libbpf: Sanitize global functions

In case the kernel doesn't support BTF_FUNC_GLOBAL sanitize BTF produced by the compiler for global functions.

Alexei Starovoitov committed 6 years ago

Commit 2d3eb671 parent f41aa382 files · +40 −1Browse files

Unified · Split

2 files

tools/include/uapi/linux/btf.h +6 −0
tools/lib/bpf/libbpf.c +34 −1

@@ -146,6 +146,12 @@ enum { · 145 unmodified lines
146	146	BTF_VAR_GLOBAL_EXTERN = 2,
147	147	};
148	148
	149	+enum btf_func_linkage {
	150	+ BTF_FUNC_STATIC = 0,
	151	+ BTF_FUNC_GLOBAL = 1,
	152	+ BTF_FUNC_EXTERN = 2,
	153	+};
	154	+
149	155	/* BTF_KIND_VAR is followed by a single "struct btf_var" to describe
150	156	* additional information related to the variable such as its linkage.
151	157	*/

tools/lib/bpf/libbpf.c+34−1

@@ -173,6 +173,8 @@ struct bpf_capabilities { · 172 unmodified lines
173	173	__u32 btf_datasec:1;
174	174	/* BPF_F_MMAPABLE is supported for arrays */
175	175	__u32 array_mmap:1;
	176	+ /* BTF_FUNC_GLOBAL is supported */
	177	+ __u32 btf_func_global:1;
176	178	};
177	179
178	180	enum reloc_type {
@@ -2209,13 +2211,14 @@ static bool section_have_execinstr(struct bpf_object *obj, int idx) · 2030 unmodified lines
2209	2211
2210	2212	static void bpf_object__sanitize_btf(struct bpf_object *obj)
2211	2213	{
	2214	+ bool has_func_global = obj->caps.btf_func_global;
2212	2215	bool has_datasec = obj->caps.btf_datasec;
2213	2216	bool has_func = obj->caps.btf_func;
2214	2217	struct btf *btf = obj->btf;
2215	2218	struct btf_type *t;
2216	2219	int i, j, vlen;
2217	2220
2218		− if (!obj->btf \|\| (has_func && has_datasec))
	2221	+ if (!obj->btf \|\| (has_func && has_datasec && has_func_global))
2219	2222	return;
2220	2223
2221	2224	for (i = 1; i <= btf__get_nr_types(btf); i++) {
@@ -2263,6 +2266,9 @@ static void bpf_object__sanitize_btf(struct bpf_object *obj) · 41 unmodified lines
2263	2266	} else if (!has_func && btf_is_func(t)) {
2264	2267	/* replace FUNC with TYPEDEF */
2265	2268	t->info = BTF_INFO_ENC(BTF_KIND_TYPEDEF, 0, 0);
	2269	+ } else if (!has_func_global && btf_is_func(t)) {
	2270	+ /* replace BTF_FUNC_GLOBAL with BTF_FUNC_STATIC */
	2271	+ t->info = BTF_INFO_ENC(BTF_KIND_FUNC, 0, 0);
2266	2272	}
2267	2273	}
2268	2274	}
@@ -3205,6 +3211,32 @@ static int bpf_object__probe_btf_func(struct bpf_object *obj) · 936 unmodified lines
3205	3211	return 0;
3206	3212	}
3207	3213
	3214	+static int bpf_object__probe_btf_func_global(struct bpf_object *obj)
	3215	+{
	3216	+ static const char strs[] = "\0int\0x\0a";
	3217	+ /* static void x(int a) {} */
	3218	+ __u32 types[] = {
	3219	+ /* int */
	3220	+ BTF_TYPE_INT_ENC(1, BTF_INT_SIGNED, 0, 32, 4), /* [1] */
	3221	+ /* FUNC_PROTO / / [2] */
	3222	+ BTF_TYPE_ENC(0, BTF_INFO_ENC(BTF_KIND_FUNC_PROTO, 0, 1), 0),
	3223	+ BTF_PARAM_ENC(7, 1),
	3224	+ /* FUNC x BTF_FUNC_GLOBAL / / [3] */
	3225	+ BTF_TYPE_ENC(5, BTF_INFO_ENC(BTF_KIND_FUNC, 0, BTF_FUNC_GLOBAL), 2),
	3226	+ };
	3227	+ int btf_fd;
	3228	+
	3229	+ btf_fd = libbpf__load_raw_btf((char *)types, sizeof(types),
	3230	+ strs, sizeof(strs));
	3231	+ if (btf_fd >= 0) {
	3232	+ obj->caps.btf_func_global = 1;
	3233	+ close(btf_fd);
	3234	+ return 1;
	3235	+ }
	3236	+
	3237	+ return 0;
	3238	+}
	3239	+
3208	3240	static int bpf_object__probe_btf_datasec(struct bpf_object *obj)
3209	3241	{
3210	3242	static const char strs[] = "\0x\0.data";
@@ -3260,6 +3292,7 @@ bpf_object__probe_caps(struct bpf_object *obj) · 49 unmodified lines
3260	3292	bpf_object__probe_name,
3261	3293	bpf_object__probe_global_data,
3262	3294	bpf_object__probe_btf_func,
	3295	+ bpf_object__probe_btf_func_global,
3263	3296	bpf_object__probe_btf_datasec,
3264	3297	bpf_object__probe_array_mmap,
3265	3298	};