Remove fd_dup and change fd_replace to fd_renumber.

This avoids committing core WASI to the "file descriptor" vs "file
description" distinction. And `dup` is mainly useful for (a) things that
really ought to be done in other ways, and (b) manipulating file
descriptors in the proximity of a fork, and wasi doesn't have fork.

This also removes the emulated mmap's support for PROT_WRITE, since it
depened on dup, however this wasn't very useful.

Author: sunfishcode

expected/wasm32-wasi/defined-symbols.txt

@@ -243,6 +243,7 @@ __uflow
 __unlist_locked_file
 __uselocale
 __utc
+__wasilibc_fd_renumber
 __wasilibc_register_preopened_fd
 __wcscoll_l
 __wcsftime_l
@@ -410,8 +411,6 @@ dprintf
 drand48
 drem
 dremf
-dup
-dup2
 duplocale
 eaccess
 ecvt

expected/wasm32-wasi/predefined-macros.txt

@@ -1455,7 +1455,6 @@
 #define MON_9 0x20022
 #define MORECTL 1
 #define MOREDATA 2
-#define MQ_PRIO_MAX 32768
 #define MSG_ANY 0x02
 #define MSG_BAND 0x04
 #define MSG_CTRUNC __WASI_SOCK_RECV_FDS_TRUNCATED
@@ -2711,19 +2710,11 @@
 #define _POSIX_FSYNC _POSIX_VERSION
 #define _POSIX_HOST_NAME_MAX 255
 #define _POSIX_IPV6 _POSIX_VERSION
-#define _POSIX_JOB_CONTROL 1
 #define _POSIX_LINK_MAX 8
 #define _POSIX_LOGIN_NAME_MAX 9
-#define _POSIX_MAPPED_FILES _POSIX_VERSION
 #define _POSIX_MAX_CANON 255
 #define _POSIX_MAX_INPUT 255
-#define _POSIX_MEMLOCK _POSIX_VERSION
-#define _POSIX_MEMLOCK_RANGE _POSIX_VERSION
-#define _POSIX_MEMORY_PROTECTION _POSIX_VERSION
-#define _POSIX_MESSAGE_PASSING _POSIX_VERSION
 #define _POSIX_MONOTONIC_CLOCK _POSIX_VERSION
-#define _POSIX_MQ_OPEN_MAX 8
-#define _POSIX_MQ_PRIO_MAX 32
 #define _POSIX_NAME_MAX 14
 #define _POSIX_NGROUPS_MAX 8
 #define _POSIX_NO_TRUNC 1
@@ -2736,14 +2727,11 @@
 #define _POSIX_REGEXP 1
 #define _POSIX_RE_DUP_MAX 255
 #define _POSIX_RTSIG_MAX 8
-#define _POSIX_SAVED_IDS 1
 #define _POSIX_SEMAPHORES _POSIX_VERSION
 #define _POSIX_SEM_NSEMS_MAX 256
 #define _POSIX_SEM_VALUE_MAX 32767
 #define _POSIX_SHARED_MEMORY_OBJECTS _POSIX_VERSION
-#define _POSIX_SHELL 1
 #define _POSIX_SIGQUEUE_MAX 32
-#define _POSIX_SPAWN _POSIX_VERSION
 #define _POSIX_SPIN_LOCKS _POSIX_VERSION
 #define _POSIX_SSIZE_MAX 32767
 #define _POSIX_SS_REPL_MAX 4

expected/wasm32-wasi/undefined-symbols.txt

@@ -27,11 +27,10 @@ __wasi_clock_res_get
 __wasi_clock_time_get
 __wasi_fd_close
 __wasi_fd_datasync
-__wasi_fd_dup
 __wasi_fd_pread
 __wasi_fd_pwrite
 __wasi_fd_read
-__wasi_fd_replace
+__wasi_fd_renumber
 __wasi_fd_seek
 __wasi_fd_stat_get
 __wasi_fd_stat_put

libc-bottom-half/cloudlibc/src/libc/unistd/dup.c

@@ -1 +1,2 @@
-int __wasilibc_register_preopened_fd(int, const char *);
+int __wasilibc_register_preopened_fd(int fd, const char *path);
+int __wasilibc_fd_renumber(int fd, int newfd);

libc-bottom-half/cloudlibc/src/libc/unistd/dup2.c

@@ -564,11 +564,6 @@ __wasi_errno_t __wasi_fd_datasync(
     __wasi_fd_t fd
 ) __WASI_SYSCALL_NAME(fd_datasync) __attribute__((__warn_unused_result__));
 
-__wasi_errno_t __wasi_fd_dup(
-    __wasi_fd_t from,
-    __wasi_fd_t *fd
-) __WASI_SYSCALL_NAME(fd_dup) __attribute__((__warn_unused_result__));
-
 __wasi_errno_t __wasi_fd_pread(
     __wasi_fd_t fd,
     const __wasi_iovec_t *iovs,
@@ -592,10 +587,10 @@ __wasi_errno_t __wasi_fd_read(
     size_t *nread
 ) __WASI_SYSCALL_NAME(fd_read) __attribute__((__warn_unused_result__));
 
-__wasi_errno_t __wasi_fd_replace(
+__wasi_errno_t __wasi_fd_renumber(
     __wasi_fd_t from,
     __wasi_fd_t to
-) __WASI_SYSCALL_NAME(fd_replace) __attribute__((__warn_unused_result__));
+) __WASI_SYSCALL_NAME(fd_renumber) __attribute__((__warn_unused_result__));
 
 __wasi_errno_t __wasi_fd_seek(
     __wasi_fd_t fd,

libc-bottom-half/headers/private/wasi-libc.h

@@ -15,7 +15,6 @@
 #include <sys/types.h>
 
 struct map {
-    int dup_fd;
     int prot;
     int flags;
     off_t offset;
@@ -50,7 +49,10 @@ void *mmap(void *addr, size_t length, int prot, int flags,
 
     // Check for unsupported protection requests.
     if (prot == PROT_NONE ||
-        (prot & PROT_EXEC) != 0)
+#ifdef PROT_EXEC
+        (prot & PROT_EXEC) != 0 ||
+#endif
+        0)
     {
         errno = EINVAL;
         return MAP_FAILED;
@@ -63,12 +65,7 @@ void *mmap(void *addr, size_t length, int prot, int flags,
         return MAP_FAILED;
     }
 
-    int dup_fd = dup(fd);
-    if (dup_fd < 0)
-        return MAP_FAILED;
-
     // Initialize the header.
-    map->dup_fd = dup_fd;
     map->prot = prot;
     map->flags = flags;
     map->offset = offset;
@@ -79,7 +76,7 @@ void *mmap(void *addr, size_t length, int prot, int flags,
     if ((flags & MAP_ANON) == 0) {
         char *body = map->body;
         while (length > 0) {
-            ssize_t nread = pread(dup_fd, body, length, offset);
+            ssize_t nread = pread(fd, body, length, offset);
             if (nread < 0) {
                 if (errno == EINTR)
                     continue;
@@ -100,7 +97,6 @@ void *mmap(void *addr, size_t length, int prot, int flags,
 
 int munmap(void *addr, size_t length) {
     struct map *map = (struct map *)addr - 1;
-    int dup_fd = map->dup_fd;
     off_t offset = map->offset;
     int flags = map->flags;
     int prot = map->prot;
@@ -111,30 +107,6 @@ int munmap(void *addr, size_t length) {
         return -1;
     }
 
-    // If needed, sync the contents of memory back to the file.
-    if ((flags & MAP_ANON) == 0 &&
-        (flags & MAP_SHARED) != 0 &&
-        (prot & PROT_WRITE) != 0)
-    {
-        char *body = map->body;
-        while (length > 0) {
-            ssize_t nwritten = pwrite(dup_fd, body, length, offset);
-            if (nwritten < 0) {
-                if (errno == EINTR)
-                    continue;
-                return -1;
-            }
-            length -= (size_t)nwritten;
-            offset += (size_t)nwritten;
-            body += (size_t)nwritten;
-        }
-    }
-
-    // Close the dup'd file descriptor.
-    if (close(dup_fd) != 0) {
-        return -1;
-    }
-
     // Release the memory.
     free(map);
 

libc-bottom-half/headers/public/wasi.h

@@ -0,0 +1,12 @@
+#include <wasi.h>
+#include <errno.h>
+#include <unistd.h>
+
+int __wasilibc_fd_renumber(int fd, int newfd) {
+    __wasi_errno_t error = __wasi_fd_renumber(fd, newfd);
+    if (error != 0) {
+        errno = error;
+        return -1;
+    }
+    return 0;
+}

libc-bottom-half/mman/mman.c

@@ -1,7 +1,13 @@
-#include <unistd.h>
+#include <stddef.h>
+#include <errno.h>
 #include <wasi.h>
 
 int pause(void) {
     size_t n;
-    (void)__wasi_poll_oneoff(0, 0, 0, &n);
+    __wasi_errno_t error = __wasi_poll_oneoff(0, 0, 0, &n);
+    if (error != 0) {
+        errno = error;
+        return -1;
+    }
+    __builtin_trap();
 }