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bpf: Introduce bpf_jit_binary_pack_[alloc|finalize|free]

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This is the jit binary allocator built on top of bpf_prog_pack.

bpf_prog_pack allocates RO memory, which cannot be used directly by the
JIT engine. Therefore, a temporary rw buffer is allocated for the JIT
engine. Once JIT is done, bpf_jit_binary_pack_finalize is used to copy
the program to the RO memory.

bpf_jit_binary_pack_alloc reserves 16 bytes of extra space for illegal
instructions, which is small than the 128 bytes space reserved by
bpf_jit_binary_alloc. This change is necessary for bpf_jit_binary_hdr
to find the correct header. Also, flag use_bpf_prog_pack is added to
differentiate a program allocated by bpf_jit_binary_pack_alloc.

Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220204185742.271030-9-song@kernel.org
This commit is contained in:
Song Liu
2022-02-04 10:57:41 -08:00
committed by Alexei Starovoitov
parent 57631054fa
commit 33c9805860
3 changed files with 120 additions and 10 deletions
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21
include/linux/filter.h
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@@ -890,15 +890,6 @@ static inline void bpf_jit_binary_lock_ro(struct bpf_binary_header *hdr)
set_memory_x((unsigned long)hdr, hdr->size >> PAGE_SHIFT);
}
static inline struct bpf_binary_header *
bpf_jit_binary_hdr(const struct bpf_prog *fp)
{
unsigned long real_start = (unsigned long)fp->bpf_func;
unsigned long addr = real_start & PAGE_MASK;
return (void *)addr;
}
int sk_filter_trim_cap(struct sock *sk, struct sk_buff *skb, unsigned int cap);
static inline int sk_filter(struct sock *sk, struct sk_buff *skb)
{
@@ -1068,6 +1059,18 @@ void *bpf_jit_alloc_exec(unsigned long size);
void bpf_jit_free_exec(void *addr);
void bpf_jit_free(struct bpf_prog *fp);
struct bpf_binary_header *
bpf_jit_binary_pack_alloc(unsigned int proglen, u8 **ro_image,
unsigned int alignment,
struct bpf_binary_header **rw_hdr,
u8 **rw_image,
bpf_jit_fill_hole_t bpf_fill_ill_insns);
int bpf_jit_binary_pack_finalize(struct bpf_prog *prog,
struct bpf_binary_header *ro_header,
struct bpf_binary_header *rw_header);
void bpf_jit_binary_pack_free(struct bpf_binary_header *ro_header,
struct bpf_binary_header *rw_header);
int bpf_jit_add_poke_descriptor(struct bpf_prog *prog,
struct bpf_jit_poke_descriptor *poke);