Fix metal bugs so deathstar.com runs in qemu (#20)

- Remove XD bit in page tables
- Fix cylinder+head+sector arithmetic
- Implement fstat() for serial file descriptors on metal

Here's how to boot an Actually Portable Executable in QEMU:

    make -j12 o//tool/viz/deathstar.com
    qemu-system-x86_64 -serial stdio -fda o//tool/viz/deathstar.com

Here's a screenshot of DEATHSTAR.COM booted in QEMU:
https://justine.lol/cosmopolitan/cosmo-metal-qemu.png

Thus metal support is in much better shape now, but still incomplete.
Only a few system calls have been polyfilled. To figure out which ones
your program needs, simply boot it in the blinkenlights emulator with a
breakpoint, and press CTRL-C to continue to the system call breakpoint.
If it doesn't break then you should be good. (Note: to emulate normally
you can press 'c' and use CTRL-T and ALT-T to tune the speed.)

    m=tiny
    make -j12 SILENT=0 MODE=$m          \
      o/$m/tool/build/blinkenlights.com \
      o/$m/tool/viz/deathstar.com
    o/$m/tool/build/blinkenlights.com   \
      -r -t -b systemfive.linux         \
      o/$m/tool/viz/deathstar.com

Thank @Theldus for the bug report that made this change possible.
Fixes #20 which explains this change further.

ape/ape.S

@@ -239,18 +239,17 @@ pc:	cld
 /	can have an understanding of physical locality, which deeply
 /	impacts the latency of operations.
 /
-/	 - 160KB:  1 head  × 40 cylinders ×  8 sectors × 512 =   163,840
-/	 - 180KB:  1 head  × 40 cylinders ×  9 sectors × 512 =   184,320
-/	 - 320KB:  2 heads × 40 cylinders ×  8 sectors × 512 =   327,680
-/	 - 360KB:  2 heads × 40 cylinders ×  9 sectors × 512 =   368,640
-/	 - 720KB:  2 heads × 80 cylinders ×  9 sectors × 512 =   737,280
-/	 - 1.2MB:  2 heads × 80 cylinders × 15 sectors × 512 = 1,228,800
-/	 - 1.44MB: 2 heads × 80 cylinders × 18 sectors × 512 = 1,474,560
+/	 - 160KB:  40 cylinders × 1 head  ×  8 sectors × 512 =   163,840
+/	 - 180KB:  40 cylinders × 1 head  ×  9 sectors × 512 =   184,320
+/	 - 320KB:  40 cylinders × 2 heads ×  8 sectors × 512 =   327,680
+/	 - 360KB:  40 cylinders × 2 heads ×  9 sectors × 512 =   368,640
+/	 - 720KB:  80 cylinders × 2 heads ×  9 sectors × 512 =   737,280
+/	 - 1.2MB:  80 cylinders × 2 heads × 15 sectors × 512 = 1,228,800
+/	 - 1.44MB: 80 cylinders × 2 heads × 18 sectors × 512 = 1,474,560
 /
 /	Terminology
 /
-/	 - Cylinder / Tracks should mean the same thing
-/	 - Heads / Sides / Spindles should mean the same thing
+/	 - Heads are also known as Tracks
 /
 /	Disk Base Table
 /
@@ -341,18 +340,18 @@ pcread:	push	%ax
 	pop	%cx
 	pop	%ax
 	jc	9f
-	mov	%es,%si
+	mov	%es,%si			# addr += 512
 	add	$512>>4,%si
 	mov	%si,%es
-	inc	%al
+	inc	%al			# ++sector
 	cmp	XLM(DRIVE_LAST_SECTOR),%al
 	jbe	2f
 	mov	$1,%al
-	inc	%cx
-	cmp	XLM(DRIVE_LAST_CYLINDER),%cx
-	jbe	2f
-	xor	%cx,%cx
-	inc	%dh
+	inc	%dh			# ++head
+	cmp	XLM(DRIVE_LAST_HEAD),%cx
+	jb	2f
+	xor	%dh,%dh
+	inc	%cx			# ++cylinder
 2:	ret
 9:	push	%ax
 	xor	%ax,%ax			# try disk reset on error

ape/lib/mapimage.c

@@ -30,7 +30,7 @@ textreal static void __map_segment(uint64_t k, uint64_t a, uint64_t b) {
 
 textreal void __map_image(void) {
   __map_segment(PAGE_V | PAGE_U, 0, (uintptr_t)_etext - IMAGE_BASE_VIRTUAL);
-  __map_segment(PAGE_V | PAGE_U | PAGE_RW | PAGE_XD,
+  __map_segment(PAGE_V | PAGE_U | PAGE_RW,
                 (uintptr_t)_etext - IMAGE_BASE_VIRTUAL,
                 (uintptr_t)_end - IMAGE_BASE_VIRTUAL);
 }

examples/stat.c

@@ -11,6 +11,7 @@
 #include "libc/calls/struct/stat.h"
 #include "libc/errno.h"
 #include "libc/fmt/fmt.h"
+#include "libc/log/check.h"
 #include "libc/runtime/gc.h"
 #include "libc/stdio/stdio.h"
 #include "libc/x/x.h"
@@ -23,32 +24,29 @@
 
 void PrintFileMetadata(const char *pathname, struct stat *st) {
   printf("\n%s:", pathname);
-  if (stat(pathname, st) != -1) {
-    printf(
-        "\n"
-        "%-32s%,ld\n"
-        "%-32s%,ld\n"
-        "%-32s%#lx\n"
-        "%-32s%#lx\n"
-        "%-32s%ld\n"
-        "%-32s%#o\n"
-        "%-32s%d\n"
-        "%-32s%d\n"
-        "%-32s%d\n"
-        "%-32s%ld\n"
-        "%-32s%s\n"
-        "%-32s%s\n"
-        "%-32s%s\n",
-        "bytes in file", st->st_size, "physical bytes", st->st_blocks * 512,
-        "device id w/ file", st->st_dev, "inode", st->st_ino, "hard link count",
-        st->st_nlink, "mode / permissions", st->st_mode, "owner id", st->st_uid,
-        "group id", st->st_gid, "device id (if special)", st->st_rdev,
-        "block size", st->st_blksize, "access time", gc(xiso8601(&st->st_atim)),
-        "modified time", gc(xiso8601(&st->st_mtim)), "c[omplicated]time",
-        gc(xiso8601(&st->st_ctim)));
-  } else {
-    printf(" %s\n", strerror(errno));
-  }
+  CHECK_NE(-1, stat(pathname, st));
+  printf("\n"
+         "%-32s%,ld\n"
+         "%-32s%,ld\n"
+         "%-32s%#lx\n"
+         "%-32s%#lx\n"
+         "%-32s%ld\n"
+         "%-32s%#o\n"
+         "%-32s%d\n"
+         "%-32s%d\n"
+         "%-32s%d\n"
+         "%-32s%ld\n"
+         "%-32s%s\n"
+         "%-32s%s\n"
+         "%-32s%s\n",
+         "bytes in file", st->st_size, "physical bytes", st->st_blocks * 512,
+         "device id w/ file", st->st_dev, "inode", st->st_ino,
+         "hard link count", st->st_nlink, "mode / permissions", st->st_mode,
+         "owner id", st->st_uid, "group id", st->st_gid,
+         "device id (if special)", st->st_rdev, "block size", st->st_blksize,
+         "access time", gc(xiso8601(&st->st_atim)), "modified time",
+         gc(xiso8601(&st->st_mtim)), "c[omplicated]time",
+         gc(xiso8601(&st->st_ctim)));
 }
 
 int main(int argc, char *argv[]) {

libc/calls/fstat-metal.c

@@ -0,0 +1,38 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2021 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/internal.h"
+#include "libc/calls/struct/stat.h"
+#include "libc/str/str.h"
+#include "libc/sysv/consts/s.h"
+#include "libc/sysv/errfuns.h"
+
+int fstat$metal(int fd, struct stat *st) {
+  if (fd < 0) return einval();
+  if (fd < g_fds.n && g_fds.p[fd].kind == kFdSerial) {
+    memset(st, 0, sizeof(*st));
+    st->st_dev = g_fds.p[fd].handle;
+    st->st_rdev = g_fds.p[fd].handle;
+    st->st_nlink = 1;
+    st->st_mode = S_IFCHR | 0600;
+    st->st_blksize = 1;
+    return 0;
+  } else {
+    return ebadf();
+  }
+}

libc/calls/fstat-nt.c

@@ -35,34 +35,47 @@ textwindows int fstat$nt(int64_t handle, struct stat *st) {
   uint64_t actualsize;
   struct NtFileCompressionInfo fci;
   struct NtByHandleFileInformation wst;
-  if (GetFileInformationByHandle(handle, &wst)) {
+  if ((filetype = GetFileType(handle))) {
     memset(st, 0, sizeof(*st));
-    filetype = GetFileType(handle);
-    st->st_mode =
-        (S_IRUSR | S_IXUSR |
-         (!(wst.dwFileAttributes & kNtFileAttributeReadonly) ? S_IWUSR : 0) |
-         ((wst.dwFileAttributes & kNtFileAttributeNormal) ? S_IFREG : 0) |
-         ((wst.dwFileAttributes & kNtFileFlagOpenReparsePoint) ? S_IFLNK : 0) |
-         ((wst.dwFileAttributes & kNtFileAttributeDirectory)
-              ? S_IFDIR
-              : (((filetype == kNtFileTypeDisk) ? S_IFBLK : 0) |
-                 ((filetype == kNtFileTypeChar) ? S_IFCHR : 0) |
-                 ((filetype == kNtFileTypePipe) ? S_IFIFO : 0))));
-    st->st_atim = FileTimeToTimeSpec(wst.ftLastAccessFileTime);
-    st->st_mtim = FileTimeToTimeSpec(wst.ftLastWriteFileTime);
-    st->st_ctim = FileTimeToTimeSpec(wst.ftCreationFileTime);
-    st->st_size = (uint64_t)wst.nFileSizeHigh << 32 | wst.nFileSizeLow;
-    st->st_blksize = PAGESIZE;
-    st->st_dev = wst.dwVolumeSerialNumber;
-    st->st_ino = (uint64_t)wst.nFileIndexHigh << 32 | wst.nFileIndexLow;
-    st->st_nlink = wst.nNumberOfLinks;
-    if (GetFileInformationByHandleEx(handle, kNtFileCompressionInfo, &fci,
-                                     sizeof(fci))) {
-      actualsize = fci.CompressedFileSize;
-    } else {
-      actualsize = st->st_size;
+    switch (filetype) {
+      case kNtFileTypeChar:
+        st->st_mode = S_IFCHR | 0600;
+        break;
+      case kNtFileTypePipe:
+        st->st_mode = S_IFIFO | 0600;
+        break;
+      case kNtFileTypeDisk:
+        if (GetFileInformationByHandle(handle, &wst)) {
+          dprintf(1, "handle = %ld\n", handle);
+          st->st_mode =
+              (S_IRUSR | S_IXUSR |
+               (!(wst.dwFileAttributes & kNtFileAttributeReadonly) ? S_IWUSR
+                                                                   : 0) |
+               ((wst.dwFileAttributes & kNtFileAttributeNormal) ? S_IFREG : 0) |
+               ((wst.dwFileAttributes & kNtFileFlagOpenReparsePoint) ? S_IFLNK
+                                                                     : 0) |
+               ((wst.dwFileAttributes & kNtFileAttributeDirectory) ? S_IFDIR
+                                                                   : 0));
+          st->st_atim = FileTimeToTimeSpec(wst.ftLastAccessFileTime);
+          st->st_mtim = FileTimeToTimeSpec(wst.ftLastWriteFileTime);
+          st->st_ctim = FileTimeToTimeSpec(wst.ftCreationFileTime);
+          st->st_size = (uint64_t)wst.nFileSizeHigh << 32 | wst.nFileSizeLow;
+          st->st_blksize = PAGESIZE;
+          st->st_dev = wst.dwVolumeSerialNumber;
+          st->st_ino = (uint64_t)wst.nFileIndexHigh << 32 | wst.nFileIndexLow;
+          st->st_nlink = wst.nNumberOfLinks;
+          if (GetFileInformationByHandleEx(handle, kNtFileCompressionInfo, &fci,
+                                           sizeof(fci))) {
+            actualsize = fci.CompressedFileSize;
+          } else {
+            actualsize = st->st_size;
+          }
+          st->st_blocks = roundup(actualsize, PAGESIZE) / 512;
+        }
+        break;
+      default:
+        break;
     }
-    st->st_blocks = roundup(actualsize, PAGESIZE) / 512;
     return 0;
   } else {
     return __winerr();

libc/calls/fstat.c

@@ -32,7 +32,11 @@ int fstat(int fd, struct stat *st) {
     return weaken(__zipos_fstat)(
         (struct ZiposHandle *)(intptr_t)g_fds.p[fd].handle, st);
   } else if (!IsWindows()) {
-    return fstat$sysv(fd, st);
+    if (!IsMetal()) {
+      return fstat$sysv(fd, st);
+    } else {
+      return fstat$metal(fd, st);
+    }
   } else {
     if (!__isfdkind(fd, kFdFile)) return ebadf();
     return fstat$nt(g_fds.p[fd].handle, st);

libc/calls/internal.h

@@ -267,6 +267,12 @@ int64_t __winerr(void) nocallback privileged;
 int __mkntpath(const char *, char16_t[hasatleast PATH_MAX - 16]) hidden;
 int __mkntpath2(const char *, char16_t[hasatleast PATH_MAX - 16], int) hidden;
 
+/*───────────────────────────────────────────────────────────────────────────│─╗
+│ cosmopolitan § syscalls » metal                                          ─╬─│┼
+╚────────────────────────────────────────────────────────────────────────────│*/
+
+int fstat$metal(int, struct stat *);
+
 /*───────────────────────────────────────────────────────────────────────────│─╗
 │ cosmopolitan § syscalls » drivers                                        ─╬─│┼
 ╚────────────────────────────────────────────────────────────────────────────│*/

libc/calls/ischardev.c

@@ -30,16 +30,11 @@
 textstartup bool32 ischardev(int fd) {
   int olderr;
   struct stat st;
-  if (!IsWindows()) {
-    olderr = errno;
-    if (fstat$sysv(fd, &st) != -1) {
-      return S_ISCHR(st.st_mode);
-    } else {
-      errno = olderr;
-      return false;
-    }
+  olderr = errno;
+  if (fstat(fd, &st) != -1) {
+    return S_ISCHR(st.st_mode);
   } else {
-    return __isfdkind(fd, kFdFile) &&
-           GetFileType(g_fds.p[fd].handle) == kNtFileTypeChar;
+    errno = olderr;
+    return false;
   }
 }

libc/calls/madvise-nt.c

@@ -31,7 +31,7 @@ forceinline typeof(PrefetchVirtualMemory) *GetPrefetchVirtualMemory(void) {
   if (!once) {
     once = true;
     PrefetchVirtualMemory_ = /* win8.1+ */
-        GetProcAddressModule("KernelBase.dll", "PrefetchVirtualMemory");
+        GetProcAddressModule("Kernel32.dll", "PrefetchVirtualMemory");
   }
   return PrefetchVirtualMemory_;
 }
@@ -42,7 +42,7 @@ forceinline typeof(OfferVirtualMemory) *GetOfferVirtualMemory(void) {
   if (!once) {
     once = true;
     OfferVirtualMemory_ = /* win8.1+ */
-        GetProcAddressModule("KernelBase.dll", "OfferVirtualMemory");
+        GetProcAddressModule("Kernel32.dll", "OfferVirtualMemory");
   }
   return OfferVirtualMemory_;
 }

libc/calls/nanosleep.c

@@ -27,10 +27,14 @@
 int nanosleep(const struct timespec *req, struct timespec *rem) {
   if (!req) return efault();
   if (!IsWindows()) {
-    if (!IsXnu()) {
-      return nanosleep$sysv(req, rem);
+    if (!IsMetal()) {
+      if (!IsXnu()) {
+        return nanosleep$sysv(req, rem);
+      } else {
+        return nanosleep$xnu(req, rem);
+      }
     } else {
-      return nanosleep$xnu(req, rem);
+      return enosys(); /* TODO: Sleep on Metal */
     }
   } else {
     return nanosleep$nt(req, rem);

libc/calls/sigaction.c

@@ -141,32 +141,36 @@ int(sigaction)(int sig, const struct sigaction *act, struct sigaction *oldact) {
     return efault();
   }
   if (!IsWindows()) {
-    if (act) {
-      memcpy(&copy, act, sizeof(copy));
-      ap = ©
-      if (IsXnu()) {
-        ap->sa_restorer = (void *)&xnutrampoline;
-        ap->sa_handler = (void *)&xnutrampoline;
-      } else {
-        if (IsLinux()) {
-          if (!(ap->sa_flags & SA_RESTORER)) {
-            ap->sa_flags |= SA_RESTORER;
-            ap->sa_restorer = &__restore_rt;
+    if (!IsMetal()) {
+      if (act) {
+        memcpy(&copy, act, sizeof(copy));
+        ap = ©
+        if (IsXnu()) {
+          ap->sa_restorer = (void *)&xnutrampoline;
+          ap->sa_handler = (void *)&xnutrampoline;
+        } else {
+          if (IsLinux()) {
+            if (!(ap->sa_flags & SA_RESTORER)) {
+              ap->sa_flags |= SA_RESTORER;
+              ap->sa_restorer = &__restore_rt;
+            }
+          }
+          if (rva >= kSigactionMinRva) {
+            ap->sa_sigaction = (sigaction_f)__sigenter;
           }
         }
-        if (rva >= kSigactionMinRva) {
-          ap->sa_sigaction = (sigaction_f)__sigenter;
-        }
+        sigaction$cosmo2native((union metasigaction *)ap);
+      } else {
+        ap = NULL;
       }
-      sigaction$cosmo2native((union metasigaction *)ap);
+      rc = sigaction$sysv(
+          sig, ap, oldact,
+          (!IsXnu() ? 8 /* or linux whines */
+                    : (int64_t)(intptr_t)oldact /* from go code */));
+      if (rc != -1) sigaction$native2cosmo((union metasigaction *)oldact);
     } else {
-      ap = NULL;
+      return enosys(); /* TODO: Signals on Metal */
     }
-    rc = sigaction$sysv(
-        sig, ap, oldact,
-        (!IsXnu() ? 8 /* or linux whines */
-                  : (int64_t)(intptr_t)oldact /* from go code */));
-    if (rc != -1) sigaction$native2cosmo((union metasigaction *)oldact);
   } else {
     if (oldact) {
       memset(oldact, 0, sizeof(*oldact));

libc/runtime/program_invocation_short_name.S

@@ -28,7 +28,10 @@ program_invocation_short_name:
 
 	.init.start 400,_init_program_invocation_short_name
 	push	%rsi
-	mov	(%r13),%rsi
+	xor	%eax,%eax
+	test	%r12d,%r12d		# argc
+	jz	2f
+	mov	(%r13),%rsi		# argv[0]
 	mov	%rsi,%rcx
 1:	lodsb
 	cmp	$'/,%al
@@ -39,5 +42,5 @@ program_invocation_short_name:
 	jnz	1b
 	xchg	%rcx,%rax
 	pop	%rsi
-	stosq
+2:	stosq
 	.init.end 400,_init_program_invocation_short_name