5135b3ae6e
The linker only needs to mark the text segment as writable iff the file has text relocations. Unnecessarily calling mprotect when it isn't necessary is slow, and some security enhanced kernels don't like it. Pages which are simultaneously writable and executable are considered a no-no. The vast majority of executables / shared libraries on Android do NOT have text relocations. Change-Id: Ic38ce30a99b7e33ecf21efd9c108547a58eafa35
257 lines
6.3 KiB
C
257 lines
6.3 KiB
C
/*
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* Copyright (C) 2008 The Android Open Source Project
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#ifndef _LINKER_H_
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#define _LINKER_H_
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#include <unistd.h>
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#include <sys/types.h>
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#include <elf.h>
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#include <sys/exec_elf.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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#undef PAGE_MASK
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#undef PAGE_SIZE
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#define PAGE_SIZE 4096
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#define PAGE_MASK (PAGE_SIZE-1)
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/* Convenience macros to make page address/offset computations more explicit */
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/* Returns the address of the page starting at address 'x' */
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#define PAGE_START(x) ((x) & ~PAGE_MASK)
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/* Returns the offset of address 'x' in its memory page, i.e. this is the
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* same than 'x' - PAGE_START(x) */
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#define PAGE_OFFSET(x) ((x) & PAGE_MASK)
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/* Returns the address of the next page after address 'x', unless 'x' is
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* itself at the start of a page. Equivalent to:
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*
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* (x == PAGE_START(x)) ? x : PAGE_START(x)+PAGE_SIZE
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*/
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#define PAGE_END(x) PAGE_START((x) + (PAGE_SIZE-1))
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void debugger_init();
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const char *addr_to_name(unsigned addr);
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/* magic shared structures that GDB knows about */
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struct link_map
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{
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uintptr_t l_addr;
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char * l_name;
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uintptr_t l_ld;
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struct link_map * l_next;
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struct link_map * l_prev;
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};
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/* needed for dl_iterate_phdr to be passed to the callbacks provided */
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struct dl_phdr_info
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{
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Elf32_Addr dlpi_addr;
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const char *dlpi_name;
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const Elf32_Phdr *dlpi_phdr;
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Elf32_Half dlpi_phnum;
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};
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// Values for r_debug->state
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enum {
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RT_CONSISTENT,
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RT_ADD,
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RT_DELETE
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};
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struct r_debug
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{
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int32_t r_version;
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struct link_map * r_map;
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void (*r_brk)(void);
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int32_t r_state;
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uintptr_t r_ldbase;
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};
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typedef struct soinfo soinfo;
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#define FLAG_LINKED 0x00000001
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#define FLAG_ERROR 0x00000002
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#define FLAG_EXE 0x00000004 // The main executable
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#define FLAG_LINKER 0x00000010 // The linker itself
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#define SOINFO_NAME_LEN 128
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struct soinfo
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{
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char name[SOINFO_NAME_LEN];
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const Elf32_Phdr *phdr;
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int phnum;
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unsigned entry;
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unsigned base;
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unsigned size;
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int unused; // DO NOT USE, maintained for compatibility.
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unsigned *dynamic;
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unsigned unused2; // DO NOT USE, maintained for compatibility
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unsigned unused3; // DO NOT USE, maintained for compatibility
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soinfo *next;
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unsigned flags;
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const char *strtab;
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Elf32_Sym *symtab;
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unsigned nbucket;
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unsigned nchain;
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unsigned *bucket;
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unsigned *chain;
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unsigned *plt_got;
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Elf32_Rel *plt_rel;
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unsigned plt_rel_count;
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Elf32_Rel *rel;
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unsigned rel_count;
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unsigned *preinit_array;
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unsigned preinit_array_count;
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unsigned *init_array;
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unsigned init_array_count;
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unsigned *fini_array;
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unsigned fini_array_count;
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void (*init_func)(void);
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void (*fini_func)(void);
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#if defined(ANDROID_ARM_LINKER)
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/* ARM EABI section used for stack unwinding. */
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unsigned *ARM_exidx;
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unsigned ARM_exidx_count;
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#elif defined(ANDROID_MIPS_LINKER)
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#if 0
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/* not yet */
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unsigned *mips_pltgot
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#endif
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unsigned mips_symtabno;
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unsigned mips_local_gotno;
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unsigned mips_gotsym;
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#endif /* ANDROID_*_LINKER */
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unsigned refcount;
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struct link_map linkmap;
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int constructors_called;
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/* When you read a virtual address from the ELF file, add this
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* value to get the corresponding address in the process' address space */
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Elf32_Addr load_bias;
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int has_text_relocations;
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};
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extern soinfo libdl_info;
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#include <asm/elf.h>
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#if defined(ANDROID_ARM_LINKER)
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// These aren't defined in <arch-arm/asm/elf.h>.
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#define R_ARM_REL32 3
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#define R_ARM_COPY 20
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#define R_ARM_GLOB_DAT 21
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#define R_ARM_JUMP_SLOT 22
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#define R_ARM_RELATIVE 23
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#elif defined(ANDROID_MIPS_LINKER)
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// These aren't defined in <arch-arm/mips/elf.h>.
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#define R_MIPS_JUMP_SLOT 127
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#define DT_MIPS_PLTGOT 0x70000032
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#define DT_MIPS_RWPLT 0x70000034
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#elif defined(ANDROID_X86_LINKER)
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// x86 has everything it needs in <arch-arm/x86/elf.h>.
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#endif /* ANDROID_*_LINKER */
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#ifndef DT_INIT_ARRAY
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#define DT_INIT_ARRAY 25
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#endif
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#ifndef DT_FINI_ARRAY
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#define DT_FINI_ARRAY 26
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#endif
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#ifndef DT_INIT_ARRAYSZ
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#define DT_INIT_ARRAYSZ 27
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#endif
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#ifndef DT_FINI_ARRAYSZ
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#define DT_FINI_ARRAYSZ 28
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#endif
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#ifndef DT_PREINIT_ARRAY
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#define DT_PREINIT_ARRAY 32
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#endif
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#ifndef DT_PREINIT_ARRAYSZ
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#define DT_PREINIT_ARRAYSZ 33
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#endif
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soinfo *find_library(const char *name);
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Elf32_Sym *lookup(const char *name, soinfo **found, soinfo *start);
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soinfo *find_containing_library(const void *addr);
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const char *linker_get_error(void);
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unsigned soinfo_unload(soinfo *si);
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Elf32_Sym *soinfo_find_symbol(soinfo* si, const void *addr);
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Elf32_Sym *soinfo_lookup(soinfo *si, const char *name);
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void soinfo_call_constructors(soinfo *si);
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#if defined(ANDROID_ARM_LINKER)
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typedef long unsigned int *_Unwind_Ptr;
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_Unwind_Ptr dl_unwind_find_exidx(_Unwind_Ptr pc, int *pcount);
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#elif defined(ANDROID_X86_LINKER) || defined(ANDROID_MIPS_LINKER)
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int dl_iterate_phdr(int (*cb)(struct dl_phdr_info *, size_t, void *), void *);
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#endif
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#ifdef __cplusplus
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};
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#endif
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#endif
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