = bpf_arch_text_poke(poke->ip, type,
ret = bpf_arch_text_poke(poke->ip, BPF_MOD_JUMP,
old ? (u8 *)old->bpf_func +
poke->adj_off : NULL,
new ? (u8 *)new->bpf_func +

8
kernel/bpf/trampoline.c
View file

@ -77,7 +77,7 @@ static int bpf_trampoline_update(struct bpf_trampoline *tr)
int err;
if (fentry_cnt + fexit_cnt == 0) {
err = bpf_arch_text_poke(tr->func.addr, BPF_MOD_CALL_TO_NOP,
err = bpf_arch_text_poke(tr->func.addr, BPF_MOD_CALL,
old_image, NULL);
tr->selector = 0;
goto out;
@ -105,12 +105,12 @@ static int bpf_trampoline_update(struct bpf_trampoline *tr)
if (tr->selector)
/* progs already running at this address */
err = bpf_arch_text_poke(tr->func.addr, BPF_MOD_CALL_TO_CALL,
err = bpf_arch_text_poke(tr->func.addr, BPF_MOD_CALL,
old_image, new_image);
else
/* first time registering */
err = bpf_arch_text_poke(tr->func.addr, BPF_MOD_NOP_TO_CALL,
NULL, new_image);
err = bpf_arch_text_poke(tr->func.addr, BPF_MOD_CALL, NULL,
new_image);
if (err)
goto out;
tr->selector++;