netdev - [PATCH bpf-next 1/4] libbpf: Refactor relocations

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Date:   Mon, 11 Feb 2019 16:47:26 -0800
From:   Joe Stringer <joe@...d.net.nz>
To:     bpf@...r.kernel.org
Cc:     netdev@...r.kernel.org, daniel@...earbox.net, ast@...nel.org
Subject: [PATCH bpf-next 1/4] libbpf: Refactor relocations

Adjust the code for relocations slightly with no functional changes, so
that upcoming patches that will introduce support for relocations into
the .data and .bss sections can be added independent of these changes.

Signed-off-by: Joe Stringer <joe@...d.net.nz>
---
 tools/lib/bpf/libbpf.c | 62 ++++++++++++++++++++++--------------------
 1 file changed, 32 insertions(+), 30 deletions(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index e3c39edfb9d3..1ec28d5154dc 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -852,20 +852,20 @@ static int bpf_object__elf_collect(struct bpf_object *obj, int flags)
 				obj->efile.symbols = data;
 				obj->efile.strtabidx = sh.sh_link;
 			}
-		} else if ((sh.sh_type == SHT_PROGBITS) &&
-			   (sh.sh_flags & SHF_EXECINSTR) &&
-			   (data->d_size > 0)) {
-			if (strcmp(name, ".text") == 0)
-				obj->efile.text_shndx = idx;
-			err = bpf_object__add_program(obj, data->d_buf,
-						      data->d_size, name, idx);
-			if (err) {
-				char errmsg[STRERR_BUFSIZE];
-				char *cp = libbpf_strerror_r(-err, errmsg,
-							     sizeof(errmsg));
-
-				pr_warning("failed to alloc program %s (%s): %s",
-					   name, obj->path, cp);
+		} else if (sh.sh_type == SHT_PROGBITS && data->d_size > 0) {
+			if (sh.sh_flags & SHF_EXECINSTR) {
+				if (strcmp(name, ".text") == 0)
+					obj->efile.text_shndx = idx;
+				err = bpf_object__add_program(obj, data->d_buf,
+							      data->d_size, name, idx);
+				if (err) {
+					char errmsg[STRERR_BUFSIZE];
+					char *cp = libbpf_strerror_r(-err, errmsg,
+								     sizeof(errmsg));
+
+					pr_warning("failed to alloc program %s (%s): %s",
+						   name, obj->path, cp);
+				}
 			}
 		} else if (sh.sh_type == SHT_REL) {
 			void *reloc = obj->efile.reloc;
@@ -1027,24 +1027,26 @@ bpf_program__collect_reloc(struct bpf_program *prog, GElf_Shdr *shdr,
 			return -LIBBPF_ERRNO__RELOC;
 		}
 
-		/* TODO: 'maps' is sorted. We can use bsearch to make it faster. */
-		for (map_idx = 0; map_idx < nr_maps; map_idx++) {
-			if (maps[map_idx].offset == sym.st_value) {
-				pr_debug("relocation: find map %zd (%s) for insn %u\n",
-					 map_idx, maps[map_idx].name, insn_idx);
-				break;
+		if (sym.st_shndx == maps_shndx) {
+			/* TODO: 'maps' is sorted. We can use bsearch to make it faster. */
+			for (map_idx = 0; map_idx < nr_maps; map_idx++) {
+				if (maps[map_idx].offset == sym.st_value) {
+					pr_debug("relocation: find map %zd (%s) for insn %u\n",
+						 map_idx, maps[map_idx].name, insn_idx);
+					break;
+				}
 			}
-		}
 
-		if (map_idx >= nr_maps) {
-			pr_warning("bpf relocation: map_idx %d large than %d\n",
-				   (int)map_idx, (int)nr_maps - 1);
-			return -LIBBPF_ERRNO__RELOC;
-		}
+			if (map_idx >= nr_maps) {
+				pr_warning("bpf relocation: map_idx %d large than %d\n",
+					   (int)map_idx, (int)nr_maps - 1);
+				return -LIBBPF_ERRNO__RELOC;
+			}
 
-		prog->reloc_desc[i].type = RELO_LD64;
-		prog->reloc_desc[i].insn_idx = insn_idx;
-		prog->reloc_desc[i].map_idx = map_idx;
+			prog->reloc_desc[i].type = RELO_LD64;
+			prog->reloc_desc[i].insn_idx = insn_idx;
+			prog->reloc_desc[i].map_idx = map_idx;
+		}
 	}
 	return 0;
 }
@@ -1392,7 +1394,7 @@ bpf_program__relocate(struct bpf_program *prog, struct bpf_object *obj)
 			}
 			insns[insn_idx].src_reg = BPF_PSEUDO_MAP_FD;
 			insns[insn_idx].imm = obj->maps[map_idx].fd;
-		} else {
+		} else if (prog->reloc_desc[i].type == RELO_CALL) {
 			err = bpf_program__reloc_text(prog, obj,
 						      &prog->reloc_desc[i]);
 			if (err)
-- 
2.19.1