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Cleanup shared-object support mechanics
The former ldso-startup static library (now called ldso_so_support) is used to spice each shared object/library with local support code for the dynamic linker (execution of static constructors and ARM-EABI). Therefore, the library must be statically linked to each dynamic library. As a result recipes for dynamic libraries must always depend on the "so" API, which makes ldso_so_support.mk and so_support.c available independent of "base". Additionally, ldso_so_support is also provided in the libc API to cut the dependency early for libc/posix libraries. Issue #3720
This commit is contained in:
Christian Helmuth
Norman Feske
parent
589b416ca8
commit
42fddf8390
@ -1,3 +0,0 @@
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SRC_CC += startup.cc
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vpath startup.cc $(BASE_DIR)/src/lib/ldso/startup
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3
repos/base/lib/mk/ldso_so_support.mk
Normal file
3
repos/base/lib/mk/ldso_so_support.mk
Normal file
@ -0,0 +1,3 @@
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SRC_C = so_support.c
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vpath so_support.c $(call select_from_repositories,src/lib/ldso)
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@ -1,5 +0,0 @@
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SRC_CC += unwind_exidx.cc
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vpath unwind_exidx.cc $(REP_DIR)/src/lib/ldso/startup
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include $(call select_from_repositories,lib/mk/ldso-startup.mk)
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@ -81,7 +81,7 @@ include $(BASE_DIR)/mk/base-libs.mk
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include $(LIB_MK)
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ifdef SHARED_LIB
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LIBS += ldso-startup
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LIBS += ldso_so_support
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endif
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#
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@ -181,10 +181,11 @@ $(LIB_A): $(OBJECTS)
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$(VERBOSE)$(AR) -rcs $@ $(OBJECTS)
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#
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# Link ldso-startup library to each shared library
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# Link ldso-support library to each shared library to provide local hook
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# functions for constructors and ARM
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#
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ifdef SHARED_LIB
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override ARCHIVES += ldso-startup.lib.a
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override ARCHIVES += ldso_so_support.lib.a
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endif
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#
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@ -208,10 +209,6 @@ STATIC_LIBS_BRIEF := $(subst $(LIB_CACHE_DIR),$$libs,$(STATIC_LIBS))
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# (LIB_SO_DEPS) to the library to store the library-dependency information in
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# the generated shared object.
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#
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# The 'ldso-startup/startup.o' object file, which contains the support code for
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# constructing static objects must be specified as object file to prevent the
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# linker from garbage-collecting it.
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#
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#
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# Default entry point of shared libraries
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@ -7,7 +7,7 @@ include:
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mkdir -p include
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cp -r $(REP_DIR)/include/* $@/
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LIB_MK_FILES := base.mk ld.mk ldso-startup.mk
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LIB_MK_FILES := base.mk ld.mk ldso_so_support.mk
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lib:
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mkdir -p lib/mk lib/symbols
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@ -21,6 +21,11 @@ mk/spec:
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mkdir -p $@
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cp $(foreach spec,$(SPECS),$(REP_DIR)/mk/spec/$(spec).mk) $@
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content: lib/mk/ldso_so_support.mk src/lib/ldso/so_support.c
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lib/mk/ldso_so_support.mk src/lib/ldso/so_support.c:
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$(mirror_from_rep_dir)
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LICENSE:
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cp $(GENODE_DIR)/LICENSE $@
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@ -1,6 +1,6 @@
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content: lib/mk/ldso-startup.mk LICENSE
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content: lib/mk/ldso_so_support.mk src/lib/ldso/so_support.c LICENSE
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lib/mk/ldso-startup.mk:
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lib/mk/ldso_so_support.mk src/lib/ldso/so_support.c:
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$(mirror_from_rep_dir)
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LICENSE:
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71
repos/base/src/lib/ldso/so_support.c
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71
repos/base/src/lib/ldso/so_support.c
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@ -0,0 +1,71 @@
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/**
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* \brief Shared-object support code
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* \author Sebastian Sumpf
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* \author Christian Helmuth
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* \date 2009-08-14
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*
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* Support code comprises hooks for execution of static constructors and
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* ARM-EABI dynamic linking.
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*
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* The ARM cross compiler uses the __gnu_Unwind_Find_exidx hook to locate a
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* 'ARM.exidx' section within a shared object. For this to work
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* 'dl_unwind_find_exidx' is excuted by 'ldso', which returns the section
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* address if it finds a shared object within the range of the provieded
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* program counter.
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*/
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/*
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* Copyright (C) 2009-2020 Genode Labs GmbH
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*
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* This file is part of the Genode OS framework, which is distributed
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* under the terms of the GNU Affero General Public License version 3.
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*/
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#define BEG { (ld_hook) ~1U }
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#define END { (ld_hook) 0 }
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#define SECTION(x) __attribute__((used,section( x )))
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typedef void (*ld_hook)(void);
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static ld_hook _lctors_start[1] SECTION("_mark_ctors_start") = BEG;
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static ld_hook _lctors_end[1] SECTION("_mark_ctors_end") = END;
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/*
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* '__dso_handle' needs to be defined in the main program and in each shared
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* object. Because ld.lib.so is both of them, '__dso_handle' is weak here.
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*/
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void *__dso_handle __attribute__((__visibility__("hidden")))
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__attribute__((weak)) = &__dso_handle;
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/* called by dynamic linker on library startup (ld.lib.so) */
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extern void _init(void) __attribute__((used,section(".init")));
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extern void _init(void)
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{
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/* call static constructors */
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for (ld_hook *func = _lctors_end; func > _lctors_start + 1; (*--func)());
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}
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/*
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* from gcc/config/arm/unwind-arm.h
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*/
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typedef unsigned _Unwind_Ptr __attribute__((__mode__(__pointer__)));
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/*
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* Dummy for static libs, implemented in ldso for dynamic case
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*/
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extern _Unwind_Ptr dl_unwind_find_exidx(_Unwind_Ptr pc, int *pcount) __attribute__((weak));
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extern _Unwind_Ptr dl_unwind_find_exidx(_Unwind_Ptr pc, int *pcount)
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{
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return 0;
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}
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/*
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* Called from libgcc_eh.a file 'gcc/config/arm/unwind-arm.c' in function
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* 'get_eit_entry'
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*/
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extern _Unwind_Ptr __gnu_Unwind_Find_exidx (_Unwind_Ptr pc, int *pcount)
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{
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return dl_unwind_find_exidx(pc, pcount);
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}
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@ -1,38 +0,0 @@
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/**
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* \brief Shared object startup code
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* \author Sebastian Sumpf
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* \date 2009-08-14
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*/
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/*
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* Copyright (C) 2009-2017 Genode Labs GmbH
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*
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* This file is part of the Genode OS framework, which is distributed
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* under the terms of the GNU Affero General Public License version 3.
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*/
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#define BEG { (ld_hook) ~1U }
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#define END { (ld_hook) 0 }
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#define SECTION(x) __attribute__((used,section( x )))
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typedef void (*ld_hook)(void);
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static ld_hook _lctors_start[1] SECTION("_mark_ctors_start") = BEG;
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static ld_hook _lctors_end[1] SECTION("_mark_ctors_end") = END;
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/*
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* '__dso_handle' needs to be defined in the main program and in each shared
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* object. Because ld.lib.so is both of them, '__dso_handle' is weak here.
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*/
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void *__dso_handle __attribute__((__visibility__("hidden")))
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__attribute__((weak)) = &__dso_handle;
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/* called by dynamic linker on library startup (ld-genode.so) */
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extern "C" {
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void _init(void) __attribute__((used,section(".init")));
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void _init(void)
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{
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/* call static constructors */
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for(ld_hook *func = _lctors_end; func > _lctors_start + 1; (*--func)());
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}
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}
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@ -1,48 +0,0 @@
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/*
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* \brief Our implementation of __gnu_Unwind_Find_exidx
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* \author Sebastian Sumpf <Sebastian.Sumpf@genode-labs.com>
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* \date 2010-07-05
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*
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* This file is used for ARM-EABI dynamic linking, only. The ARM cross-compiler
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* uses this hook to locate a 'ARM.exidx' section within a shared object. For
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* this to work 'dl_unwind_find_exidx' is excuted by 'ldso', which returns the
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* section address if it finds a shared object within the range of the provieded
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* progam counter
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*/
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/*
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* Copyright (C) 2010-2017 Genode Labs GmbH
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*
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* This file is part of the Genode OS framework, which is distributed
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* under the terms of the GNU Affero General Public License version 3.
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*/
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#include <base/log.h>
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/*
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* from gcc/config/arm/unwind-arm.h
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*/
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typedef unsigned _Unwind_Ptr __attribute__((__mode__(__pointer__)));
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/*
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* Implemented in ldso
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* */
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extern "C" _Unwind_Ptr __attribute__((weak)) dl_unwind_find_exidx(_Unwind_Ptr pc, int *pcount);
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extern "C" _Unwind_Ptr dl_unwind_find_exidx(_Unwind_Ptr /* pc */, int * /* pcount */)
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{
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Genode::error("dl_unwind_find_exidx called");
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return 0;
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}
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/*
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* Called from libgcc_eh.a file 'gcc/config/arm/unwind-arm.c' in function
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* 'get_eit_entry'
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*/
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extern "C" _Unwind_Ptr __gnu_Unwind_Find_exidx (_Unwind_Ptr pc, int *pcount)
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{
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return dl_unwind_find_exidx(pc, pcount);
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}
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@ -18,6 +18,12 @@ include:
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cp -r $(REP_DIR)/include/libc-genode $@/
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cp $(REP_DIR)/src/lib/libc/internal/legacy.h $@/libc/
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content: lib/mk/ldso_so_support.mk src/lib/ldso/so_support.c
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lib/mk/ldso_so_support.mk src/lib/ldso/so_support.c:
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mkdir -p $(dir $@)
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cp $(GENODE_DIR)/repos/base/$@ $@
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content: LICENSE
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LICENSE:
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@ -1,14 +1,10 @@
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MIRROR_FROM_REP_DIR := lib/symbols/posix lib/import/import-posix.mk
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content: $(MIRROR_FROM_REP_DIR) LICENSE lib/mk/base.mk lib/mk/ldso-startup.mk
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content: $(MIRROR_FROM_REP_DIR) LICENSE
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$(MIRROR_FROM_REP_DIR):
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$(mirror_from_rep_dir)
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lib/mk/base.mk lib/mk/ldso-startup.mk:
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mkdir -p $(dir $@)
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touch $@
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LICENSE:
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cp $(GENODE_DIR)/LICENSE $@
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@ -1,2 +1,3 @@
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base
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libc
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so
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@ -6,3 +6,4 @@ report_session
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rtc_session
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terminal_session
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vfs
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so
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