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.

1 files changed, 15 insertions, 80 deletions

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;