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misc: Optimize internal usage of __libc_single_threaded
By adding an internal alias to avoid the GOT indirection. On some architecture, __libc_single_thread may be accessed through copy relocations and thus it requires to update also the copies default copy. This is done by adding a new internal macro, libc_hidden_data_{proto,def}, which has an addition argument that specifies the alias name (instead of default __GI_ one). Checked on x86_64-linux-gnu and i686-linux-gnu. Reviewed-by: Fangrui Song <maskray@google.com>
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@ -38,7 +38,7 @@ __libc_early_init (_Bool initial)
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__libc_single_threaded = initial;
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#ifdef SHARED
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__libc_initial = initial;
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__libc_single_threaded_internal = __libc_initial = initial;
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#endif
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__pthread_early_init ();
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@ -534,11 +534,15 @@ for linking")
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__attribute__ ((visibility ("hidden"), ##attrs))
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# define hidden_proto(name, attrs...) \
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__hidden_proto (name, , __GI_##name, ##attrs)
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# define hidden_proto_alias(name, alias, attrs...) \
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__hidden_proto_alias (name, , alias, ##attrs)
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# define hidden_tls_proto(name, attrs...) \
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__hidden_proto (name, __thread, __GI_##name, ##attrs)
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# define __hidden_proto(name, thread, internal, attrs...) \
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extern thread __typeof (name) name __asm__ (__hidden_asmname (#internal)) \
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__hidden_proto_hiddenattr (attrs);
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# define __hidden_proto_alias(name, thread, internal, attrs...) \
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extern thread __typeof (name) internal __hidden_proto_hiddenattr (attrs);
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# define __hidden_asmname(name) \
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__hidden_asmname1 (__USER_LABEL_PREFIX__, name)
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# define __hidden_asmname1(prefix, name) __hidden_asmname2(prefix, name)
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@ -554,7 +558,10 @@ for linking")
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# define hidden_ver(local, name) __hidden_ver1(local, __GI_##name, name);
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# define hidden_data_ver(local, name) hidden_ver(local, name)
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# define hidden_def(name) __hidden_ver1(__GI_##name, name, name);
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# define hidden_def_alias(name, internal) \
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strong_alias (name, internal)
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# define hidden_data_def(name) hidden_def(name)
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# define hidden_data_def_alias(name, alias) hidden_def_alias(name, alias)
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# define hidden_tls_def(name) \
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__hidden_ver2 (__thread, __GI_##name, name, name);
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# define hidden_weak(name) \
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@ -581,9 +588,11 @@ for linking")
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hidden_proto doesn't make sense for assembly but the equivalent
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is to call via the HIDDEN_JUMPTARGET macro instead of JUMPTARGET. */
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# define hidden_def(name) strong_alias (name, __GI_##name)
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# define hidden_def_alias(name, alias) strong_alias (name, alias)
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# define hidden_weak(name) hidden_def (name)
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# define hidden_ver(local, name) strong_alias (local, __GI_##name)
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# define hidden_data_def(name) strong_data_alias (name, __GI_##name)
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# define hidden_data_def_alias(name, alias) strong_data_alias (name, alias)
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# define hidden_tls_def(name) hidden_data_def (name)
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# define hidden_data_weak(name) hidden_data_def (name)
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# define hidden_data_ver(local, name) strong_data_alias (local, __GI_##name)
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@ -598,12 +607,17 @@ for linking")
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__attribute__ ((visibility ("hidden"), ##attrs))
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# define hidden_proto(name, attrs...) \
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__hidden_proto (name, , name, ##attrs)
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# define hidden_proto_alias(name, alias, attrs...) \
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__hidden_proto_alias (name, , alias, ##attrs)
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# define hidden_tls_proto(name, attrs...) \
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__hidden_proto (name, __thread, name, ##attrs)
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# define __hidden_proto(name, thread, internal, attrs...) \
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extern thread __typeof (name) name __hidden_proto_hiddenattr (attrs);
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# define __hidden_proto_alias(name, thread, internal, attrs...) \
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extern thread __typeof (name) internal __hidden_proto_hiddenattr (attrs);
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# else
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# define hidden_proto(name, attrs...)
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# define hidden_proto_alias(name, alias, attrs...)
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# define hidden_tls_proto(name, attrs...)
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# endif
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# else
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@ -611,9 +625,11 @@ for linking")
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# endif /* Not __ASSEMBLER__ */
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# define hidden_weak(name)
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# define hidden_def(name)
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# define hidden_def_alias(name, alias)
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# define hidden_ver(local, name)
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# define hidden_data_weak(name)
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# define hidden_data_def(name)
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# define hidden_data_def_alias(name, alias)
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# define hidden_tls_def(name)
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# define hidden_data_ver(local, name)
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# define hidden_nolink(name, lib, version)
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@ -621,22 +637,28 @@ for linking")
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#if IS_IN (libc)
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# define libc_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
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# define libc_hidden_proto_alias(name, alias, attrs...) \
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hidden_proto_alias (name, alias, ##attrs)
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# define libc_hidden_tls_proto(name, attrs...) hidden_tls_proto (name, ##attrs)
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# define libc_hidden_def(name) hidden_def (name)
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# define libc_hidden_def_alias(name, alias) hidden_def_alias (name, alias)
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# define libc_hidden_weak(name) hidden_weak (name)
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# define libc_hidden_nolink_sunrpc(name, version) hidden_nolink (name, libc, version)
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# define libc_hidden_ver(local, name) hidden_ver (local, name)
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# define libc_hidden_data_def(name) hidden_data_def (name)
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# define libc_hidden_data_def_alias(name, alias) hidden_data_def_alias (name, alias)
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# define libc_hidden_tls_def(name) hidden_tls_def (name)
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# define libc_hidden_data_weak(name) hidden_data_weak (name)
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# define libc_hidden_data_ver(local, name) hidden_data_ver (local, name)
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#else
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# define libc_hidden_proto(name, attrs...)
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# define libc_hidden_proto_alias(name, alias, attrs...)
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# define libc_hidden_tls_proto(name, attrs...)
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# define libc_hidden_def(name)
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# define libc_hidden_weak(name)
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# define libc_hidden_ver(local, name)
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# define libc_hidden_data_def(name)
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# define libc_hidden_data_def_alias(name, alias)
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# define libc_hidden_tls_def(name)
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# define libc_hidden_data_weak(name)
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# define libc_hidden_data_ver(local, name)
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@ -1 +1,12 @@
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#include <misc/sys/single_threaded.h>
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#ifndef _ISOMAC
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libc_hidden_proto_alias (__libc_single_threaded,
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__libc_single_threaded_internal);
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#if !defined SHARED || !IS_IN(libc)
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# define __libc_single_threaded_internal __libc_single_threaded
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#endif
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#endif
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@ -25,3 +25,5 @@ char __libc_single_threaded;
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#else
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char __libc_single_threaded = 1;
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#endif
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libc_hidden_data_def_alias (__libc_single_threaded,
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__libc_single_threaded_internal)
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@ -624,9 +624,12 @@ __pthread_create_2_1 (pthread_t *newthread, const pthread_attr_t *attr,
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/* Avoid a data race in the multi-threaded case, and call the
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deferred initialization only once. */
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if (__libc_single_threaded)
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if (__libc_single_threaded_internal)
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{
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late_init ();
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__libc_single_threaded_internal = 0;
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/* __libc_single_threaded can be accessed through copy relocations, so
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it requires to update the external copy. */
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__libc_single_threaded = 0;
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}
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@ -45,7 +45,7 @@ __libc_fork (void)
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requirement for fork (Austin Group tracker issue #62) this is
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best effort to make is async-signal-safe at least for single-thread
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case. */
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bool multiple_threads = __libc_single_threaded == 0;
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bool multiple_threads = __libc_single_threaded_internal == 0;
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uint64_t lastrun;
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lastrun = __run_prefork_handlers (multiple_threads);
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@ -29,7 +29,7 @@
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#define INLINE_SETXID_SYSCALL(name, nr, args...) \
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({ \
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int __result; \
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if (!__libc_single_threaded) \
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if (!__libc_single_threaded_internal) \
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{ \
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struct xid_command __cmd; \
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__cmd.syscall_no = __NR_##name; \
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