添加 __text 校验以及忽略一些不需要的符号

symdl/symdl/symdl.c

@@ -20,6 +20,7 @@
 #include <mach-o/nlist.h>
 #include <pthread/pthread.h>
 
+typedef struct load_command load_command_t;
 #ifdef __LP64__
 typedef struct mach_header_64 mach_header_t;
 typedef struct segment_command_64 segment_command_t;
@@ -48,6 +49,66 @@ static int cache_next_index = 0;
 static int cache_capacity = 128;
 static pthread_rwlock_t rwlock = PTHREAD_RWLOCK_INITIALIZER;
 
+static bool cstringPrefix(const char *str, const char *pre) {
+ return strncmp(pre, str, strlen(pre)) == 0;
+}
+
+static void forEachLoadCommand(const struct mach_header *header, void (^callback)(const load_command_t *cmd, bool *stop)) {
+ bool stop = false;
+ const load_command_t *startCmds = NULL;
+ if (header->magic == MH_MAGIC_64)
+ startCmds = (load_command_t *)((char *)header + sizeof(struct mach_header_64));
+ else if (header->magic == MH_MAGIC)
+ startCmds = (load_command_t *)((char *)header + sizeof(struct mach_header));
+ else if (header->magic == MH_CIGAM || header->magic == MH_CIGAM_64)
+ return; // can't process big endian mach-o
+ else {
+ return; // not a mach-o file
+ }
+ const load_command_t *const cmdsEnd = (load_command_t *)((char *)startCmds + header->sizeofcmds);
+ const load_command_t *cmd = startCmds;
+ for (uint32_t i = 0; i < header->ncmds; ++i) {
+ const load_command_t *nextCmd = (load_command_t *)((char *)cmd + cmd->cmdsize);
+ if (cmd->cmdsize < 8) {
+ return;
+ }
+ // FIXME: add check the cmdsize is pointer aligned (might reveal bin compat issues)
+ if ((nextCmd > cmdsEnd) || (nextCmd < startCmds)) {
+ return;
+ }
+ callback(cmd, &stop);
+ if (stop)
+ return;
+ cmd = nextCmd;
+ }
+}
+
+static void forEachSection(const struct mach_header *header, void (^callback)(const section_t *sectInfo, bool *stop)) {
+ __block uint32_t segIndex = 0;
+ forEachLoadCommand(header, ^(const load_command_t *cmd, bool *stop) {
+ if (cmd->cmd == LC_SEGMENT_64) {
+ const segment_command_t *segCmd = (segment_command_t *)cmd;
+ const section_t *const sectionsStart = (section_t *)((char *)segCmd + sizeof(segment_command_t));
+ const section_t *const sectionsEnd = &sectionsStart[segCmd->nsects];
+ for (const section_t *sect = sectionsStart; !(*stop) && (sect < sectionsEnd); ++sect) {
+ callback(sect, stop);
+ }
+ ++segIndex;
+ }
+ });
+}
+
+//edit from dyld: bool MachOAnalyzer::inCodeSection
+static bool inCodeSection(const struct mach_header *header, intptr_t slide, intptr_t address) {
+ __block bool result = false;
+ forEachSection(header, ^(const section_t *sectInfo, bool *stop) {
+ if ((sectInfo->addr + slide <= address) && (address < (sectInfo->addr + sectInfo->size + slide))) {
+ result = ((sectInfo->flags & S_ATTR_PURE_INSTRUCTIONS) || (sectInfo->flags & S_ATTR_SOME_INSTRUCTIONS));
+ *stop = true;
+ }
+ });
+ return result;
+}
 
 
 static void *func_pointer_with_name_in_image(const char *name, const struct mach_header *header, intptr_t slide){
@@ -83,14 +144,36 @@ static void *func_pointer_with_name_in_image(const char *name, const struct mach
 
  uint32_t cmdsize = symtab_cmd->nsyms;
  for (uint32_t i = 0; i < cmdsize; i++) {
- nlist_t *nlist = &symtab[i];
- if ((nlist->n_type & N_STAB) || (nlist->n_type & N_TYPE) != N_SECT || nlist->n_sect != 1) {
+ nlist_t *nlist = &symtab[i];
+
+ if ((nlist->n_type & N_STAB) || (nlist->n_type & N_TYPE) != N_SECT) {
  continue;
  }
+
  const char *symbol_name = strtab + nlist->n_un.n_strx;
  bool symbol_name_longer_than_1 = symbol_name[0] && symbol_name[1];
+ // <redirect>
+ // $ ___Z C++
+ // +/- objc
+ // __swift swift
+ if (!symbol_name_longer_than_1
+ || symbol_name[0] == '<'
+ || symbol_name[0] == '-'
+ || symbol_name[0] == '+'
+ || symbol_name[1] == '$'
+ || cstringPrefix(symbol_name, "__Z")
+ || cstringPrefix(symbol_name, "___")
+ || cstringPrefix(symbol_name, "__swift")) {
+ continue;
+ }
+
+ intptr_t functionAddress = (intptr_t)(nlist->n_value + slide);
+ if (!inCodeSection(header, slide, functionAddress)) {
+ continue;
+ }
+
  if (symbol_name_longer_than_1 && strcmp(&symbol_name[1], name) == 0) {
- return (void *)(nlist->n_value + slide);;
+ return (void *)functionAddress;;
  }
  }
 

symdl_example/symdl_example/AppDelegate.m

@@ -25,16 +25,11 @@ - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(
  my_load(write);
  my_load(read);
 
- symdl("fopen");
- symdl("fclose");
- symdl("write");
- symdl("read");
-
- symdl("fopen");
- symdl("fclose");
- symdl("write");
- symdl("read");
-
+ assert(symdl("fopen") == fopen);
+ assert(symdl("fclose") == fclose);
+ assert(symdl("write") == write);
+ assert(symdl("read") == read);
+
  // Override point for customization after application launch.
  return YES;
 }