[BZ #5786]

* elf/dl-sysdep.c: Undefine ROUND after use.
	* sysdeps/generic/ldsodefs.h [HAVE_DL_DISCOVER_OSVERSION]
	(struct rtld_global_ro): Add _dl_tls_get_addr_soft element.
	* elf/rtld.c (rtld_global_ro): Initialize _dl_discover_osversion.
	* sysdeps/unix/sysv/linux/dl-osinfo.h: Move _dl_discover_osversion
	to ...
	* sysdeps/unix/sysv/linux/dl-sysdep.c: ...here.
	* sysdeps/unix/sysv/linux/dl-sysdep.h: Declare _dl_discover_osversion
	if necessary.
	* sysdeps/unix/sysv/linux/sysconf.c: Handle _SC_ARG_MAX here.

sysdeps/unix/sysv/linux/dl-sysdep.c

@@ -1,5 +1,5 @@
 /* Dynamic linker system dependencies for Linux.
-   Copyright (C) 1995,1997,2001,2004,2005,2006 Free Software Foundation, Inc.
+   Copyright (C) 1995,1997,2001,2004,2005,2006, 2008 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
@@ -20,7 +20,10 @@
 /* Linux needs some special initialization, but otherwise uses
    the generic dynamic linker system interface code.  */
 
+#include <string.h>
+#include <fcntl.h>
 #include <unistd.h>
+#include <sys/utsname.h>
 #include <ldsodefs.h>
 #include <kernel-features.h>
 
@@ -54,3 +57,96 @@ frob_brk (void)
 }
 
 #include <elf/dl-sysdep.c>
+
+
+int
+attribute_hidden
+_dl_discover_osversion (void)
+{
+#if (defined NEED_DL_SYSINFO || defined NEED_DL_SYSINFO_DSO) && defined 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 (uint_fast16_t 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
+
+  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 = __open ("/proc/sys/kernel/osrelease", O_RDONLY);
+      if (fd < 0)
+	return -1;
+      ssize_t reslen = __read (fd, bufmem, sizeof (bufmem));
+      __close (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;
+}