Support decompression of ZSTD sections and add support
for it when -SWz is used:
...
[30] .debug_abbrev PROGBITS 0000000000000000 00001f9d 00000168 0 C
0 0 1
[ELF ZSTD (2) 000002fc 1]
...
One TODO I see is that:
+libelf_so_LDLIBS = $(libelf_so_DEPS) -lz -lzstd
should be conditional based on HAVE_ZSTD. But I don't know how to do that?
And the second part should cover elfcompress where it should support ZSTD
compression,
leaving that for now.
Martin
libelf/ChangeLog:
* Makefile.am: Add -lzstd.
* elf.h (ELFCOMPRESS_ZSTD): Add new value.
* elf_compress.c (__libelf_decompress): Dispatch based
on the compression algorithm.
(__libelf_decompress_zlib): New.
(__libelf_decompress_zstd): New.
(__libelf_decompress_elf): Pass type of compression to
__libelf_decompress.
* elf_compress_gnu.c (elf_compress_gnu): Use ELFCOMPRESS_ZLIB
as .z* sections can be only compressed with ZLIB.
* libelfP.h (__libelf_decompress): Change signature.
m4/ChangeLog:
* zstd.m4: New file.
src/ChangeLog:
* readelf.c (elf_ch_type_name): Use switch and support ZSTD.
---
libelf/Makefile.am | 2 +-
libelf/elf.h | 3 +++
libelf/elf_compress.c | 56 ++++++++++++++++++++++++++++++++++++---
libelf/elf_compress_gnu.c | 2 +-
libelf/libelfP.h | 2 +-
m4/zstd.m4 | 23 ++++++++++++++++
src/readelf.c | 18 ++++++++-----
7 files changed, 93 insertions(+), 13 deletions(-)
create mode 100644 m4/zstd.m4
diff --git a/libelf/Makefile.am b/libelf/Makefile.am
index 560ed45f..33f3a0a1 100644
--- a/libelf/Makefile.am
+++ b/libelf/Makefile.am
@@ -106,7 +106,7 @@ libelf_pic_a_SOURCES =
am_libelf_pic_a_OBJECTS = $(libelf_a_SOURCES:.c=.os)
libelf_so_DEPS = ../lib/libeu.a
-libelf_so_LDLIBS = $(libelf_so_DEPS) -lz
+libelf_so_LDLIBS = $(libelf_so_DEPS) -lz -lzstd
if USE_LOCKS
libelf_so_LDLIBS += -lpthread
endif
diff --git a/libelf/elf.h b/libelf/elf.h
index 02a1b3f5..f0f0ec7d 100644
--- a/libelf/elf.h
+++ b/libelf/elf.h
@@ -506,6 +506,9 @@ typedef struct
/* Legal values for ch_type (compression algorithm). */
#define ELFCOMPRESS_ZLIB 1 /* ZLIB/DEFLATE algorithm. */
+#define ELFCOMPRESS_ZSTD 2 /* Compressed with zstd */
+ /* (see http://www.zstandard.org). */
+
#define ELFCOMPRESS_LOOS 0x60000000 /* Start of OS-specific. */
#define ELFCOMPRESS_HIOS 0x6fffffff /* End of OS-specific. */
#define ELFCOMPRESS_LOPROC 0x70000000 /* Start of processor-specific. */
diff --git a/libelf/elf_compress.c b/libelf/elf_compress.c
index d7f53af2..62b41b20 100644
--- a/libelf/elf_compress.c
+++ b/libelf/elf_compress.c
@@ -39,6 +39,10 @@
#include <string.h>
#include <zlib.h>
+#ifdef USE_ZSTD
+#include <zstd.h>
+#endif
+
/* Cleanup and return result. Don't leak memory. */
static void *
do_deflate_cleanup (void *result, z_stream *z, void *out_buf,
@@ -207,7 +211,7 @@ __libelf_compress (Elf_Scn *scn, size_t hsize, int ei_data,
void *
internal_function
-__libelf_decompress (void *buf_in, size_t size_in, size_t size_out)
+__libelf_decompress_zlib (void *buf_in, size_t size_in, size_t size_out)
{
/* Catch highly unlikely compression ratios so we don't allocate
some giant amount of memory for nothing. The max compression
@@ -260,6 +264,50 @@ __libelf_decompress (void *buf_in, size_t size_in, size_t
size_out)
return buf_out;
}
+#ifdef USE_ZSTD
+void *
+internal_function
+__libelf_decompress_zstd (void *buf_in, size_t size_in, size_t size_out)
+{
+ /* Malloc might return NULL when requestion zero size. This is highly
+ unlikely, it would only happen when the compression was forced.
+ But we do need a non-NULL buffer to return and set as result.
+ Just make sure to always allocate at least 1 byte. */
+ void *buf_out = malloc (size_out ?: 1);
+ if (unlikely (buf_out == NULL))
+ {
+ __libelf_seterrno (ELF_E_NOMEM);
+ return NULL;
+ }
+
+ size_t ret = ZSTD_decompress (buf_out, size_out, buf_in, size_in);
+ if (ZSTD_isError (ret))
+ {
+ free (buf_out);
+ __libelf_seterrno (ELF_E_DECOMPRESS_ERROR);
+ return NULL;
+ }
+ else
+ return buf_out;
+}
+#endif
+
+void *
+internal_function
+__libelf_decompress (int chtype, void *buf_in, size_t size_in, size_t size_out)
+{
+ if (chtype == ELFCOMPRESS_ZLIB)
+ return __libelf_decompress_zlib (buf_in, size_in, size_out);
+ else
+ {
+#ifdef USE_ZSTD
+ return __libelf_decompress_zstd (buf_in, size_in, size_out);
+#else
+ return 0;
+#endif
+ }
+}
+
void *
internal_function
__libelf_decompress_elf (Elf_Scn *scn, size_t *size_out, size_t *addralign)
@@ -268,7 +316,7 @@ __libelf_decompress_elf (Elf_Scn *scn, size_t *size_out,
size_t *addralign)
if (gelf_getchdr (scn, &chdr) == NULL)
return NULL;
- if (chdr.ch_type != ELFCOMPRESS_ZLIB)
+ if (chdr.ch_type != ELFCOMPRESS_ZLIB && chdr.ch_type != ELFCOMPRESS_ZSTD)
{
__libelf_seterrno (ELF_E_UNKNOWN_COMPRESSION_TYPE);
return NULL;
@@ -295,7 +343,9 @@ __libelf_decompress_elf (Elf_Scn *scn, size_t *size_out,
size_t *addralign)
? sizeof (Elf32_Chdr) : sizeof (Elf64_Chdr));
size_t size_in = data->d_size - hsize;
void *buf_in = data->d_buf + hsize;
- void *buf_out = __libelf_decompress (buf_in, size_in, chdr.ch_size);
+ void *buf_out
+ = __libelf_decompress (chdr.ch_type, buf_in, size_in, chdr.ch_size);
+
*size_out = chdr.ch_size;
*addralign = chdr.ch_addralign;
return buf_out;
diff --git a/libelf/elf_compress_gnu.c b/libelf/elf_compress_gnu.c
index 3d2977e7..be9e990e 100644
--- a/libelf/elf_compress_gnu.c
+++ b/libelf/elf_compress_gnu.c
@@ -178,7 +178,7 @@ elf_compress_gnu (Elf_Scn *scn, int inflate, unsigned int
flags)
size_t size = gsize;
size_t size_in = data->d_size - hsize;
void *buf_in = data->d_buf + hsize;
- void *buf_out = __libelf_decompress (buf_in, size_in, size);
+ void *buf_out = __libelf_decompress (ELFCOMPRESS_ZLIB, buf_in, size_in,
size);
if (buf_out == NULL)
return -1;
diff --git a/libelf/libelfP.h b/libelf/libelfP.h
index d88a613c..ab82357c 100644
--- a/libelf/libelfP.h
+++ b/libelf/libelfP.h
@@ -577,7 +577,7 @@ extern void * __libelf_compress (Elf_Scn *scn, size_t
hsize, int ei_data,
size_t *size, bool force)
internal_function;
-extern void * __libelf_decompress (void *buf_in, size_t size_in,
+extern void * __libelf_decompress (int chtype, void *buf_in, size_t size_in,
size_t size_out) internal_function;
extern void * __libelf_decompress_elf (Elf_Scn *scn,
size_t *size_out, size_t *addralign)
diff --git a/m4/zstd.m4 b/m4/zstd.m4
new file mode 100644
index 00000000..6da4db68
--- /dev/null
+++ b/m4/zstd.m4
@@ -0,0 +1,23 @@
+dnl Copyright (C) 2022 Free Software Foundation, Inc.
+dnl This file is free software, distributed under the terms of the GNU
+dnl General Public License. As a special exception to the GNU General
+dnl Public License, this file may be distributed as part of a program
+dnl that contains a configuration script generated by Autoconf, under
+dnl the same distribution terms as the rest of that program.
+
+dnl Enable features using the zstd library.
+AC_DEFUN([AC_ZSTD], [
+AC_ARG_WITH(zstd,
+ [AS_HELP_STRING([--with-zstd], [support zstd compressed debug sections
(default=auto)])],
+ [], [with_zstd=auto])
+
+AS_IF([test "$with_zstd" != no],
+ [PKG_CHECK_MODULES(ZSTD, [libzstd], [
+ AC_DEFINE(HAVE_ZSTD, 1, [Define to 1 if zstd is enabled.])
+ ], [
+ if test "$with_zstd" = yes; then
+ AC_MSG_ERROR([--with-zstd was given, but pkgconfig/libzstd.pc is not
found])
+ fi
+ ])
+ ])
+])
diff --git a/src/readelf.c b/src/readelf.c
index a206e60e..1af20e35 100644
--- a/src/readelf.c
+++ b/src/readelf.c
@@ -1229,13 +1229,17 @@ get_visibility_type (int value)
static const char *
elf_ch_type_name (unsigned int code)
{
- if (code == 0)
- return "NONE";
-
- if (code == ELFCOMPRESS_ZLIB)
- return "ZLIB";
-
- return "UNKNOWN";
+ switch (code)
+ {
+ case 0:
+ return "NONE";
+ case ELFCOMPRESS_ZLIB:
+ return "ZLIB";
+ case ELFCOMPRESS_ZSTD:
+ return "ZSTD";
+ default:
+ return "UNKNOWN";
+ }
}
/* Print the section headers. */
--
2.38.0
