fishhook.c - external/github.com/facebook/fishhook - Git at Google

 // Copyright (c) 2013, Facebook, Inc.
 // All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are met:
 //   * Redistributions of source code must retain the above copyright notice,
 //     this list of conditions and the following disclaimer.
 //   * Redistributions in binary form must reproduce the above copyright notice,
 //     this list of conditions and the following disclaimer in the documentation
 //     and/or other materials provided with the distribution.
 //   * Neither the name Facebook nor the names of its contributors may be used to
 //     endorse or promote products derived from this software without specific
 //     prior written permission.
 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 // AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 // IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 // DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
 // FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 // DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 // SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 // CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 // OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 #import "fishhook.h"

 #import <dlfcn.h>
 #import <stdlib.h>
 #import <string.h>
 #import <sys/types.h>
 #import <mach-o/dyld.h>
 #import <mach-o/loader.h>
 #import <mach-o/nlist.h>

 #ifdef __LP64__
 typedef struct mach_header_64 mach_header_t;
 typedef struct segment_command_64 segment_command_t;
 typedef struct section_64 section_t;
 typedef struct nlist_64 nlist_t;
 #define LC_SEGMENT_ARCH_DEPENDENT LC_SEGMENT_64
 #else
 typedef struct mach_header mach_header_t;
 typedef struct segment_command segment_command_t;
 typedef struct section section_t;
 typedef struct nlist nlist_t;
 #define LC_SEGMENT_ARCH_DEPENDENT LC_SEGMENT
 #endif

 #ifndef SEG_DATA_CONST
 #define SEG_DATA_CONST  "__DATA_CONST"
 #endif

 struct rebindings_entry {
   struct rebinding *rebindings;
   size_t rebindings_nel;
   struct rebindings_entry *next;
 };

 static struct rebindings_entry *_rebindings_head;

 static int prepend_rebindings(struct rebindings_entry **rebindings_head,
                               struct rebinding rebindings[],
                               size_t nel) {
   struct rebindings_entry *new_entry = malloc(sizeof(struct rebindings_entry));
   if (!new_entry) {
     return -1;
   }
   new_entry->rebindings = malloc(sizeof(struct rebinding) * nel);
   if (!new_entry->rebindings) {
     free(new_entry);
     return -1;
   }
   memcpy(new_entry->rebindings, rebindings, sizeof(struct rebinding) * nel);
   new_entry->rebindings_nel = nel;
   new_entry->next = *rebindings_head;
   *rebindings_head = new_entry;
   return 0;
 }

 static void perform_rebinding_with_section(struct rebindings_entry *rebindings,
                                            section_t *section,
                                            intptr_t slide,
                                            nlist_t *symtab,
                                            char *strtab,
                                            uint32_t *indirect_symtab) {
   uint32_t *indirect_symbol_indices = indirect_symtab + section->reserved1;
   void **indirect_symbol_bindings = (void **)((uintptr_t)slide + section->addr);
   for (uint i = 0; i < section->size / sizeof(void *); i++) {
     uint32_t symtab_index = indirect_symbol_indices[i];
     if (symtab_index == INDIRECT_SYMBOL_ABS || symtab_index == INDIRECT_SYMBOL_LOCAL ||
         symtab_index == (INDIRECT_SYMBOL_LOCAL   | INDIRECT_SYMBOL_ABS)) {
       continue;
     }
     uint32_t strtab_offset = symtab[symtab_index].n_un.n_strx;
     char *symbol_name = strtab + strtab_offset;
     if (strnlen(symbol_name, 2) < 2) {
       continue;
     }
     struct rebindings_entry *cur = rebindings;
     while (cur) {
       for (uint j = 0; j < cur->rebindings_nel; j++) {
         if (strcmp(&symbol_name[1], cur->rebindings[j].name) == 0) {
           if (cur->rebindings[j].replaced != NULL &&
               indirect_symbol_bindings[i] != cur->rebindings[j].replacement) {
             *(cur->rebindings[j].replaced) = indirect_symbol_bindings[i];
           }
           indirect_symbol_bindings[i] = cur->rebindings[j].replacement;
           goto symbol_loop;
         }
       }
       cur = cur->next;
     }
   symbol_loop:;
   }
 }

 static void rebind_symbols_for_image(struct rebindings_entry *rebindings,
                                      const struct mach_header *header,
                                      intptr_t slide) {
   Dl_info info;
   if (dladdr(header, &info) == 0) {
     return;
   }

   segment_command_t *cur_seg_cmd;
   segment_command_t *linkedit_segment = NULL;
   struct symtab_command* symtab_cmd = NULL;
   struct dysymtab_command* dysymtab_cmd = NULL;

   uintptr_t cur = (uintptr_t)header + sizeof(mach_header_t);
   for (uint i = 0; i < header->ncmds; i++, cur += cur_seg_cmd->cmdsize) {
     cur_seg_cmd = (segment_command_t *)cur;
     if (cur_seg_cmd->cmd == LC_SEGMENT_ARCH_DEPENDENT) {
       if (strcmp(cur_seg_cmd->segname, SEG_LINKEDIT) == 0) {
         linkedit_segment = cur_seg_cmd;
       }
     } else if (cur_seg_cmd->cmd == LC_SYMTAB) {
       symtab_cmd = (struct symtab_command*)cur_seg_cmd;
     } else if (cur_seg_cmd->cmd == LC_DYSYMTAB) {
       dysymtab_cmd = (struct dysymtab_command*)cur_seg_cmd;
     }
   }

   if (!symtab_cmd || !dysymtab_cmd || !linkedit_segment ||
       !dysymtab_cmd->nindirectsyms) {
     return;
   }

   // Find base symbol/string table addresses
   uintptr_t linkedit_base = (uintptr_t)slide + linkedit_segment->vmaddr - linkedit_segment->fileoff;
   nlist_t *symtab = (nlist_t *)(linkedit_base + symtab_cmd->symoff);
   char *strtab = (char *)(linkedit_base + symtab_cmd->stroff);

   // Get indirect symbol table (array of uint32_t indices into symbol table)
   uint32_t *indirect_symtab = (uint32_t *)(linkedit_base + dysymtab_cmd->indirectsymoff);

   cur = (uintptr_t)header + sizeof(mach_header_t);
   for (uint i = 0; i < header->ncmds; i++, cur += cur_seg_cmd->cmdsize) {
     cur_seg_cmd = (segment_command_t *)cur;
     if (cur_seg_cmd->cmd == LC_SEGMENT_ARCH_DEPENDENT) {
       if (strcmp(cur_seg_cmd->segname, SEG_DATA) != 0 &&
           strcmp(cur_seg_cmd->segname, SEG_DATA_CONST) != 0) {
         continue;
       }
       for (uint j = 0; j < cur_seg_cmd->nsects; j++) {
         section_t *sect =
           (section_t *)(cur + sizeof(segment_command_t)) + j;
         if ((sect->flags & SECTION_TYPE) == S_LAZY_SYMBOL_POINTERS) {
           perform_rebinding_with_section(rebindings, sect, slide, symtab, strtab, indirect_symtab);
         }
         if ((sect->flags & SECTION_TYPE) == S_NON_LAZY_SYMBOL_POINTERS) {
           perform_rebinding_with_section(rebindings, sect, slide, symtab, strtab, indirect_symtab);
         }
       }
     }
   }
 }

 static void _rebind_symbols_for_image(const struct mach_header *header,
                                       intptr_t slide) {
     rebind_symbols_for_image(_rebindings_head, header, slide);
 }

 int rebind_symbols_image(void *header,
                          intptr_t slide,
                          struct rebinding rebindings[],
                          size_t rebindings_nel) {
     struct rebindings_entry *rebindings_head = NULL;
     int retval = prepend_rebindings(&rebindings_head, rebindings, rebindings_nel);
     rebind_symbols_for_image(rebindings_head, header, slide);
     free(rebindings_head);
     return retval;
 }

 int rebind_symbols(struct rebinding rebindings[], size_t rebindings_nel) {
   int retval = prepend_rebindings(&_rebindings_head, rebindings, rebindings_nel);
   if (retval < 0) {
     return retval;
   }
   // If this was the first call, register callback for image additions (which is also invoked for
   // existing images, otherwise, just run on existing images
   if (!_rebindings_head->next) {
     _dyld_register_func_for_add_image(_rebind_symbols_for_image);
   } else {
     uint32_t c = _dyld_image_count();
     for (uint32_t i = 0; i < c; i++) {
       _rebind_symbols_for_image(_dyld_get_image_header(i), _dyld_get_image_vmaddr_slide(i));
     }
   }
   return retval;
 }
	// Copyright (c) 2013, Facebook, Inc.
	// All rights reserved.
	// Redistribution and use in source and binary forms, with or without
	// modification, are permitted provided that the following conditions are met:
	// * Redistributions of source code must retain the above copyright notice,
	// this list of conditions and the following disclaimer.
	// * Redistributions in binary form must reproduce the above copyright notice,
	// this list of conditions and the following disclaimer in the documentation
	// and/or other materials provided with the distribution.
	// * Neither the name Facebook nor the names of its contributors may be used to
	// endorse or promote products derived from this software without specific
	// prior written permission.
	// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
	// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
	// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
	// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
	// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
	// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
	// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

	#import "fishhook.h"

	#import <dlfcn.h>
	#import <stdlib.h>
	#import <string.h>
	#import <sys/types.h>
	#import <mach-o/dyld.h>
	#import <mach-o/loader.h>
	#import <mach-o/nlist.h>

	#ifdef __LP64__
	typedef struct mach_header_64 mach_header_t;
	typedef struct segment_command_64 segment_command_t;
	typedef struct section_64 section_t;
	typedef struct nlist_64 nlist_t;
	#define LC_SEGMENT_ARCH_DEPENDENT LC_SEGMENT_64
	#else
	typedef struct mach_header mach_header_t;
	typedef struct segment_command segment_command_t;
	typedef struct section section_t;
	typedef struct nlist nlist_t;
	#define LC_SEGMENT_ARCH_DEPENDENT LC_SEGMENT
	#endif

	#ifndef SEG_DATA_CONST
	#define SEG_DATA_CONST "__DATA_CONST"
	#endif

	struct rebindings_entry {
	struct rebinding *rebindings;
	size_t rebindings_nel;
	struct rebindings_entry *next;
	};

	static struct rebindings_entry *_rebindings_head;

	static int prepend_rebindings(struct rebindings_entry **rebindings_head,
	struct rebinding rebindings[],
	size_t nel) {
	struct rebindings_entry *new_entry = malloc(sizeof(struct rebindings_entry));
	if (!new_entry) {
	return -1;
	}
	new_entry->rebindings = malloc(sizeof(struct rebinding) * nel);
	if (!new_entry->rebindings) {
	free(new_entry);
	return -1;
	}
	memcpy(new_entry->rebindings, rebindings, sizeof(struct rebinding) * nel);
	new_entry->rebindings_nel = nel;
	new_entry->next = *rebindings_head;
	*rebindings_head = new_entry;
	return 0;
	}

	static void perform_rebinding_with_section(struct rebindings_entry *rebindings,
	section_t *section,
	intptr_t slide,
	nlist_t *symtab,
	char *strtab,
	uint32_t *indirect_symtab) {
	uint32_t *indirect_symbol_indices = indirect_symtab + section->reserved1;
	void indirect_symbol_bindings = (void )((uintptr_t)slide + section->addr);
	for (uint i = 0; i < section->size / sizeof(void *); i++) {
	uint32_t symtab_index = indirect_symbol_indices[i];
	if (symtab_index == INDIRECT_SYMBOL_ABS \|\| symtab_index == INDIRECT_SYMBOL_LOCAL \|\|
	symtab_index == (INDIRECT_SYMBOL_LOCAL \| INDIRECT_SYMBOL_ABS)) {
	continue;
	}
	uint32_t strtab_offset = symtab[symtab_index].n_un.n_strx;
	char *symbol_name = strtab + strtab_offset;
	if (strnlen(symbol_name, 2) < 2) {
	continue;
	}
	struct rebindings_entry *cur = rebindings;
	while (cur) {
	for (uint j = 0; j < cur->rebindings_nel; j++) {
	if (strcmp(&symbol_name[1], cur->rebindings[j].name) == 0) {
	if (cur->rebindings[j].replaced != NULL &&
	indirect_symbol_bindings[i] != cur->rebindings[j].replacement) {
	*(cur->rebindings[j].replaced) = indirect_symbol_bindings[i];
	}
	indirect_symbol_bindings[i] = cur->rebindings[j].replacement;
	goto symbol_loop;
	}
	}
	cur = cur->next;
	}
	symbol_loop:;
	}
	}

	static void rebind_symbols_for_image(struct rebindings_entry *rebindings,
	const struct mach_header *header,
	intptr_t slide) {
	Dl_info info;
	if (dladdr(header, &info) == 0) {
	return;
	}

	segment_command_t *cur_seg_cmd;
	segment_command_t *linkedit_segment = NULL;
	struct symtab_command* symtab_cmd = NULL;
	struct dysymtab_command* dysymtab_cmd = NULL;

	uintptr_t cur = (uintptr_t)header + sizeof(mach_header_t);
	for (uint i = 0; i < header->ncmds; i++, cur += cur_seg_cmd->cmdsize) {
	cur_seg_cmd = (segment_command_t *)cur;
	if (cur_seg_cmd->cmd == LC_SEGMENT_ARCH_DEPENDENT) {
	if (strcmp(cur_seg_cmd->segname, SEG_LINKEDIT) == 0) {
	linkedit_segment = cur_seg_cmd;
	}
	} else if (cur_seg_cmd->cmd == LC_SYMTAB) {
	symtab_cmd = (struct symtab_command*)cur_seg_cmd;
	} else if (cur_seg_cmd->cmd == LC_DYSYMTAB) {
	dysymtab_cmd = (struct dysymtab_command*)cur_seg_cmd;
	}
	}

	if (!symtab_cmd \|\| !dysymtab_cmd \|\| !linkedit_segment \|\|
	!dysymtab_cmd->nindirectsyms) {
	return;
	}

	// Find base symbol/string table addresses
	uintptr_t linkedit_base = (uintptr_t)slide + linkedit_segment->vmaddr - linkedit_segment->fileoff;
	nlist_t symtab = (nlist_t )(linkedit_base + symtab_cmd->symoff);
	char strtab = (char )(linkedit_base + symtab_cmd->stroff);

	// Get indirect symbol table (array of uint32_t indices into symbol table)
	uint32_t indirect_symtab = (uint32_t )(linkedit_base + dysymtab_cmd->indirectsymoff);

	cur = (uintptr_t)header + sizeof(mach_header_t);
	for (uint i = 0; i < header->ncmds; i++, cur += cur_seg_cmd->cmdsize) {
	cur_seg_cmd = (segment_command_t *)cur;
	if (cur_seg_cmd->cmd == LC_SEGMENT_ARCH_DEPENDENT) {
	if (strcmp(cur_seg_cmd->segname, SEG_DATA) != 0 &&
	strcmp(cur_seg_cmd->segname, SEG_DATA_CONST) != 0) {
	continue;
	}
	for (uint j = 0; j < cur_seg_cmd->nsects; j++) {
	section_t *sect =
	(section_t *)(cur + sizeof(segment_command_t)) + j;
	if ((sect->flags & SECTION_TYPE) == S_LAZY_SYMBOL_POINTERS) {
	perform_rebinding_with_section(rebindings, sect, slide, symtab, strtab, indirect_symtab);
	}
	if ((sect->flags & SECTION_TYPE) == S_NON_LAZY_SYMBOL_POINTERS) {
	perform_rebinding_with_section(rebindings, sect, slide, symtab, strtab, indirect_symtab);
	}
	}
	}
	}
	}

	static void _rebind_symbols_for_image(const struct mach_header *header,
	intptr_t slide) {
	rebind_symbols_for_image(_rebindings_head, header, slide);
	}

	int rebind_symbols_image(void *header,
	intptr_t slide,
	struct rebinding rebindings[],
	size_t rebindings_nel) {
	struct rebindings_entry *rebindings_head = NULL;
	int retval = prepend_rebindings(&rebindings_head, rebindings, rebindings_nel);
	rebind_symbols_for_image(rebindings_head, header, slide);
	free(rebindings_head);
	return retval;
	}

	int rebind_symbols(struct rebinding rebindings[], size_t rebindings_nel) {
	int retval = prepend_rebindings(&_rebindings_head, rebindings, rebindings_nel);
	if (retval < 0) {
	return retval;
	}
	// If this was the first call, register callback for image additions (which is also invoked for
	// existing images, otherwise, just run on existing images
	if (!_rebindings_head->next) {
	_dyld_register_func_for_add_image(_rebind_symbols_for_image);
	} else {
	uint32_t c = _dyld_image_count();
	for (uint32_t i = 0; i < c; i++) {
	_rebind_symbols_for_image(_dyld_get_image_header(i), _dyld_get_image_vmaddr_slide(i));
	}
	}
	return retval;
	}