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bpf: rename poke descriptor's 'ip' member to 'tailcall_target'

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Reflect the actual purpose of poke->ip and rename it to
poke->tailcall_target so that it will not the be confused with another
poke target that will be introduced in next commit.

While at it, do the same thing with poke->ip_stable - rename it to
poke->tailcall_target_stable.

Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Maciej Fijalkowski 2020-09-16 23:10:06 +02:00 committed by Alexei Starovoitov
parent a748c6975d
commit cf71b174d3
4 changed files with 24 additions and 20 deletions
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20
arch/x86/net/bpf_jit_comp.c
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@ -434,7 +434,7 @@ static void emit_bpf_tail_call_direct(struct bpf_jit_poke_descriptor *poke,
EMIT3(0x83, 0xC0, 0x01); /* add eax, 1 */
EMIT2_off32(0x89, 0x85, -36 - MAX_BPF_STACK); /* mov dword ptr [rbp -548], eax */
poke->ip = image + (addr - X86_PATCH_SIZE);
poke->tailcall_target = image + (addr - X86_PATCH_SIZE);
poke->adj_off = PROLOGUE_SIZE;
memcpy(prog, ideal_nops[NOP_ATOMIC5], X86_PATCH_SIZE);
@ -453,7 +453,7 @@ static void bpf_tail_call_direct_fixup(struct bpf_prog *prog)
for (i = 0; i < prog->aux->size_poke_tab; i++) {
poke = &prog->aux->poke_tab[i];
WARN_ON_ONCE(READ_ONCE(poke->ip_stable));
WARN_ON_ONCE(READ_ONCE(poke->tailcall_target_stable));
if (poke->reason != BPF_POKE_REASON_TAIL_CALL)
continue;
@ -464,18 +464,20 @@ static void bpf_tail_call_direct_fixup(struct bpf_prog *prog)
if (target) {
/* Plain memcpy is used when image is not live yet
* and still not locked as read-only. Once poke
* location is active (poke->ip_stable), any parallel
* bpf_arch_text_poke() might occur still on the
* read-write image until we finally locked it as
* read-only. Both modifications on the given image
* are under text_mutex to avoid interference.
* location is active (poke->tailcall_target_stable),
* any parallel bpf_arch_text_poke() might occur
* still on the read-write image until we finally
* locked it as read-only. Both modifications on
* the given image are under text_mutex to avoid
* interference.
*/
ret = __bpf_arch_text_poke(poke->ip, BPF_MOD_JUMP, NULL,
ret = __bpf_arch_text_poke(poke->tailcall_target,
BPF_MOD_JUMP, NULL,
(u8 *)target->bpf_func +
poke->adj_off, false);
BUG_ON(ret < 0);
}
WRITE_ONCE(poke->ip_stable, true);
WRITE_ONCE(poke->tailcall_target_stable, true);
mutex_unlock(&array->aux->poke_mutex);
}
}

4
include/linux/bpf.h
View File

@ -697,14 +697,14 @@ enum bpf_jit_poke_reason {
/* Descriptor of pokes pointing /into/ the JITed image. */
struct bpf_jit_poke_descriptor {
void *ip;
void *tailcall_target;
union {
struct {
struct bpf_map *map;
u32 key;
} tail_call;
};
bool ip_stable;
bool tailcall_target_stable;
u8 adj_off;
u16 reason;
u32 insn_idx;

17
kernel/bpf/arraymap.c
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@ -918,12 +918,13 @@ static void prog_array_map_poke_run(struct bpf_map *map, u32 key,
* there could be danger of use after free otherwise.
* 2) Initially when we start tracking aux, the program
* is not JITed yet and also does not have a kallsyms
* entry. We skip these as poke->ip_stable is not
* active yet. The JIT will do the final fixup before
* setting it stable. The various poke->ip_stable are
* successively activated, so tail call updates can
* arrive from here while JIT is still finishing its
* final fixup for non-activated poke entries.
* entry. We skip these as poke->tailcall_target_stable
* is not active yet. The JIT will do the final fixup
* before setting it stable. The various
* poke->tailcall_target_stable are successively
* activated, so tail call updates can arrive from here
* while JIT is still finishing its final fixup for
* non-activated poke entries.
* 3) On program teardown, the program's kallsym entry gets
* removed out of RCU callback, but we can only untrack
* from sleepable context, therefore bpf_arch_text_poke()
@ -940,7 +941,7 @@ static void prog_array_map_poke_run(struct bpf_map *map, u32 key,
* 5) Any other error happening below from bpf_arch_text_poke()
* is a unexpected bug.
*/
if (!READ_ONCE(poke->ip_stable))
if (!READ_ONCE(poke->tailcall_target_stable))
continue;
if (poke->reason != BPF_POKE_REASON_TAIL_CALL)
continue;
@ -948,7 +949,7 @@ 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, BPF_MOD_JUMP,
ret = bpf_arch_text_poke(poke->tailcall_target, BPF_MOD_JUMP,
old ? (u8 *)old->bpf_func +
poke->adj_off : NULL,
new ? (u8 *)new->bpf_func +

3
kernel/bpf/core.c
View File

@ -775,7 +775,8 @@ int bpf_jit_add_poke_descriptor(struct bpf_prog *prog,
if (size > poke_tab_max)
return -ENOSPC;
if (poke->ip || poke->ip_stable || poke->adj_off)
if (poke->tailcall_target || poke->tailcall_target_stable ||
poke->adj_off)
return -EINVAL;
switch (poke->reason) {