diff options
Diffstat (limited to 'include/libc-symbols.h')
-rw-r--r-- | include/libc-symbols.h | 443 |
1 files changed, 364 insertions, 79 deletions
diff --git a/include/libc-symbols.h b/include/libc-symbols.h index 4548e097dc..8b9273c13a 100644 --- a/include/libc-symbols.h +++ b/include/libc-symbols.h @@ -1,6 +1,6 @@ /* Support macros for making weak and strong aliases for symbols, and for using symbol sets and linker warnings with GNU ld. - Copyright (C) 1995-2016 Free Software Foundation, Inc. + Copyright (C) 1995-2018 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 @@ -20,26 +20,46 @@ #ifndef _LIBC_SYMBOLS_H #define _LIBC_SYMBOLS_H 1 -#define IN_MODULE PASTE_NAME (MODULE_, MODULE_NAME) -#define IS_IN(lib) (IN_MODULE == MODULE_##lib) +/* This file is included implicitly in the compilation of every source file, + using -include. It includes config.h. */ -/* 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 symbol: +/* Enable declarations of GNU extensions, since we are compiling them. */ +#define _GNU_SOURCE 1 + +#ifdef MODULE_NAME + +/* Use `#if IS_IN (module)` to detect what component is being compiled. */ +#define PASTE_NAME1(a,b) a##b +#define PASTE_NAME(a,b) PASTE_NAME1 (a,b) +#define IN_MODULE PASTE_NAME (MODULE_, MODULE_NAME) +#define IS_IN(lib) (IN_MODULE == MODULE_##lib) + +/* True if the current module is a versioned library. Versioned + library names culled from shlib-versions files are assigned a + MODULE_* value greater than MODULE_LIBS_BEGIN. */ +#define IS_IN_LIB (IN_MODULE > MODULE_LIBS_BEGIN) + +/* The testsuite, and some other ancillary code, should be compiled against + as close an approximation to the installed headers as possible. + Defining this symbol disables most internal-use-only declarations + provided by this header, and all those provided by other internal + wrapper headers. */ +#if IS_IN (testsuite) || defined IS_IN_build || defined __cplusplus +# define _ISOMAC 1 +#endif - * HAVE_ASM_SET_DIRECTIVE if we have `.set B, A' instead of `A = B'. +#else +/* The generation process for a few files created very early in the + build (notably libc-modules.h itself) involves preprocessing this + header without defining MODULE_NAME. Under these conditions, + internal declarations (especially from config.h) must be visible, + but IS_IN should always evaluate as false. */ +# define IS_IN(lib) 0 +# define IS_IN_LIB 0 +# define IN_MODULE (-1) +#endif - */ +#ifndef _ISOMAC /* This is defined for the compilation of all C library code. features.h tests this to avoid inclusion of stubs.h while compiling the library, @@ -50,13 +70,28 @@ itself is being compiled, or just some generator program. */ #define _LIBC 1 -/* 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 +/* Some files must be compiled with optimization on. */ +#if !defined __ASSEMBLER__ && !defined __OPTIMIZE__ +# error "glibc cannot be compiled without optimization" +#endif + +/* -ffast-math cannot be applied to the C library, as it alters the ABI. + Some test components that use -ffast-math are currently not part of + IS_IN (testsuite) for technical reasons, so we have a secondary override. */ +#if defined __FAST_MATH__ && !defined TEST_FAST_MATH +# error "glibc must not be compiled with -ffast-math" +#endif #include <config.h> +/* When PIC is defined and SHARED isn't defined, we are building PIE + by default. */ +#if defined PIC && !defined SHARED +# define BUILD_PIE_DEFAULT 1 +#else +# define BUILD_PIE_DEFAULT 0 +#endif + /* Define this for the benefit of portable GNU code that wants to check it. Code that checks with #if will not #include <config.h> again, since we've already done it (and this file is implicitly included in every compile, @@ -121,6 +156,21 @@ # 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__ */ @@ -145,13 +195,6 @@ #endif /* __ASSEMBLER__ */ -/* On some platforms we can make internal function calls (i.e., calls of - functions not exported) a bit faster by using a different calling - convention. */ -#ifndef internal_function -# define internal_function /* empty */ -#endif - /* Determine the return address. */ #define RETURN_ADDRESS(nr) \ __builtin_extract_return_addr (__builtin_return_address (nr)) @@ -174,16 +217,6 @@ static const char __evoke_link_warning_##symbol[] \ __attribute__ ((used, section (".gnu.warning." #symbol __sec_comment))) \ = msg; -#define libc_freeres_ptr(decl) \ - __make_section_unallocated ("__libc_freeres_ptrs, \"aw\", %nobits") \ - decl __attribute__ ((section ("__libc_freeres_ptrs" __sec_comment))) -#define __libc_freeres_fn_section \ - __attribute__ ((section ("__libc_freeres_fn"))) - -#define libc_freeres_fn(name) \ - static void name (void) __attribute_used__ __libc_freeres_fn_section; \ - text_set_element (__libc_subfreeres, name); \ - static void name (void) /* A canned warning for sysdeps/stub functions. */ #define stub_warning(name) \ @@ -201,6 +234,79 @@ requires at runtime the shared libraries from the glibc version used \ for linking") #endif +/* Resource Freeing Hooks: + + Normally a process exits and the OS cleans up any allocated + memory. However, when tooling like mtrace or valgrind is monitoring + the process we need to free all resources that are part of the + process in order to provide the consistency required to track + memory leaks. + + A single public API exists and is __libc_freeres(), and this is used + by applications like valgrind to freee resouces. + + There are 3 cases: + + (a) __libc_freeres + + In this case all you need to do is define the freeing routine: + + foo.c: + libfoo_freeres_fn (foo_freeres) + { + complex_free (mem); + } + + This ensures the function is called at the right point to free + resources. + + (b) __libc_freeres_ptr + + The framework for (a) iterates over the list of pointers-to-free + in (b) and frees them. + + foo.c: + libc_freeres_ptr (static char *foo_buffer); + + Freeing these resources alaways happens last and is equivalent + to registering a function that does 'free (foo_buffer)'. + + (c) Explicit lists of free routines to call or objects to free. + + It is the intended goal to remove (a) and (b) which have some + non-determinism based on link order, and instead use explicit + lists of functions and frees to resolve cleanup ordering issues + and make it easy to debug and maintain. + + As of today the following subsystems use (c): + + Per-thread cleanup: + * malloc/thread-freeres.c + + libdl cleanup: + * dlfcn/dlfreeres.c + + libpthread cleanup: + * nptl/nptlfreeres.c + + So if you need any shutdown routines to run you should add them + directly to the appropriate subsystem's shutdown list. */ + +/* Resource pointers to free in libc.so. */ +#define libc_freeres_ptr(decl) \ + __make_section_unallocated ("__libc_freeres_ptrs, \"aw\", %nobits") \ + decl __attribute__ ((section ("__libc_freeres_ptrs" __sec_comment))) + +/* Resource freeing functions from libc.so go in this section. */ +#define __libc_freeres_fn_section \ + __attribute__ ((section ("__libc_freeres_fn"))) + +/* Resource freeing functions for libc.so. */ +#define libc_freeres_fn(name) \ + static void name (void) __attribute_used__ __libc_freeres_fn_section; \ + text_set_element (__libc_subfreeres, name); \ + static void name (void) + /* Declare SYMBOL to be TYPE (`function' or `object') of SIZE bytes alias to ORIGINAL, when the assembler supports such declarations (such as in ELF). @@ -282,19 +388,28 @@ for linking") 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__ -# define _symbol_version(real, name, version) \ - .symver real, name##@##version # define _default_symbol_version(real, name, version) \ .symver real, name##@##@##version # else -# define _symbol_version(real, name, version) \ - __asm__ (".symver " #real "," #name "@" #version) # define _default_symbol_version(real, name, version) \ __asm__ (".symver " #real "," #name "@@" #version) # endif @@ -304,7 +419,8 @@ for linking") strong_alias(real, name) #endif -#if defined SHARED || defined LIBC_NONSHARED +#if defined SHARED || defined LIBC_NONSHARED \ + || (BUILD_PIE_DEFAULT && IS_IN (libc)) # define attribute_hidden __attribute__ ((visibility ("hidden"))) #else # define attribute_hidden @@ -314,6 +430,16 @@ for linking") #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, @@ -443,8 +569,21 @@ for linking") # endif #else # ifndef __ASSEMBLER__ -# define hidden_proto(name, attrs...) -# define hidden_tls_proto(name, attrs...) +# if !defined SHARED && IS_IN (libc) && !defined LIBC_NONSHARED \ + && (!defined PIC || !defined NO_HIDDEN_EXTERN_FUNC_IN_PIE) \ + && !defined NO_HIDDEN +# define __hidden_proto_hiddenattr(attrs...) \ + __attribute__ ((visibility ("hidden"), ##attrs)) +# define hidden_proto(name, attrs...) \ + __hidden_proto (name, , name, ##attrs) +# define hidden_tls_proto(name, attrs...) \ + __hidden_proto (name, __thread, name, ##attrs) +# define __hidden_proto(name, thread, internal, attrs...) \ + extern thread __typeof (name) name __hidden_proto_hiddenattr (attrs); +# else +# define hidden_proto(name, attrs...) +# define hidden_tls_proto(name, attrs...) +# endif # else # define HIDDEN_JUMPTARGET(name) JUMPTARGET(name) # endif /* Not __ASSEMBLER__ */ @@ -483,7 +622,7 @@ for linking") # define libc_hidden_data_ver(local, name) #endif -#if IS_IN (rtld) +#if IS_IN (rtld) && !defined NO_RTLD_HIDDEN # define rtld_hidden_proto(name, attrs...) hidden_proto (name, ##attrs) # define rtld_hidden_tls_proto(name, attrs...) hidden_tls_proto (name, ##attrs) # define rtld_hidden_def(name) hidden_def (name) @@ -631,6 +770,12 @@ for linking") # define libnsl_hidden_proto(name, attrs...) hidden_proto (name, ##attrs) # define libnsl_hidden_tls_proto(name, attrs...) \ hidden_tls_proto (name, ##attrs) +# ifdef LINK_OBSOLETE_NSL + /* libnsl_hidden_nolink should only get used in libnsl code. */ +# define libnsl_hidden_nolink_def(name, version) libnsl_hidden_def (name) +# else +# define libnsl_hidden_nolink_def(name, version) hidden_nolink (name, libnsl, version) +# endif # define libnsl_hidden_def(name) hidden_def (name) # define libnsl_hidden_weak(name) hidden_weak (name) # define libnsl_hidden_ver(local, name) hidden_ver (local, name) @@ -713,42 +858,138 @@ for linking") # 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 \ + __typeof (type_name) *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; \ + __typeof (type_name) *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); + + 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. -#define libc_ifunc_hidden_def(name) \ - libc_ifunc_hidden_def1 (__GI_##name, name) + 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 @@ -759,5 +1000,49 @@ for linking") #else # define inhibit_loop_to_libcall #endif + +/* These macros facilitate sharing source files with gnulib. + + They are here instead of sys/cdefs.h because they should not be + used in public header files. + + Their definitions should be kept consistent with the definitions in + gnulib-common.m4, but it is not necessary to cater to old non-GCC + compilers, since they will only be used while building glibc itself. + (Note that _GNUC_PREREQ cannot be used in this file.) */ + +/* Define as a marker that can be attached to declarations that might not + be used. This helps to reduce warnings, such as from + GCC -Wunused-parameter. */ +#if __GNUC__ >= 3 || (__GNUC__ == 2 && __GNUC_MINOR__ >= 7) +# define _GL_UNUSED __attribute__ ((__unused__)) +#else +# define _GL_UNUSED +#endif + +/* gcc supports the "unused" attribute on possibly unused labels, and + g++ has since version 4.5. Note to support C++ as well as C, + _GL_UNUSED_LABEL should be used with a trailing ; */ +#if !defined __cplusplus || __GNUC__ > 4 \ + || (__GNUC__ == 4 && __GNUC_MINOR__ >= 5) +# define _GL_UNUSED_LABEL _GL_UNUSED +#else +# define _GL_UNUSED_LABEL +#endif + +/* The __pure__ attribute was added in gcc 2.96. */ +#if __GNUC__ > 2 || (__GNUC__ == 2 && __GNUC_MINOR__ >= 96) +# define _GL_ATTRIBUTE_PURE __attribute__ ((__pure__)) +#else +# define _GL_ATTRIBUTE_PURE /* empty */ +#endif + +/* The __const__ attribute was added in gcc 2.95. */ +#if __GNUC__ > 2 || (__GNUC__ == 2 && __GNUC_MINOR__ >= 95) +# define _GL_ATTRIBUTE_CONST __attribute__ ((__const__)) +#else +# define _GL_ATTRIBUTE_CONST /* empty */ +#endif +#endif /* !_ISOMAC */ #endif /* libc-symbols.h */ |