Adding upstream version 8.4.4.upstream/8.4.4upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1385 insertions, 0 deletions

diff --git a/lib/elf_py.c b/lib/elf_py.c
new file mode 100644
index 0000000..7c503cf
--- /dev/null
+++ b/lib/elf_py.c
@@ -0,0 +1,1385 @@
+/*
+ * fast ELF file accessor
+ * Copyright (C) 2018-2020  David Lamparter for NetDEF, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; see the file COPYING; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/* Note: this wrapper is intended to be used as build-time helper.  While
+ * it should be generally correct and proper, there may be the occasional
+ * memory leak or SEGV for things that haven't been well-tested.
+ *     _
+ *    / \    This code is NOT SUITABLE FOR UNTRUSTED ELF FILES.  It's used
+ *   / ! \   in FRR to read files created by its own build.  Don't take it out
+ *  /_____\  of FRR and use it to parse random ELF files you found somewhere.
+ *
+ * If you're working with this code (or even reading it), you really need to
+ * read a bunch of the ELF specs.  There's no way around it, things in here
+ * just represent pieces of ELF pretty much 1:1.  Also, readelf & objdump are
+ * your friends.
+ *
+ * Required reading:
+ *   https://refspecs.linuxfoundation.org/elf/elf.pdf
+ *   https://refspecs.linuxfoundation.org/elf/x86_64-SysV-psABI.pdf
+ * Recommended reading:
+ *   https://github.com/ARM-software/abi-aa/releases/download/2020Q4/aaelf64.pdf
+ *
+ * The core ELF spec is *not* enough, you should read at least one of the
+ * processor specific (psABI) docs.  They define what & how relocations work.
+ * Luckily we don't need to care about the processor specifics since this only
+ * does data relocations, but without looking at the psABI, some things aren't
+ * quite clear.
+ */
+
+/* the API of this module roughly follows a very small subset of the one
+ * provided by the python elfutils package, which unfortunately is painfully
+ * slow.
+ */
+
+#define PY_SSIZE_T_CLEAN
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+#include <Python.h>
+#include "structmember.h"
+#include <string.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+#include <fcntl.h>
+
+#if defined(__sun__) && (__SIZEOF_POINTER__ == 4)
+/* Solaris libelf bails otherwise ... */
+#undef _FILE_OFFSET_BITS
+#define _FILE_OFFSET_BITS 32
+#endif
+
+#include <elf.h>
+#include <libelf.h>
+#include <gelf.h>
+
+#include "typesafe.h"
+#include "jhash.h"
+#include "clippy.h"
+
+static bool debug;
+
+#define debugf(...)                                                            \
+	do {                                                                   \
+		if (debug)                                                     \
+			fprintf(stderr, __VA_ARGS__);                          \
+	} while (0)
+
+/* Exceptions */
+static PyObject *ELFFormatError;
+static PyObject *ELFAccessError;
+
+/* most objects can only be created as return values from one of the methods */
+static PyObject *refuse_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
+{
+	PyErr_SetString(PyExc_ValueError,
+			"cannot create instances of this type");
+	return NULL;
+}
+
+struct elfreloc;
+struct elfsect;
+
+PREDECL_HASH(elfrelocs);
+
+/* ELFFile and ELFSection intentionally share some behaviour, particularly
+ * subscript[123:456] access to file data.  This is because relocatables
+ * (.o files) do things section-based, but linked executables/libraries do
+ * things file-based.  Having the two behave similar allows simplifying the
+ * Python code.
+ */
+
+/* class ELFFile:
+ *
+ * overall entry point, instantiated by reading in an ELF file
+ */
+struct elffile {
+	PyObject_HEAD
+
+	char *filename;
+	char *mmap, *mmend;
+	size_t len;
+	Elf *elf;
+
+	/* note from here on there are several instances of
+	 *
+	 *   GElf_Something *x, _x;
+	 *
+	 * this is a pattern used by libelf's generic ELF routines; the _x
+	 * field is used to create a copy of the ELF structure from the file
+	 * with 32/64bit and endianness adjusted.
+	 */
+
+	GElf_Ehdr *ehdr, _ehdr;
+	Elf_Scn *symtab;
+	size_t nsym, symstridx;
+	Elf_Data *symdata;
+
+	PyObject **sects;
+	size_t n_sect;
+
+	struct elfrelocs_head dynrelocs;
+
+	int elfclass;
+	bool bigendian;
+	bool has_symbols;
+};
+
+/* class ELFSection:
+ *
+ * note that executables and shared libraries can have their section headers
+ * removed, though in practice this is only used as an obfuscation technique.
+ */
+struct elfsect {
+	PyObject_HEAD
+
+	const char *name;
+	struct elffile *ef;
+
+	GElf_Shdr _shdr, *shdr;
+	Elf_Scn *scn;
+	unsigned long idx, len;
+
+	struct elfrelocs_head relocs;
+};
+
+/* class ELFReloc:
+ *
+ * note: relocations in object files (.o) are section-based while relocations
+ * in executables and shared libraries are file-based.
+ *
+ * Whenever accessing something that is a pointer in the ELF file, the Python
+ * code needs to check for a relocation;  if the pointer is pointing to some
+ * unresolved symbol the file will generally contain 0 bytes.  The relocation
+ * will tell what the pointer is actually pointing to.
+ *
+ * This represents both static (.o file) and dynamic (.so/exec) relocations.
+ */
+struct elfreloc {
+	PyObject_HEAD
+
+	struct elfrelocs_item elfrelocs_item;
+
+	struct elfsect *es;
+	struct elffile *ef;
+
+	/* there's also old-fashioned GElf_Rel; we're converting that to
+	 * GElf_Rela in elfsect_add_relocations()
+	 */
+	GElf_Rela _rela, *rela;
+	GElf_Sym _sym, *sym;
+	size_t symidx;
+	const char *symname;
+
+	/* documented below in python docstrings */
+	bool symvalid, unresolved, relative;
+	unsigned long long st_value;
+};
+
+static int elfreloc_cmp(const struct elfreloc *a, const struct elfreloc *b);
+static uint32_t elfreloc_hash(const struct elfreloc *reloc);
+
+DECLARE_HASH(elfrelocs, struct elfreloc, elfrelocs_item,
+	     elfreloc_cmp, elfreloc_hash);
+
+static Elf_Scn *elf_find_addr(struct elffile *ef, uint64_t addr, size_t *idx);
+static PyObject *elffile_secbyidx(struct elffile *w, Elf_Scn *scn, size_t idx);
+static PyObject *elfreloc_getsection(PyObject *self, PyObject *args);
+static PyObject *elfreloc_getaddend(PyObject *obj, void *closure);
+
+/* --- end of declarations -------------------------------------------------- */
+
+/*
+ * class ELFReloc:
+ */
+
+static const char elfreloc_doc[] =
+	"Represents an ELF relocation record\n"
+	"\n"
+	"(struct elfreloc * in elf_py.c)";
+
+#define member(name, type, doc)                                                \
+	{                                                                      \
+		(char *)#name, type, offsetof(struct elfreloc, name), READONLY,\
+		(char *)doc "\n\n(\"" #name "\", " #type " in elf_py.c)"       \
+	}
+static PyMemberDef members_elfreloc[] = {
+	member(symname, T_STRING,
+	       "Name of symbol this relocation refers to.\n"
+	       "\n"
+	       "Will frequently be `None` in executables and shared libraries."
+	),
+	member(symvalid, T_BOOL,
+	       "Target symbol has a valid type, i.e. not STT_NOTYPE"),
+	member(unresolved, T_BOOL,
+	       "Target symbol refers to an existing section"),
+	member(relative, T_BOOL,
+	       "Relocation is a REL (not RELA) record and thus relative."),
+	member(st_value, T_ULONGLONG,
+	       "Target symbol's value, if known\n\n"
+	       "Will be zero for unresolved/external symbols."),
+	{}
+};
+#undef member
+
+static PyGetSetDef getset_elfreloc[] = {
+	{ .name = (char *)"r_addend", .get = elfreloc_getaddend, .doc =
+		(char *)"Relocation addend value"},
+	{}
+};
+
+static PyMethodDef methods_elfreloc[] = {
+	{"getsection", elfreloc_getsection, METH_VARARGS,
+		"Find relocation target's ELF section\n\n"
+		"Args: address of relocatee (TODO: fix/remove?)\n"
+		"Returns: ELFSection or None\n\n"
+		"Not possible if section headers have been stripped."},
+	{}
+};
+
+static int elfreloc_cmp(const struct elfreloc *a, const struct elfreloc *b)
+{
+	if (a->rela->r_offset < b->rela->r_offset)
+		return -1;
+	if (a->rela->r_offset > b->rela->r_offset)
+		return 1;
+	return 0;
+}
+
+static uint32_t elfreloc_hash(const struct elfreloc *reloc)
+{
+	return jhash(&reloc->rela->r_offset, sizeof(reloc->rela->r_offset),
+		     0xc9a2b7f4);
+}
+
+static struct elfreloc *elfrelocs_get(struct elfrelocs_head *head,
+				      GElf_Addr offset)
+{
+	struct elfreloc dummy;
+
+	dummy.rela = &dummy._rela;
+	dummy.rela->r_offset = offset;
+	return elfrelocs_find(head, &dummy);
+}
+
+static PyObject *elfreloc_getsection(PyObject *self, PyObject *args)
+{
+	struct elfreloc *w = (struct elfreloc *)self;
+	long data;
+
+	if (!PyArg_ParseTuple(args, "k", &data))
+		return NULL;
+
+	if (!w->es)
+		Py_RETURN_NONE;
+
+	if (!w->symvalid || w->symidx == 0) {
+		size_t idx = 0;
+		Elf_Scn *scn;
+
+		data = (w->relative ? data : 0) + w->rela->r_addend;
+		scn = elf_find_addr(w->es->ef, data, &idx);
+		if (!scn)
+			Py_RETURN_NONE;
+		return elffile_secbyidx(w->es->ef, scn, idx);
+	}
+	return elffile_secbyidx(w->es->ef, NULL, w->sym->st_shndx);
+}
+
+static PyObject *elfreloc_getaddend(PyObject *obj, void *closure)
+{
+	struct elfreloc *w = (struct elfreloc *)obj;
+
+	return Py_BuildValue("K", (unsigned long long)w->rela->r_addend);
+}
+
+static PyObject *elfreloc_repr(PyObject *arg)
+{
+	struct elfreloc *w = (struct elfreloc *)arg;
+
+	return PyUnicode_FromFormat("<ELFReloc @%lu %s+%lu>",
+				    (unsigned long)w->rela->r_offset,
+				    (w->symname && w->symname[0]) ? w->symname
+						: "[0]",
+				    (unsigned long)w->rela->r_addend);
+}
+
+static void elfreloc_free(void *arg)
+{
+	struct elfreloc *w = arg;
+
+	(void)w;
+}
+
+static PyTypeObject typeobj_elfreloc = {
+	PyVarObject_HEAD_INIT(NULL, 0).tp_name = "_clippy.ELFReloc",
+	.tp_basicsize = sizeof(struct elfreloc),
+	.tp_flags = Py_TPFLAGS_DEFAULT,
+	.tp_doc = elfreloc_doc,
+	.tp_new = refuse_new,
+	.tp_free = elfreloc_free,
+	.tp_repr = elfreloc_repr,
+	.tp_members = members_elfreloc,
+	.tp_methods = methods_elfreloc,
+	.tp_getset = getset_elfreloc,
+};
+
+/*
+ * class ELFSection:
+ */
+
+static const char elfsect_doc[] =
+	"Represents an ELF section\n"
+	"\n"
+	"To access section contents, use subscript notation, e.g.\n"
+	"  section[123:456]\n"
+	"To read null terminated C strings, replace the end with str:\n"
+	"  section[123:str]\n\n"
+	"(struct elfsect * in elf_py.c)";
+
+static PyObject *elfsect_getaddr(PyObject *self, void *closure);
+
+#define member(name, type, doc)                                                \
+	{                                                                      \
+		(char *)#name, type, offsetof(struct elfsect, name), READONLY, \
+		(char *)doc "\n\n(\"" #name "\", " #type " in elf_py.c)"       \
+	}
+static PyMemberDef members_elfsect[] = {
+	member(name, T_STRING,
+	       "Section name, e.g. \".text\""),
+	member(idx, T_ULONG,
+	       "Section index in file"),
+	member(len, T_ULONG,
+	       "Section length in bytes"),
+	{},
+};
+#undef member
+
+static PyGetSetDef getset_elfsect[] = {
+	{ .name = (char *)"sh_addr", .get = elfsect_getaddr, .doc =
+		(char *)"Section virtual address (mapped program view)"},
+	{}
+};
+
+static PyObject *elfsect_getaddr(PyObject *self, void *closure)
+{
+	struct elfsect *w = (struct elfsect *)self;
+
+	return Py_BuildValue("K", (unsigned long long)w->shdr->sh_addr);
+}
+
+
+static PyObject *elfsect_getreloc(PyObject *self, PyObject *args)
+{
+	struct elfsect *w = (struct elfsect *)self;
+	struct elfreloc *relw;
+	unsigned long offs;
+	PyObject *ret;
+
+	if (!PyArg_ParseTuple(args, "k", &offs))
+		return NULL;
+
+	relw = elfrelocs_get(&w->relocs, offs + w->shdr->sh_addr);
+	if (!relw)
+		Py_RETURN_NONE;
+
+	ret = (PyObject *)relw;
+	Py_INCREF(ret);
+	return ret;
+}
+
+static PyMethodDef methods_elfsect[] = {
+	{"getreloc", elfsect_getreloc, METH_VARARGS,
+		"Check for / get relocation at offset into section\n\n"
+		"Args: byte offset into section to check\n"
+		"Returns: ELFReloc or None"},
+	{}
+};
+
+static PyObject *elfsect_subscript(PyObject *self, PyObject *key)
+{
+	Py_ssize_t start, stop, step, sllen;
+	struct elfsect *w = (struct elfsect *)self;
+	PySliceObject *slice;
+	unsigned long offs, len = ~0UL;
+
+	if (!PySlice_Check(key)) {
+		PyErr_SetString(PyExc_IndexError,
+				"ELFSection subscript must be slice");
+		return NULL;
+	}
+	slice = (PySliceObject *)key;
+	if (PyLong_Check(slice->stop)) {
+		if (PySlice_GetIndicesEx(key, w->shdr->sh_size,
+					 &start, &stop, &step, &sllen))
+			return NULL;
+
+		if (step != 1) {
+			PyErr_SetString(PyExc_IndexError,
+					"ELFSection subscript slice step must be 1");
+			return NULL;
+		}
+		if ((GElf_Xword)stop > w->shdr->sh_size) {
+			PyErr_Format(ELFAccessError,
+				     "access (%lu) beyond end of section %lu/%s (%lu)",
+				     stop, w->idx, w->name, w->shdr->sh_size);
+			return NULL;
+		}
+
+		offs = start;
+		len = sllen;
+	} else {
+		if (slice->stop != (void *)&PyUnicode_Type
+		    || !PyLong_Check(slice->start)) {
+			PyErr_SetString(PyExc_IndexError, "invalid slice");
+			return NULL;
+		}
+
+		offs = PyLong_AsUnsignedLongLong(slice->start);
+		len = ~0UL;
+	}
+
+	offs += w->shdr->sh_offset;
+	if (offs > w->ef->len) {
+		PyErr_Format(ELFAccessError,
+			     "access (%lu) beyond end of file (%lu)",
+			     offs, w->ef->len);
+		return NULL;
+	}
+	if (len == ~0UL)
+		len = strnlen(w->ef->mmap + offs, w->ef->len - offs);
+
+	Py_ssize_t pylen = len;
+
+#if PY_MAJOR_VERSION >= 3
+	return Py_BuildValue("y#", w->ef->mmap + offs, pylen);
+#else
+	return Py_BuildValue("s#", w->ef->mmap + offs, pylen);
+#endif
+}
+
+static PyMappingMethods mp_elfsect = {
+	.mp_subscript = elfsect_subscript,
+};
+
+static void elfsect_free(void *arg)
+{
+	struct elfsect *w = arg;
+
+	(void)w;
+}
+
+static PyObject *elfsect_repr(PyObject *arg)
+{
+	struct elfsect *w = (struct elfsect *)arg;
+
+	return PyUnicode_FromFormat("<ELFSection %s>", w->name);
+}
+
+static PyTypeObject typeobj_elfsect = {
+	PyVarObject_HEAD_INIT(NULL, 0).tp_name = "_clippy.ELFSection",
+	.tp_basicsize = sizeof(struct elfsect),
+	.tp_flags = Py_TPFLAGS_DEFAULT,
+	.tp_doc = elfsect_doc,
+	.tp_new = refuse_new,
+	.tp_free = elfsect_free,
+	.tp_repr = elfsect_repr,
+	.tp_as_mapping = &mp_elfsect,
+	.tp_members = members_elfsect,
+	.tp_methods = methods_elfsect,
+	.tp_getset = getset_elfsect,
+};
+
+static void elfsect_add_relocations(struct elfsect *w, Elf_Scn *rel,
+				    GElf_Shdr *relhdr)
+{
+	size_t i, entries;
+	Elf_Scn *symtab = elf_getscn(w->ef->elf, relhdr->sh_link);
+	GElf_Shdr _symhdr, *symhdr = gelf_getshdr(symtab, &_symhdr);
+	Elf_Data *symdata = elf_getdata(symtab, NULL);
+	Elf_Data *reldata = elf_getdata(rel, NULL);
+
+	entries = relhdr->sh_size / relhdr->sh_entsize;
+	for (i = 0; i < entries; i++) {
+		struct elfreloc *relw;
+		size_t symidx;
+		GElf_Rela *rela;
+		GElf_Sym *sym;
+
+		relw = (struct elfreloc *)typeobj_elfreloc.tp_alloc(
+				&typeobj_elfreloc, 0);
+		relw->es = w;
+
+		if (relhdr->sh_type == SHT_REL) {
+			GElf_Rel _rel, *rel;
+
+			rel = gelf_getrel(reldata, i, &_rel);
+			relw->rela = &relw->_rela;
+			relw->rela->r_offset = rel->r_offset;
+			relw->rela->r_info = rel->r_info;
+			relw->rela->r_addend = 0;
+			relw->relative = true;
+		} else
+			relw->rela = gelf_getrela(reldata, i, &relw->_rela);
+
+		rela = relw->rela;
+		if (rela->r_offset < w->shdr->sh_addr
+		    || rela->r_offset >= w->shdr->sh_addr + w->shdr->sh_size)
+			continue;
+
+		symidx = relw->symidx = GELF_R_SYM(rela->r_info);
+		sym = relw->sym = gelf_getsym(symdata, symidx, &relw->_sym);
+		if (sym) {
+			relw->symname = elf_strptr(w->ef->elf, symhdr->sh_link,
+						   sym->st_name);
+			relw->symvalid = GELF_ST_TYPE(sym->st_info)
+					!= STT_NOTYPE;
+			relw->unresolved = sym->st_shndx == SHN_UNDEF;
+			relw->st_value = sym->st_value;
+		} else {
+			relw->symname = NULL;
+			relw->symvalid = false;
+			relw->unresolved = false;
+			relw->st_value = 0;
+		}
+
+		debugf("reloc @ %016llx sym %5llu %016llx %s\n",
+		       (long long)rela->r_offset, (unsigned long long)symidx,
+		       (long long)rela->r_addend, relw->symname);
+
+		elfrelocs_add(&w->relocs, relw);
+	}
+}
+
+/*
+ * bindings & loading code between ELFFile and ELFSection
+ */
+
+static PyObject *elfsect_wrap(struct elffile *ef, Elf_Scn *scn, size_t idx,
+			      const char *name)
+{
+	struct elfsect *w;
+	size_t i;
+
+	w = (struct elfsect *)typeobj_elfsect.tp_alloc(&typeobj_elfsect, 0);
+	if (!w)
+		return NULL;
+
+	w->name = name;
+	w->ef = ef;
+	w->scn = scn;
+	w->shdr = gelf_getshdr(scn, &w->_shdr);
+	w->len = w->shdr->sh_size;
+	w->idx = idx;
+	elfrelocs_init(&w->relocs);
+
+	for (i = 0; i < ef->ehdr->e_shnum; i++) {
+		Elf_Scn *scn = elf_getscn(ef->elf, i);
+		GElf_Shdr _shdr, *shdr = gelf_getshdr(scn, &_shdr);
+
+		if (shdr->sh_type != SHT_RELA && shdr->sh_type != SHT_REL)
+			continue;
+		if (shdr->sh_info && shdr->sh_info != idx)
+			continue;
+		elfsect_add_relocations(w, scn, shdr);
+	}
+
+	return (PyObject *)w;
+}
+
+static Elf_Scn *elf_find_section(struct elffile *ef, const char *name,
+		size_t *idx)
+{
+	size_t i;
+	const char *secname;
+
+	for (i = 0; i < ef->ehdr->e_shnum; i++) {
+		Elf_Scn *scn = elf_getscn(ef->elf, i);
+		GElf_Shdr _shdr, *shdr = gelf_getshdr(scn, &_shdr);
+
+		secname = elf_strptr(ef->elf, ef->ehdr->e_shstrndx,
+				     shdr->sh_name);
+		if (strcmp(secname, name))
+			continue;
+		if (idx)
+			*idx = i;
+		return scn;
+	}
+	return NULL;
+}
+
+static Elf_Scn *elf_find_addr(struct elffile *ef, uint64_t addr, size_t *idx)
+{
+	size_t i;
+
+	for (i = 0; i < ef->ehdr->e_shnum; i++) {
+		Elf_Scn *scn = elf_getscn(ef->elf, i);
+		GElf_Shdr _shdr, *shdr = gelf_getshdr(scn, &_shdr);
+
+		/* virtual address is kinda meaningless for TLS sections */
+		if (shdr->sh_flags & SHF_TLS)
+			continue;
+		if (addr < shdr->sh_addr ||
+		    addr >= shdr->sh_addr + shdr->sh_size)
+			continue;
+
+		if (idx)
+			*idx = i;
+		return scn;
+	}
+	return NULL;
+}
+
+/*
+ * class ELFFile:
+ */
+
+static const char elffile_doc[] =
+	"Represents an ELF file\n"
+	"\n"
+	"Args: filename to load\n"
+	"\n"
+	"To access raw file contents, use subscript notation, e.g.\n"
+	"  file[123:456]\n"
+	"To read null terminated C strings, replace the end with str:\n"
+	"  file[123:str]\n\n"
+	"(struct elffile * in elf_py.c)";
+
+
+#define member(name, type, doc)                                                \
+	{                                                                      \
+		(char *)#name, type, offsetof(struct elffile, name), READONLY, \
+		(char *)doc "\n\n(\"" #name "\", " #type " in elf_py.c)"       \
+	}
+static PyMemberDef members_elffile[] = {
+	member(filename, T_STRING,
+	       "Original file name as given when opening"),
+	member(elfclass, T_INT,
+	       "ELF class (architecture bit size)\n\n"
+	       "Either 32 or 64, straight integer."),
+	member(bigendian, T_BOOL,
+	       "ELF file is big-endian\n\n"
+	       "All internal ELF structures are automatically converted."),
+	member(has_symbols, T_BOOL,
+	       "A symbol section is present\n\n"
+	       "Note: only refers to .symtab/SHT_SYMTAB section, not DT_SYMTAB"
+	),
+	{},
+};
+#undef member
+
+static PyObject *elffile_secbyidx(struct elffile *w, Elf_Scn *scn, size_t idx)
+{
+	const char *name;
+	PyObject *ret;
+
+	if (!scn)
+		scn = elf_getscn(w->elf, idx);
+	if (!scn || idx >= w->n_sect)
+		Py_RETURN_NONE;
+
+	if (!w->sects[idx]) {
+		GElf_Shdr _shdr, *shdr = gelf_getshdr(scn, &_shdr);
+
+		name = elf_strptr(w->elf, w->ehdr->e_shstrndx, shdr->sh_name);
+		w->sects[idx] = elfsect_wrap(w, scn, idx, name);
+	}
+
+	ret = w->sects[idx];
+	Py_INCREF(ret);
+	return ret;
+}
+
+static PyObject *elffile_get_section(PyObject *self, PyObject *args)
+{
+	const char *name;
+	struct elffile *w = (struct elffile *)self;
+	Elf_Scn *scn;
+	size_t idx = 0;
+
+	if (!PyArg_ParseTuple(args, "s", &name))
+		return NULL;
+
+	scn = elf_find_section(w, name, &idx);
+	return elffile_secbyidx(w, scn, idx);
+}
+
+static PyObject *elffile_get_section_addr(PyObject *self, PyObject *args)
+{
+	unsigned long long addr;
+	struct elffile *w = (struct elffile *)self;
+	Elf_Scn *scn;
+	size_t idx = 0;
+
+	if (!PyArg_ParseTuple(args, "K", &addr))
+		return NULL;
+
+	scn = elf_find_addr(w, addr, &idx);
+	return elffile_secbyidx(w, scn, idx);
+}
+
+static PyObject *elffile_get_section_idx(PyObject *self, PyObject *args)
+{
+	unsigned long long idx;
+	struct elffile *w = (struct elffile *)self;
+
+	if (!PyArg_ParseTuple(args, "K", &idx))
+		return NULL;
+
+	return elffile_secbyidx(w, NULL, idx);
+}
+
+static PyObject *elffile_get_symbol(PyObject *self, PyObject *args)
+{
+	const char *name, *symname;
+	struct elffile *w = (struct elffile *)self;
+	GElf_Sym _sym, *sym;
+	size_t i;
+
+	if (!PyArg_ParseTuple(args, "s", &name))
+		return NULL;
+
+	for (i = 0; i < w->nsym; i++) {
+		sym = gelf_getsym(w->symdata, i, &_sym);
+		if (sym->st_name == 0)
+			continue;
+		symname = elf_strptr(w->elf, w->symstridx, sym->st_name);
+		if (strcmp(symname, name))
+			continue;
+
+		PyObject *pysect;
+		Elf_Scn *scn = elf_getscn(w->elf, sym->st_shndx);
+
+		if (scn)
+			pysect = elffile_secbyidx(w, scn, sym->st_shndx);
+		else {
+			pysect = Py_None;
+			Py_INCREF(pysect);
+		}
+		return Py_BuildValue("sKN", symname,
+				(unsigned long long)sym->st_value, pysect);
+	}
+	Py_RETURN_NONE;
+}
+
+static PyObject *elffile_getreloc(PyObject *self, PyObject *args)
+{
+	struct elffile *w = (struct elffile *)self;
+	struct elfreloc *relw;
+	unsigned long offs;
+	PyObject *ret;
+
+	if (!PyArg_ParseTuple(args, "k", &offs))
+		return NULL;
+
+	relw = elfrelocs_get(&w->dynrelocs, offs);
+	if (!relw)
+		Py_RETURN_NONE;
+
+	ret = (PyObject *)relw;
+	Py_INCREF(ret);
+	return ret;
+}
+
+static PyObject *elffile_find_note(PyObject *self, PyObject *args)
+{
+#if defined(HAVE_GELF_GETNOTE) && defined(HAVE_ELF_GETDATA_RAWCHUNK)
+	const char *owner;
+	const uint8_t *ids;
+	GElf_Word id;
+	struct elffile *w = (struct elffile *)self;
+	size_t i;
+
+	if (!PyArg_ParseTuple(args, "ss", &owner, &ids))
+		return NULL;
+
+	if (strlen((char *)ids) != 4) {
+		PyErr_SetString(PyExc_ValueError,
+				"ELF note ID must be exactly 4-byte string");
+		return NULL;
+	}
+	if (w->bigendian)
+		id = (ids[0] << 24) | (ids[1] << 16) | (ids[2] << 8) | ids[3];
+	else
+		id = (ids[3] << 24) | (ids[2] << 16) | (ids[1] << 8) | ids[0];
+
+	for (i = 0; i < w->ehdr->e_phnum; i++) {
+		GElf_Phdr _phdr, *phdr = gelf_getphdr(w->elf, i, &_phdr);
+		Elf_Data *notedata;
+		size_t offset;
+
+		if (phdr->p_type != PT_NOTE)
+			continue;
+
+		notedata = elf_getdata_rawchunk(w->elf, phdr->p_offset,
+						phdr->p_filesz, ELF_T_NHDR);
+
+		GElf_Nhdr nhdr[1];
+		size_t nameoffs, dataoffs;
+
+		offset = 0;
+		while ((offset = gelf_getnote(notedata, offset, nhdr,
+					      &nameoffs, &dataoffs))) {
+			if (phdr->p_offset + nameoffs >= w->len)
+				continue;
+
+			const char *name = w->mmap + phdr->p_offset + nameoffs;
+
+			if (strcmp(name, owner))
+				continue;
+			if (id != nhdr->n_type)
+				continue;
+
+			PyObject *s, *e;
+
+			s = PyLong_FromUnsignedLongLong(
+				phdr->p_vaddr + dataoffs);
+			e = PyLong_FromUnsignedLongLong(
+				phdr->p_vaddr + dataoffs + nhdr->n_descsz);
+			return PySlice_New(s, e, NULL);
+		}
+	}
+#endif
+	Py_RETURN_NONE;
+}
+
+#ifdef HAVE_ELF_GETDATA_RAWCHUNK
+static bool elffile_virt2file(struct elffile *w, GElf_Addr virt,
+			      GElf_Addr *offs)
+{
+	*offs = 0;
+
+	for (size_t i = 0; i < w->ehdr->e_phnum; i++) {
+		GElf_Phdr _phdr, *phdr = gelf_getphdr(w->elf, i, &_phdr);
+
+		if (phdr->p_type != PT_LOAD)
+			continue;
+
+		if (virt < phdr->p_vaddr
+		    || virt >= phdr->p_vaddr + phdr->p_memsz)
+			continue;
+
+		if (virt >= phdr->p_vaddr + phdr->p_filesz)
+			return false;
+
+		*offs = virt - phdr->p_vaddr + phdr->p_offset;
+		return true;
+	}
+
+	return false;
+}
+#endif /* HAVE_ELF_GETDATA_RAWCHUNK */
+
+static PyObject *elffile_subscript(PyObject *self, PyObject *key)
+{
+	Py_ssize_t start, stop, step;
+	PySliceObject *slice;
+	struct elffile *w = (struct elffile *)self;
+	bool str = false;
+
+	if (!PySlice_Check(key)) {
+		PyErr_SetString(PyExc_IndexError,
+				"ELFFile subscript must be slice");
+		return NULL;
+	}
+	slice = (PySliceObject *)key;
+	stop = -1;
+	step = 1;
+	if (PyLong_Check(slice->stop)) {
+		start = PyLong_AsSsize_t(slice->start);
+		if (PyErr_Occurred())
+			return NULL;
+		if (slice->stop != Py_None) {
+			stop = PyLong_AsSsize_t(slice->stop);
+			if (PyErr_Occurred())
+				return NULL;
+		}
+		if (slice->step != Py_None) {
+			step = PyLong_AsSsize_t(slice->step);
+			if (PyErr_Occurred())
+				return NULL;
+		}
+	} else {
+		if (slice->stop != (void *)&PyUnicode_Type
+		    || !PyLong_Check(slice->start)) {
+			PyErr_SetString(PyExc_IndexError, "invalid slice");
+			return NULL;
+		}
+
+		str = true;
+		start = PyLong_AsUnsignedLongLong(slice->start);
+	}
+	if (step != 1) {
+		PyErr_SetString(PyExc_IndexError,
+				"ELFFile subscript slice step must be 1");
+		return NULL;
+	}
+
+	GElf_Addr xstart = start, xstop = stop;
+
+	for (size_t i = 0; i < w->ehdr->e_phnum; i++) {
+		GElf_Phdr _phdr, *phdr = gelf_getphdr(w->elf, i, &_phdr);
+
+		if (phdr->p_type != PT_LOAD)
+			continue;
+
+		if (xstart < phdr->p_vaddr
+		    || xstart >= phdr->p_vaddr + phdr->p_memsz)
+			continue;
+		if (!str && (xstop < phdr->p_vaddr
+		    || xstop > phdr->p_vaddr + phdr->p_memsz)) {
+			PyErr_Format(ELFAccessError,
+				     "access (%llu) beyond end of program header (%llu)",
+				     (long long)xstop,
+				     (long long)(phdr->p_vaddr +
+						 phdr->p_memsz));
+			return NULL;
+		}
+
+		xstart = xstart - phdr->p_vaddr + phdr->p_offset;
+
+		if (str)
+			xstop = strlen(w->mmap + xstart);
+		else
+			xstop = xstop - phdr->p_vaddr + phdr->p_offset;
+
+		Py_ssize_t pylen = xstop - xstart;
+
+#if PY_MAJOR_VERSION >= 3
+		return Py_BuildValue("y#", w->mmap + xstart, pylen);
+#else
+		return Py_BuildValue("s#", w->mmap + xstart, pylen);
+#endif
+	};
+
+	return PyErr_Format(ELFAccessError,
+			    "virtual address (%llu) not found in program headers",
+			    (long long)start);
+}
+
+static PyMethodDef methods_elffile[] = {
+	{"find_note", elffile_find_note, METH_VARARGS,
+		"find specific note entry"},
+	{"getreloc", elffile_getreloc, METH_VARARGS,
+		"find relocation"},
+	{"get_symbol", elffile_get_symbol, METH_VARARGS,
+		"find symbol by name"},
+	{"get_section", elffile_get_section, METH_VARARGS,
+		"find section by name"},
+	{"get_section_addr", elffile_get_section_addr, METH_VARARGS,
+		"find section by address"},
+	{"get_section_idx", elffile_get_section_idx, METH_VARARGS,
+		"find section by index"},
+	{}
+};
+
+static PyObject *elffile_load(PyTypeObject *type, PyObject *args,
+			     PyObject *kwds);
+
+static void elffile_free(void *arg)
+{
+	struct elffile *w = arg;
+
+	elf_end(w->elf);
+	munmap(w->mmap, w->len);
+	free(w->filename);
+}
+
+static PyMappingMethods mp_elffile = {
+	.mp_subscript = elffile_subscript,
+};
+
+static PyTypeObject typeobj_elffile = {
+	PyVarObject_HEAD_INIT(NULL, 0).tp_name = "_clippy.ELFFile",
+	.tp_basicsize = sizeof(struct elffile),
+	.tp_flags = Py_TPFLAGS_DEFAULT,
+	.tp_doc = elffile_doc,
+	.tp_new = elffile_load,
+	.tp_free = elffile_free,
+	.tp_as_mapping = &mp_elffile,
+	.tp_members = members_elffile,
+	.tp_methods = methods_elffile,
+};
+
+#ifdef HAVE_ELF_GETDATA_RAWCHUNK
+static char *elfdata_strptr(Elf_Data *data, size_t offset)
+{
+	char *p;
+
+	if (offset >= data->d_size)
+		return NULL;
+
+	p = (char *)data->d_buf + offset;
+	if (strnlen(p, data->d_size - offset) >= data->d_size - offset)
+		return NULL;
+
+	return p;
+}
+
+static void elffile_add_dynreloc(struct elffile *w, Elf_Data *reldata,
+				 size_t entries, Elf_Data *symdata,
+				 Elf_Data *strdata, Elf_Type typ)
+{
+	size_t i;
+
+	for (i = 0; i < entries; i++) {
+		struct elfreloc *relw;
+		size_t symidx;
+		GElf_Rela *rela;
+		GElf_Sym *sym;
+		GElf_Addr rel_offs = 0;
+
+		relw = (struct elfreloc *)typeobj_elfreloc.tp_alloc(
+				&typeobj_elfreloc, 0);
+		relw->ef = w;
+
+		if (typ == ELF_T_REL) {
+			GElf_Rel _rel, *rel;
+			GElf_Addr offs;
+
+			rel = gelf_getrel(reldata, i, &_rel);
+			relw->rela = &relw->_rela;
+			relw->rela->r_offset = rel->r_offset;
+			relw->rela->r_info = rel->r_info;
+			relw->rela->r_addend = 0;
+			relw->relative = true;
+
+			/* REL uses the pointer contents itself instead of the
+			 * RELA addend field :( ... theoretically this could
+			 * be some weird platform specific encoding, but since
+			 * we only care about data relocations it should
+			 * always be a pointer...
+			 */
+			if (elffile_virt2file(w, rel->r_offset, &offs)) {
+				Elf_Data *ptr;
+
+				/* NB: this endian-converts! */
+				ptr = elf_getdata_rawchunk(w->elf, offs,
+							   w->elfclass / 8,
+							   ELF_T_ADDR);
+
+				if (ptr) {
+					char *dst = (char *)&rel_offs;
+
+					/* sigh.  it endian-converts.  but
+					 * doesn't size-convert.
+					 */
+					if (BYTE_ORDER == BIG_ENDIAN &&
+					    ptr->d_size < sizeof(rel_offs))
+						dst += sizeof(rel_offs) -
+						       ptr->d_size;
+
+					memcpy(dst, ptr->d_buf, ptr->d_size);
+
+					relw->relative = false;
+					relw->rela->r_addend = rel_offs;
+				}
+			}
+		} else
+			relw->rela = gelf_getrela(reldata, i, &relw->_rela);
+
+		rela = relw->rela;
+		symidx = relw->symidx = GELF_R_SYM(rela->r_info);
+		sym = relw->sym = gelf_getsym(symdata, symidx, &relw->_sym);
+		if (sym) {
+			relw->symname = elfdata_strptr(strdata, sym->st_name);
+			relw->symvalid = GELF_ST_TYPE(sym->st_info)
+					!= STT_NOTYPE;
+			relw->unresolved = sym->st_shndx == SHN_UNDEF;
+			relw->st_value = sym->st_value;
+		} else {
+			relw->symname = NULL;
+			relw->symvalid = false;
+			relw->unresolved = false;
+			relw->st_value = 0;
+		}
+
+		if (typ == ELF_T_RELA)
+			debugf("dynrela @ %016llx sym %5llu %016llx %s\n",
+			       (long long)rela->r_offset,
+			       (unsigned long long)symidx,
+			       (long long)rela->r_addend, relw->symname);
+		else
+			debugf("dynrel @ %016llx sym %5llu (%016llx) %s\n",
+			       (long long)rela->r_offset,
+			       (unsigned long long)symidx,
+			       (unsigned long long)rel_offs, relw->symname);
+
+		elfrelocs_add(&w->dynrelocs, relw);
+	}
+
+}
+#endif /* HAVE_ELF_GETDATA_RAWCHUNK */
+
+/* primary (only, really) entry point to anything in this module */
+static PyObject *elffile_load(PyTypeObject *type, PyObject *args,
+			      PyObject *kwds)
+{
+	const char *filename;
+	static const char * const kwnames[] = {"filename", NULL};
+	struct elffile *w;
+	struct stat st;
+	int fd, err;
+
+	w = (struct elffile *)typeobj_elffile.tp_alloc(&typeobj_elffile, 0);
+	if (!w)
+		return NULL;
+
+	if (!PyArg_ParseTupleAndKeywords(args, kwds, "s", (char **)kwnames,
+					 &filename))
+		return NULL;
+
+	w->filename = strdup(filename);
+	fd = open(filename, O_RDONLY | O_NOCTTY);
+	if (fd < 0 || fstat(fd, &st)) {
+		PyErr_SetFromErrnoWithFilename(PyExc_OSError, filename);
+		close(fd);
+		goto out;
+	}
+	w->len = st.st_size;
+	w->mmap = mmap(NULL, st.st_size, PROT_READ, MAP_SHARED, fd, 0);
+	if (!w->mmap) {
+		PyErr_SetFromErrnoWithFilename(PyExc_IOError, filename);
+		close(fd);
+		goto out;
+	}
+	close(fd);
+	w->mmend = w->mmap + st.st_size;
+
+	if (w->len < EI_NIDENT || memcmp(w->mmap, ELFMAG, SELFMAG)) {
+		PyErr_SetString(ELFFormatError, "invalid ELF signature");
+		goto out;
+	}
+
+	switch (w->mmap[EI_CLASS]) {
+	case ELFCLASS32:
+		w->elfclass = 32;
+		break;
+	case ELFCLASS64:
+		w->elfclass = 64;
+		break;
+	default:
+		PyErr_SetString(ELFFormatError, "invalid ELF class");
+		goto out;
+	}
+	switch (w->mmap[EI_DATA]) {
+	case ELFDATA2LSB:
+		w->bigendian = false;
+		break;
+	case ELFDATA2MSB:
+		w->bigendian = true;
+		break;
+	default:
+		PyErr_SetString(ELFFormatError, "invalid ELF byte order");
+		goto out;
+	}
+
+	w->elf = elf_memory(w->mmap, w->len);
+	if (!w->elf)
+		goto out_elferr;
+	w->ehdr = gelf_getehdr(w->elf, &w->_ehdr);
+	if (!w->ehdr)
+		goto out_elferr;
+
+	for (size_t i = 0; i < w->ehdr->e_shnum; i++) {
+		Elf_Scn *scn = elf_getscn(w->elf, i);
+		GElf_Shdr _shdr, *shdr = gelf_getshdr(scn, &_shdr);
+
+		if (shdr->sh_type == SHT_SYMTAB) {
+			w->symtab = scn;
+			w->nsym = shdr->sh_size / shdr->sh_entsize;
+			w->symdata = elf_getdata(scn, NULL);
+			w->symstridx = shdr->sh_link;
+			break;
+		}
+	}
+	w->has_symbols = w->symtab && w->symstridx;
+	elfrelocs_init(&w->dynrelocs);
+
+#ifdef HAVE_ELF_GETDATA_RAWCHUNK
+	for (size_t i = 0; i < w->ehdr->e_phnum; i++) {
+		GElf_Phdr _phdr, *phdr = gelf_getphdr(w->elf, i, &_phdr);
+
+		if (phdr->p_type != PT_DYNAMIC)
+			continue;
+
+		Elf_Data *dyndata = elf_getdata_rawchunk(w->elf,
+				phdr->p_offset, phdr->p_filesz, ELF_T_DYN);
+
+		GElf_Addr dynrela = 0, dynrel = 0, symtab = 0, strtab = 0;
+		size_t dynrelasz = 0, dynrelaent = 0;
+		size_t dynrelsz = 0, dynrelent = 0;
+		size_t strsz = 0;
+		GElf_Dyn _dyn, *dyn;
+
+		for (size_t j = 0;; j++) {
+			dyn = gelf_getdyn(dyndata, j, &_dyn);
+
+			if (dyn->d_tag == DT_NULL)
+				break;
+
+			switch (dyn->d_tag) {
+			case DT_SYMTAB:
+				symtab = dyn->d_un.d_ptr;
+				break;
+
+			case DT_STRTAB:
+				strtab = dyn->d_un.d_ptr;
+				break;
+			case DT_STRSZ:
+				strsz = dyn->d_un.d_val;
+				break;
+
+			case DT_RELA:
+				dynrela = dyn->d_un.d_ptr;
+				break;
+			case DT_RELASZ:
+				dynrelasz = dyn->d_un.d_val;
+				break;
+			case DT_RELAENT:
+				dynrelaent = dyn->d_un.d_val;
+				break;
+
+			case DT_REL:
+				dynrel = dyn->d_un.d_ptr;
+				break;
+			case DT_RELSZ:
+				dynrelsz = dyn->d_un.d_val;
+				break;
+			case DT_RELENT:
+				dynrelent = dyn->d_un.d_val;
+				break;
+			}
+		}
+
+		GElf_Addr offset;
+		Elf_Data *symdata = NULL, *strdata = NULL;
+
+		if (elffile_virt2file(w, symtab, &offset))
+			symdata = elf_getdata_rawchunk(w->elf, offset,
+						       w->len - offset,
+						       ELF_T_SYM);
+		if (elffile_virt2file(w, strtab, &offset))
+			strdata = elf_getdata_rawchunk(w->elf, offset,
+						       strsz, ELF_T_BYTE);
+
+		size_t c;
+
+		if (dynrela && dynrelasz && dynrelaent
+		    && elffile_virt2file(w, dynrela, &offset)) {
+			Elf_Data *reladata = NULL;
+
+			debugf("dynrela @%llx/%llx+%llx\n", (long long)dynrela,
+			       (long long)offset, (long long)dynrelasz);
+
+			reladata = elf_getdata_rawchunk(w->elf, offset,
+							dynrelasz, ELF_T_RELA);
+
+			c = dynrelasz / dynrelaent;
+			elffile_add_dynreloc(w, reladata, c, symdata, strdata,
+					     ELF_T_RELA);
+		}
+
+		if (dynrel && dynrelsz && dynrelent
+		    && elffile_virt2file(w, dynrel, &offset)) {
+			Elf_Data *reldata = NULL;
+
+			debugf("dynrel @%llx/%llx+%llx\n", (long long)dynrel,
+			       (long long)offset, (long long)dynrelsz);
+
+			reldata = elf_getdata_rawchunk(w->elf, offset, dynrelsz,
+						       ELF_T_REL);
+
+			c = dynrelsz / dynrelent;
+			elffile_add_dynreloc(w, reldata, c, symdata, strdata,
+					     ELF_T_REL);
+		}
+	}
+#endif
+
+	w->sects = calloc(sizeof(PyObject *), w->ehdr->e_shnum);
+	w->n_sect = w->ehdr->e_shnum;
+
+	return (PyObject *)w;
+
+out_elferr:
+	err = elf_errno();
+
+	PyErr_Format(ELFFormatError, "libelf error %d: %s",
+		     err, elf_errmsg(err));
+out:
+	if (w->elf)
+		elf_end(w->elf);
+	free(w->filename);
+	return NULL;
+}
+
+static PyObject *elfpy_debug(PyObject *self, PyObject *args)
+{
+	int arg;
+
+	if (!PyArg_ParseTuple(args, "p", &arg))
+		return NULL;
+
+	debug = arg;
+
+	Py_RETURN_NONE;
+}
+
+static PyMethodDef methods_elfpy[] = {
+	{"elfpy_debug", elfpy_debug, METH_VARARGS, "switch debuging on/off"},
+	{}
+};
+
+bool elf_py_init(PyObject *pymod)
+{
+	if (PyType_Ready(&typeobj_elffile) < 0)
+		return false;
+	if (PyType_Ready(&typeobj_elfsect) < 0)
+		return false;
+	if (PyType_Ready(&typeobj_elfreloc) < 0)
+		return false;
+	if (elf_version(EV_CURRENT) == EV_NONE)
+		return false;
+
+#if PY_MAJOR_VERSION >= 3 && PY_MINOR_VERSION >= 5
+	PyModule_AddFunctions(pymod, methods_elfpy);
+#else
+	(void)methods_elfpy;
+#endif
+
+	ELFFormatError = PyErr_NewException("_clippy.ELFFormatError",
+					    PyExc_ValueError, NULL);
+	PyModule_AddObject(pymod, "ELFFormatError", ELFFormatError);
+	ELFAccessError = PyErr_NewException("_clippy.ELFAccessError",
+					    PyExc_IndexError, NULL);
+	PyModule_AddObject(pymod, "ELFAccessError", ELFAccessError);
+
+	Py_INCREF(&typeobj_elffile);
+	PyModule_AddObject(pymod, "ELFFile", (PyObject *)&typeobj_elffile);
+	Py_INCREF(&typeobj_elfsect);
+	PyModule_AddObject(pymod, "ELFSection", (PyObject *)&typeobj_elfsect);
+	Py_INCREF(&typeobj_elfreloc);
+	PyModule_AddObject(pymod, "ELFReloc", (PyObject *)&typeobj_elfreloc);
+	return true;
+}