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bpf: use bpf_prog_pack for bpf_dispatcher

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Allocate bpf_dispatcher with bpf_prog_pack_alloc so that bpf_dispatcher
can share pages with bpf programs.

arch_prepare_bpf_dispatcher() is updated to provide a RW buffer as working
area for arch code to write to.

This also fixes CPA W^X warnning like:

CPA refuse W^X violation: 8000000000000163 -> 0000000000000163 range: ...

Signed-off-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20220926184739.3512547-2-song@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Song Liu 2022-09-26 11:47:38 -07:00 • committed by Alexei Starovoitov
parent 30b8fdbbe3
commit 19c02415da
5 changed files with 43 additions and 17 deletions
Download patch file Download diff file Expand all files Collapse all files

9
kernel/bpf/core.c
View file

@ -825,6 +825,11 @@ struct bpf_prog_pack {
unsigned long bitmap[];
};
void bpf_jit_fill_hole_with_zero(void *area, unsigned int size)
{
memset(area, 0, size);
}
#define BPF_PROG_SIZE_TO_NBITS(size) (round_up(size, BPF_PROG_CHUNK_SIZE) / BPF_PROG_CHUNK_SIZE)
static DEFINE_MUTEX(pack_mutex);
@ -864,7 +869,7 @@ static struct bpf_prog_pack *alloc_new_pack(bpf_jit_fill_hole_t bpf_fill_ill_ins
return pack;
}
static void *bpf_prog_pack_alloc(u32 size, bpf_jit_fill_hole_t bpf_fill_ill_insns)
void *bpf_prog_pack_alloc(u32 size, bpf_jit_fill_hole_t bpf_fill_ill_insns)
{
unsigned int nbits = BPF_PROG_SIZE_TO_NBITS(size);
struct bpf_prog_pack *pack;
@ -905,7 +910,7 @@ out:
return ptr;
}
static void bpf_prog_pack_free(struct bpf_binary_header *hdr)
void bpf_prog_pack_free(struct bpf_binary_header *hdr)
{
struct bpf_prog_pack *pack = NULL, *tmp;
unsigned int nbits;

27
kernel/bpf/dispatcher.c
View file

@ -85,12 +85,12 @@ static bool bpf_dispatcher_remove_prog(struct bpf_dispatcher *d,
return false;
}
int __weak arch_prepare_bpf_dispatcher(void *image, s64 *funcs, int num_funcs)
int __weak arch_prepare_bpf_dispatcher(void *image, void *buf, s64 *funcs, int num_funcs)
{
return -ENOTSUPP;
}
static int bpf_dispatcher_prepare(struct bpf_dispatcher *d, void *image)
static int bpf_dispatcher_prepare(struct bpf_dispatcher *d, void *image, void *buf)
{
s64 ips[BPF_DISPATCHER_MAX] = {}, *ipsp = &ips[0];
int i;
@ -99,12 +99,12 @@ static int bpf_dispatcher_prepare(struct bpf_dispatcher *d, void *image)
if (d->progs[i].prog)
*ipsp++ = (s64)(uintptr_t)d->progs[i].prog->bpf_func;
}
return arch_prepare_bpf_dispatcher(image, &ips[0], d->num_progs);
return arch_prepare_bpf_dispatcher(image, buf, &ips[0], d->num_progs);
}
static void bpf_dispatcher_update(struct bpf_dispatcher *d, int prev_num_progs)
{
void *old, *new;
void *old, *new, *tmp;
u32 noff;
int err;
@ -117,8 +117,14 @@ static void bpf_dispatcher_update(struct bpf_dispatcher *d, int prev_num_progs)
}
new = d->num_progs ? d->image + noff : NULL;
tmp = d->num_progs ? d->rw_image + noff : NULL;
if (new) {
if (bpf_dispatcher_prepare(d, new))
/* Prepare the dispatcher in d->rw_image. Then use
* bpf_arch_text_copy to update d->image, which is RO+X.
*/
if (bpf_dispatcher_prepare(d, new, tmp))
return;
if (IS_ERR(bpf_arch_text_copy(new, tmp, PAGE_SIZE / 2)))
return;
}
@ -140,9 +146,18 @@ void bpf_dispatcher_change_prog(struct bpf_dispatcher *d, struct bpf_prog *from,
mutex_lock(&d->mutex);
if (!d->image) {
d->image = bpf_jit_alloc_exec_page();
d->image = bpf_prog_pack_alloc(PAGE_SIZE, bpf_jit_fill_hole_with_zero);
if (!d->image)
goto out;
d->rw_image = bpf_jit_alloc_exec(PAGE_SIZE);
if (!d->rw_image) {
u32 size = PAGE_SIZE;
bpf_arch_text_copy(d->image, &size, sizeof(size));
bpf_prog_pack_free((struct bpf_binary_header *)d->image);
d->image = NULL;
goto out;
}
bpf_image_ksym_add(d->image, &d->ksym);
}