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From: Andrii Nakryiko <andriin@fb.com>
To: <andrii.nakryiko@gmail.com>, <bpf@vger.kernel.org>,
	<netdev@vger.kernel.org>, <ast@fb.com>, <daniel@iogearbox.net>,
	<kernel-team@fb.com>
Cc: Andrii Nakryiko <andriin@fb.com>
Subject: [PATCH bpf-next 2/8] libbpf: extract BTF loading and simplify ELF parsing logic
Date: Mon, 10 Jun 2019 21:47:41 -0700
Message-ID: <20190611044747.44839-3-andriin@fb.com> (raw)
In-Reply-To: <20190611044747.44839-1-andriin@fb.com>

As a preparation for adding BTF-based BPF map loading, extract .BTF and
.BTF.ext loading logic. Also simplify error handling in
bpf_object__elf_collect() by returning early, as there is no common
clean up to be done.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
---
 tools/lib/bpf/libbpf.c | 137 ++++++++++++++++++++++-------------------
 1 file changed, 75 insertions(+), 62 deletions(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index ba89d9727137..9e39a0a33aeb 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -1078,6 +1078,58 @@ static void bpf_object__sanitize_btf_ext(struct bpf_object *obj)
 	}
 }
 
+static int bpf_object__load_btf(struct bpf_object *obj,
+				Elf_Data *btf_data,
+				Elf_Data *btf_ext_data)
+{
+	int err = 0;
+
+	if (btf_data) {
+		obj->btf = btf__new(btf_data->d_buf, btf_data->d_size);
+		if (IS_ERR(obj->btf)) {
+			pr_warning("Error loading ELF section %s: %d.\n",
+				   BTF_ELF_SEC, err);
+			goto out;
+		}
+		err = btf__finalize_data(obj, obj->btf);
+		if (err) {
+			pr_warning("Error finalizing %s: %d.\n",
+				   BTF_ELF_SEC, err);
+			goto out;
+		}
+		bpf_object__sanitize_btf(obj);
+		err = btf__load(obj->btf);
+		if (err) {
+			pr_warning("Error loading %s into kernel: %d.\n",
+				   BTF_ELF_SEC, err);
+			goto out;
+		}
+	}
+	if (btf_ext_data) {
+		if (!obj->btf) {
+			pr_debug("Ignore ELF section %s because its depending ELF section %s is not found.\n",
+				 BTF_EXT_ELF_SEC, BTF_ELF_SEC);
+			goto out;
+		}
+		obj->btf_ext = btf_ext__new(btf_ext_data->d_buf,
+					    btf_ext_data->d_size);
+		if (IS_ERR(obj->btf_ext)) {
+			pr_warning("Error loading ELF section %s: %ld. Ignored and continue.\n",
+				   BTF_EXT_ELF_SEC, PTR_ERR(obj->btf_ext));
+			obj->btf_ext = NULL;
+			goto out;
+		}
+		bpf_object__sanitize_btf_ext(obj);
+	}
+out:
+	if (err || IS_ERR(obj->btf)) {
+		if (!IS_ERR_OR_NULL(obj->btf))
+			btf__free(obj->btf);
+		obj->btf = NULL;
+	}
+	return 0;
+}
+
 static int bpf_object__elf_collect(struct bpf_object *obj, int flags)
 {
 	Elf *elf = obj->efile.elf;
@@ -1102,24 +1154,21 @@ static int bpf_object__elf_collect(struct bpf_object *obj, int flags)
 		if (gelf_getshdr(scn, &sh) != &sh) {
 			pr_warning("failed to get section(%d) header from %s\n",
 				   idx, obj->path);
-			err = -LIBBPF_ERRNO__FORMAT;
-			goto out;
+			return -LIBBPF_ERRNO__FORMAT;
 		}
 
 		name = elf_strptr(elf, ep->e_shstrndx, sh.sh_name);
 		if (!name) {
 			pr_warning("failed to get section(%d) name from %s\n",
 				   idx, obj->path);
-			err = -LIBBPF_ERRNO__FORMAT;
-			goto out;
+			return -LIBBPF_ERRNO__FORMAT;
 		}
 
 		data = elf_getdata(scn, 0);
 		if (!data) {
 			pr_warning("failed to get section(%d) data from %s(%s)\n",
 				   idx, name, obj->path);
-			err = -LIBBPF_ERRNO__FORMAT;
-			goto out;
+			return -LIBBPF_ERRNO__FORMAT;
 		}
 		pr_debug("section(%d) %s, size %ld, link %d, flags %lx, type=%d\n",
 			 idx, name, (unsigned long)data->d_size,
@@ -1130,10 +1179,14 @@ static int bpf_object__elf_collect(struct bpf_object *obj, int flags)
 			err = bpf_object__init_license(obj,
 						       data->d_buf,
 						       data->d_size);
+			if (err)
+				return err;
 		} else if (strcmp(name, "version") == 0) {
 			err = bpf_object__init_kversion(obj,
 							data->d_buf,
 							data->d_size);
+			if (err)
+				return err;
 		} else if (strcmp(name, "maps") == 0) {
 			obj->efile.maps_shndx = idx;
 		} else if (strcmp(name, BTF_ELF_SEC) == 0) {
@@ -1144,11 +1197,10 @@ static int bpf_object__elf_collect(struct bpf_object *obj, int flags)
 			if (obj->efile.symbols) {
 				pr_warning("bpf: multiple SYMTAB in %s\n",
 					   obj->path);
-				err = -LIBBPF_ERRNO__FORMAT;
-			} else {
-				obj->efile.symbols = data;
-				obj->efile.strtabidx = sh.sh_link;
+				return -LIBBPF_ERRNO__FORMAT;
 			}
+			obj->efile.symbols = data;
+			obj->efile.strtabidx = sh.sh_link;
 		} else if (sh.sh_type == SHT_PROGBITS && data->d_size > 0) {
 			if (sh.sh_flags & SHF_EXECINSTR) {
 				if (strcmp(name, ".text") == 0)
@@ -1162,6 +1214,7 @@ static int bpf_object__elf_collect(struct bpf_object *obj, int flags)
 
 					pr_warning("failed to alloc program %s (%s): %s",
 						   name, obj->path, cp);
+					return err;
 				}
 			} else if (strcmp(name, ".data") == 0) {
 				obj->efile.data = data;
@@ -1173,8 +1226,8 @@ static int bpf_object__elf_collect(struct bpf_object *obj, int flags)
 				pr_debug("skip section(%d) %s\n", idx, name);
 			}
 		} else if (sh.sh_type == SHT_REL) {
+			int nr_reloc = obj->efile.nr_reloc;
 			void *reloc = obj->efile.reloc;
-			int nr_reloc = obj->efile.nr_reloc + 1;
 			int sec = sh.sh_info; /* points to other section */
 
 			/* Only do relo for section with exec instructions */
@@ -1184,79 +1237,39 @@ static int bpf_object__elf_collect(struct bpf_object *obj, int flags)
 				continue;
 			}
 
-			reloc = reallocarray(reloc, nr_reloc,
+			reloc = reallocarray(reloc, nr_reloc + 1,
 					     sizeof(*obj->efile.reloc));
 			if (!reloc) {
 				pr_warning("realloc failed\n");
-				err = -ENOMEM;
-			} else {
-				int n = nr_reloc - 1;
+				return -ENOMEM;
+			}
 
-				obj->efile.reloc = reloc;
-				obj->efile.nr_reloc = nr_reloc;
+			obj->efile.reloc = reloc;
+			obj->efile.nr_reloc++;
 
-				obj->efile.reloc[n].shdr = sh;
-				obj->efile.reloc[n].data = data;
-			}
+			obj->efile.reloc[nr_reloc].shdr = sh;
+			obj->efile.reloc[nr_reloc].data = data;
 		} else if (sh.sh_type == SHT_NOBITS && strcmp(name, ".bss") == 0) {
 			obj->efile.bss = data;
 			obj->efile.bss_shndx = idx;
 		} else {
 			pr_debug("skip section(%d) %s\n", idx, name);
 		}
-		if (err)
-			goto out;
 	}
 
 	if (!obj->efile.strtabidx || obj->efile.strtabidx >= idx) {
 		pr_warning("Corrupted ELF file: index of strtab invalid\n");
 		return -LIBBPF_ERRNO__FORMAT;
 	}
-	if (btf_data) {
-		obj->btf = btf__new(btf_data->d_buf, btf_data->d_size);
-		if (IS_ERR(obj->btf)) {
-			pr_warning("Error loading ELF section %s: %ld. Ignored and continue.\n",
-				   BTF_ELF_SEC, PTR_ERR(obj->btf));
-			obj->btf = NULL;
-		} else {
-			err = btf__finalize_data(obj, obj->btf);
-			if (!err) {
-				bpf_object__sanitize_btf(obj);
-				err = btf__load(obj->btf);
-			}
-			if (err) {
-				pr_warning("Error finalizing and loading %s into kernel: %d. Ignored and continue.\n",
-					   BTF_ELF_SEC, err);
-				btf__free(obj->btf);
-				obj->btf = NULL;
-				err = 0;
-			}
-		}
-	}
-	if (btf_ext_data) {
-		if (!obj->btf) {
-			pr_debug("Ignore ELF section %s because its depending ELF section %s is not found.\n",
-				 BTF_EXT_ELF_SEC, BTF_ELF_SEC);
-		} else {
-			obj->btf_ext = btf_ext__new(btf_ext_data->d_buf,
-						    btf_ext_data->d_size);
-			if (IS_ERR(obj->btf_ext)) {
-				pr_warning("Error loading ELF section %s: %ld. Ignored and continue.\n",
-					   BTF_EXT_ELF_SEC,
-					   PTR_ERR(obj->btf_ext));
-				obj->btf_ext = NULL;
-			} else {
-				bpf_object__sanitize_btf_ext(obj);
-			}
-		}
-	}
+	err = bpf_object__load_btf(obj, btf_data, btf_ext_data);
+	if (err)
+		return err;
 	if (bpf_object__has_maps(obj)) {
 		err = bpf_object__init_maps(obj, flags);
 		if (err)
-			goto out;
+			return err;
 	}
 	err = bpf_object__init_prog_names(obj);
-out:
 	return err;
 }
 
-- 
2.17.1


  parent reply index

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-11  4:47 [PATCH bpf-next 0/8] BTF-defined BPF map definitions Andrii Nakryiko
2019-06-11  4:47 ` [PATCH bpf-next 1/8] libbpf: add common min/max macro to libbpf_internal.h Andrii Nakryiko
2019-06-15 20:26   ` Song Liu
2019-06-11  4:47 ` Andrii Nakryiko [this message]
2019-06-15 20:25   ` [PATCH bpf-next 2/8] libbpf: extract BTF loading and simplify ELF parsing logic Song Liu
2019-06-15 20:28     ` Song Liu
2019-06-17 17:46       ` Andrii Nakryiko
2019-06-17 17:24     ` Andrii Nakryiko
2019-06-17 18:07       ` Song Liu
2019-06-17 18:35         ` Andrii Nakryiko
2019-06-11  4:47 ` [PATCH bpf-next 3/8] libbpf: refactor map initialization Andrii Nakryiko
2019-06-11  4:47 ` [PATCH bpf-next 4/8] libbpf: identify maps by section index in addition to offset Andrii Nakryiko
2019-06-11  4:47 ` [PATCH bpf-next 5/8] libbpf: split initialization and loading of BTF Andrii Nakryiko
2019-06-15 21:21   ` Song Liu
2019-06-11  4:47 ` [PATCH bpf-next 6/8] libbpf: allow specifying map definitions using BTF Andrii Nakryiko
2019-06-15 22:00   ` Song Liu
2019-06-17 18:33     ` Andrii Nakryiko
2019-06-11  4:47 ` [PATCH bpf-next 7/8] selftests/bpf: add test for BTF-defined maps Andrii Nakryiko
2019-06-15 22:05   ` Song Liu
2019-06-11  4:47 ` [PATCH bpf-next 8/8] selftests/bpf: switch tests to BTF-defined map definitions Andrii Nakryiko
2019-06-14 23:23   ` Stanislav Fomichev
2019-06-14 23:43     ` Andrii Nakryiko
2019-06-15  0:01       ` Stanislav Fomichev
2019-06-17 19:30         ` Andrii Nakryiko
2019-06-17 21:07           ` Stanislav Fomichev
2019-06-11  5:21 ` [PATCH bpf-next 0/8] BTF-defined BPF " Andrii Nakryiko

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