Implement __zipos_dup (#972)

* Implement __zipos_dup

Makes ZiposHandle reference-counted by an `rc` field in a union with its
freelist `next` pointer. The functions `__zipos_free` and `__zipos_keep`
function as incref/decref for it. Adds `__zipos_postdup` to fix metadata
on file descriptors after dup-like operations, and adds zipos support to
`sys_dup_nt` + `sys_close_nt`.

* Remove noop __zipos_postdup

rc is never a zipos file because it is always a previously unused file
descriptor. fd is never a zipos file because that case has been handled
above by __zipos_fcntl.

Author: mrdomino

libc/calls/close-nt.c

@@ -24,6 +24,7 @@
 #include "libc/nt/enum/filetype.h"
 #include "libc/nt/files.h"
 #include "libc/nt/runtime.h"
+#include "libc/runtime/zipos.internal.h"
 #include "libc/sock/syscall_fd.internal.h"
 #include "libc/sysv/consts/o.h"
 #include "libc/sysv/errfuns.h"
@@ -32,6 +33,8 @@ textwindows int sys_close_nt(int fd, int fildes) {
   if (fd + 0u >= g_fds.n) return ebadf();
   struct Fd *f = g_fds.p + fd;
   switch (f->kind) {
+    case kFdZip:
+      return _weaken(__zipos_close)(fd);
     case kFdEmpty:
       return ebadf();
     case kFdFile:

libc/calls/dup-nt.c

@@ -59,30 +59,34 @@ static textwindows int sys_dup_nt_impl(int oldfd, int newfd, int flags,
       return -1;
     }
     if (g_fds.p[newfd].kind) {
-      if (g_fds.p[newfd].kind == kFdZip) {
-        _weaken(__zipos_close)(newfd);
-      } else {
-        sys_close_nt(newfd, newfd);
-      }
+      sys_close_nt(newfd, newfd);
     }
   }
 
-  if (DuplicateHandle(GetCurrentProcess(), g_fds.p[oldfd].handle,
-                      GetCurrentProcess(), &handle, 0, true,
-                      kNtDuplicateSameAccess)) {
-    g_fds.p[newfd] = g_fds.p[oldfd];
-    g_fds.p[newfd].handle = handle;
-    if (flags & _O_CLOEXEC) {
-      g_fds.p[newfd].flags |= _O_CLOEXEC;
-    } else {
-      g_fds.p[newfd].flags &= ~_O_CLOEXEC;
-    }
+  if (__isfdkind(oldfd, kFdZip)) {
+    handle = (intptr_t)_weaken(__zipos_keep)(
+        (struct ZiposHandle *)(intptr_t)g_fds.p[oldfd].handle);
     rc = newfd;
   } else {
-    __releasefd(newfd);
-    rc = __winerr();
+    if (DuplicateHandle(GetCurrentProcess(), g_fds.p[oldfd].handle,
+                        GetCurrentProcess(), &handle, 0, true,
+                        kNtDuplicateSameAccess)) {
+      rc = newfd;
+    } else {
+      rc = __winerr();
+      __releasefd(newfd);
+      __fds_unlock();
+      return rc;
+    }
   }
 
+  g_fds.p[newfd] = g_fds.p[oldfd];
+  g_fds.p[newfd].handle = handle;
+  if (flags & _O_CLOEXEC) {
+    g_fds.p[newfd].flags |= _O_CLOEXEC;
+  } else {
+    g_fds.p[newfd].flags &= ~_O_CLOEXEC;
+  }
   __fds_unlock();
   return rc;
 }

libc/calls/dup.c

@@ -22,7 +22,9 @@
 #include "libc/calls/syscall-sysv.internal.h"
 #include "libc/dce.h"
 #include "libc/intrin/strace.internal.h"
+#include "libc/intrin/weaken.h"
 #include "libc/sysv/errfuns.h"
+#include "libc/runtime/zipos.internal.h"
 
 /**
  * Duplicates file descriptor.
@@ -51,10 +53,11 @@
  */
 int dup(int fd) {
   int rc;
-  if (__isfdkind(fd, kFdZip)) {
-    rc = enotsup();
-  } else if (!IsWindows()) {
+  if (!IsWindows()) {
     rc = sys_dup(fd);
+    if (rc != -1 && __isfdkind(fd, kFdZip)) {
+      _weaken(__zipos_postdup)(fd, rc);
+    }
   } else {
     rc = sys_dup_nt(fd, -1, 0, -1);
   }

libc/calls/dup2.c

@@ -67,20 +67,24 @@ int dup2(int oldfd, int newfd) {
   int rc;
   // helps guarantee stderr log gets duplicated before user closes
   if (_weaken(kloghandle)) _weaken(kloghandle)();
-  if (__isfdkind(oldfd, kFdZip)) {
-    rc = enotsup();
 #ifdef __aarch64__
-  } else if (oldfd == newfd) {
+  if (oldfd == newfd) {
     // linux aarch64 defines dup3() but not dup2(), which wasn't such a
     // great decision, since the two syscalls don't behave the same way
     if (!(rc = read(oldfd, 0, 0))) rc = oldfd;
+  } else
 #endif
-  } else if (!IsWindows()) {
-    rc = sys_dup2(oldfd, newfd, 0);
-    if (rc != -1 && oldfd != newfd && __isfdkind(newfd, kFdZip) && !__vforked) {
-      _weaken(__zipos_free)(
-          (struct ZiposHandle *)(intptr_t)g_fds.p[newfd].handle);
-      bzero(g_fds.p + newfd, sizeof(*g_fds.p));
+  if (!IsWindows()) {
+    if (__isfdkind(oldfd, kFdZip) || __isfdkind(newfd, kFdZip)) {
+      if (__vforked) {
+        return enotsup();
+      }
+      rc = sys_dup2(oldfd, newfd, 0);
+      if (rc != -1) {
+        _weaken(__zipos_postdup)(oldfd, newfd);
+      }
+    } else {
+      rc = sys_dup2(oldfd, newfd, 0);
     }
   } else if (newfd < 0) {
     rc = ebadf();

libc/calls/dup3.c

@@ -70,14 +70,17 @@ int dup3(int oldfd, int newfd, int flags) {
     rc = einval();  // NetBSD doesn't do this
   } else if (oldfd < 0 || newfd < 0) {
     rc = ebadf();
-  } else if (__isfdkind(oldfd, kFdZip)) {
-    rc = enotsup();
   } else if (!IsWindows()) {
-    rc = sys_dup3(oldfd, newfd, flags);
-    if (rc != -1 && __isfdkind(newfd, kFdZip) && !__vforked) {
-      _weaken(__zipos_free)(
-          (struct ZiposHandle *)(intptr_t)g_fds.p[newfd].handle);
-      bzero(g_fds.p + newfd, sizeof(*g_fds.p));
+    if (__isfdkind(oldfd, kFdZip) || __isfdkind(newfd, kFdZip)) {
+      if (__vforked) {
+        return enotsup();
+      }
+      rc = sys_dup3(oldfd, newfd, flags);
+      if (rc != -1) {
+        _weaken(__zipos_postdup)(oldfd, newfd);
+      }
+    } else {
+      rc = sys_dup3(oldfd, newfd, flags);
     }
   } else {
     rc = sys_dup_nt(oldfd, newfd, flags, -1);

libc/runtime/zipos-fcntl.c

@@ -16,13 +16,30 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/createfileflags.internal.h"
 #include "libc/calls/internal.h"
+#include "libc/calls/syscall-nt.internal.h"
+#include "libc/calls/syscall-sysv.internal.h"
 #include "libc/runtime/zipos.internal.h"
 #include "libc/sysv/consts/f.h"
 #include "libc/sysv/consts/fd.h"
 #include "libc/sysv/consts/o.h"
 #include "libc/sysv/errfuns.h"
 
+static int __zipos_dupfd(int fd, int cmd, int start) {
+  int rc;
+  if (start < 0) return einval();
+  if (IsWindows()) {
+    return sys_dup_nt(fd, -1, (cmd == F_DUPFD_CLOEXEC ? _O_CLOEXEC : 0),
+                      start);
+  }
+  rc = sys_fcntl(fd, cmd, start, __sys_fcntl);
+  if (rc != -1) {
+    __zipos_postdup(fd, rc);
+  }
+  return rc;
+}
+
 int __zipos_fcntl(int fd, int cmd, uintptr_t arg) {
   if (cmd == F_GETFD) {
     if (g_fds.p[fd].flags & O_CLOEXEC) {
@@ -38,6 +55,8 @@ int __zipos_fcntl(int fd, int cmd, uintptr_t arg) {
       g_fds.p[fd].flags &= ~O_CLOEXEC;
       return 0;
     }
+  } else if (cmd == F_DUPFD || cmd == F_DUPFD_CLOEXEC) {
+    return __zipos_dupfd(fd, cmd, arg);
   } else {
     return einval();
   }

libc/runtime/zipos-open.c

@@ -78,7 +78,20 @@ static void *__zipos_mmap_space(size_t mapsize) {
   return start + offset;
 }
 
+struct ZiposHandle *__zipos_keep(struct ZiposHandle *h) {
+  atomic_fetch_add_explicit(&h->refs, 1, memory_order_relaxed);
+  return h;
+}
+
+static bool __zipos_drop(struct ZiposHandle *h) {
+  int refs = atomic_load_explicit(&h->refs, memory_order_acquire);
+  return -1 == refs || -1 == atomic_fetch_sub(&h->refs, 1);
+}
+
 void __zipos_free(struct ZiposHandle *h) {
+  if (!__zipos_drop(h)) {
+    return;
+  }
   if (IsAsan()) {
     __asan_poison((char *)h + sizeof(struct ZiposHandle),
                   h->mapsize - sizeof(struct ZiposHandle), kAsanHeapFree);
@@ -100,7 +113,7 @@ static struct ZiposHandle *__zipos_alloc(struct Zipos *zipos, size_t size) {
   while ((h = *ph)) {
     if (h->mapsize >= mapsize) {
       if (!_cmpxchg(ph, h, h->next)) goto StartOver;
-      h->next = 0;
+      atomic_init(&h->refs, 0);
       break;
     }
     ph = &h->next;
@@ -209,6 +222,27 @@ static int __zipos_load(struct Zipos *zipos, size_t cf, int flags,
   return -1;
 }
 
+void __zipos_postdup(int oldfd, int newfd) {
+  if (oldfd == newfd) {
+    return;
+  }
+  if (__isfdkind(newfd, kFdZip)) {
+    __zipos_free((struct ZiposHandle *)(intptr_t)g_fds.p[newfd].handle);
+    if (!__isfdkind(oldfd, kFdZip)) {
+      __fds_lock();
+      bzero(g_fds.p + newfd, sizeof(*g_fds.p));
+      __fds_unlock();
+    }
+  }
+  if (__isfdkind(oldfd, kFdZip)) {
+    __zipos_keep((struct ZiposHandle *)(intptr_t)g_fds.p[oldfd].handle);
+    __fds_lock();
+    __ensurefds_unlocked(newfd);
+    g_fds.p[newfd] = g_fds.p[oldfd];
+    __fds_unlock();
+  }
+}
+
 /**
  * Loads compressed file from αcτµαlly pδrταblε εxεcµταblε object store.
  *

libc/runtime/zipos.S

@@ -33,6 +33,9 @@
 	.yoink	__zipos_stat
 	.yoink	__zipos_notat
 	.yoink	__zipos_mmap
+	.yoink  __zipos_postdup
+	.yoink  __zipos_keep
+	.yoink  __zipos_free
 
 //	TODO(jart): why does corruption happen when zip has no assets?
 	.yoink	.cosmo

libc/runtime/zipos.internal.h

@@ -20,8 +20,9 @@ struct ZiposHandle {
   struct Zipos *zipos;
   size_t size;
   size_t mapsize;
-  size_t pos;
   size_t cfile;
+  _Atomic(int) refs;
+  size_t pos;         // TODO atomic
   uint8_t *mem;
   uint8_t data[];
 };
@@ -38,13 +39,15 @@ struct Zipos {
 
 int __zipos_close(int);
 void __zipos_free(struct ZiposHandle *);
+struct ZiposHandle *__zipos_keep(struct ZiposHandle *);
 struct Zipos *__zipos_get(void) pureconst;
 size_t __zipos_normpath(char *, const char *, size_t);
 ssize_t __zipos_find(struct Zipos *, struct ZiposUri *);
 ssize_t __zipos_scan(struct Zipos *, struct ZiposUri *);
 ssize_t __zipos_parseuri(const char *, struct ZiposUri *);
 uint64_t __zipos_inode(struct Zipos *, int64_t, const void *, size_t);
 int __zipos_open(struct ZiposUri *, int);
+void __zipos_postdup(int, int);
 int __zipos_access(struct ZiposUri *, int);
 int __zipos_stat(struct ZiposUri *, struct stat *);
 int __zipos_fstat(struct ZiposHandle *, struct stat *);

test/libc/calls/dup_test.c

@@ -75,7 +75,7 @@ TEST(dup, bigNumber) {
   ASSERT_SYS(0, 0, close(100));
 }
 
-TEST(dup2, zipos) {
+TEST(dup2, ziposdest) {
   ASSERT_SYS(0, 3, creat("real", 0644));
   ASSERT_SYS(0, 4, open("/zip/libc/testlib/hyperion.txt", O_RDONLY));
   ASSERT_SYS(0, 2, write(3, "hi", 2));
@@ -86,6 +86,15 @@ TEST(dup2, zipos) {
   ASSERT_SYS(0, 0, close(3));
 }
 
+TEST(dup2, zipossrc) {
+  char b[8];
+  ASSERT_SYS(0, 3, open("/zip/libc/testlib/hyperion.txt", O_RDONLY));
+  ASSERT_SYS(0, 4, dup2(3, 4));
+  ASSERT_SYS(0, 8, read(4, b, 8));
+  ASSERT_SYS(0, 0, close(4));
+  ASSERT_SYS(0, 0, close(3));
+}
+
 #ifdef __x86_64__
 TEST(dup, clearsCloexecFlag) {
   static bool once;