stdio: Ensure *_chk routines have their hidden builtin definition available

If libc_hidden_builtin_{def,proto} isn't properly set for *_chk routines,
there are unwanted PLT entries in libc.so.

There is a special case with __asprintf_chk:
If ldbl_* macros are used for asprintf, ABI gets broken on s390x,
if it isn't, ppc64le isn't building due to multiple asm redirections.

This is due to the inclusion of bits/stdio-lbdl.h for ppc64le whereas it
isn't for s390x. This header creates redirections, which are not
compatible with the ones generated using libc_hidden_def.
Yet, we can't use libc_hidden_ldbl_proto on s390x since it will not
create a simple strong alias (e.g. as done on x86_64), but a versioned
alias, leading to ABI breakage.

This results in errors on s390x:
/usr/bin/ld: glibc/iconv/../libio/bits/stdio2.h:137: undefined reference
to `__asprintf_chk'

Original __asprintf_chk symbols:
00000000001395b0 T __asprintf_chk
0000000000177e90 T __nldbl___asprintf_chk

__asprintf_chk symbols with ldbl_* macros:
000000000012d590 t ___asprintf_chk
000000000012d590 t __asprintf_chk@@GLIBC_2.4
000000000012d590 t __GI___asprintf_chk
000000000012d590 t __GL____asprintf_chk___asprintf_chk
0000000000172240 T __nldbl___asprintf_chk

__asprintf_chk symbols with the patch:
000000000012d590 t ___asprintf_chk
000000000012d590 T __asprintf_chk
000000000012d590 t __GI___asprintf_chk
0000000000172240 T __nldbl___asprintf_chk

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

4 files changed, 20 insertions, 1 deletions

diff --git a/debug/asprintf_chk.c b/debug/asprintf_chk.c
index 651c2cd76b..e233d5d737 100644
--- a/debug/asprintf_chk.c
+++ b/debug/asprintf_chk.c
@@ -22,7 +22,7 @@
 /* Write formatted output from FORMAT to a string which is
    allocated with malloc and stored in *STRING_PTR.  */
 int
-__asprintf_chk (char **result_ptr, int flag, const char *format, ...)
+___asprintf_chk (char **result_ptr, int flag, const char *format, ...)
 {
   /* For flag > 0 (i.e. __USE_FORTIFY_LEVEL > 1) request that %n
      can only come from read-only format strings.  */
@@ -36,3 +36,19 @@ __asprintf_chk (char **result_ptr, int flag, const char *format, ...)
 
   return ret;
 }
+#if defined __LDBL_COMPAT || __LDOUBLE_REDIRECTS_TO_FLOAT128_ABI == 1
+/* This is needed since <bits/stdio-lbdl.h> is included in this case, leading to
+ * multiple asm redirection of the same symbol
+ */
+ldbl_hidden_def (___asprintf_chk, __asprintf_chk)
+ldbl_strong_alias (___asprintf_chk, __asprintf_chk)
+#else
+/* On some systems introduction of ldbl_* macros lead to ABI breakage due to the
+ * long_double_symbol aliasing, e.g. on s390x:
+ * /usr/bin/ld: glibc/iconv/../libio/bits/stdio2.h:137: undefined reference to
+ * `__asprintf_chk'
+ * Due to __asprintf_chk@@GLIBC_2.4 alias replacing __asprintf_chk.
+ */
+strong_alias (___asprintf_chk, __asprintf_chk)
+libc_hidden_def (__asprintf_chk)
+#endif
diff --git a/debug/fgets_u_chk.c b/debug/fgets_u_chk.c
index a16ba655e6..74275381f5 100644
--- a/debug/fgets_u_chk.c
+++ b/debug/fgets_u_chk.c
@@ -56,3 +56,4 @@ __fgets_unlocked_chk (char *buf, size_t size, int n, FILE *fp)
   fp->_flags |= old_error;
   return result;
 }
+libc_hidden_builtin_def (__fgets_unlocked_chk)
diff --git a/debug/fprintf_chk.c b/debug/fprintf_chk.c
index b57d538d03..273051ef91 100644
--- a/debug/fprintf_chk.c
+++ b/debug/fprintf_chk.c
@@ -35,4 +35,5 @@ ___fprintf_chk (FILE *fp, int flag, const char *format, ...)
 
   return ret;
 }
+ldbl_hidden_def (___fprintf_chk, __fprintf_chk)
 ldbl_strong_alias (___fprintf_chk, __fprintf_chk)
diff --git a/debug/sprintf_chk.c b/debug/sprintf_chk.c
index b27f4afae8..e45f1e7b3b 100644
--- a/debug/sprintf_chk.c
+++ b/debug/sprintf_chk.c
@@ -42,4 +42,5 @@ ___sprintf_chk (char *s, int flag, size_t slen, const char *format, ...)
 
   return ret;
 }
+ldbl_hidden_def (___sprintf_chk, __sprintf_chk)
 ldbl_strong_alias (___sprintf_chk, __sprintf_chk)