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Remove kernel version check

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The kernel version check is used to avoid glibc to run on older
kernels where some syscall are not available and fallback code are
not enabled to handle graciously fail.  However, it does not prevent
if the kernel does not correctly advertise its version through
vDSO note, uname or procfs.

Also kernel version checks are sometime not desirable by users,
where they want to deploy on different system with different kernel
version knowing the minimum set of syscall is always presented on
such systems.

The kernel version check has been removed along with the
LD_ASSUME_KERNEL environment variable.  The minimum kernel used to
built glibc is still provided through NT_GNU_ABI_TAG ELF note and
also printed when libc.so is issued.

Checked on x86_64-linux-gnu.
This commit is contained in:
Adhemerval Zanella 2022-02-21 08:32:32 -03:00
parent 97a912f7a8
commit b46d250656
17 changed files with 33 additions and 309 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
NEWS
View File

@ -22,6 +22,11 @@ Deprecated and removed features, and other changes affecting compatibility:
removal of the LD_TRACE_PRELINKING, and LD_USE_LOAD_BIAS, environment
variables and their functionality in the dynamic loader.
* The Linux kernel version check has been removed along with the
LD_ASSUME_KERNEL environment variable. The minimum kernel used to built
glibc is still provided through NT_GNU_ABI_TAG ELF note and also printed
when libc.so is issued directly.
Changes to build and runtime requirements:
[Add changes to build and runtime requirements here]

3
config.h.in
View File

@ -135,6 +135,9 @@
/* Linux specific: minimum supported kernel version. */
#undef __LINUX_KERNEL_VERSION
/* Linux specific: __LINUX_KERNEL_VERSION as a string. */
#undef __LINUX_KERNEL_VERSION_STR
/* Override abi-tags ABI version if necessary. */
#undef __ABI_TAG_VERSION

8
csu/libc-start.c
View File

@ -313,14 +313,6 @@ LIBC_START_MAIN (int (*main) (int, char **, char ** MAIN_AUXVEC_DECL),
__stack_chk_guard = stack_chk_guard;
# endif
# ifdef DL_SYSDEP_OSCHECK
{
/* This needs to run to initiliaze _dl_osversion before TLS
setup might check it. */
DL_SYSDEP_OSCHECK (__libc_fatal);
}
# endif
/* Initialize libpthread if linked in. */
if (__pthread_initialize_minimal != NULL)
__pthread_initialize_minimal ();

3
csu/version.c
View File

@ -33,6 +33,9 @@ Compiled by GNU CC version "__VERSION__".\n"
#ifdef LIBC_ABIS_STRING
LIBC_ABIS_STRING
#endif
#ifdef __LINUX_KERNEL_VERSION_STR
"Minimum supported kernel: " __LINUX_KERNEL_VERSION_STR "\n"
#endif
"For bug reporting instructions, please see:\n\
"REPORT_BUGS_TO".\n";

3
elf/dl-cache.c
View File

@ -297,9 +297,6 @@ search_cache (const char *string_table, uint32_t string_table_size,
if ((libnew->hwcap & hwcap_exclude) && !named_hwcap)
continue;
if (GLRO (dl_osversion)
&& libnew->osversion > GLRO (dl_osversion))
continue;
if (_DL_PLATFORMS_COUNT
&& (libnew->hwcap & _DL_HWCAP_PLATFORM) != 0
&& ((libnew->hwcap & _DL_HWCAP_PLATFORM)

5
elf/dl-diagnostics.c
View File

@ -231,10 +231,6 @@ print_version (void)
void
_dl_print_diagnostics (char **environ)
{
#ifdef HAVE_DL_DISCOVER_OSVERSION
_dl_diagnostics_print_labeled_value
("dl_discover_osversion", _dl_discover_osversion ());
#endif
_dl_diagnostics_print_labeled_string ("dl_dst_lib", DL_DST_LIB);
_dl_diagnostics_print_labeled_value ("dl_hwcap", GLRO (dl_hwcap));
_dl_diagnostics_print_labeled_value ("dl_hwcap_important", HWCAP_IMPORTANT);
@ -243,7 +239,6 @@ _dl_print_diagnostics (char **environ)
("dl_hwcaps_subdirs", _dl_hwcaps_subdirs);
_dl_diagnostics_print_labeled_value
("dl_hwcaps_subdirs_active", _dl_hwcaps_subdirs_active ());
_dl_diagnostics_print_labeled_value ("dl_osversion", GLRO (dl_osversion));
_dl_diagnostics_print_labeled_value ("dl_pagesize", GLRO (dl_pagesize));
_dl_diagnostics_print_labeled_string ("dl_platform", GLRO (dl_platform));
_dl_diagnostics_print_labeled_string

95
elf/dl-load.c
View File

@ -1591,13 +1591,6 @@ open_verify (const char *name, int fd,
[EI_OSABI] = ELFOSABI_SYSV,
[EI_ABIVERSION] = 0
};
static const struct
{
ElfW(Word) vendorlen;
ElfW(Word) datalen;
ElfW(Word) type;
char vendor[4];
} expected_note = { 4, 16, 1, "GNU" };
/* Initialize it to make the compiler happy. */
const char *errstring = NULL;
int errval = 0;
@ -1628,10 +1621,7 @@ open_verify (const char *name, int fd,
if (fd != -1)
{
ElfW(Ehdr) *ehdr;
ElfW(Phdr) *phdr, *ph;
ElfW(Word) *abi_note;
ElfW(Word) *abi_note_malloced = NULL;
unsigned int osversion;
ElfW(Phdr) *phdr;
size_t maplength;
/* We successfully opened the file. Now verify it is a file
@ -1695,13 +1685,16 @@ open_verify (const char *name, int fd,
#endif
)
errstring = N_("invalid ELF header");
else if (ehdr->e_ident[EI_CLASS] != ELFW(CLASS))
{
/* This is not a fatal error. On architectures where
32-bit and 64-bit binaries can be run this might
happen. */
*found_other_class = true;
goto close_and_out;
__close_nocancel (fd);
__set_errno (ENOENT);
return -1;
}
else if (ehdr->e_ident[EI_DATA] != byteorder)
{
@ -1736,7 +1729,11 @@ open_verify (const char *name, int fd,
goto lose;
}
if (! __glibc_likely (elf_machine_matches_host (ehdr)))
goto close_and_out;
{
__close_nocancel (fd);
__set_errno (ENOENT);
return -1;
}
else if (__glibc_unlikely (ehdr->e_type != ET_DYN
&& ehdr->e_type != ET_EXEC))
{
@ -1758,7 +1755,6 @@ open_verify (const char *name, int fd,
if ((size_t) __pread64_nocancel (fd, (void *) phdr, maplength,
ehdr->e_phoff) != maplength)
{
read_error:
errval = errno;
errstring = N_("cannot read file data");
goto lose;
@ -1768,73 +1764,12 @@ open_verify (const char *name, int fd,
if (__glibc_unlikely (elf_machine_reject_phdr_p
(phdr, ehdr->e_phnum, fbp->buf, fbp->len,
loader, fd)))
goto close_and_out;
{
__close_nocancel (fd);
__set_errno (ENOENT);
return -1;
}
/* Check .note.ABI-tag if present. */
for (ph = phdr; ph < &phdr[ehdr->e_phnum]; ++ph)
if (ph->p_type == PT_NOTE && ph->p_filesz >= 32
&& (ph->p_align == 4 || ph->p_align == 8))
{
ElfW(Addr) size = ph->p_filesz;
if (ph->p_offset + size <= (size_t) fbp->len)
abi_note = (void *) (fbp->buf + ph->p_offset);
else
{
/* Note: __libc_use_alloca is not usable here, because
thread info may not have been set up yet. */
if (size < __MAX_ALLOCA_CUTOFF)
abi_note = alloca (size);
else
{
/* There could be multiple PT_NOTEs. */
abi_note_malloced = realloc (abi_note_malloced, size);
if (abi_note_malloced == NULL)
goto read_error;
abi_note = abi_note_malloced;
}
if (__pread64_nocancel (fd, (void *) abi_note, size,
ph->p_offset) != size)
{
free (abi_note_malloced);
goto read_error;
}
}
while (memcmp (abi_note, &expected_note, sizeof (expected_note)))
{
ElfW(Addr) note_size
= ELF_NOTE_NEXT_OFFSET (abi_note[0], abi_note[1],
ph->p_align);
if (size - 32 < note_size)
{
size = 0;
break;
}
size -= note_size;
abi_note = (void *) abi_note + note_size;
}
if (size == 0)
continue;
osversion = (abi_note[5] & 0xff) * 65536
+ (abi_note[6] & 0xff) * 256
+ (abi_note[7] & 0xff);
if (abi_note[4] != __ABI_TAG_OS
|| (GLRO(dl_osversion) && GLRO(dl_osversion) < osversion))
{
close_and_out:
__close_nocancel (fd);
__set_errno (ENOENT);
fd = -1;
}
break;
}
free (abi_note_malloced);
}
return fd;

6
elf/dl-support.c
View File

@ -145,8 +145,6 @@ size_t _dl_minsigstacksize = CONSTANT_MINSIGSTKSZ;
int _dl_inhibit_cache;
unsigned int _dl_osversion;
/* All known directories in sorted order. */
struct r_search_path_elem *_dl_all_dirs;
@ -327,10 +325,6 @@ _dl_non_dynamic_init (void)
DL_PLATFORM_INIT;
#endif
#ifdef DL_OSVERSION_INIT
DL_OSVERSION_INIT;
#endif
/* Now determine the length of the platform string. */
if (_dl_platform != NULL)
_dl_platformlen = strlen (_dl_platform);

15
elf/rtld.c
View File

@ -384,9 +384,6 @@ struct rtld_global_ro _rtld_global_ro attribute_relro =
._dl_error_free = _dl_error_free,
._dl_tls_get_addr_soft = _dl_tls_get_addr_soft,
._dl_libc_freeres = __rtld_libc_freeres,
#ifdef HAVE_DL_DISCOVER_OSVERSION
._dl_discover_osversion = _dl_discover_osversion
#endif
};
/* If we would use strong_alias here the compiler would see a
non-hidden definition. This would undo the effect of the previous
@ -1710,10 +1707,6 @@ dl_main (const ElfW(Phdr) *phdr,
/* With vDSO setup we can initialize the function pointers. */
setup_vdso_pointers ();
#ifdef DL_SYSDEP_OSCHECK
DL_SYSDEP_OSCHECK (_dl_fatal_printf);
#endif
/* Initialize the data structures for the search paths for shared
objects. */
call_init_paths (&state);
@ -2638,14 +2631,6 @@ process_envvars (struct dl_main_state *state)
GLRO(dl_dynamic_weak) = 1;
break;
case 13:
/* We might have some extra environment variable with length 13
to handle. */
#ifdef EXTRA_LD_ENVVARS_13
EXTRA_LD_ENVVARS_13
#endif
break;
case 14:
/* Where to place the profiling data file. */
if (!__libc_enable_secure

6
sysdeps/generic/ldsodefs.h
View File

@ -552,8 +552,6 @@ struct rtld_global_ro
/* These two are used only internally. */
#define DL_DEBUG_HELP (1 << 10)
/* OS version. */
EXTERN unsigned int _dl_osversion;
/* Platform name. */
EXTERN const char *_dl_platform;
EXTERN size_t _dl_platformlen;
@ -701,10 +699,6 @@ struct rtld_global_ro
dlopen. */
int (*_dl_find_object) (void *, struct dl_find_object *);
#ifdef HAVE_DL_DISCOVER_OSVERSION
int (*_dl_discover_osversion) (void);
#endif
/* Dynamic linker operations used after static dlopen. */
const struct dlfcn_hook *_dl_dlfcn_hook;

5
sysdeps/unix/sysv/linux/configure vendored
View File

@ -70,6 +70,7 @@ fi
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for kernel header at least $minimum_kernel" >&5
$as_echo_n "checking for kernel header at least $minimum_kernel... " >&6; }
decnum=`echo "$minimum_kernel.0.0.0" | sed 's/\([0-9]*\)\.\([0-9]*\)\.\([0-9]*\).*/(\1 * 65536 + \2 * 256 + \3)/'`;
abinumstr=`echo "$minimum_kernel.0.0.0" | sed 's/\([0-9]*\)\.\([0-9]*\)\.\([0-9]*\).*/\1.\2.\3/'`;
abinum=`echo "$minimum_kernel.0.0.0" | sed 's/\([0-9]*\)\.\([0-9]*\)\.\([0-9]*\).*/\1,\2,\3/'`;
cat confdefs.h - <<_ACEOF >conftest.$ac_ext
/* end confdefs.h. */
@ -96,6 +97,10 @@ $as_echo "$libc_minimum_kernel" >&6; }
if test "$libc_minimum_kernel" = ok; then
cat >>confdefs.h <<_ACEOF
#define __LINUX_KERNEL_VERSION $decnum
_ACEOF
cat >>confdefs.h <<_ACEOF
#define __LINUX_KERNEL_VERSION_STR "$abinumstr"
_ACEOF
cat >>confdefs.h <<_ACEOF

2
sysdeps/unix/sysv/linux/configure.ac
View File

@ -50,6 +50,7 @@ fi
AC_MSG_CHECKING(for kernel header at least $minimum_kernel)
changequote(,)dnl
decnum=`echo "$minimum_kernel.0.0.0" | sed 's/\([0-9]*\)\.\([0-9]*\)\.\([0-9]*\).*/(\1 * 65536 + \2 * 256 + \3)/'`;
abinumstr=`echo "$minimum_kernel.0.0.0" | sed 's/\([0-9]*\)\.\([0-9]*\)\.\([0-9]*\).*/\1.\2.\3/'`;
abinum=`echo "$minimum_kernel.0.0.0" | sed 's/\([0-9]*\)\.\([0-9]*\)\.\([0-9]*\).*/\1,\2,\3/'`;
changequote([,])dnl
AC_PREPROC_IFELSE([AC_LANG_PROGRAM([[#include <linux/version.h>
@ -59,6 +60,7 @@ AC_PREPROC_IFELSE([AC_LANG_PROGRAM([[#include <linux/version.h>
AC_MSG_RESULT($libc_minimum_kernel)
if test "$libc_minimum_kernel" = ok; then
AC_DEFINE_UNQUOTED(__LINUX_KERNEL_VERSION, $decnum)
AC_DEFINE_UNQUOTED(__LINUX_KERNEL_VERSION_STR, "$abinumstr")
AC_DEFINE_UNQUOTED(__ABI_TAG_VERSION, $abinum)
else
AC_MSG_ERROR([*** The available kernel headers are older than the requested

59
sysdeps/unix/sysv/linux/dl-librecon.h
View File

@ -1,59 +0,0 @@
/* Optional code to distinguish library flavours.
Copyright (C) 2001-2022 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#ifndef _DL_LIBRECON_H
#define _DL_LIBRECON_H 1
static inline void __attribute__ ((unused, always_inline))
_dl_osversion_init (char *assume_kernel)
{
unsigned long int i, j, osversion = 0;
char *p = assume_kernel, *q;
for (i = 0; i < 3; i++, p = q + 1)
{
j = _dl_strtoul (p, &q);
if (j >= 255 || p == q || (i < 2 && *q && *q != '.'))
{
osversion = 0;
break;
}
osversion |= j << (16 - 8 * i);
if (!*q)
break;
}
if (osversion)
GLRO(dl_osversion) = osversion;
}
/* Recognizing extra environment variables. */
#define EXTRA_LD_ENVVARS_13 \
if (memcmp (envline, "ASSUME_KERNEL", 13) == 0) \
{ \
_dl_osversion_init (&envline[14]); \
break; \
}
#define DL_OSVERSION_INIT \
do { \
char *assume_kernel = getenv ("LD_ASSUME_KERNEL"); \
if (assume_kernel) \
_dl_osversion_init (assume_kernel); \
} while (0)
#endif /* dl-librecon.h */

25
sysdeps/unix/sysv/linux/dl-osinfo.h
View File

@ -22,31 +22,6 @@
#include <stdint.h>
#include <not-cancel.h>
#ifndef MIN
# define MIN(a,b) (((a)<(b))?(a):(b))
#endif
#define DL_SYSDEP_OSCHECK(FATAL) \
do { \
/* Test whether the kernel is new enough. This test is only performed \
if the library is not compiled to run on all kernels. */ \
\
int version = _dl_discover_osversion (); \
if (__glibc_likely (version >= 0)) \
{ \
if (__builtin_expect (GLRO(dl_osversion) == 0, 1) \
|| GLRO(dl_osversion) > version) \
GLRO(dl_osversion) = version; \
\
/* Now we can test with the required version. */ \
if (__LINUX_KERNEL_VERSION > 0 && version < __LINUX_KERNEL_VERSION) \
/* Not sufficent. */ \
FATAL ("FATAL: kernel too old\n"); \
} \
else if (__LINUX_KERNEL_VERSION > 0) \
FATAL ("FATAL: cannot determine kernel version\n"); \
} while (0)
static inline uintptr_t __attribute__ ((always_inline))
_dl_setup_stack_chk_guard (void *dl_random)
{

93
sysdeps/unix/sysv/linux/dl-sysdep.c
View File

@ -250,96 +250,3 @@ _dl_show_auxv (void)
}
#endif /* SHARED */
int
attribute_hidden
_dl_discover_osversion (void)
{
#ifdef SHARED
if (GLRO(dl_sysinfo_map) != NULL)
{
/* If the kernel-supplied DSO contains a note indicating the kernel's
version, we don't need to call uname or parse any strings. */
static const struct
{
ElfW(Nhdr) hdr;
char vendor[8];
} expected_note = { { sizeof "Linux", sizeof (ElfW(Word)), 0 }, "Linux" };
const ElfW(Phdr) *const phdr = GLRO(dl_sysinfo_map)->l_phdr;
const ElfW(Word) phnum = GLRO(dl_sysinfo_map)->l_phnum;
for (unsigned int i = 0; i < phnum; ++i)
if (phdr[i].p_type == PT_NOTE)
{
const ElfW(Addr) start = (phdr[i].p_vaddr
+ GLRO(dl_sysinfo_map)->l_addr);
const ElfW(Nhdr) *note = (const void *) start;
while ((ElfW(Addr)) (note + 1) - start < phdr[i].p_memsz)
{
if (!memcmp (note, &expected_note, sizeof expected_note))
return *(const ElfW(Word) *) ((const void *) note
+ sizeof expected_note);
#define ROUND(len) (((len) + sizeof note->n_type - 1) & -sizeof note->n_type)
note = ((const void *) (note + 1)
+ ROUND (note->n_namesz) + ROUND (note->n_descsz));
#undef ROUND
}
}
}
#endif /* SHARED */
char bufmem[64];
char *buf = bufmem;
unsigned int version;
int parts;
char *cp;
struct utsname uts;
/* Try the uname system call. */
if (__uname (&uts))
{
/* This was not successful. Now try reading the /proc filesystem. */
int fd = __open64_nocancel ("/proc/sys/kernel/osrelease", O_RDONLY);
if (fd < 0)
return -1;
ssize_t reslen = __read_nocancel (fd, bufmem, sizeof (bufmem));
__close_nocancel (fd);
if (reslen <= 0)
/* This also didn't work. We give up since we cannot
make sure the library can actually work. */
return -1;
buf[MIN (reslen, (ssize_t) sizeof (bufmem) - 1)] = '\0';
}
else
buf = uts.release;
/* Now convert it into a number. The string consists of at most
three parts. */
version = 0;
parts = 0;
cp = buf;
while ((*cp >= '0') && (*cp <= '9'))
{
unsigned int here = *cp++ - '0';
while ((*cp >= '0') && (*cp <= '9'))
{
here *= 10;
here += *cp++ - '0';
}
++parts;
version <<= 8;
version |= here;
if (*cp++ != '.' || parts == 3)
/* Another part following? */
break;
}
if (parts < 3)
version <<= 8 * (3 - parts);
return version;
}

7
sysdeps/unix/sysv/linux/dl-sysdep.h
View File

@ -24,10 +24,3 @@
we aren't making direct use of it. So enable this across the board. */
#define NEED_DL_SYSINFO_DSO 1
#ifndef __ASSEMBLER__
/* Get version of the OS. */
extern int _dl_discover_osversion (void) attribute_hidden;
# define HAVE_DL_DISCOVER_OSVERSION 1
#endif

2
sysdeps/unix/sysv/linux/i386/dl-librecon.h
View File

@ -18,8 +18,6 @@
#ifndef _DL_LIBRECON_H
#include <sysdeps/unix/sysv/linux/dl-librecon.h>
#define DISTINGUISH_LIB_VERSIONS \
do \
{ \