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bpf: Add initial poke descriptor table for jit images

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Add initial poke table data structures and management to the BPF
prog that can later be used by JITs. Also add an instance of poke
specific data for tail call maps; plan for later work is to extend
this also for BPF static keys.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/1db285ec2ea4207ee0455b3f8e191a4fc58b9ade.1574452833.git.daniel@iogearbox.net
This commit is contained in:
Daniel Borkmann 2019-11-22 21:07:57 +01:00 committed by Alexei Starovoitov
parent 2beee5f574
commit a66886fe6c
3 changed files with 64 additions and 0 deletions
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20
include/linux/bpf.h
View File

@ -488,6 +488,24 @@ struct bpf_func_info_aux {
bool unreliable;
};
enum bpf_jit_poke_reason {
BPF_POKE_REASON_TAIL_CALL,
};
/* Descriptor of pokes pointing /into/ the JITed image. */
struct bpf_jit_poke_descriptor {
void *ip;
union {
struct {
struct bpf_map *map;
u32 key;
} tail_call;
};
bool ip_stable;
u8 adj_off;
u16 reason;
};
struct bpf_prog_aux {
atomic64_t refcnt;
u32 used_map_cnt;
@ -513,6 +531,8 @@ struct bpf_prog_aux {
const char *attach_func_name;
struct bpf_prog **func;
void *jit_data; /* JIT specific data. arch dependent */
struct bpf_jit_poke_descriptor *poke_tab;
u32 size_poke_tab;
struct latch_tree_node ksym_tnode;
struct list_head ksym_lnode;
const struct bpf_prog_ops *ops;

10
include/linux/filter.h
View File

@ -952,6 +952,9 @@ void *bpf_jit_alloc_exec(unsigned long size);
void bpf_jit_free_exec(void *addr);
void bpf_jit_free(struct bpf_prog *fp);
int bpf_jit_add_poke_descriptor(struct bpf_prog *prog,
struct bpf_jit_poke_descriptor *poke);
int bpf_jit_get_func_addr(const struct bpf_prog *prog,
const struct bpf_insn *insn, bool extra_pass,
u64 *func_addr, bool *func_addr_fixed);
@ -1055,6 +1058,13 @@ static inline bool bpf_prog_ebpf_jited(const struct bpf_prog *fp)
return false;
}
static inline int
bpf_jit_add_poke_descriptor(struct bpf_prog *prog,
struct bpf_jit_poke_descriptor *poke)
{
return -ENOTSUPP;
}
static inline void bpf_jit_free(struct bpf_prog *fp)
{
bpf_prog_unlock_free(fp);

34
kernel/bpf/core.c
View File

@ -256,6 +256,7 @@ void __bpf_prog_free(struct bpf_prog *fp)
{
if (fp->aux) {
free_percpu(fp->aux->stats);
kfree(fp->aux->poke_tab);
kfree(fp->aux);
}
vfree(fp);
@ -756,6 +757,39 @@ int bpf_get_kallsym(unsigned int symnum, unsigned long *value, char *type,
return ret;
}
int bpf_jit_add_poke_descriptor(struct bpf_prog *prog,
struct bpf_jit_poke_descriptor *poke)
{
struct bpf_jit_poke_descriptor *tab = prog->aux->poke_tab;
static const u32 poke_tab_max = 1024;
u32 slot = prog->aux->size_poke_tab;
u32 size = slot + 1;
if (size > poke_tab_max)
return -ENOSPC;
if (poke->ip || poke->ip_stable || poke->adj_off)
return -EINVAL;
switch (poke->reason) {
case BPF_POKE_REASON_TAIL_CALL:
if (!poke->tail_call.map)
return -EINVAL;
break;
default:
return -EINVAL;
}
tab = krealloc(tab, size * sizeof(*poke), GFP_KERNEL);
if (!tab)
return -ENOMEM;
memcpy(&tab[slot], poke, sizeof(*poke));
prog->aux->size_poke_tab = size;
prog->aux->poke_tab = tab;
return slot;
}
static atomic_long_t bpf_jit_current;
/* Can be overridden by an arch's JIT compiler if it has a custom,