ahill/kmod
1
0
Fork 0
mirror of https://github.com/kmod-project/kmod.git synced 2026-01-26 15:39:08 +00:00
Code Issues Packages Projects Releases Wiki Activity

libkmod: Add ELF notes to compression libraries

Browse Source 
Follow the new spec for ELF notes as detailed in
https://systemd.io/ELF_PACKAGE_METADATA/.

We can copy mostly verbatim the macros from systemd codebase.

Example output:

	$ meson setup --native-file build-dev.ini -Dxz=disabled -Ddlopen=zlib build
	...
	    dlopen           : zlib

	    features         : +ZSTD -XZ +ZLIB +OPENSSL

	$ dlopen-notes.py build/libkmod.so.2
	# build/libkmod.so.2
	[
	  {
	    "feature": "xz",
	    "description": "Support for uncompressing xz-compressed modules",
	    "priority": "recommended",
	    "soname": [
	      "liblzma.so.5"
	    ]
	  }
	]

Signed-off-by: Lucas De Marchi <lucas.de.marchi@gmail.com>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Link: https://github.com/kmod-project/kmod/pull/262
This commit is contained in:
Lucas De Marchi 2024-12-04 09:24:49 -06:00
parent bbab061e51
commit c9f80c49b1
7 changed files with 77 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
Makefile.am
View File

@ -58,6 +58,7 @@ noinst_LTLIBRARIES = shared/libshared.la
shared_libshared_la_SOURCES = \
shared/array.c \
shared/array.h \
shared/elf-note.h \
shared/hash.c \
shared/hash.h \
shared/macro.h \

9
libkmod/libkmod-file-xz.c
View File

@ -14,6 +14,7 @@
#include <sys/types.h>
#include <unistd.h>
#include <shared/elf-note.h>
#include <shared/util.h>
#include "libkmod.h"
@ -29,12 +30,16 @@ DL_SYMBOL_TABLE(DECLARE_SYM)
static int dlopen_lzma(void)
{
#if !DLSYM_LOCALLY_ENABLED
return 0;
#else
static void *dl = NULL;
if (!DLSYM_LOCALLY_ENABLED)
return 0;
ELF_NOTE_DLOPEN("xz", "Support for uncompressing xz-compressed modules",
ELF_NOTE_DLOPEN_PRIORITY_RECOMMENDED, "liblzma.so.5");
return dlsym_many(&dl, "liblzma.so.5", DL_SYMBOL_TABLE(DLSYM_ARG) NULL);
#endif
}
static void xz_uncompress_belch(struct kmod_file *file, lzma_ret ret)

9
libkmod/libkmod-file-zlib.c
View File

@ -14,6 +14,7 @@
#include <unistd.h>
#include <zlib.h>
#include <shared/elf-note.h>
#include <shared/util.h>
#include "libkmod.h"
@ -32,12 +33,16 @@ DL_SYMBOL_TABLE(DECLARE_SYM)
static int dlopen_zlib(void)
{
#if !DLSYM_LOCALLY_ENABLED
return 0;
#else
static void *dl = NULL;
if (!DLSYM_LOCALLY_ENABLED)
return 0;
ELF_NOTE_DLOPEN("zlib", "Support for uncompressing zlib-compressed modules",
ELF_NOTE_DLOPEN_PRIORITY_RECOMMENDED, "libz.so.1");
return dlsym_many(&dl, "libz.so.1", DL_SYMBOL_TABLE(DLSYM_ARG) NULL);
#endif
}
int kmod_file_load_zlib(struct kmod_file *file)

9
libkmod/libkmod-file-zstd.c
View File

@ -15,6 +15,7 @@
#include <unistd.h>
#include <zstd.h>
#include <shared/elf-note.h>
#include <shared/util.h>
#include "libkmod.h"
@ -31,12 +32,16 @@ DL_SYMBOL_TABLE(DECLARE_SYM)
static int dlopen_zstd(void)
{
#if !DLSYM_LOCALLY_ENABLED
return 0;
#else
static void *dl = NULL;
if (!DLSYM_LOCALLY_ENABLED)
return 0;
ELF_NOTE_DLOPEN("zstd", "Support for uncompressing zstd-compressed modules",
ELF_NOTE_DLOPEN_PRIORITY_RECOMMENDED, "libzstd.so.1");
return dlsym_many(&dl, "libzstd.so.1", DL_SYMBOL_TABLE(DLSYM_ARG) NULL);
#endif
}
int kmod_file_load_zstd(struct kmod_file *file)

1
meson.build
View File

@ -363,6 +363,7 @@ libshared = static_library(
files(
'shared/array.c',
'shared/array.h',
'shared/elf-note.h',
'shared/hash.c',
'shared/hash.h',
'shared/macro.h',

53
shared/elf-note.h Normal file
View File

@ -0,0 +1,53 @@
/* SPDX-License-Identifier: LGPL-2.1-or-later */
#pragma once
#include "macro.h"
/*
* Originally from systemd codebase.
*
* Reference: https://systemd.io/ELF_PACKAGE_METADATA/
*/
// clang-format off
#define ELF_NOTE_DLOPEN_VENDOR "FDO"
#define ELF_NOTE_DLOPEN_TYPE UINT32_C(0x407c0c0a)
#define ELF_NOTE_DLOPEN_PRIORITY_REQUIRED "required"
#define ELF_NOTE_DLOPEN_PRIORITY_RECOMMENDED "recommended"
#define ELF_NOTE_DLOPEN_PRIORITY_SUGGESTED "suggested"
/* Add an ".note.dlopen" ELF note to our binary that declares our weak dlopen() dependency. This
* information can be read from an ELF file via "readelf -p .note.dlopen" or an equivalent command. */
#define _ELF_NOTE_DLOPEN(json, variable_name) \
__attribute__((used, section(".note.dlopen"))) _Alignas(sizeof(uint32_t)) static const struct { \
struct { \
uint32_t n_namesz, n_descsz, n_type; \
} nhdr; \
char name[sizeof(ELF_NOTE_DLOPEN_VENDOR)]; \
_Alignas(sizeof(uint32_t)) char dlopen_json[sizeof(json)]; \
} variable_name = { \
.nhdr = { \
.n_namesz = sizeof(ELF_NOTE_DLOPEN_VENDOR), \
.n_descsz = sizeof(json), \
.n_type = ELF_NOTE_DLOPEN_TYPE, \
}, \
.name = ELF_NOTE_DLOPEN_VENDOR, \
.dlopen_json = json, \
}
#define _SONAME_ARRAY1(a) "[\""a"\"]"
#define _SONAME_ARRAY2(a, b) "[\""a"\",\""b"\"]"
#define _SONAME_ARRAY3(a, b, c) "[\""a"\",\""b"\",\""c"\"]"
#define _SONAME_ARRAY4(a, b, c, d) "[\""a"\",\""b"\",\""c"\"",\""d"\"]"
#define _SONAME_ARRAY5(a, b, c, d, e) "[\""a"\",\""b"\",\""c"\"",\""d"\",\""e"\"]"
#define _SONAME_ARRAY_GET(_1,_2,_3,_4,_5,NAME,...) NAME
#define _SONAME_ARRAY(...) _SONAME_ARRAY_GET(__VA_ARGS__, _SONAME_ARRAY5, _SONAME_ARRAY4, _SONAME_ARRAY3, _SONAME_ARRAY2, _SONAME_ARRAY1)(__VA_ARGS__)
/* The 'priority' must be one of 'required', 'recommended' or 'suggested' as per specification, use the
* macro defined above to specify it.
* Multiple sonames can be passed and they will be automatically constructed into a json array (but note that
* due to preprocessor language limitations if more than the limit defined above is used, a new
* _SONAME_ARRAY<X+1> will need to be added). */
#define ELF_NOTE_DLOPEN(feature, description, priority, ...) \
_ELF_NOTE_DLOPEN("[{\"feature\":\"" feature "\",\"description\":\"" description "\",\"priority\":\"" priority "\",\"soname\":" _SONAME_ARRAY(__VA_ARGS__) "}]", UNIQ_T(s, UNIQ))

1
shared/macro.h
View File

@ -37,6 +37,7 @@
#define XCONCATENATE(x, y) x##y
#define CONCATENATE(x, y) XCONCATENATE(x, y)
#define UNIQ(x) CONCATENATE(x, __COUNTER__)
#define UNIQ_T(x, uniq) CONCATENATE(__unique_prefix_, CONCATENATE(x, uniq))
/* Attributes */