[roland/nptl] Clean up NPTL fork to be compat-only.
Commit Message
(This is on the branch after the big change only because the file moved and
I didn't want to futz around more. It's actually orthogonal.) AFAIK there
was never any reason whatsoever to have fork/__fork in the libpthread.so
ABI. We can get rid of it for the future, and optimize it marginally for
IFUNC-capable configurations.
Tested x86_64-linux-gnu.
Thanks,
Roland
* nptl/pt-fork.c: Rewritten. Put everything under
[SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_20)].
Use IFUNC to redirect when possible.
Comments
On Mon, 23 Jun 2014, Roland McGrath wrote:
> +/* libpthread once had its own fork, though there was no apparent reason
> + for it. There is no use in having a separate symbol in libpthread, but
> + the historical ABI requires it. For static linking, there is no need to
> + provide anything here--the libc version will be linked in. For shared
> + library ABI compatibility, there must be __vfork and vfork symbols in
__fork and fork not __vfork and vfork?
> On Mon, 23 Jun 2014, Roland McGrath wrote:
>
> > +/* libpthread once had its own fork, though there was no apparent reason
> > + for it. There is no use in having a separate symbol in libpthread, but
> > + the historical ABI requires it. For static linking, there is no need to
> > + provide anything here--the libc version will be linked in. For shared
> > + library ABI compatibility, there must be __vfork and vfork symbols in
>
> __fork and fork not __vfork and vfork?
Oops! Yes. Fixed on the branch.
Thanks,
Roland
@@ -17,11 +17,55 @@
<http://www.gnu.org/licenses/>. */
#include <unistd.h>
+#include <shlib-compat.h>
+/* libpthread once had its own fork, though there was no apparent reason
+ for it. There is no use in having a separate symbol in libpthread, but
+ the historical ABI requires it. For static linking, there is no need to
+ provide anything here--the libc version will be linked in. For shared
+ library ABI compatibility, there must be __vfork and vfork symbols in
+ libpthread.so; so we define them using IFUNC to redirect to the libc
+ function. */
-pid_t
-__fork (void)
+#if SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_20)
+
+# if HAVE_IFUNC
+
+static __typeof (fork) *
+__attribute__ ((used))
+fork_resolve (void)
+{
+ return &__libc_fork;
+}
+
+# ifdef HAVE_ASM_SET_DIRECTIVE
+# define DEFINE_FORK(name) \
+ asm (".set " #name ", fork_resolve\n" \
+ ".globl " #name "\n" \
+ ".type " #name ", %gnu_indirect_function");
+# else
+# define DEFINE_FORK(name) \
+ asm (#name " = fork_resolve\n" \
+ ".globl " #name "\n" \
+ ".type " #name ", %gnu_indirect_function");
+# endif
+
+# else /* !HAVE_IFUNC */
+
+static pid_t __attribute__ ((used))
+fork_compat (void)
{
return __libc_fork ();
}
-strong_alias (__fork, fork)
+
+# define DEFINE_FORK(name) strong_alias (fork_compat, name)
+
+# endif /* HAVE_IFUNC */
+
+DEFINE_FORK (fork_ifunc)
+compat_symbol (libpthread, fork_ifunc, fork, GLIBC_2_0);
+
+DEFINE_FORK (__fork_ifunc)
+compat_symbol (libpthread, __fork_ifunc, __fork, GLIBC_2_1_2);
+
+#endif