[tmp] libbpf: support new LLVM llvm/llvm-project#149715

Signed-off-by: Anton Protopopov <[email protected]>

Author: aspsk

tools/lib/bpf/libbpf.c

@@ -372,6 +372,7 @@ enum reloc_type {
 	RELO_EXTERN_CALL,
 	RELO_SUBPROG_ADDR,
 	RELO_CORE,
+	RELO_INSN_ARRAY,
 };
 
 struct reloc_desc {
@@ -383,6 +384,7 @@ struct reloc_desc {
 			int map_idx;
 			int sym_off;
 			int ext_idx;
+			int sym_size;
 		};
 	};
 };
@@ -664,6 +666,7 @@ struct elf_state {
 	Elf_Data *symbols;
 	Elf_Data *arena_data;
 	Elf_Data *jt_sizes_data;
+	Elf_Data *jumptables_data;
 	size_t shstrndx; /* section index for section name strings */
 	size_t strtabidx;
 	struct elf_sec_desc *secs;
@@ -675,6 +678,7 @@ struct elf_state {
 	bool has_st_ops;
 	int arena_data_shndx;
 	int jt_sizes_data_shndx;
+	int jumptables_data_shndx;
 };
 
 struct usdt_manager;
@@ -4064,6 +4068,11 @@ static int bpf_object__elf_collect(struct bpf_object *obj)
 			} else if (strcmp(name, ARENA_SEC) == 0) {
 				obj->efile.arena_data = data;
 				obj->efile.arena_data_shndx = idx;
+			} else if (strcmp(name, ".jumptables") == 0) {
+				// XXX, do it properly, otherwise ->d_buf is eventually corrupted
+				obj->efile.jumptables_data = calloc(1, sizeof(*data));
+				memcpy(obj->efile.jumptables_data, data, sizeof(*data));
+				obj->efile.jumptables_data_shndx = idx;
 			} else {
 				pr_info("elf: skipping unrecognized data section(%d) %s\n",
 					idx, name);
@@ -4712,6 +4721,16 @@ static int bpf_program__record_reloc(struct bpf_program *prog,
 		return 0;
 	}
 
+	/* jump table data relocation */
+	if (shdr_idx == obj->efile.jumptables_data_shndx) {
+		reloc_desc->type = RELO_INSN_ARRAY;
+		reloc_desc->insn_idx = insn_idx;
+		reloc_desc->map_idx = -1;
+		reloc_desc->sym_off = sym->st_value; // XXX ?
+		reloc_desc->sym_size = sym->st_size;
+		return 0;
+	}
+
 	/* generic map reference relocation */
 	if (type == LIBBPF_MAP_UNSPEC) {
 		if (!bpf_object__shndx_is_maps(obj, shdr_idx)) {
@@ -6204,12 +6223,7 @@ static void poison_kfunc_call(struct bpf_program *prog, int relo_idx,
 	insn->imm = POISON_CALL_KFUNC_BASE + ext_idx;
 }
 
-static bool map_fd_is_rodata(struct bpf_object *obj, int map_fd)
-{
-	return map_fd == obj->rodata_map_fd;
-}
-
-static int create_jt_map(const struct jt *jt, int adjust_off)
+static int create_jt_map(struct bpf_object *obj, int off, int size, int adjust_off)
 {
 	static union bpf_attr attr = {
 		.map_type = BPF_MAP_TYPE_INSN_ARRAY,
@@ -6221,15 +6235,20 @@ static int create_jt_map(const struct jt *jt, int adjust_off)
 	int map_fd;
 	int err;
 	__u32 i;
+	__u32 *jt;
 
-	attr.max_entries = jt->jump_target_cnt;
+	attr.max_entries = size / 4;
 
 	map_fd = syscall(__NR_bpf, BPF_MAP_CREATE, &attr, sizeof(attr));
 	if (map_fd < 0)
 		return map_fd;
 
-	for (i = 0; i < jt->jump_target_cnt; i++) {
-		val.xlated_off = jt->jump_target[i] + adjust_off;
+	jt = (__u32 *)(obj->efile.jumptables_data->d_buf + off);
+	if (!jt)
+		return -EINVAL;
+
+	for (i = 0; i < attr.max_entries; i++) {
+		val.xlated_off = jt[2*i]/8 + adjust_off;
 		err = bpf_map_update_elem(map_fd, &i, &val, 0);
 		if (err) {
 			close(map_fd);
@@ -6257,6 +6276,7 @@ static int subprog_insn_off(struct bpf_program *prog, int insn_idx)
 	return -prog->sec_insn_off;
 }
 
+
 /* Relocate data references within program code:
  *  - map references;
  *  - global variable references;
@@ -6294,31 +6314,8 @@ bpf_object__relocate_data(struct bpf_object *obj, struct bpf_program *prog)
 				insn[0].src_reg = BPF_PSEUDO_MAP_IDX_VALUE;
 				insn[0].imm = relo->map_idx;
 			} else if (map->autocreate) {
-				const struct jt *jt;
-				int ajdust_insn_off;
-				int map_fd = map->fd;
-
-				/*
-				 * Set imm to proper map file descriptor. In normal case,
-				 * it is just map->fd. However, in case of a jump table,
-				 * a new map file descriptor should be created
-				 */
-				jt = bpf_object__find_jt(obj, insn[1].imm / 8);
-				if (map_fd_is_rodata(obj, map_fd) && !IS_ERR(jt)) {
-					ajdust_insn_off = subprog_insn_off(prog, relo->insn_idx);
-					map_fd = create_jt_map(jt, ajdust_insn_off);
-					if (map_fd < 0) {
-						pr_warn("prog '%s': relo #%d: failed to create a jt map for .rodata offset %u\n",
-								prog->name, i, insn[1].imm / 8);
-						return map_fd;
-					}
-
-					/* a new map is created, so offset should be 0 */
-					insn[1].imm = 0;
-				}
-
 				insn[0].src_reg = BPF_PSEUDO_MAP_VALUE;
-				insn[0].imm = map_fd;
+				insn[0].imm = map->fd;
 			} else {
 				poison_map_ldimm64(prog, i, relo->insn_idx, insn,
 						   relo->map_idx, map);
@@ -6371,6 +6368,20 @@ bpf_object__relocate_data(struct bpf_object *obj, struct bpf_program *prog)
 		case RELO_CORE:
 			/* will be handled by bpf_program_record_relos() */
 			break;
+		case RELO_INSN_ARRAY: {
+			int map_fd;
+
+			map_fd = create_jt_map(obj, relo->sym_off, relo->sym_size, subprog_insn_off(prog, relo->insn_idx));
+			if (map_fd < 0) {
+				pr_warn("prog '%s': relo #%d: failed to create a jt map for .rodata offset %u\n",
+						prog->name, i, relo->sym_off);
+				return map_fd;
+			}
+				insn[0].src_reg = BPF_PSEUDO_MAP_VALUE;
+			insn->imm = map_fd;
+			insn->off = 0;
+		}
+			break;
 		default:
 			pr_warn("prog '%s': relo #%d: bad relo type %d\n",
 				prog->name, i, relo->type);

tools/lib/bpf/linker.c

@@ -29,6 +29,7 @@
 
 #define BTF_EXTERN_SEC ".extern"
 #define RODATA_REL_SEC ".rel.rodata"
+#define JUMPTABLES_REL_SEC ".rel.jumptables"
 #define LLVM_JT_SIZES_REL_SEC ".rel.llvm_jump_table_sizes"
 
 struct src_sec {
@@ -2084,6 +2085,9 @@ static int linker_append_elf_sym(struct bpf_linker *linker, struct src_obj *obj,
 			obj->sym_map[src_sym_idx] = dst_sec->sec_sym_idx;
 			return 0;
 		}
+
+		if (!strcmp(src_sec->sec_name, ".jumptables"))
+			goto add_sym;
 	}
 
 	if (sym_bind == STB_LOCAL)
@@ -2331,7 +2335,8 @@ static int linker_append_elf_relos(struct bpf_linker *linker, struct src_obj *ob
 					else
 						insn->imm += sec->dst_off;
 				} else if (strcmp(src_sec->sec_name, LLVM_JT_SIZES_REL_SEC) &&
-					   strcmp(src_sec->sec_name, RODATA_REL_SEC)) {
+					   strcmp(src_sec->sec_name, RODATA_REL_SEC) &&
+					   strcmp(src_sec->sec_name, JUMPTABLES_REL_SEC)) {
 					pr_warn("relocation against STT_SECTION in section %s is not supported!\n",
 						src_sec->sec_name);
 					return -EINVAL;