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libelf: add compression header support

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GNU and Oracle libelf implementations added support for section
compression, intended to reduce the size of DWARF debug info (which
might be an order of magnitude larger than the code).

There are two compressed ELF section formats:

1. Old GNU - sections are renmaed to start with 'z'.  Section contains
   a magic number, uncompressed size, and compressed data.

2. Oracle and New GNU - compressed sections use the SHF_COMPRESSED flag.
   The compression header contains the compression type, uncompressed
   size, and uncompressed alignment.

The second style is preferred and this change implements only that one.

Submitted by:	Tiger Gao <tig@FreeBSDFoundation.org>
Reviewed by:	markj
MFC after:	2 weeks
Relnotes:	Yes
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D24566
This commit is contained in:
Ed Maste 2020-10-23 16:35:23 +00:00
parent 3862838921
commit 573456a931
9 changed files with 326 additions and 2 deletions
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9
contrib/elftoolchain/libelf/Version.map
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@ -91,6 +91,13 @@ global:
gelf_update_symshndx;
gelf_xlatetof;
gelf_xlatetom;
};
R1.1 {
global:
elf32_getchdr;
elf64_getchdr;
gelf_getchdr;
local:
*;
};
} R1.0;

1
contrib/elftoolchain/libelf/_libelf.h
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@ -220,6 +220,7 @@ size_t _libelf_fsize(Elf_Type _t, int _elfclass, unsigned int _version,
size_t count);
_libelf_translator_function *_libelf_get_translator(Elf_Type _t,
int _direction, int _elfclass, int _elfmachine);
void *_libelf_getchdr(Elf_Scn *_e, int _elfclass);
void *_libelf_getphdr(Elf *_e, int _elfclass);
void *_libelf_getshdr(Elf_Scn *_scn, int _elfclass);
void _libelf_init_elf(Elf *_e, Elf_Kind _kind);

6
contrib/elftoolchain/libelf/gelf.3
View File

@ -23,7 +23,7 @@
.\"
.\" $Id: gelf.3 3743 2019-06-12 19:36:30Z jkoshy $
.\"
.Dd June 12, 2019
.Dd October 23, 2020
.Dt GELF 3
.Os
.Sh NAME
@ -45,6 +45,8 @@ The GElf API defines the following class-independent data structures:
.Bl -tag -width GElf_Sxword
.It Vt GElf_Addr
A representation of ELF addresses.
.It Vt GElf_Chdr
A class-independent representation of an ELF Compression Header.
.It Vt GElf_Dyn
A class-independent representation of ELF
.Sy .dynamic
@ -144,6 +146,8 @@ native representation.
.El
.It "Retrieving ELF Data"
.Bl -tag -compact -width indent
.It Fn gelf_getchdr
Retrieve an ELF Compression Header from the underlying ELF descriptor.
.It Fn gelf_getdyn
Retrieve an ELF
.Sy .dynamic

2
contrib/elftoolchain/libelf/gelf.h
View File

@ -39,6 +39,7 @@ typedef Elf64_Sxword GElf_Sxword; /* Signed long words (64 bit) */
typedef Elf64_Word GElf_Word; /* Unsigned words (32 bit) */
typedef Elf64_Xword GElf_Xword; /* Unsigned long words (64 bit) */
typedef Elf64_Chdr GElf_Chdr; /* Compressed section header */
typedef Elf64_Dyn GElf_Dyn; /* ".dynamic" section entries */
typedef Elf64_Ehdr GElf_Ehdr; /* ELF header */
typedef Elf64_Phdr GElf_Phdr; /* Program header */
@ -73,6 +74,7 @@ extern "C" {
long gelf_checksum(Elf *_elf);
size_t gelf_fsize(Elf *_elf, Elf_Type _type, size_t _count,
unsigned int _version);
GElf_Chdr *gelf_getchdr(Elf_Scn *_scn, GElf_Chdr *_dst);
int gelf_getclass(Elf *_elf);
GElf_Dyn *gelf_getdyn(Elf_Data *_data, int _index, GElf_Dyn *_dst);
GElf_Ehdr *gelf_getehdr(Elf *_elf, GElf_Ehdr *_dst);

82
contrib/elftoolchain/libelf/gelf_chdr.c Normal file
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@ -0,0 +1,82 @@
/*-
* SPDX-License-Identifier: BSD-2-Clause
*
* Copyright (c) 2020 The FreeBSD Foundation
*
* This software was developed by Tiger Gao under sponsorship from
* the FreeBSD Foundation.
*
* 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 <assert.h>
#include <gelf.h>
#include <libelf.h>
#include <limits.h>
#include <stdint.h>
#include "_libelf.h"
Elf32_Chdr *
elf32_getchdr(Elf_Scn *s)
{
return (_libelf_getchdr(s, ELFCLASS32));
}
Elf64_Chdr *
elf64_getchdr(Elf_Scn *s)
{
return (_libelf_getchdr(s, ELFCLASS64));
}
GElf_Chdr *
gelf_getchdr(Elf_Scn *s, GElf_Chdr *d)
{
int ec;
void *ch;
Elf32_Chdr *ch32;
Elf64_Chdr *ch64;
if (d == NULL) {
LIBELF_SET_ERROR(ARGUMENT, 0);
return (NULL);
}
if ((ch = _libelf_getchdr(s, ELFCLASSNONE)) == NULL)
return (NULL);
ec = s->s_elf->e_class;
assert(ec == ELFCLASS32 || ec == ELFCLASS64);
if (ec == ELFCLASS32) {
ch32 = (Elf32_Chdr *)ch;
d->ch_type = (Elf64_Word)ch32->ch_type;
d->ch_size = (Elf64_Xword)ch32->ch_size;
d->ch_addralign = (Elf64_Xword)ch32->ch_addralign;
} else {
ch64 = (Elf64_Chdr *)ch;
*d = *ch64;
}
return (d);
}

117
contrib/elftoolchain/libelf/gelf_getchdr.3 Normal file
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@ -0,0 +1,117 @@
.\" SPDX-License-Identifier: BSD-2-Clause
.\"
.\" Copyright (c) 2020 The FreeBSD Foundation
.\"
.\" This document was written by Tiger Gao under sponsorship from
.\" the FreeBSD Foundation.
.\"
.\" 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.
.\"
.\" $Id: gelf_getchdr.3 3639 2020-10-20 16:07:02Z tig $
.\"
.Dd October 23, 2020
.Dt GELF_GETCHDR 3
.Os
.Sh NAME
.Nm elf32_getchdr ,
.Nm elf64_getchdr ,
.Nm gelf_getchdr
.Nd retrieve the compression header of a section
.Sh LIBRARY
.Lb libelf
.Sh SYNOPSIS
.In libelf.h
.Ft "Elf32_Chdr *"
.Fn elf32_getchdr "Elf_Scn *s"
.Ft "Elf64_Chdr *"
.Fn elf64_getchdr "Elf_Scn *s"
.In gelf.h
.Ft "GElf_Chdr *"
.Fn gelf_getchdr "Elf_Scn *scn" "GElf_Chdr *chdr"
.Sh DESCRIPTION
These functions return a pointer to the ELF Compression Header data
structure associated with section descriptor
.Ar scn .
.Pp
Function
.Fn elf32_getchdr
retrieves a pointer to an
.Vt Elf32_Chdr
structure.
Section descriptor
.Ar scn
must be associated with an ELF descriptor of class
.Dv ELFCLASS32 .
.Pp
Function
.Fn elf64_getchdr
retrieves a pointer to an
.Vt Elf64_Chdr
structure.
Section descriptor
.Ar scn
must be associated with an ELF descriptor of class
.Dv ELFCLASS64 .
.Pp
Function
.Fn gelf_getchdr
copies the values in the compression header associated with argument
.Ar scn
to the structure pointed to be argument
.Ar dst .
The
.Vt GElf_Chdr
data structure is described in
.Xr gelf 3 .
.Sh RETURN VALUES
Functions
.Fn elf32_getchdr
and
.Fn elf64_getchdr
return a valid pointer to the appropriate compression header on success
or NULL if an error was encountered.
.Pp
Function
.Fn gelf_getchdr
returns argument
.Ar dst
if successful, or NULL if an error was encountered.
.Sh ERRORS
These functions may fail with the following errors:
.Bl -tag -width "[ELF_E_RESOURCE]"
.It Bq Er ELF_E_INVALID_SECTION_FLAGS
Arguments
.Ar scn
has invalid flags.
.It Bq Er ELF_E_INVALID_SECTION_TYPE
Argument
.Ar scn
has invalid type.
.It Bq Er ELF_E_NOT_COMPRESSED
Argument
.Ar scn
is not compressed.
.El
.Sh SEE ALSO
.Xr elf 3 ,
.Xr elf_getscn 3 ,
.Xr gelf 3 ,

5
contrib/elftoolchain/libelf/libelf.h
View File

@ -162,6 +162,9 @@ enum Elf_Error {
ELF_E_SEQUENCE, /* API calls out of sequence */
ELF_E_UNIMPL, /* Feature is unimplemented */
ELF_E_VERSION, /* Unknown API version */
ELF_E_INVALID_SECTION_FLAGS, /* Invalid ELF section header flags */
ELF_E_INVALID_SECTION_TYPE, /* Invalid ELF section header type */
ELF_E_NOT_COMPRESSED, /* Section is not compressed */
ELF_E_NUM /* Max error number */
};
@ -227,6 +230,7 @@ unsigned int elf_version(unsigned int _version);
long elf32_checksum(Elf *_elf);
size_t elf32_fsize(Elf_Type _type, size_t _count,
unsigned int _version);
Elf32_Chdr *elf32_getchdr(Elf_Scn *_scn);
Elf32_Ehdr *elf32_getehdr(Elf *_elf);
Elf32_Phdr *elf32_getphdr(Elf *_elf);
Elf32_Shdr *elf32_getshdr(Elf_Scn *_scn);
@ -240,6 +244,7 @@ Elf_Data *elf32_xlatetom(Elf_Data *_dst, const Elf_Data *_src,
long elf64_checksum(Elf *_elf);
size_t elf64_fsize(Elf_Type _type, size_t _count,
unsigned int _version);
Elf64_Chdr *elf64_getchdr(Elf_Scn *_scn);
Elf64_Ehdr *elf64_getehdr(Elf *_elf);
Elf64_Phdr *elf64_getphdr(Elf *_elf);
Elf64_Shdr *elf64_getshdr(Elf_Scn *_scn);

104
contrib/elftoolchain/libelf/libelf_chdr.c Normal file
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@ -0,0 +1,104 @@
/*-
* SPDX-License-Identifier: BSD-2-Clause
*
* Copyright (c) 2020 The FreeBSD Foundation
*
* This software was developed by Tiger Gao under sponsorship from
* the FreeBSD Foundation.
*
* 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 <gelf.h>
#include <libelf.h>
#include "_libelf.h"
void *
_libelf_getchdr(Elf_Scn *s, int ec)
{
Elf *e;
void *sh;
Elf32_Shdr *sh32;
Elf64_Shdr *sh64;
sh32 = NULL;
sh64 = NULL;
if (s == NULL || (e = s->s_elf) == NULL || e->e_kind != ELF_K_ELF) {
LIBELF_SET_ERROR(ARGUMENT, 0);
return (NULL);
}
if (ec == ELFCLASSNONE) {
ec = e->e_class;
} else if (ec != e->e_class) {
LIBELF_SET_ERROR(CLASS, 0);
return (NULL);
}
if ((sh = _libelf_getshdr(s, ec)) == NULL) {
LIBELF_SET_ERROR(HEADER, 0);
return (NULL);
}
if (ec == ELFCLASS32) {
sh32 = (Elf32_Shdr *)sh;
if ((sh32->sh_flags & SHF_ALLOC) != 0) {
LIBELF_SET_ERROR(INVALID_SECTION_FLAGS, 0);
return (NULL);
}
if (sh32->sh_type == SHT_NULL || sh32->sh_type == SHT_NOBITS) {
LIBELF_SET_ERROR(INVALID_SECTION_TYPE, 0);
return (NULL);
}
if ((sh32->sh_flags & SHF_COMPRESSED) == 0) {
LIBELF_SET_ERROR(NOT_COMPRESSED, 0);
return (NULL);
}
} else {
sh64 = (Elf64_Shdr *)sh;
if ((sh64->sh_flags & SHF_ALLOC) != 0) {
LIBELF_SET_ERROR(INVALID_SECTION_FLAGS, 0);
return (NULL);
}
if (sh64->sh_type == SHT_NULL || sh64->sh_type == SHT_NOBITS) {
LIBELF_SET_ERROR(INVALID_SECTION_TYPE, 0);
return (NULL);
}
if ((sh64->sh_flags & SHF_COMPRESSED) == 0) {
LIBELF_SET_ERROR(NOT_COMPRESSED, 0);
return (NULL);
}
}
Elf_Data *d = elf_getdata(s, NULL);
if (!d)
return (NULL);
return ((void *)d->d_buf);
}

2
lib/libelf/Makefile
View File

@ -38,6 +38,7 @@ SRCS= elf.c \
elf_update.c \
elf_version.c \
gelf_cap.c \
gelf_chdr.c \
gelf_checksum.c \
gelf_dyn.c \
gelf_ehdr.c \
@ -57,6 +58,7 @@ SRCS= elf.c \
libelf_allocate.c \
libelf_ar.c \
libelf_ar_util.c \
libelf_chdr.c \
libelf_checksum.c \
libelf_data.c \
libelf_ehdr.c \