/* Support macros for making weak and strong aliases for symbols,
and for using symbol sets and linker warnings with GNU ld.
- Copyright (C) 1995-2014 Free Software Foundation, Inc.
+ Copyright (C) 1995-2017 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
#ifndef _LIBC_SYMBOLS_H
#define _LIBC_SYMBOLS_H 1
-/* Pull in definitions for the MODULE_* macros. */
-#include <libc-modules.h>
-
+#define IN_MODULE PASTE_NAME (MODULE_, MODULE_NAME)
#define IS_IN(lib) (IN_MODULE == MODULE_##lib)
+/* Returns true if the current module is a versioned library. Versioned
+ library names culled from shlib-versions files are assigned a MODULE_*
+ value lower than MODULE_LIBS_BEGIN. */
+#define IS_IN_LIB (IN_MODULE > MODULE_LIBS_BEGIN)
+
+#define PASTE_NAME(a,b) PASTE_NAME1 (a,b)
+#define PASTE_NAME1(a,b) a##b
+
/* This file's macros are included implicitly in the compilation of every
file in the C library by -imacros.
We include config.h which is generated by configure.
- It should define for us the following symbols:
+ It should define for us the following symbol:
* HAVE_ASM_SET_DIRECTIVE if we have `.set B, A' instead of `A = B'.
- * HAVE_ASM_WEAK_DIRECTIVE if we have weak symbols using `.weak'.
- * HAVE_ASM_WEAKEXT_DIRECTIVE if we have weak symbols using `.weakext'.
*/
/* Enable declarations of GNU extensions, since we are compiling them. */
#define _GNU_SOURCE 1
-/* And we also need the data for the reentrant functions. */
-#define _REENTRANT 1
#include <config.h>
/* The symbols in all the user (non-_) macros are C symbols. */
-#if !defined HAVE_ASM_WEAK_DIRECTIVE && !defined HAVE_ASM_WEAKEXT_DIRECTIVE
-# error "weak symbol support needed"
-#endif
-
#ifndef __SYMBOL_PREFIX
# define __SYMBOL_PREFIX
#endif
# define ASM_LINE_SEP ;
#endif
-#ifdef HAVE_ASM_GLOBAL_DOT_NAME
-# ifndef C_SYMBOL_DOT_NAME
-# if defined __GNUC__ && defined __GNUC_MINOR__ \
- && (__GNUC__ << 16) + __GNUC_MINOR__ >= (3 << 16) + 1
-# define C_SYMBOL_DOT_NAME(name) .name
-# else
-# define C_SYMBOL_DOT_NAME(name) .##name
-# endif
-# endif
-#endif
-
#ifndef __ASSEMBLER__
/* GCC understands weak symbols and aliases; use its interface where
possible, instead of embedded assembly language. */
# define weak_extern(symbol) _weak_extern (weak symbol)
# define _weak_extern(expr) _Pragma (#expr)
+/* In shared builds, the expression call_function_static_weak
+ (FUNCTION-SYMBOL, ARGUMENTS) invokes FUNCTION-SYMBOL (an
+ identifier) unconditionally, with the (potentially empty) argument
+ list ARGUMENTS. In static builds, if FUNCTION-SYMBOL has a
+ definition, the function is invoked as before; if FUNCTION-SYMBOL
+ is NULL, no call is performed. */
+# ifdef SHARED
+# define call_function_static_weak(func, ...) func (__VA_ARGS__)
+# else /* !SHARED */
+# define call_function_static_weak(func, ...) \
+ ({ \
+ extern __typeof__ (func) func weak_function; \
+ (func != NULL ? func (__VA_ARGS__) : (void)0); \
+ })
+# endif
#else /* __ASSEMBLER__ */
# ifdef HAVE_ASM_SET_DIRECTIVE
-# ifdef HAVE_ASM_GLOBAL_DOT_NAME
-# define strong_alias(original, alias) \
- .globl C_SYMBOL_NAME (alias) ASM_LINE_SEP \
- .set C_SYMBOL_NAME (alias),C_SYMBOL_NAME (original) ASM_LINE_SEP \
- .globl C_SYMBOL_DOT_NAME (alias) ASM_LINE_SEP \
- .set C_SYMBOL_DOT_NAME (alias),C_SYMBOL_DOT_NAME (original)
-# define strong_data_alias(original, alias) \
- .globl C_SYMBOL_NAME (alias) ASM_LINE_SEP \
- .set C_SYMBOL_NAME (alias),C_SYMBOL_NAME (original)
-# else
-# define strong_alias(original, alias) \
+# define strong_alias(original, alias) \
.globl C_SYMBOL_NAME (alias) ASM_LINE_SEP \
.set C_SYMBOL_NAME (alias),C_SYMBOL_NAME (original)
-# define strong_data_alias(original, alias) strong_alias(original, alias)
-# endif
+# define strong_data_alias(original, alias) strong_alias(original, alias)
# else
-# ifdef HAVE_ASM_GLOBAL_DOT_NAME
-# define strong_alias(original, alias) \
- .globl C_SYMBOL_NAME (alias) ASM_LINE_SEP \
- C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original) ASM_LINE_SEP \
- .globl C_SYMBOL_DOT_NAME (alias) ASM_LINE_SEP \
- C_SYMBOL_DOT_NAME (alias) = C_SYMBOL_DOT_NAME (original)
-# define strong_data_alias(original, alias) \
+# define strong_alias(original, alias) \
.globl C_SYMBOL_NAME (alias) ASM_LINE_SEP \
C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original)
-# else
-# define strong_alias(original, alias) \
- .globl C_SYMBOL_NAME (alias) ASM_LINE_SEP \
- C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original)
-# define strong_data_alias(original, alias) strong_alias(original, alias)
-# endif
+# define strong_data_alias(original, alias) strong_alias(original, alias)
# endif
-# ifdef HAVE_ASM_WEAKEXT_DIRECTIVE
-# ifdef HAVE_ASM_GLOBAL_DOT_NAME
-# define weak_alias(original, alias) \
- .weakext C_SYMBOL_NAME (alias), C_SYMBOL_NAME (original) ASM_LINE_SEP \
- .weakext C_SYMBOL_DOT_NAME (alias), C_SYMBOL_DOT_NAME (original)
-# else
-# define weak_alias(original, alias) \
- .weakext C_SYMBOL_NAME (alias), C_SYMBOL_NAME (original)
-# endif
-# define weak_extern(symbol) \
- .weakext C_SYMBOL_NAME (symbol)
-
-# else /* ! HAVE_ASM_WEAKEXT_DIRECTIVE */
-
-# ifdef HAVE_ASM_GLOBAL_DOT_NAME
-# define weak_alias(original, alias) \
- .weak C_SYMBOL_NAME (alias) ASM_LINE_SEP \
- C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original) ASM_LINE_SEP \
- .weak C_SYMBOL_DOT_NAME (alias) ASM_LINE_SEP \
- C_SYMBOL_DOT_NAME (alias) = C_SYMBOL_DOT_NAME (original)
-# else
-# define weak_alias(original, alias) \
+# define weak_alias(original, alias) \
.weak C_SYMBOL_NAME (alias) ASM_LINE_SEP \
C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original)
-# endif
-# define weak_extern(symbol) \
+# define weak_extern(symbol) \
.weak C_SYMBOL_NAME (symbol)
-# endif /* ! HAVE_ASM_WEAKEXT_DIRECTIVE */
-
#endif /* __ASSEMBLER__ */
/* On some platforms we can make internal function calls (i.e., calls of
/* When a reference to SYMBOL is encountered, the linker will emit a
warning message MSG. */
/* We want the .gnu.warning.SYMBOL section to be unallocated. */
-#ifdef HAVE_ASM_PREVIOUS_DIRECTIVE
-# define __make_section_unallocated(section_string) \
+#define __make_section_unallocated(section_string) \
asm (".section " section_string "\n\t.previous");
-#elif defined HAVE_ASM_POPSECTION_DIRECTIVE
-# define __make_section_unallocated(section_string) \
- asm (".pushsection " section_string "\n\t.popsection");
-#else
-# define __make_section_unallocated(section_string)
-#endif
/* Tacking on "\n\t#" to the section name makes gcc put it's bogus
section attributes on what looks like a comment to the assembler. */
past the last element in SET. */
#define symbol_set_end_p(set, ptr) ((ptr) >= (void *const *) &__stop_##set)
+/* Use symbol_version_reference to specify the version a symbol
+ reference should link to. Use symbol_version or
+ default_symbol_version for the definition of a versioned symbol.
+ The difference is that the latter is a no-op in non-shared
+ builds. */
+#ifdef __ASSEMBLER__
+# define symbol_version_reference(real, name, version) \
+ .symver real, name##@##version
+#else /* !__ASSEMBLER__ */
+# define symbol_version_reference(real, name, version) \
+ __asm__ (".symver " #real "," #name "@" #version)
+#endif
+
#ifdef SHARED
# define symbol_version(real, name, version) \
- _symbol_version(real, name, version)
+ symbol_version_reference(real, name, version)
# define default_symbol_version(real, name, version) \
_default_symbol_version(real, name, version)
# ifdef __ASSEMBLER__
-# ifdef HAVE_ASM_GLOBAL_DOT_NAME
-# define _symbol_version(real, name, version) \
- .symver real, name##@##version ASM_LINE_SEP \
- .symver C_SYMBOL_DOT_NAME(real), C_SYMBOL_DOT_NAME(name##@##version)
-# define _default_symbol_version(real, name, version) \
- .symver real, name##@##@##version ASM_LINE_SEP \
- .symver C_SYMBOL_DOT_NAME(real), C_SYMBOL_DOT_NAME(name##@##@##version)
-# else
-# define _symbol_version(real, name, version) \
- .symver real, name##@##version
-# define _default_symbol_version(real, name, version) \
+# define _default_symbol_version(real, name, version) \
.symver real, name##@##@##version
-# endif
# else
-# ifdef HAVE_ASM_GLOBAL_DOT_NAME
-# define _symbol_version(real, name, version) \
- __asm__ (".symver " #real "," #name "@" #version "\n\t" \
- ".symver ." #real ",." #name "@" #version)
-# define _default_symbol_version(real, name, version) \
- __asm__ (".symver " #real "," #name "@@" #version "\n\t" \
- ".symver ." #real ",." #name "@@" #version)
-# else
-# define _symbol_version(real, name, version) \
- __asm__ (".symver " #real "," #name "@" #version)
-# define _default_symbol_version(real, name, version) \
+# define _default_symbol_version(real, name, version) \
__asm__ (".symver " #real "," #name "@@" #version)
-# endif
# endif
#else
# define symbol_version(real, name, version)
#define attribute_relro __attribute__ ((section (".data.rel.ro")))
+
+/* Used to disable stack protection in sensitive places, like ifunc
+ resolvers and early static TLS init. */
+#ifdef HAVE_CC_NO_STACK_PROTECTOR
+# define inhibit_stack_protector \
+ __attribute__ ((__optimize__ ("-fno-stack-protector")))
+#else
+# define inhibit_stack_protector
+#endif
+
/* The following macros are used for PLT bypassing within libc.so
(and if needed other libraries similarly).
First of all, you need to have the function prototyped somewhere,
# define hidden_data_def(name) strong_data_alias (name, __GI_##name)
# define hidden_data_weak(name) hidden_data_def (name)
# define hidden_data_ver(local, name) strong_data_alias (local, __GI_##name)
-# ifdef HAVE_ASM_GLOBAL_DOT_NAME
-# define HIDDEN_JUMPTARGET(name) .__GI_##name
-# else
-# define HIDDEN_JUMPTARGET(name) __GI_##name
-# endif
+# define HIDDEN_JUMPTARGET(name) __GI_##name
# endif
#else
# ifndef __ASSEMBLER__
# define hidden_nolink(name, lib, version)
#endif
-#if !defined NOT_IN_libc
+#if IS_IN (libc)
# define libc_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
# define libc_hidden_tls_proto(name, attrs...) hidden_tls_proto (name, ##attrs)
# define libc_hidden_def(name) hidden_def (name)
# define libm_hidden_data_ver(local, name)
#endif
+#if IS_IN (libmvec)
+# define libmvec_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
+# define libmvec_hidden_tls_proto(name, attrs...) hidden_tls_proto (name, ##attrs)
+# define libmvec_hidden_def(name) hidden_def (name)
+# define libmvec_hidden_weak(name) hidden_weak (name)
+# define libmvec_hidden_ver(local, name) hidden_ver (local, name)
+# define libmvec_hidden_data_def(name) hidden_data_def (name)
+# define libmvec_hidden_data_weak(name) hidden_data_weak (name)
+# define libmvec_hidden_data_ver(local, name) hidden_data_ver (local, name)
+#else
+# define libmvec_hidden_proto(name, attrs...)
+# define libmvec_hidden_tls_proto(name, attrs...)
+# define libmvec_hidden_def(name)
+# define libmvec_hidden_weak(name)
+# define libmvec_hidden_ver(local, name)
+# define libmvec_hidden_data_def(name)
+# define libmvec_hidden_data_weak(name)
+# define libmvec_hidden_data_ver(local, name)
+#endif
+
#if IS_IN (libresolv)
# define libresolv_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
# define libresolv_hidden_tls_proto(name, attrs...) \
# define compat_data_section .section ".data.compat", "aw";
#endif
-/* Marker used for indirection function symbols. */
-#define libc_ifunc(name, expr) \
- extern void *name##_ifunc (void) __asm__ (#name); \
- void *name##_ifunc (void) \
+/* Helper / base macros for indirect function symbols. */
+#define __ifunc_resolver(type_name, name, expr, arg, init, classifier) \
+ classifier inhibit_stack_protector void *name##_ifunc (arg) \
{ \
- INIT_ARCH (); \
- __typeof (name) *res = expr; \
+ init (); \
+ __typeof (type_name) *res = expr; \
return res; \
- } \
- __asm__ (".type " #name ", %gnu_indirect_function");
+ }
-/* The body of the function is supposed to use __get_cpu_features
- which will, if necessary, initialize the data first. */
-#define libm_ifunc(name, expr) \
- extern void *name##_ifunc (void) __asm__ (#name); \
- void *name##_ifunc (void) \
- { \
- __typeof (name) *res = expr; \
- return res; \
- } \
- __asm__ (".type " #name ", %gnu_indirect_function");
-
-#ifdef HAVE_ASM_SET_DIRECTIVE
-# define libc_ifunc_hidden_def1(local, name) \
- __asm__ (".globl " #local "\n\t" \
- ".hidden " #local "\n\t" \
- ".set " #local ", " #name);
+#ifdef HAVE_GCC_IFUNC
+# define __ifunc(type_name, name, expr, arg, init) \
+ extern __typeof (type_name) name __attribute__ \
+ ((ifunc (#name "_ifunc"))); \
+ __ifunc_resolver (type_name, name, expr, arg, init, static)
+
+# define __ifunc_hidden(type_name, name, expr, arg, init) \
+ __ifunc (type_name, name, expr, arg, init)
#else
-# define libc_ifunc_hidden_def1(local, name) \
- __asm__ (".globl " #local "\n\t" \
- ".hidden " #local "\n\t" \
- #local " = " #name);
-#endif
+/* Gcc does not support __attribute__ ((ifunc (...))). Use the old behaviour
+ as fallback. But keep in mind that the debug information for the ifunc
+ resolver functions is not correct. It contains the ifunc'ed function as
+ DW_AT_linkage_name. E.g. lldb uses this field and an inferior function
+ call of the ifunc'ed function will fail due to "no matching function for
+ call to ..." because the ifunc'ed function and the resolver function have
+ different signatures. (Gcc support is disabled at least on a ppc64le
+ Ubuntu 14.04 system.) */
+
+# define __ifunc(type_name, name, expr, arg, init) \
+ extern __typeof (type_name) name; \
+ void *name##_ifunc (arg) __asm__ (#name); \
+ __ifunc_resolver (type_name, name, expr, arg, init,) \
+ __asm__ (".type " #name ", %gnu_indirect_function");
+
+# define __ifunc_hidden(type_name, name, expr, arg, init) \
+ extern __typeof (type_name) __libc_##name; \
+ __ifunc (type_name, __libc_##name, expr, arg, init) \
+ strong_alias (__libc_##name, name);
+#endif /* !HAVE_GCC_IFUNC */
+
+/* The following macros are used for indirect function symbols in libc.so.
+ First of all, you need to have the function prototyped somewhere,
+ say in foo.h:
+
+ int foo (int __bar);
+
+ If you have an implementation for foo which e.g. uses a special hardware
+ feature which isn't available on all machines where this libc.so will be
+ used but decideable if available at runtime e.g. via hwcaps, you can provide
+ two or multiple implementations of foo:
+
+ int __foo_default (int __bar)
+ {
+ return __bar;
+ }
+
+ int __foo_special (int __bar)
+ {
+ return __bar;
+ }
+
+ If your function foo has no libc_hidden_proto (foo) defined for PLT
+ bypassing, you can use:
+
+ #define INIT_ARCH() unsigned long int hwcap = __GLRO(dl_hwcap);
+
+ libc_ifunc (foo, (hwcap & HWCAP_SPECIAL) ? __foo_special : __foo_default);
-#define libc_ifunc_hidden_def(name) \
- libc_ifunc_hidden_def1 (__GI_##name, name)
+ This will define a resolver function for foo which returns __foo_special or
+ __foo_default depending on your specified expression. Please note that you
+ have to define a macro function INIT_ARCH before using libc_ifunc macro as
+ it is called by the resolver function before evaluating the specified
+ expression. In this example it is used to prepare the hwcap variable.
+ The resolver function is assigned to an ifunc'ed symbol foo. Calls to foo
+ from inside or outside of libc.so will be indirected by a PLT call.
+
+ If your function foo has a libc_hidden_proto (foo) defined for PLT bypassing
+ and calls to foo within libc.so should always go to one specific
+ implementation of foo e.g. __foo_default then you have to add:
+
+ __hidden_ver1 (__foo_default, __GI_foo, __foo_default);
+
+ or a tweaked definition of libc_hidden_def macro after the __foo_default
+ function definition. Calls to foo within libc.so will always go directly to
+ __foo_default. Calls to foo from outside libc.so will be indirected by a
+ PLT call to ifunc'ed symbol foo which you have to define in a separate
+ compile unit:
+
+ #define foo __redirect_foo
+ #include <foo.h>
+ #undef foo
+
+ extern __typeof (__redirect_foo) __foo_default attribute_hidden;
+ extern __typeof (__redirect_foo) __foo_special attribute_hidden;
+
+ libc_ifunc_redirected (__redirect_foo, foo,
+ (hwcap & HWCAP_SPECIAL)
+ ? __foo_special
+ : __foo_default);
+
+ This will define the ifunc'ed symbol foo like above. The redirection of foo
+ in header file is needed to omit an additional defintion of __GI_foo which
+ would end in a linker error while linking libc.so. You have to specify
+ __redirect_foo as first parameter which is used within libc_ifunc_redirected
+ macro in conjunction with typeof to define the ifunc'ed symbol foo.
+
+ If your function foo has a libc_hidden_proto (foo) defined and calls to foo
+ within or from outside libc.so should go via ifunc'ed symbol, then you have
+ to use:
+
+ libc_ifunc_hidden (foo, foo,
+ (hwcap & HWCAP_SPECIAL)
+ ? __foo_special
+ : __foo_default);
+ libc_hidden_def (foo)
+
+ The first parameter foo of libc_ifunc_hidden macro is used in the same way
+ as for libc_ifunc_redirected macro. */
+
+#define libc_ifunc(name, expr) __ifunc (name, name, expr, void, INIT_ARCH)
+
+#define libc_ifunc_redirected(redirected_name, name, expr) \
+ __ifunc (redirected_name, name, expr, void, INIT_ARCH)
+
+#define libc_ifunc_hidden(redirected_name, name, expr) \
+ __ifunc_hidden (redirected_name, name, expr, void, INIT_ARCH)
+
+/* The body of the function is supposed to use __get_cpu_features
+ which will, if necessary, initialize the data first. */
+#define libm_ifunc_init()
+#define libm_ifunc(name, expr) \
+ __ifunc (name, name, expr, void, libm_ifunc_init)
/* Add the compiler optimization to inhibit loop transformation to library
calls. This is used to avoid recursive calls in memset and memmove
projects / thirdparty / glibc.git / blobdiff