libkldelf: add a private library for kernel/kld-related ELF parsing

The libkldelf library was originally a part of kldxref(8). It exposed
ELF parsing helpers specialized in parsing KLDs and the kernel
executable. The library can be used to read metadata such as linker_set,
mod_depend, mod_version and PNP match info, and raw data from the ELF.

To promote the reuse of the facilities the ELF parsing code is separated
from kldxref(8) into a new private library.

kldxref(8) is modified to link against the libkldelf library.

Sponsored by:	Juniper Networks, Inc.
Reviewed by:	markj
Differential Revision:	https://reviews.freebsd.org/D46719

1 files changed, 97 insertions, 0 deletions

diff --git a/lib/libkldelf/ef_i386.c b/lib/libkldelf/ef_i386.c
new file mode 100644
index 000000000000..ae571e2d50f2
--- /dev/null
+++ b/lib/libkldelf/ef_i386.c
@@ -0,0 +1,97 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2003 Jake Burkholder.
+ * Copyright 1996-1998 John D. Polstra.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/endian.h>
+
+#include <err.h>
+#include <errno.h>
+#include <gelf.h>
+
+#include "kldelf.h"
+
+/*
+ * Apply relocations to the values obtained from the file. `relbase' is the
+ * target relocation address of the section, and `dataoff/len' is the region
+ * that is to be relocated, and has been copied to *dest
+ */
+static int
+ef_i386_reloc(struct elf_file *ef, const void *reldata, Elf_Type reltype,
+    GElf_Addr relbase, GElf_Addr dataoff, size_t len, void *dest)
+{
+	char *where;
+	GElf_Addr addr, addend;
+	GElf_Size rtype, symidx;
+	const GElf_Rel *rel;
+	const GElf_Rela *rela;
+
+	switch (reltype) {
+	case ELF_T_REL:
+		rel = (const GElf_Rel *)reldata;
+		where = (char *)dest + (relbase + rel->r_offset - dataoff);
+		addend = 0;
+		rtype = GELF_R_TYPE(rel->r_info);
+		symidx = GELF_R_SYM(rel->r_info);
+		break;
+	case ELF_T_RELA:
+		rela = (const GElf_Rela *)reldata;
+		where = (char *)dest + (relbase + rela->r_offset - dataoff);
+		addend = rela->r_addend;
+		rtype = GELF_R_TYPE(rela->r_info);
+		symidx = GELF_R_SYM(rela->r_info);
+		break;
+	default:
+		return (EINVAL);
+	}
+
+	if (where < (char *)dest || where >= (char *)dest + len)
+		return (0);
+
+	if (reltype == ELF_T_REL)
+		addend = le32dec(where);
+
+	switch (rtype) {
+	case R_386_RELATIVE:	/* B + A */
+		addr = relbase + addend;
+		le32enc(where, addr);
+		break;
+	case R_386_32:	/* S + A - P */
+		addr = EF_SYMADDR(ef, symidx) + addend;
+		le32enc(where, addr);
+		break;
+	case R_386_GLOB_DAT:	/* S */
+		addr = EF_SYMADDR(ef, symidx);
+		le32enc(where, addr);
+		break;
+	default:
+		warnx("unhandled relocation type %d", (int)rtype);
+	}
+	return (0);
+}
+
+ELF_RELOC(ELFCLASS32, ELFDATA2LSB, EM_386, ef_i386_reloc);