improve: port ptracer to C

This commit ports the C++ to C99 from zygisk-ptracer code, allowing a ~3x size reduce in its binary.

Author: ThePedroo

loader/build.gradle.kts

@@ -26,6 +26,8 @@ val ccachePath by lazy {
 }
 
 val defaultCFlags = arrayOf(
+    "-D_GNU_SOURCE",
+
     "-Wall", "-Wextra",
     "-fno-rtti", "-fno-exceptions",
     "-fno-stack-protector", "-fomit-frame-pointer",

loader/src/CMakeLists.txt

@@ -10,7 +10,7 @@ add_definitions(-DZKSU_VERSION=\"${ZKSU_VERSION}\")
 aux_source_directory(common COMMON_SRC_LIST)
 add_library(common STATIC ${COMMON_SRC_LIST})
 target_include_directories(common PRIVATE include)
-target_link_libraries(common cxx::cxx log)
+target_link_libraries(common log)
 
 aux_source_directory(injector INJECTOR_SRC_LIST)
 add_library(zygisk SHARED ${INJECTOR_SRC_LIST})
@@ -20,6 +20,5 @@ target_link_libraries(zygisk cxx::cxx log common lsplt_static phmap)
 aux_source_directory(ptracer PTRACER_SRC_LIST)
 add_executable(libzygisk_ptrace.so ${PTRACER_SRC_LIST})
 target_include_directories(libzygisk_ptrace.so PRIVATE include)
-target_link_libraries(libzygisk_ptrace.so cxx::cxx log common)
-
+target_link_libraries(libzygisk_ptrace.so log common)
 add_subdirectory(external)

loader/src/common/daemon.c

@@ -1,8 +1,3 @@
-// #include <unistd.h>
-// #include <sys/types.h>
-// #include <sys/stat.h>
-// #include <dirent.h>
-// #include <fcntl.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <stdbool.h>
@@ -15,19 +10,6 @@
 
 #include "daemon.h"
 
-char daemon_path[PATH_MAX];
-
-void rezygiskd_init(const char *path) {
-  snprintf(daemon_path, sizeof(daemon_path), "%s/%s", path, SOCKET_FILE_NAME);
-}
-
-void rezygiskd_get_path(char *buf, size_t buf_size) {
-  size_t fileless_daemon_path = strlen(daemon_path) - strlen("/") - strlen(SOCKET_FILE_NAME);
-
-  strncpy(buf, daemon_path, buf_size > fileless_daemon_path ? fileless_daemon_path : buf_size);
-  buf[fileless_daemon_path] = '\0';
-}
-
 int rezygiskd_connect(uint8_t retry) {
   retry++;
 
@@ -49,7 +31,7 @@ int rezygiskd_connect(uint8_t retry) {
     Sources:
      - https://pubs.opengroup.org/onlinepubs/009696699/basedefs/sys/un.h.html
   */
-  strcpy(addr.sun_path, daemon_path);
+  strcpy(addr.sun_path, TMP_PATH "/" SOCKET_FILE_NAME);
   socklen_t socklen = sizeof(addr);
 
   while (--retry) {
@@ -343,15 +325,18 @@ bool rezygiskd_update_mns(enum mount_namespace_state nms_state, char *buf, size_
   write_uint8_t(fd, (uint8_t)nms_state);
 
   uint32_t target_pid = 0;
-  read_uint32_t(fd, &target_pid);
-  if (target_pid == 0) {
+  if (read_uint32_t(fd, &target_pid) < 0) {
+    PLOGE("Failed to read target pid");
+
     close(fd);
 
     return false;
   }
 
-  int target_fd = read_fd(fd);
-  if (target_fd == -1) {
+  uint32_t target_fd = 0;
+  if (read_uint32_t(fd, &target_fd) < 0) {
+    PLOGE("Failed to read target fd");
+
     close(fd);
 
     return false;

loader/src/common/elf_util.c

@@ -1,5 +1,3 @@
-/* INFO: This file is written in C99 */
-
 #include <stdlib.h>
 #include <stdint.h>
 #include <stdbool.h>

loader/src/common/misc.c

@@ -1,14 +1,14 @@
 int parse_int(const char *str) {
-    int val = 0;
+  int val = 0;
 
-    char *c = (char *)str;
-    while (*c) {
-        if (*c > '9' || *c < '0')
-            return -1;
+  char *c = (char *)str;
+  while (*c) {
+    if (*c > '9' || *c < '0')
+      return -1;
 
-        val = val * 10 + *c - '0';
-        c++;
-    }
+    val = val * 10 + *c - '0';
+    c++;
+  }
 
-    return val;
+  return val;
 }

loader/src/include/daemon.h

@@ -1,9 +1,12 @@
 #ifndef DAEMON_H
 #define DAEMON_H
+
 #ifdef __cplusplus
 extern "C" {
 #endif /* __cplusplus */
 
+#include <stdbool.h>
+
 #include <unistd.h>
 
 #ifdef __LP64__
@@ -51,9 +54,11 @@ enum mount_namespace_state {
   Module
 };
 
-void rezygiskd_init(const char *path);
+#define TMP_PATH "/data/adb/rezygisk"
 
-void rezygiskd_get_path(char *buf, size_t buf_size);
+static inline const char *rezygiskd_get_path() {
+  return TMP_PATH;
+}
 
 int rezygiskd_connect(uint8_t retry);
 

loader/src/include/native_bridge_callbacks.h

@@ -10,9 +10,9 @@ size_t block_size = 0;
 extern "C" [[gnu::visibility("default")]]
 void entry(void* addr, size_t size, const char* path) {
     LOGD("Zygisk library injected, version %s", ZKSU_VERSION);
+
     start_addr = addr;
     block_size = size;
-    rezygiskd_init(path);
 
     if (!rezygiskd_ping()) {
         LOGE("Zygisk daemon is not running");

loader/src/injector/entry.cpp

@@ -181,8 +181,6 @@ DCL_HOOK_FUNC(int, unshare, int flags) {
             update_mnt_ns(Rooted, false);
         } else if (!(g_ctx->flags[DO_REVERT_UNMOUNT])) {
             update_mnt_ns(Module, false);
-        } else {
-            LOGI("Process [%s] is on denylist, skipping unmount", g_ctx->process);
         }
 
         old_unshare(CLONE_NEWNS);
@@ -636,6 +634,7 @@ void ZygiskContext::run_modules_pre() {
 
   for (auto &m : modules) {
     m.onLoad(env);
+
     if (flags[APP_SPECIALIZE]) m.preAppSpecialize(args.app);
     else if (flags[SERVER_FORK_AND_SPECIALIZE]) m.preServerSpecialize(args.server);
   }
@@ -674,6 +673,12 @@ void ZygiskContext::app_specialize_pre() {
     if ((info_flags & (PROCESS_IS_MANAGER | PROCESS_ROOT_IS_MAGISK)) == (PROCESS_IS_MANAGER | PROCESS_ROOT_IS_MAGISK)) {
         LOGD("Manager process detected. Notifying that Zygisk has been enabled.");
 
+        /* INFO: This environment variable is related to Magisk Zygisk/Manager. It
+                   it used by Magisk's Zygisk to communicate to Magisk Manager whether
+                   Zygisk is working or not.
+
+                 To allow Zygisk modules to both work properly and for the manager to
+                   identify Zygisk, being it not built-in, as working, we also set it. */
         setenv("ZYGISK_ENABLED", "1", 1);
     } else {
         run_modules_pre();
@@ -818,7 +823,7 @@ void clean_trace(const char* path, size_t load, size_t unload, bool spoof_maps)
 
     if (load > 0 || unload > 0) solist_reset_counters(load, unload);
 
-    LOGI("Dropping solist record for %s", path);
+    LOGD("Dropping solist record for %s", path);
 
     bool path_found = solist_drop_so_path(path);
     if (!path_found || !spoof_maps) return;

loader/src/injector/hook.cpp

@@ -1,5 +1,3 @@
-/* INFO: This file is written in C99 */
-
 #include <stdio.h>
 #include <stdbool.h>
 #include <string.h>