support kernels with no SYS_open syscall, only SYS_openat

open is handled specially because it is used from so many places, in
so many variants (2 or 3 arguments, setting errno or not, and
cancellable or not). trying to do it as a function would not only
increase bloat, but would also risk subtle breakage.

this is the first step towards supporting "new" archs where linux
lacks "old" syscalls.

src/env/__libc_start_main.c

@@ -50,7 +50,7 @@ void __init_libc(char **envp, char *pn)
 	struct pollfd pfd[3] = { {.fd=0}, {.fd=1}, {.fd=2} };
 	__syscall(SYS_poll, pfd, 3, 0);
 	for (i=0; i<3; i++) if (pfd[i].revents&POLLNVAL)
-		if (__syscall(SYS_open, "/dev/null", O_RDWR|O_LARGEFILE)<0)
+		if (__sys_open("/dev/null", O_RDWR)<0)
 			a_crash();
 	libc.secure = 1;
 }

src/fcntl/open.c

@@ -10,7 +10,7 @@ int open(const char *filename, int flags, ...)
 	va_start(ap, flags);
 	mode = va_arg(ap, mode_t);
 	va_end(ap);
-	return syscall_cp(SYS_open, filename, flags|O_LARGEFILE, mode);
+	return sys_open_cp(filename, flags, mode);
 }
 
 LFS64(open);

src/internal/syscall.h

@@ -187,3 +187,21 @@ long __syscall_ret(unsigned long), __syscall(syscall_arg_t, ...),
 #define __SC_accept4     18
 #define __SC_recvmmsg    19
 #define __SC_sendmmsg    20
+
+#ifdef SYS_open
+#define __sys_open2(x,pn,fl) __syscall2(SYS_open, pn, (fl)|O_LARGEFILE)
+#define __sys_open3(x,pn,fl,mo) __syscall3(SYS_open, pn, (fl)|O_LARGEFILE, mo)
+#define __sys_open_cp2(x,pn,fl) __syscall_cp2(SYS_open, pn, (fl)|O_LARGEFILE)
+#define __sys_open_cp3(x,pn,fl,mo) __syscall_cp3(SYS_open, pn, (fl)|O_LARGEFILE, mo)
+#else
+#define __sys_open2(x,pn,fl) __syscall2(SYS_openat, AT_FDCWD, pn, (fl)|O_LARGEFILE)
+#define __sys_open3(x,pn,fl,mo) __syscall3(SYS_openat, AT_FDCWD, pn, (fl)|O_LARGEFILE, mo)
+#define __sys_open_cp2(x,pn,fl) __syscall_cp2(SYS_openat, AT_FDCWD, pn, (fl)|O_LARGEFILE)
+#define __sys_open_cp3(x,pn,fl,mo) __syscall_cp3(SYS_openat, AT_FDCWD, pn, (fl)|O_LARGEFILE, mo)
+#endif
+
+#define __sys_open(...) __SYSCALL_DISP(__sys_open,,__VA_ARGS__)
+#define sys_open(...) __syscall_ret(__sys_open(__VA_ARGS__))
+
+#define __sys_open_cp(...) __SYSCALL_DISP(__sys_open_cp,,__VA_ARGS__)
+#define sys_open_cp(...) __syscall_ret(__sys_open_cp(__VA_ARGS__))

src/misc/realpath.c

@@ -22,7 +22,7 @@ char *realpath(const char *restrict filename, char *restrict resolved)
 		return 0;
 	}
 
-	fd = syscall(SYS_open, filename, O_PATH|O_NONBLOCK|O_CLOEXEC|O_LARGEFILE);
+	fd = sys_open(filename, O_PATH|O_NONBLOCK|O_CLOEXEC);
 	if (fd < 0) return 0;
 	__procfdname(buf, fd);
 

src/process/posix_spawn.c

@@ -96,8 +96,7 @@ static int child(void *args_vp)
 					goto fail;
 				break;
 			case FDOP_OPEN:
-				fd = __syscall(SYS_open, op->path,
-					op->oflag | O_LARGEFILE, op->mode);
+				fd = __sys_open(op->path, op->oflag, op->mode);
 				if ((ret=fd) < 0) goto fail;
 				if (fd != op->fd) {
 					if ((ret=__syscall(SYS_dup2, fd, op->fd))<0)

src/stdio/__fopen_rb_ca.c

@@ -6,7 +6,7 @@ FILE *__fopen_rb_ca(const char *filename, FILE *f, unsigned char *buf, size_t le
 {
 	memset(f, 0, sizeof *f);
 
-	f->fd = syscall(SYS_open, filename, O_RDONLY|O_LARGEFILE|O_CLOEXEC, 0);
+	f->fd = sys_open(filename, O_RDONLY|O_CLOEXEC);
 	if (f->fd < 0) return 0;
 
 	f->flags = F_NOWR | F_PERM;

src/stdio/fopen.c

@@ -18,7 +18,7 @@ FILE *fopen(const char *restrict filename, const char *restrict mode)
 	/* Compute the flags to pass to open() */
 	flags = __fmodeflags(mode);
 
-	fd = syscall_cp(SYS_open, filename, flags|O_LARGEFILE, 0666);
+	fd = sys_open_cp(filename, flags, 0666);
 	if (fd < 0) return 0;
 
 	f = __fdopen(fd, mode);

src/stdio/tmpfile.c

@@ -14,7 +14,7 @@ FILE *tmpfile(void)
 	for (try=0; try<MAXTRIES; try++) {
 		s = tmpnam(buf);
 		if (!s) return 0;
-		fd = syscall(SYS_open, s, O_RDWR|O_CREAT|O_EXCL|O_LARGEFILE, 0600);
+		fd = sys_open(s, O_RDWR|O_CREAT|O_EXCL, 0600);
 		if (fd >= 0) {
 			f = __fdopen(fd, "w+");
 			__syscall(SYS_unlink, s);

src/time/__map_file.c

@@ -9,8 +9,7 @@ const char unsigned *__map_file(const char *pathname, size_t *size)
 {
 	struct stat st;
 	const unsigned char *map = MAP_FAILED;
-	int flags = O_RDONLY|O_LARGEFILE|O_CLOEXEC|O_NONBLOCK;
-	int fd = __syscall(SYS_open, pathname, flags);
+	int fd = __sys_open(pathname, O_RDONLY|O_CLOEXEC|O_NONBLOCK);
 	if (fd < 0) return 0;
 	if (!__syscall(SYS_fstat, fd, &st))
 		map = __mmap(0, st.st_size, PROT_READ, MAP_SHARED, fd, 0);