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author | Lawrence Brakmo <brakmo@fb.com> | 2018-01-25 16:14:08 -0800 |
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committer | Alexei Starovoitov <ast@kernel.org> | 2018-01-25 16:41:14 -0800 |
commit | b73042b8a28e2603ac178295ab96c876ba5a97a1 (patch) | |
tree | c3db00b9c7a9b9816bb3392f9fa59f7d8b4a5e49 /net/core | |
parent | 34d367c59233464dbd1f07445c4665099a7128ec (diff) | |
download | linux-b73042b8a28e2603ac178295ab96c876ba5a97a1.tar.gz linux-b73042b8a28e2603ac178295ab96c876ba5a97a1.tar.bz2 linux-b73042b8a28e2603ac178295ab96c876ba5a97a1.zip |
bpf: Add write access to tcp_sock and sock fields
This patch adds a macro, SOCK_OPS_SET_FIELD, for writing to
struct tcp_sock or struct sock fields. This required adding a new
field "temp" to struct bpf_sock_ops_kern for temporary storage that
is used by sock_ops_convert_ctx_access. It is used to store and recover
the contents of a register, so the register can be used to store the
address of the sk. Since we cannot overwrite the dst_reg because it
contains the pointer to ctx, nor the src_reg since it contains the value
we want to store, we need an extra register to contain the address
of the sk.
Also adds the macro SOCK_OPS_GET_OR_SET_FIELD that calls one of the
GET or SET macros depending on the value of the TYPE field.
Signed-off-by: Lawrence Brakmo <brakmo@fb.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'net/core')
-rw-r--r-- | net/core/filter.c | 48 |
1 files changed, 48 insertions, 0 deletions
diff --git a/net/core/filter.c b/net/core/filter.c index dbb6d2f60680..c356ec02b1a5 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -4491,6 +4491,54 @@ static u32 sock_ops_convert_ctx_access(enum bpf_access_type type, offsetof(OBJ, OBJ_FIELD)); \ } while (0) +/* Helper macro for adding write access to tcp_sock or sock fields. + * The macro is called with two registers, dst_reg which contains a pointer + * to ctx (context) and src_reg which contains the value that should be + * stored. However, we need an additional register since we cannot overwrite + * dst_reg because it may be used later in the program. + * Instead we "borrow" one of the other register. We first save its value + * into a new (temp) field in bpf_sock_ops_kern, use it, and then restore + * it at the end of the macro. + */ +#define SOCK_OPS_SET_FIELD(BPF_FIELD, OBJ_FIELD, OBJ) \ + do { \ + int reg = BPF_REG_9; \ + BUILD_BUG_ON(FIELD_SIZEOF(OBJ, OBJ_FIELD) > \ + FIELD_SIZEOF(struct bpf_sock_ops, BPF_FIELD)); \ + if (si->dst_reg == reg || si->src_reg == reg) \ + reg--; \ + if (si->dst_reg == reg || si->src_reg == reg) \ + reg--; \ + *insn++ = BPF_STX_MEM(BPF_DW, si->dst_reg, reg, \ + offsetof(struct bpf_sock_ops_kern, \ + temp)); \ + *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF( \ + struct bpf_sock_ops_kern, \ + is_fullsock), \ + reg, si->dst_reg, \ + offsetof(struct bpf_sock_ops_kern, \ + is_fullsock)); \ + *insn++ = BPF_JMP_IMM(BPF_JEQ, reg, 0, 2); \ + *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF( \ + struct bpf_sock_ops_kern, sk),\ + reg, si->dst_reg, \ + offsetof(struct bpf_sock_ops_kern, sk));\ + *insn++ = BPF_STX_MEM(BPF_FIELD_SIZEOF(OBJ, OBJ_FIELD), \ + reg, si->src_reg, \ + offsetof(OBJ, OBJ_FIELD)); \ + *insn++ = BPF_LDX_MEM(BPF_DW, reg, si->dst_reg, \ + offsetof(struct bpf_sock_ops_kern, \ + temp)); \ + } while (0) + +#define SOCK_OPS_GET_OR_SET_FIELD(BPF_FIELD, OBJ_FIELD, OBJ, TYPE) \ + do { \ + if (TYPE == BPF_WRITE) \ + SOCK_OPS_SET_FIELD(BPF_FIELD, OBJ_FIELD, OBJ); \ + else \ + SOCK_OPS_GET_FIELD(BPF_FIELD, OBJ_FIELD, OBJ); \ + } while (0) + case offsetof(struct bpf_sock_ops, snd_cwnd): SOCK_OPS_GET_FIELD(snd_cwnd, snd_cwnd, struct tcp_sock); break; |