libbpf: Sanitize BPF program code for bpf_probe_read_{kernel, user}[_str] (109cea5a) · Commits · 戴 / test

tools/lib/bpf/libbpf.c

+80 −0

Original line number	Diff line number	Diff line
		@@ -180,6 +180,8 @@ enum kern_feature_id {
		FEAT_ARRAY_MMAP,
		/* kernel support for expected_attach_type in BPF_PROG_LOAD */
		FEAT_EXP_ATTACH_TYPE,
		/* bpf_probe_read_{kernel,user}[_str] helpers */
		FEAT_PROBE_READ_KERN,
		__FEAT_CNT,
		};

		@@ -3591,6 +3593,27 @@ static int probe_kern_exp_attach_type(void)
		return probe_fd(bpf_load_program_xattr(&attr, NULL, 0));
		}

		static int probe_kern_probe_read_kernel(void)
		{
		struct bpf_load_program_attr attr;
		struct bpf_insn insns[] = {
		BPF_MOV64_REG(BPF_REG_1, BPF_REG_10), /* r1 = r10 (fp) */
		BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -8), /* r1 += -8 */
		BPF_MOV64_IMM(BPF_REG_2, 8), /* r2 = 8 */
		BPF_MOV64_IMM(BPF_REG_3, 0), /* r3 = 0 */
		BPF_RAW_INSN(BPF_JMP \| BPF_CALL, 0, 0, 0, BPF_FUNC_probe_read_kernel),
		BPF_EXIT_INSN(),
		};

		memset(&attr, 0, sizeof(attr));
		attr.prog_type = BPF_PROG_TYPE_KPROBE;
		attr.insns = insns;
		attr.insns_cnt = ARRAY_SIZE(insns);
		attr.license = "GPL";

		return probe_fd(bpf_load_program_xattr(&attr, NULL, 0));
		}

		enum kern_feature_result {
		FEAT_UNKNOWN = 0,
		FEAT_SUPPORTED = 1,
		@@ -3626,6 +3649,9 @@ static struct kern_feature_desc {
		"BPF_PROG_LOAD expected_attach_type attribute",
		probe_kern_exp_attach_type,
		},
		[FEAT_PROBE_READ_KERN] = {
		"bpf_probe_read_kernel() helper", probe_kern_probe_read_kernel,
		}
		};

		static bool kernel_supports(enum kern_feature_id feat_id)
		@@ -5335,6 +5361,53 @@ static int bpf_object__collect_reloc(struct bpf_object *obj)
		return 0;
		}

		static bool insn_is_helper_call(struct bpf_insn insn, enum bpf_func_id func_id)
		{
		__u8 class = BPF_CLASS(insn->code);

		if ((class == BPF_JMP \|\| class == BPF_JMP32) &&
		BPF_OP(insn->code) == BPF_CALL &&
		BPF_SRC(insn->code) == BPF_K &&
		insn->src_reg == 0 && insn->dst_reg == 0) {
		if (func_id)
		*func_id = insn->imm;
		return true;
		}
		return false;
		}

		static int bpf_object__sanitize_prog(struct bpf_object* obj, struct bpf_program *prog)
		{
		struct bpf_insn *insn = prog->insns;
		enum bpf_func_id func_id;
		int i;

		for (i = 0; i < prog->insns_cnt; i++, insn++) {
		if (!insn_is_helper_call(insn, &func_id))
		continue;

		/* on kernels that don't yet support
		* bpf_probe_read_{kernel,user}[_str] helpers, fall back
		* to bpf_probe_read() which works well for old kernels
		*/
		switch (func_id) {
		case BPF_FUNC_probe_read_kernel:
		case BPF_FUNC_probe_read_user:
		if (!kernel_supports(FEAT_PROBE_READ_KERN))
		insn->imm = BPF_FUNC_probe_read;
		break;
		case BPF_FUNC_probe_read_kernel_str:
		case BPF_FUNC_probe_read_user_str:
		if (!kernel_supports(FEAT_PROBE_READ_KERN))
		insn->imm = BPF_FUNC_probe_read_str;
		break;
		default:
		break;
		}
		}
		return 0;
		}

		static int
		load_program(struct bpf_program prog, struct bpf_insn insns, int insns_cnt,
		char license, __u32 kern_version, int pfd)
		@@ -5549,6 +5622,13 @@ bpf_object__load_progs(struct bpf_object *obj, int log_level)
		size_t i;
		int err;

		for (i = 0; i < obj->nr_programs; i++) {
		prog = &obj->programs[i];
		err = bpf_object__sanitize_prog(obj, prog);
		if (err)
		return err;
		}

		for (i = 0; i < obj->nr_programs; i++) {
		prog = &obj->programs[i];
		if (bpf_program__is_function_storage(prog, obj))

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