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, 0 insertions, 93 deletions

diff --git a/sysdeps/unix/sysv/linux/dl-sysdep.c b/sysdeps/unix/sysv/linux/dl-sysdep.c
index a67c454673..9e15c5bf69 100644
--- a/sysdeps/unix/sysv/linux/dl-sysdep.c
+++ b/sysdeps/unix/sysv/linux/dl-sysdep.c
@@ -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;
-}