Remove kernel version check

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.

5 files changed, 15 insertions, 109 deletions

diff --git a/elf/dl-cache.c b/elf/dl-cache.c
index 88bf78ad7c..8bbf110d02 100644
--- a/elf/dl-cache.c
+++ b/elf/dl-cache.c
@@ -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)
diff --git a/elf/dl-diagnostics.c b/elf/dl-diagnostics.c
index d29bdd6904..dd3871b1e0 100644
--- a/elf/dl-diagnostics.c
+++ b/elf/dl-diagnostics.c
@@ -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
diff --git a/elf/dl-load.c b/elf/dl-load.c
index 2fdd612997..2e4a010fc5 100644
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -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;
-
-      /* 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;
-	      }
+	{
+	  __close_nocancel (fd);
+	  __set_errno (ENOENT);
+	  return -1;
+	}
 
-	    break;
-	  }
-      free (abi_note_malloced);
     }
 
   return fd;
diff --git a/elf/dl-support.c b/elf/dl-support.c
index 153dd57ad2..1e82e8c554 100644
--- a/elf/dl-support.c
+++ b/elf/dl-support.c
@@ -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);
diff --git a/elf/rtld.c b/elf/rtld.c
index 3b2e05bf4c..a8cf9daef0 100644
--- a/elf/rtld.c
+++ b/elf/rtld.c
@@ -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