Make sure that the fortified function conditionals are constant

In _FORTIFY_SOURCE=3, the size expression may be non-constant,
resulting in branches in the inline functions remaining intact and
causing a tiny overhead.  Clang (and in future, gcc) make sure that
the -1 case is always safe, i.e. any comparison of the generated
expression with (size_t)-1 is always false so that bit is taken care
of.  The rest is avoidable since we want the _chk variant whenever we
have a size expression and it's not -1.

Rework the conditionals in a uniform way to clearly indicate two
conditions at compile time:

- Either the size is unknown (-1) or we know at compile time that the
  operation length is less than the object size.  We can call the
  original function in this case.  It could be that either the length,
  object size or both are non-constant, but the compiler, through
  range analysis, is able to fold the *comparison* to a constant.

- The size and length are known and the compiler can see at compile
  time that operation length > object size.  This is valid grounds for
  a warning at compile time, followed by emitting the _chk variant.

For everything else, emit the _chk variant.

This simplifies most of the fortified function implementations and at
the same time, ensures that only one call from _chk or the regular
function is emitted.

Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

7 files changed, 226 insertions, 438 deletions

diff --git a/io/bits/poll2.h b/io/bits/poll2.h
index be74d020f2..91cdcaf66a 100644
--- a/io/bits/poll2.h
+++ b/io/bits/poll2.h
@@ -36,16 +36,9 @@ extern int __REDIRECT (__poll_chk_warn, (struct pollfd *__fds, nfds_t __nfds,
 __fortify_function __fortified_attr_access (__write_only__, 1, 2) int
 poll (struct pollfd *__fds, nfds_t __nfds, int __timeout)
 {
-  if (__glibc_objsize (__fds) != (__SIZE_TYPE__) -1)
-    {
-      if (! __builtin_constant_p (__nfds))
-	return __poll_chk (__fds, __nfds, __timeout, __glibc_objsize (__fds));
-      else if (__glibc_objsize (__fds) / sizeof (*__fds) < __nfds)
-	return __poll_chk_warn (__fds, __nfds, __timeout,
-				__glibc_objsize (__fds));
-    }
-
-  return __poll_alias (__fds, __nfds, __timeout);
+  return __glibc_fortify (poll, __nfds, sizeof (*__fds),
+			  __glibc_objsize (__fds),
+			  __fds, __nfds, __timeout);
 }
 
 
@@ -68,17 +61,9 @@ __fortify_function __fortified_attr_access (__write_only__, 1, 2) int
 ppoll (struct pollfd *__fds, nfds_t __nfds, const struct timespec *__timeout,
        const __sigset_t *__ss)
 {
-  if (__glibc_objsize (__fds) != (__SIZE_TYPE__) -1)
-    {
-      if (! __builtin_constant_p (__nfds))
-	return __ppoll_chk (__fds, __nfds, __timeout, __ss,
-			    __glibc_objsize (__fds));
-      else if (__glibc_objsize (__fds) / sizeof (*__fds) < __nfds)
-	return __ppoll_chk_warn (__fds, __nfds, __timeout, __ss,
-				 __glibc_objsize (__fds));
-    }
-
-  return __ppoll_alias (__fds, __nfds, __timeout, __ss);
+  return __glibc_fortify (ppoll, __nfds, sizeof (*__fds),
+			  __glibc_objsize (__fds),
+			  __fds, __nfds, __timeout, __ss);
 }
 #endif
 
diff --git a/libio/bits/stdio2.h b/libio/bits/stdio2.h
index 4f016a5638..40ff16b01b 100644
--- a/libio/bits/stdio2.h
+++ b/libio/bits/stdio2.h
@@ -261,15 +261,12 @@ extern char *__REDIRECT (__fgets_chk_warn,
 __fortify_function __wur __fortified_attr_access (__write_only__, 1, 2) char *
 fgets (char *__restrict __s, int __n, FILE *__restrict __stream)
 {
-  if (__glibc_objsize (__s) != (size_t) -1)
-    {
-      if (!__builtin_constant_p (__n) || __n <= 0)
-	return __fgets_chk (__s, __glibc_objsize (__s), __n, __stream);
-
-      if ((size_t) __n > __glibc_objsize (__s))
-	return __fgets_chk_warn (__s, __glibc_objsize (__s), __n, __stream);
-    }
-  return __fgets_alias (__s, __n, __stream);
+  size_t sz = __glibc_objsize (__s);
+  if (__glibc_safe_or_unknown_len (__n, sizeof (char), sz))
+    return __fgets_alias (__s, __n, __stream);
+  if (__glibc_unsafe_len (__n, sizeof (char), sz))
+    return __fgets_chk_warn (__s, sz, __n, __stream);
+  return __fgets_chk (__s, sz, __n, __stream);
 }
 
 extern size_t __fread_chk (void *__restrict __ptr, size_t __ptrlen,
@@ -291,19 +288,12 @@ __fortify_function __wur size_t
 fread (void *__restrict __ptr, size_t __size, size_t __n,
        FILE *__restrict __stream)
 {
-  if (__glibc_objsize0 (__ptr) != (size_t) -1)
-    {
-      if (!__builtin_constant_p (__size)
-	  || !__builtin_constant_p (__n)
-	  || (__size | __n) >= (((size_t) 1) << (8 * sizeof (size_t) / 2)))
-	return __fread_chk (__ptr, __glibc_objsize0 (__ptr), __size, __n,
-			    __stream);
-
-      if (__size * __n > __glibc_objsize0 (__ptr))
-	return __fread_chk_warn (__ptr, __glibc_objsize0 (__ptr), __size, __n,
-				 __stream);
-    }
-  return __fread_alias (__ptr, __size, __n, __stream);
+  size_t sz = __glibc_objsize0 (__ptr);
+  if (__glibc_safe_or_unknown_len (__n, __size, sz))
+    return __fread_alias (__ptr, __size, __n, __stream);
+  if (__glibc_unsafe_len (__n, __size, sz))
+    return __fread_chk_warn (__ptr, sz, __size, __n, __stream);
+  return __fread_chk (__ptr, sz, __size, __n, __stream);
 }
 
 #ifdef __USE_GNU
@@ -323,17 +313,12 @@ extern char *__REDIRECT (__fgets_unlocked_chk_warn,
 __fortify_function __wur __fortified_attr_access (__write_only__, 1, 2) char *
 fgets_unlocked (char *__restrict __s, int __n, FILE *__restrict __stream)
 {
-  if (__glibc_objsize (__s) != (size_t) -1)
-    {
-      if (!__builtin_constant_p (__n) || __n <= 0)
-	return __fgets_unlocked_chk (__s, __glibc_objsize (__s), __n,
-				     __stream);
-
-      if ((size_t) __n > __glibc_objsize (__s))
-	return __fgets_unlocked_chk_warn (__s, __glibc_objsize (__s), __n,
-					  __stream);
-    }
-  return __fgets_unlocked_alias (__s, __n, __stream);
+  size_t sz = __glibc_objsize (__s);
+  if (__glibc_safe_or_unknown_len (__n, sizeof (char), sz))
+    return __fgets_unlocked_alias (__s, __n, __stream);
+  if (__glibc_unsafe_len (__n, sizeof (char), sz))
+    return __fgets_unlocked_chk_warn (__s, sz, __n, __stream);
+  return __fgets_unlocked_chk (__s, sz, __n, __stream);
 }
 #endif
 
@@ -358,41 +343,36 @@ __fortify_function __wur size_t
 fread_unlocked (void *__restrict __ptr, size_t __size, size_t __n,
 		FILE *__restrict __stream)
 {
-  if (__glibc_objsize0 (__ptr) != (size_t) -1)
+  size_t sz = __glibc_objsize0 (__ptr);
+  if (__glibc_safe_or_unknown_len (__n, __size, sz))
     {
-      if (!__builtin_constant_p (__size)
-	  || !__builtin_constant_p (__n)
-	  || (__size | __n) >= (((size_t) 1) << (8 * sizeof (size_t) / 2)))
-	return __fread_unlocked_chk (__ptr, __glibc_objsize0 (__ptr), __size,
-				     __n, __stream);
-
-      if (__size * __n > __glibc_objsize0 (__ptr))
-	return __fread_unlocked_chk_warn (__ptr, __glibc_objsize0 (__ptr),
-					  __size, __n, __stream);
-    }
-
 # ifdef __USE_EXTERN_INLINES
-  if (__builtin_constant_p (__size)
-      && __builtin_constant_p (__n)
-      && (__size | __n) < (((size_t) 1) << (8 * sizeof (size_t) / 2))
-      && __size * __n <= 8)
-    {
-      size_t __cnt = __size * __n;
-      char *__cptr = (char *) __ptr;
-      if (__cnt == 0)
-	return 0;
-
-      for (; __cnt > 0; --__cnt)
+      if (__builtin_constant_p (__size)
+	  && __builtin_constant_p (__n)
+	  && (__size | __n) < (((size_t) 1) << (8 * sizeof (size_t) / 2))
+	  && __size * __n <= 8)
 	{
-	  int __c = getc_unlocked (__stream);
-	  if (__c == EOF)
-	    break;
-	  *__cptr++ = __c;
+	  size_t __cnt = __size * __n;
+	  char *__cptr = (char *) __ptr;
+	  if (__cnt == 0)
+	    return 0;
+
+	  for (; __cnt > 0; --__cnt)
+	    {
+	      int __c = getc_unlocked (__stream);
+	      if (__c == EOF)
+		break;
+	      *__cptr++ = __c;
+	    }
+	  return (__cptr - (char *) __ptr) / __size;
 	}
-      return (__cptr - (char *) __ptr) / __size;
-    }
 # endif
-  return __fread_unlocked_alias (__ptr, __size, __n, __stream);
+      return __fread_unlocked_alias (__ptr, __size, __n, __stream);
+    }
+  if (__glibc_unsafe_len (__n, __size, sz))
+    return __fread_unlocked_chk_warn (__ptr, sz, __size, __n, __stream);
+  return __fread_unlocked_chk (__ptr, sz, __size, __n, __stream);
+
 }
 #endif
 
diff --git a/misc/sys/cdefs.h b/misc/sys/cdefs.h
index f6ab95ab81..c353d2ec4d 100644
--- a/misc/sys/cdefs.h
+++ b/misc/sys/cdefs.h
@@ -150,6 +150,53 @@
 # define __glibc_objsize(__o) __bos (__o)
 #endif
 
+/* Compile time conditions to choose between the regular, _chk and _chk_warn
+   variants.  These conditions should get evaluated to constant and optimized
+   away.  */
+
+#define __glibc_safe_len_cond(__l, __s, __osz) ((__l) <= (__osz) / (__s))
+#define __glibc_unsigned_or_positive(__l) \
+  ((__typeof (__l)) 0 < (__typeof (__l)) -1				      \
+   || (__builtin_constant_p (__l) && (__l) > 0))
+
+/* Length is known to be safe at compile time if the __L * __S <= __OBJSZ
+   condition can be folded to a constant and if it is true.  The -1 check is
+   redundant because since it implies that __glibc_safe_len_cond is true.  */
+#define __glibc_safe_or_unknown_len(__l, __s, __osz) \
+  (__glibc_unsigned_or_positive (__l)					      \
+   && __builtin_constant_p (__glibc_safe_len_cond ((__SIZE_TYPE__) (__l),     \
+						   __s, __osz))		      \
+   && __glibc_safe_len_cond ((__SIZE_TYPE__) (__l), __s, __osz))
+
+/* Conversely, we know at compile time that the length is safe if the
+   __L * __S <= __OBJSZ condition can be folded to a constant and if it is
+   false.  */
+#define __glibc_unsafe_len(__l, __s, __osz) \
+  (__glibc_unsigned_or_positive (__l)					      \
+   && __builtin_constant_p (__glibc_safe_len_cond ((__SIZE_TYPE__) (__l),     \
+						   __s, __osz))		      \
+   && !__glibc_safe_len_cond ((__SIZE_TYPE__) (__l), __s, __osz))
+
+/* Fortify function f.  __f_alias, __f_chk and __f_chk_warn must be
+   declared.  */
+
+#define __glibc_fortify(f, __l, __s, __osz, ...) \
+  (__glibc_safe_or_unknown_len (__l, __s, __osz)			      \
+   ? __ ## f ## _alias (__VA_ARGS__)					      \
+   : (__glibc_unsafe_len (__l, __s, __osz)				      \
+      ? __ ## f ## _chk_warn (__VA_ARGS__, __osz)			      \
+      : __ ## f ## _chk (__VA_ARGS__, __osz)))			      \
+
+/* Fortify function f, where object size argument passed to f is the number of
+   elements and not total size.  */
+
+#define __glibc_fortify_n(f, __l, __s, __osz, ...) \
+  (__glibc_safe_or_unknown_len (__l, __s, __osz)			      \
+   ? __ ## f ## _alias (__VA_ARGS__)					      \
+   : (__glibc_unsafe_len (__l, __s, __osz)				      \
+      ? __ ## f ## _chk_warn (__VA_ARGS__, (__osz) / (__s))		      \
+      : __ ## f ## _chk (__VA_ARGS__, (__osz) / (__s))))		      \
+
 #if __GNUC_PREREQ (4,3)
 # define __warnattr(msg) __attribute__((__warning__ (msg)))
 # define __errordecl(name, msg) \
diff --git a/posix/bits/unistd.h b/posix/bits/unistd.h
index 622adeb2b2..697dcbbf7b 100644
--- a/posix/bits/unistd.h
+++ b/posix/bits/unistd.h
@@ -35,16 +35,9 @@ extern ssize_t __REDIRECT (__read_chk_warn,
 __fortify_function __wur ssize_t
 read (int __fd, void *__buf, size_t __nbytes)
 {
-  if (__glibc_objsize0 (__buf) != (size_t) -1)
-    {
-      if (!__builtin_constant_p (__nbytes))
-	return __read_chk (__fd, __buf, __nbytes, __glibc_objsize0 (__buf));
-
-      if (__nbytes > __glibc_objsize0 (__buf))
-	return __read_chk_warn (__fd, __buf, __nbytes,
-				__glibc_objsize0 (__buf));
-    }
-  return __read_alias (__fd, __buf, __nbytes);
+  return __glibc_fortify (read, __nbytes, sizeof (char),
+			  __glibc_objsize0 (__buf),
+			  __fd, __buf, __nbytes);
 }
 
 #ifdef __USE_UNIX98
@@ -78,34 +71,17 @@ extern ssize_t __REDIRECT (__pread64_chk_warn,
 __fortify_function __wur ssize_t
 pread (int __fd, void *__buf, size_t __nbytes, __off_t __offset)
 {
-  if (__glibc_objsize0 (__buf) != (size_t) -1)
-    {
-      if (!__builtin_constant_p (__nbytes))
-	return __pread_chk (__fd, __buf, __nbytes, __offset,
-			    __glibc_objsize0 (__buf));
-
-      if ( __nbytes > __glibc_objsize0 (__buf))
-	return __pread_chk_warn (__fd, __buf, __nbytes, __offset,
-				 __glibc_objsize0 (__buf));
-    }
-  return __pread_alias (__fd, __buf, __nbytes, __offset);
+  return __glibc_fortify (pread, __nbytes, sizeof (char),
+			  __glibc_objsize0 (__buf),
+			  __fd, __buf, __nbytes, __offset);
 }
 # else
 __fortify_function __wur ssize_t
 pread (int __fd, void *__buf, size_t __nbytes, __off64_t __offset)
 {
-  if (__glibc_objsize0 (__buf) != (size_t) -1)
-    {
-      if (!__builtin_constant_p (__nbytes))
-	return __pread64_chk (__fd, __buf, __nbytes, __offset,
-			      __glibc_objsize0 (__buf));
-
-      if ( __nbytes > __glibc_objsize0 (__buf))
-	return __pread64_chk_warn (__fd, __buf, __nbytes, __offset,
-				   __glibc_objsize0 (__buf));
-    }
-
-  return __pread64_alias (__fd, __buf, __nbytes, __offset);
+  return __glibc_fortify (pread64, __nbytes, sizeof (char),
+			  __glibc_objsize0 (__buf),
+			  __fd, __buf, __nbytes, __offset);
 }
 # endif
 
@@ -113,18 +89,9 @@ pread (int __fd, void *__buf, size_t __nbytes, __off64_t __offset)
 __fortify_function __wur ssize_t
 pread64 (int __fd, void *__buf, size_t __nbytes, __off64_t __offset)
 {
-  if (__glibc_objsize0 (__buf) != (size_t) -1)
-    {
-      if (!__builtin_constant_p (__nbytes))
-	return __pread64_chk (__fd, __buf, __nbytes, __offset,
-			      __glibc_objsize0 (__buf));
-
-      if ( __nbytes > __glibc_objsize0 (__buf))
-	return __pread64_chk_warn (__fd, __buf, __nbytes, __offset,
-				   __glibc_objsize0 (__buf));
-    }
-
-  return __pread64_alias (__fd, __buf, __nbytes, __offset);
+  return __glibc_fortify (pread64, __nbytes, sizeof (char),
+			  __glibc_objsize0 (__buf),
+			  __fd, __buf, __nbytes, __offset);
 }
 # endif
 #endif
@@ -149,16 +116,9 @@ __fortify_function __nonnull ((1, 2)) __wur ssize_t
 __NTH (readlink (const char *__restrict __path, char *__restrict __buf,
 		 size_t __len))
 {
-  if (__glibc_objsize (__buf) != (size_t) -1)
-    {
-      if (!__builtin_constant_p (__len))
-	return __readlink_chk (__path, __buf, __len, __glibc_objsize (__buf));
-
-      if ( __len > __glibc_objsize (__buf))
-	return __readlink_chk_warn (__path, __buf, __len,
-				    __glibc_objsize (__buf));
-    }
-  return __readlink_alias (__path, __buf, __len);
+  return __glibc_fortify (readlink, __len, sizeof (char),
+			  __glibc_objsize (__buf),
+			  __path, __buf, __len);
 }
 #endif
 
@@ -184,17 +144,9 @@ __fortify_function __nonnull ((2, 3)) __wur ssize_t
 __NTH (readlinkat (int __fd, const char *__restrict __path,
 		   char *__restrict __buf, size_t __len))
 {
-  if (__glibc_objsize (__buf) != (size_t) -1)
-    {
-      if (!__builtin_constant_p (__len))
-	return __readlinkat_chk (__fd, __path, __buf, __len,
-				 __glibc_objsize (__buf));
-
-      if (__len > __glibc_objsize (__buf))
-	return __readlinkat_chk_warn (__fd, __path, __buf, __len,
-				      __glibc_objsize (__buf));
-    }
-  return __readlinkat_alias (__fd, __path, __buf, __len);
+  return __glibc_fortify (readlinkat, __len, sizeof (char),
+			  __glibc_objsize (__buf),
+			  __fd, __path, __buf, __len);
 }
 #endif
 
@@ -211,15 +163,9 @@ extern char *__REDIRECT_NTH (__getcwd_chk_warn,
 __fortify_function __wur char *
 __NTH (getcwd (char *__buf, size_t __size))
 {
-  if (__glibc_objsize (__buf) != (size_t) -1)
-    {
-      if (!__builtin_constant_p (__size))
-	return __getcwd_chk (__buf, __size, __glibc_objsize (__buf));
-
-      if (__size > __glibc_objsize (__buf))
-	return __getcwd_chk_warn (__buf, __size, __glibc_objsize (__buf));
-    }
-  return __getcwd_alias (__buf, __size);
+  return __glibc_fortify (getcwd, __size, sizeof (char),
+			  __glibc_objsize (__buf),
+			  __buf, __size);
 }
 
 #if defined __USE_MISC || defined __USE_XOPEN_EXTENDED
@@ -253,16 +199,9 @@ extern size_t __REDIRECT_NTH (__confstr_chk_warn,
 __fortify_function size_t
 __NTH (confstr (int __name, char *__buf, size_t __len))
 {
-  if (__glibc_objsize (__buf) != (size_t) -1)
-    {
-      if (!__builtin_constant_p (__len))
-	return __confstr_chk (__name, __buf, __len, __glibc_objsize (__buf));
-
-      if (__glibc_objsize (__buf) < __len)
-	return __confstr_chk_warn (__name, __buf, __len,
-				   __glibc_objsize (__buf));
-    }
-  return __confstr_alias (__name, __buf, __len);
+  return __glibc_fortify (confstr, __len, sizeof (char),
+			  __glibc_objsize (__buf),
+			  __name, __buf, __len);
 }
 
 
@@ -279,15 +218,9 @@ extern int __REDIRECT_NTH (__getgroups_chk_warn,
 __fortify_function int
 __NTH (getgroups (int __size, __gid_t __list[]))
 {
-  if (__glibc_objsize (__list) != (size_t) -1)
-    {
-      if (!__builtin_constant_p (__size) || __size < 0)
-	return __getgroups_chk (__size, __list, __glibc_objsize (__list));
-
-      if (__size * sizeof (__gid_t) > __glibc_objsize (__list))
-	return __getgroups_chk_warn (__size, __list, __glibc_objsize (__list));
-    }
-  return __getgroups_alias (__size, __list);
+  return __glibc_fortify (getgroups, __size, sizeof (__gid_t),
+			  __glibc_objsize (__list),
+			  __size, __list);
 }
 
 
@@ -306,17 +239,9 @@ extern int __REDIRECT_NTH (__ttyname_r_chk_warn,
 __fortify_function int
 __NTH (ttyname_r (int __fd, char *__buf, size_t __buflen))
 {
-  if (__glibc_objsize (__buf) != (size_t) -1)
-    {
-      if (!__builtin_constant_p (__buflen))
-	return __ttyname_r_chk (__fd, __buf, __buflen,
-				__glibc_objsize (__buf));
-
-      if (__buflen > __glibc_objsize (__buf))
-	return __ttyname_r_chk_warn (__fd, __buf, __buflen,
-				     __glibc_objsize (__buf));
-    }
-  return __ttyname_r_alias (__fd, __buf, __buflen);
+  return __glibc_fortify (ttyname_r, __buflen, sizeof (char),
+			  __glibc_objsize (__buf),
+			  __fd, __buf, __buflen);
 }
 
 
@@ -334,16 +259,9 @@ extern int __REDIRECT (__getlogin_r_chk_warn,
 __fortify_function int
 getlogin_r (char *__buf, size_t __buflen)
 {
-  if (__glibc_objsize (__buf) != (size_t) -1)
-    {
-      if (!__builtin_constant_p (__buflen))
-	return __getlogin_r_chk (__buf, __buflen, __glibc_objsize (__buf));
-
-      if (__buflen > __glibc_objsize (__buf))
-	return __getlogin_r_chk_warn (__buf, __buflen,
-				      __glibc_objsize (__buf));
-    }
-  return __getlogin_r_alias (__buf, __buflen);
+  return __glibc_fortify (getlogin_r, __buflen, sizeof (char),
+			  __glibc_objsize (__buf),
+			  __buf, __buflen);
 }
 #endif
 
@@ -363,16 +281,9 @@ extern int __REDIRECT_NTH (__gethostname_chk_warn,
 __fortify_function int
 __NTH (gethostname (char *__buf, size_t __buflen))
 {
-  if (__glibc_objsize (__buf) != (size_t) -1)
-    {
-      if (!__builtin_constant_p (__buflen))
-	return __gethostname_chk (__buf, __buflen, __glibc_objsize (__buf));
-
-      if (__buflen > __glibc_objsize (__buf))
-	return __gethostname_chk_warn (__buf, __buflen,
-				       __glibc_objsize (__buf));
-    }
-  return __gethostname_alias (__buf, __buflen);
+  return __glibc_fortify (gethostname, __buflen, sizeof (char),
+			  __glibc_objsize (__buf),
+			  __buf, __buflen);
 }
 #endif
 
@@ -394,15 +305,8 @@ extern int __REDIRECT_NTH (__getdomainname_chk_warn,
 __fortify_function int
 __NTH (getdomainname (char *__buf, size_t __buflen))
 {
-  if (__glibc_objsize (__buf) != (size_t) -1)
-    {
-      if (!__builtin_constant_p (__buflen))
-	return __getdomainname_chk (__buf, __buflen, __glibc_objsize (__buf));
-
-      if (__buflen > __glibc_objsize (__buf))
-	return __getdomainname_chk_warn (__buf, __buflen,
-					 __glibc_objsize (__buf));
-    }
-  return __getdomainname_alias (__buf, __buflen);
+  return __glibc_fortify (getdomainname, __buflen, sizeof (char),
+			  __glibc_objsize (__buf),
+			  __buf, __buflen);
 }
 #endif
diff --git a/socket/bits/socket2.h b/socket/bits/socket2.h
index 9c8ac69624..b28cde55f3 100644
--- a/socket/bits/socket2.h
+++ b/socket/bits/socket2.h
@@ -33,17 +33,12 @@ extern ssize_t __REDIRECT (__recv_chk_warn,
 __fortify_function ssize_t
 recv (int __fd, void *__buf, size_t __n, int __flags)
 {
-  if (__glibc_objsize0 (__buf) != (size_t) -1)
-    {
-      if (!__builtin_constant_p (__n))
-	return __recv_chk (__fd, __buf, __n, __glibc_objsize0 (__buf),
-			   __flags);
-
-      if (__n > __glibc_objsize0 (__buf))
-	return __recv_chk_warn (__fd, __buf, __n, __glibc_objsize0 (__buf),
-				__flags);
-    }
-  return __recv_alias (__fd, __buf, __n, __flags);
+  size_t sz = __glibc_objsize0 (__buf);
+  if (__glibc_safe_or_unknown_len (__n, sizeof (char), sz))
+    return __recv_alias (__fd, __buf, __n, __flags);
+  if (__glibc_unsafe_len (__n, sizeof (char), sz))
+    return __recv_chk_warn (__fd, __buf, __n, sz, __flags);
+  return __recv_chk (__fd, __buf, __n, sz, __flags);
 }
 
 extern ssize_t __recvfrom_chk (int __fd, void *__restrict __buf, size_t __n,
@@ -66,14 +61,11 @@ __fortify_function ssize_t
 recvfrom (int __fd, void *__restrict __buf, size_t __n, int __flags,
 	  __SOCKADDR_ARG __addr, socklen_t *__restrict __addr_len)
 {
-  if (__glibc_objsize0 (__buf) != (size_t) -1)
-    {
-      if (!__builtin_constant_p (__n))
-	return __recvfrom_chk (__fd, __buf, __n, __glibc_objsize0 (__buf),
-			       __flags, __addr, __addr_len);
-      if (__n > __glibc_objsize0 (__buf))
-	return __recvfrom_chk_warn (__fd, __buf, __n, __glibc_objsize0 (__buf),
-				    __flags, __addr, __addr_len);
-    }
-  return __recvfrom_alias (__fd, __buf, __n, __flags, __addr, __addr_len);
+  size_t sz = __glibc_objsize0 (__buf);
+  if (__glibc_safe_or_unknown_len (__n, sizeof (char), sz))
+    return __recvfrom_alias (__fd, __buf, __n, __flags, __addr, __addr_len);
+  if (__glibc_unsafe_len (__n, sizeof (char), sz))
+    return __recvfrom_chk_warn (__fd, __buf, __n, sz, __flags, __addr,
+				__addr_len);
+  return __recvfrom_chk (__fd, __buf, __n, sz, __flags, __addr, __addr_len);
 }
diff --git a/stdlib/bits/stdlib.h b/stdlib/bits/stdlib.h
index eae31b38f0..067115eeca 100644
--- a/stdlib/bits/stdlib.h
+++ b/stdlib/bits/stdlib.h
@@ -36,17 +36,16 @@ extern char *__REDIRECT_NTH (__realpath_chk_warn,
 __fortify_function __wur char *
 __NTH (realpath (const char *__restrict __name, char *__restrict __resolved))
 {
-  if (__glibc_objsize (__resolved) != (size_t) -1)
-    {
+  size_t sz = __glibc_objsize (__resolved);
+
+  if (sz == (size_t) -1)
+    return __realpath_alias (__name, __resolved);
+
 #if defined _LIBC_LIMITS_H_ && defined PATH_MAX
-      if (__glibc_objsize (__resolved) < PATH_MAX)
-	return __realpath_chk_warn (__name, __resolved,
-				    __glibc_objsize (__resolved));
+  if (__glibc_unsafe_len (sz, sizeof (char), PATH_MAX))
+    return __realpath_chk_warn (__name, __resolved, sz);
 #endif
-      return __realpath_chk (__name, __resolved, __glibc_objsize (__resolved));
-    }
-
-  return __realpath_alias (__name, __resolved);
+  return __realpath_chk (__name, __resolved, sz);
 }
 
 
@@ -65,16 +64,9 @@ extern int __REDIRECT_NTH (__ptsname_r_chk_warn,
 __fortify_function int
 __NTH (ptsname_r (int __fd, char *__buf, size_t __buflen))
 {
-  if (__glibc_objsize (__buf) != (size_t) -1)
-    {
-