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Create hidden aliases for non-libc syscalls automatically
- From: Joseph Myers <joseph at codesourcery dot com>
- To: <libc-alpha at sourceware dot org>
- Date: Tue, 16 Jun 2015 16:25:00 +0000
- Subject: Create hidden aliases for non-libc syscalls automatically
- Authentication-results: sourceware.org; auth=none
The syscall wrappers mechanism automatically creates hidden aliases
for syscalls with libc_hidden_def / libc_hidden_weak. The use of
libc_hidden_* has the side-effect that for syscall wrappers in
non-libc libraries those aliases are not created. In turn, this means
that three mq_* syscalls in sysdeps/unix/sysv/linux/syscalls.list list
the __GI_* names explicitly.
The use of libc_hidden_* dates back to the original introduction of
that support in
2002-08-03 Roland McGrath <roland@redhat.com>
* sysdeps/unix/make-syscalls.sh: Generate libc_hidden_def or
libc_hidden_weak for every system call symbol defined.
(predating the non-libc syscalls in question) and I see no reason for
excluding non-libc syscalls. This patch changes the code to use
hidden_def / hidden_weak (via a wrapper syscall_hidden_def in the case
where the argument is itself a macro, so that the argument gets
expanded before concatenation with __GI_), so avoiding the need to
specify the hidden aliases explicitly in this case.
Tested for x86_64 and x86 (testsuite, and that disassembly of
installed stripped shared libraries is unchanged by the patch; the
mq_* symbols change from weak to strong, which is of no significance
and two of them will shortly change back to weak as part of a fix for
bug 18545).
2015-06-16 Joseph Myers <joseph@codesourcery.com>
* sysdeps/unix/make-syscalls.sh (emit_weak_aliases): Use
hidden_def and hidden_weak instead of libc_hidden_def and
libc_hidden_weak.
(top level): Refer to hidden_def in comment.
* sysdeps/unix/syscall-template.S (syscall_hidden_def): New
macro. Use it instead of libc_hidden_def.
* sysdeps/unix/sysv/linux/syscalls.list (mq_timedsend): Do not
specify __GI_* name explicitly.
(mq_timedreceive): Likewise.
(mq_setattr): Likewise.
diff --git a/sysdeps/unix/make-syscalls.sh b/sysdeps/unix/make-syscalls.sh
index 12f664e..fbf9660 100644
--- a/sysdeps/unix/make-syscalls.sh
+++ b/sysdeps/unix/make-syscalls.sh
@@ -128,11 +128,11 @@ emit_weak_aliases()
!*)
name=`echo $name | sed 's/.//'`
echo " echo 'strong_alias ($strong, $name)'; \\"
- echo " echo 'libc_hidden_def ($name)'; \\"
+ echo " echo 'hidden_def ($name)'; \\"
;;
*)
echo " echo 'weak_alias ($strong, $name)'; \\"
- echo " echo 'libc_hidden_weak ($name)'; \\"
+ echo " echo 'hidden_weak ($name)'; \\"
;;
esac
done
@@ -287,7 +287,7 @@ while read file srcfile caller syscall args strong weak; do
echo '}'; \\
echo 'asm (".type ${strong}, %gnu_indirect_function");'; \\
EOF
- # This is doing "libc_hidden_def (${strong})", but the compiler
+ # This is doing "hidden_def (${strong})", but the compiler
# doesn't know that we've defined ${strong} in the same file, so
# we can't do it the normal way.
cat <<EOF
diff --git a/sysdeps/unix/syscall-template.S b/sysdeps/unix/syscall-template.S
index 62ebe02..e86e6a7 100644
--- a/sysdeps/unix/syscall-template.S
+++ b/sysdeps/unix/syscall-template.S
@@ -47,6 +47,9 @@
# include <sysdep.h>
#endif
+/* This indirection is needed so that SYMBOL gets macro-expanded. */
+#define syscall_hidden_def(SYMBOL) hidden_def (SYMBOL)
+
#define T_PSEUDO(SYMBOL, NAME, N) PSEUDO (SYMBOL, NAME, N)
#define T_PSEUDO_NOERRNO(SYMBOL, NAME, N) PSEUDO_NOERRNO (SYMBOL, NAME, N)
#define T_PSEUDO_ERRVAL(SYMBOL, NAME, N) PSEUDO_ERRVAL (SYMBOL, NAME, N)
@@ -84,4 +87,4 @@ T_PSEUDO_END (SYSCALL_SYMBOL)
#endif
-libc_hidden_def (SYSCALL_SYMBOL)
+syscall_hidden_def (SYSCALL_SYMBOL)
diff --git a/sysdeps/unix/sysv/linux/syscalls.list b/sysdeps/unix/sysv/linux/syscalls.list
index 42b6c2e..09dd10d 100644
--- a/sysdeps/unix/sysv/linux/syscalls.list
+++ b/sysdeps/unix/sysv/linux/syscalls.list
@@ -106,9 +106,9 @@ removexattr - removexattr i:ss removexattr
lremovexattr - lremovexattr i:ss lremovexattr
fremovexattr - fremovexattr i:is fremovexattr
-mq_timedsend - mq_timedsend Ci:ipiip __GI_mq_timedsend mq_timedsend
-mq_timedreceive - mq_timedreceive Ci:ipipp __GI_mq_timedreceive mq_timedreceive
-mq_setattr - mq_getsetattr i:ipp __GI_mq_setattr mq_setattr
+mq_timedsend - mq_timedsend Ci:ipiip mq_timedsend
+mq_timedreceive - mq_timedreceive Ci:ipipp mq_timedreceive
+mq_setattr - mq_getsetattr i:ipp mq_setattr
timerfd_create EXTRA timerfd_create i:ii timerfd_create
timerfd_settime EXTRA timerfd_settime i:iipp timerfd_settime
--
Joseph S. Myers
joseph@codesourcery.com