Support compiling against lower SDK

Reduce even more size for static binaries

native/jni/Application.mk

@@ -4,7 +4,8 @@ APP_CFLAGS := -std=gnu99 ${MAGISK_DEBUG} \
 APP_CPPFLAGS := -std=c++11
 APP_SHORT_COMMANDS := true
 ifdef OLD_PLAT
-APP_PLATFORM := android-9
+APP_PLATFORM := android-16
+APP_CFLAGS += -Wno-implicit-function-declaration
 else
 APP_PLATFORM := android-21	
 endif

native/jni/core/bootstages.c

@@ -579,7 +579,7 @@ void startup() {
 	while((entry = xreaddir(dir))) {
 		if (strcmp(entry->d_name, ".") == 0 || strcmp(entry->d_name, "..") == 0) continue;
 		snprintf(buf, PATH_MAX, "/root/%s", entry->d_name);
-		symlinkat(buf, sbin, entry->d_name);
+		xsymlinkat(buf, sbin, entry->d_name);
 	}
 
 	close(sbin);

native/jni/core/magiskinit.c

@@ -382,9 +382,9 @@ int main(int argc, char *argv[]) {
 	mknod("/null", S_IFCHR | 0666, makedev(1, 3));
 	int null = open("/null", O_RDWR | O_CLOEXEC);
 	unlink("/null");
-	dup3(null, STDIN_FILENO, O_CLOEXEC);
-	dup3(null, STDOUT_FILENO, O_CLOEXEC);
-	dup3(null, STDERR_FILENO, O_CLOEXEC);
+	xdup3(null, STDIN_FILENO, O_CLOEXEC);
+	xdup3(null, STDOUT_FILENO, O_CLOEXEC);
+	xdup3(null, STDERR_FILENO, O_CLOEXEC);
 	if (null > STDERR_FILENO)
 		close(null);
 

native/jni/include/utils.h

@@ -19,6 +19,13 @@
 
 // xwrap.c
 
+#ifndef SOCK_CLOEXEC
+#define SOCK_CLOEXEC O_CLOEXEC
+#endif
+#ifndef SOCK_NONBLOCK
+#define SOCK_NONBLOCK O_NONBLOCK
+#endif
+
 FILE *xfopen(const char *pathname, const char *mode);
 FILE *xfdopen(int fd, const char *mode);
 #define GET_MACRO(_1, _2, _3, NAME, ...) NAME
@@ -51,9 +58,12 @@ int xsocketpair(int domain, int type, int protocol, int sv[2]);
 int xstat(const char *pathname, struct stat *buf);
 int xlstat(const char *pathname, struct stat *buf);
 int xdup2(int oldfd, int newfd);
+int xdup3(int oldfd, int newfd, int flags);
 ssize_t xreadlink(const char *pathname, char *buf, size_t bufsiz);
 ssize_t xreadlinkat(int dirfd, const char *pathname, char *buf, size_t bufsiz);
 int xsymlink(const char *target, const char *linkpath);
+int xsymlinkat(const char *target, int newdirfd, const char *linkpath);
+int xlinkat(int olddirfd, const char *oldpath, int newdirfd, const char *newpath, int flags);
 int xmount(const char *source, const char *target,
 	const char *filesystemtype, unsigned long mountflags,
 	const void *data);
@@ -105,7 +115,6 @@ struct file_attr {
 	char con[128];
 };
 
-int fd_getpath(int fd, char *path, size_t size);
 int mkdirs(const char *pathname, mode_t mode);
 void in_order_walk(int dirfd, void (*callback)(int, struct dirent*));
 void rm_rf(const char *path);

native/jni/utils/file.c

@@ -28,11 +28,16 @@ static int is_excl(const char *name) {
 	return 0;
 }
 
-int fd_getpath(int fd, char *path, size_t size) {
+static int fd_getpath(int fd, char *path, size_t size) {
 	snprintf(path, size, "/proc/self/fd/%d", fd);
-	if (xreadlink(path, path, size) == -1)
-		return -1;
-	return 0;
+    return xreadlink(path, path, size) == -1;
+}
+
+static int fd_getpathat(int dirfd, const char *name, char *path, size_t size) {
+    if (fd_getpath(dirfd, path, size))
+        return 1;
+    snprintf(path, size, "%s/%s", path, name);
+    return 0;
 }
 
 int mkdirs(const char *pathname, mode_t mode) {
@@ -220,7 +225,7 @@ void clone_dir(int src, int dest) {
 			break;
 		case DT_LNK:
 			xreadlinkat(src, entry->d_name, buf, sizeof(buf));
-			symlinkat(buf, dest, entry->d_name);
+			xsymlinkat(buf, dest, entry->d_name);
 			setattrat(dest, entry->d_name, &a);
 			break;
 		}
@@ -249,7 +254,7 @@ void link_dir(int src, int dest) {
 			close(newsrc);
 			close(newdest);
 		} else {
-			linkat(src, entry->d_name, dest, entry->d_name, 0);
+			xlinkat(src, entry->d_name, dest, entry->d_name, 0);
 		}
 	}
 }
@@ -270,12 +275,9 @@ int getattr(const char *path, struct file_attr *a) {
 }
 
 int getattrat(int dirfd, const char *pathname, struct file_attr *a) {
-	int fd = xopenat(dirfd, pathname, O_PATH | O_NOFOLLOW | O_CLOEXEC);
-	if (fd < 0)
-		return -1;
-	int ret = fgetattr(fd, a);
-	close(fd);
-	return ret;
+	char path[PATH_MAX];
+	fd_getpathat(dirfd, pathname, path, sizeof(path));
+	return getattr(path, a);
 }
 
 int fgetattr(int fd, struct file_attr *a) {
@@ -304,12 +306,9 @@ int setattr(const char *path, struct file_attr *a) {
 }
 
 int setattrat(int dirfd, const char *pathname, struct file_attr *a) {
-	int fd = xopenat(dirfd, pathname, O_PATH | O_NOFOLLOW | O_CLOEXEC);
-	if (fd < 0)
-		return -1;
-	int ret = fsetattr(fd, a);
-	close(fd);
-	return ret;
+	char path[PATH_MAX];
+	fd_getpathat(dirfd, pathname, path, sizeof(path));
+	return setattr(path, a);
 }
 
 int fsetattr(int fd, struct file_attr *a) {

native/jni/utils/img.c

@@ -8,7 +8,7 @@
 #include <sys/wait.h>
 #include <sys/mount.h>
 #include <sys/sendfile.h>
-#include <sys/statvfs.h>
+#include <sys/statfs.h>
 #include <sys/sysmacros.h>
 #include <linux/loop.h>
 
@@ -70,12 +70,12 @@ static char *loopsetup(const char *img) {
 
 static void check_filesystem(struct fs_info *info, const char *img, const char *mount) {
 	struct stat st;
-	struct statvfs vfs;
+	struct statfs fs;
 	stat(img, &st);
-	statvfs(mount, &vfs);
+	statfs(mount, &fs);
 	info->size = st.st_size / 1048576;
-	info->free = vfs.f_bfree * vfs.f_frsize / 1048576;
-	info->used = (vfs.f_blocks - vfs.f_bfree) * vfs.f_frsize / 1048576;
+	info->free = fs.f_bfree * (uint64_t)fs.f_frsize / 1048576;
+	info->used = (fs.f_blocks - fs.f_bfree) * (uint64_t)fs.f_frsize / 1048576;
 }
 
 static void usage() {

native/jni/utils/xwrap.c

@@ -21,6 +21,7 @@
 #include <sys/mount.h>
 #include <sys/mman.h>
 #include <sys/sendfile.h>
+#include <sys/syscall.h>
 
 #include "logging.h"
 #include "utils.h"
@@ -100,7 +101,7 @@ int xpipe2(int pipefd[2], int flags) {
 }
 
 int xsetns(int fd, int nstype) {
-	int ret = setns(fd, nstype);
+	int ret = (int) syscall(__NR_setns, fd, nstype);
 	if (ret == -1) {
 		PLOGE("setns");
 	}
@@ -165,9 +166,14 @@ int xlisten(int sockfd, int backlog) {
 }
 
 int xaccept4(int sockfd, struct sockaddr *addr, socklen_t *addrlen, int flags) {
-	int fd = accept4(sockfd, addr, addrlen, flags);
+#ifndef __NR_accept4
+#ifdef __i386__
+#define __NR_accept4 364
+#endif
+#endif
+	int fd = (int) syscall(__NR_accept4, sockfd, addr, addrlen, flags);
 	if (fd == -1) {
-		PLOGE("accept");
+		PLOGE("accept4");
 	}
 	return fd;
 }
@@ -212,8 +218,8 @@ ssize_t xrecvmsg(int sockfd, struct msghdr *msg, int flags) {
 	return rec;
 }
 
-int xpthread_create(pthread_t *thread, const pthread_attr_t *attr,
-                          void *(*start_routine) (void *), void *arg) {
+int xpthread_create(pthread_t *thread, const pthread_attr_t *attr, 
+					void *(*start_routine) (void *), void *arg) {
 	errno = pthread_create(thread, attr, start_routine, arg);
 	if (errno) {
 		PLOGE("pthread_create");
@@ -245,6 +251,14 @@ int xdup2(int oldfd, int newfd) {
 	return ret;
 }
 
+int xdup3(int oldfd, int newfd, int flags) {
+	int ret = (int) syscall(__NR_dup3, oldfd, newfd, flags);
+	if (ret == -1) {
+		PLOGE("dup3");
+	}
+	return ret;
+}
+
 ssize_t xreadlink(const char *pathname, char *buf, size_t bufsiz) {
 	ssize_t ret = readlink(pathname, buf, bufsiz);
 	if (ret == -1) {
@@ -256,7 +270,7 @@ ssize_t xreadlink(const char *pathname, char *buf, size_t bufsiz) {
 }
 
 ssize_t xreadlinkat(int dirfd, const char *pathname, char *buf, size_t bufsiz) {
-	ssize_t ret = readlinkat(dirfd, pathname, buf, bufsiz);
+	ssize_t ret = syscall(__NR_readlinkat, dirfd, pathname, buf, bufsiz);
 	if (ret == -1) {
 		PLOGE("readlinkat %s", pathname);
 	} else {
@@ -273,10 +287,26 @@ int xsymlink(const char *target, const char *linkpath) {
 	return ret;
 }
 
+int xsymlinkat(const char *target, int newdirfd, const char *linkpath) {
+	int ret = (int) syscall(__NR_symlinkat, target, newdirfd, linkpath);
+	if (ret == -1) {
+		PLOGE("symlinkat %s->%s", target, linkpath);
+	}
+	return ret;
+}
+
+int xlinkat(int olddirfd, const char *oldpath, int newdirfd, const char *newpath, int flags) {
+	int ret = (int) syscall(__NR_linkat, olddirfd, oldpath, newdirfd, newpath, flags);
+	if (ret == -1) {
+		PLOGE("linkat %s->%s", oldpath, newpath);
+	}
+	return ret;
+}
+
 int xmount(const char *source, const char *target,
 	const char *filesystemtype, unsigned long mountflags,
 	const void *data) {
-	int ret = mount(source, target, filesystemtype, MS_SILENT | mountflags, data);
+	int ret = mount(source, target, filesystemtype, mountflags, data);
 	if (ret == -1) {
 		PLOGE("mount %s->%s", source, target);
 	}