[metal] Get zipos working again for legacy BIOS boot

examples/hellolua.c now runs again when booted as a legacy BIOS
disk image.

- output number of sectors to load as a patchable variable;
  for now the patching is done by tool/build/zipcopy.c
- remove references to _ezip
- add tweaks to metal mmap()
- implement lseek() & fstat() for metal memory files

ape/ape.S

@@ -152,10 +152,13 @@ ape_mz:
 	.short	0x0800			// MZ: increases cs load lower bound
 	.short	0x0040			// MZ: reloc table offset
 	.short	0			// MZ: overlay number
+	.ascii	"'<<'@'\n"
 	.org	0x24			// MZ: bytes reserved for you
 	.ascii	"JT"			// MZ: OEM identifier
-	.short	0			// MZ: OEM information
+	.short	1			// MZ: OEM information
-	.ascii	"' <<'@'\n"
+__ape_com_sectors:
+	.short	v_ape_allsectors	// total number of sectors to load;
+	.endobj	__ape_com_sectors,globl	// to be patched by Cosmo tools
 	.org	0x40-4			// MZ: bytes reserved for you
 #if SupportsWindows() || SupportsMetal()
 	.long	RVA(ape_pe)		// PE: the new technology
@@ -220,7 +223,7 @@ stub:	mov	$0x40,%dl		// *literally* dos
 	nop				// system five bootpoint
 	.org	0x48,0x90		// note ⌂ELF means JG 47
 	jmp	3f			// MZ also means pop r10
-2:	sub	$8,%rsp			// a.k.a. dec %ax sub %sp
+2:	push	%rax			// a.k.a. push %ax
 	xor	%edx,%edx		// MZ ate BIOS drive code
 3:	.byte	0xbd,0,0		// a.k.a. mov imm,%bp
 	jmp	pc			// real mode, is real
@@ -291,7 +294,11 @@ pc:	cld
 	mov	$1,%al				// current sector
 	xor	%cx,%cx				// current cylinder
 	xor	%dh,%dh				// current head
-	mov	$v_ape_realsectors,%di		// total sectors
+	mov	$v_ape_maxrealsectors,%di	// no. sectors for base memory
+	mov	REAL(__ape_com_sectors),%bp
+	cmp	%bp,%di
+	jb	3f
+	mov	%bp,%di
 3:	call	pcread
 	mov	%es,%si				// addr += 512
 	add	$512>>4,%si
@@ -417,13 +424,12 @@ pcread:	push	%ax
 	ror	%cl
 	or	%al,%cl
 	xor	%bx,%bx			// es:bx is destination addr
-	mov	$1,%al			// read only one disk sector
+	mov	$0x0201,%ax		// read only one disk sector
-	mov	$2,%ah			// read disk sectors ordinal
 	int	$0x13
 	pop	%cx
 	pop	%ax
 	jc	9f
-	inc	%al			// ++sector
+	inc	%ax			// ++sector
 	cmp	mm+"struct mman::pc_drive_last_sector",%al
 	jbe	2f
 	mov	$1,%al
@@ -480,7 +486,7 @@ sinit4:	mov	$4,%cx
 	jz	1f
 	push	%cx
 	push	%si
-	xchg	%ax,%di
+	xchg	%ax,%dx
 	mov	$REAL(sconf),%si
 	call	sinit
 	pop	%si
@@ -491,18 +497,16 @@ sinit4:	mov	$4,%cx
 
 //	Initializes Serial Line Communications 8250 UART 16550A
 //
-//	@param	word di tty port
+//	@param	word dx tty port
 //	@param	char (*{es:,e,r}si)[4] register initial values
+//	@clob	dx
 //	@mode	long,legacy,real
 //	@see	www.lammertbies.nl/comm/info/serial-uart.html
-sinit:	mov	%di,%dx
+sinit:	test	%dx,%dx
-	test	%dx,%dx
 	jz	2f
 	push	%dx
 	push	%si
-	xor	%cx,%cx
+	add	$UART_LCR,%dx
-	mov	$UART_LCR,%cl
-	add	%cx,%dx
 	lodsb	%ds:(%si),%al
 	pop	%si
 	or	$UART_DLAB,%al
@@ -1515,7 +1519,11 @@ cpyhi:	push	%es
 	call	unreal
 	mov	$IMAGE_BASE_REAL,%esi
 	mov	$IMAGE_BASE_PHYSICAL,%edi
-	mov	$v_ape_realdwords,%ecx
+	mov	$v_ape_maxrealsectors,%ecx
+	cmp	%bp,%cx
+	jb	1f
+	mov	%bp,%cx
+1:	shl	$9-2,%ecx		// convert sector count to dword count
 	cld
 	rep movsl %ds:(%esi),%es:(%edi)
 	sti
@@ -1545,13 +1553,16 @@ unreal:	push	%ds
 	pop	%ds
 	ret
 
-//	Reads any remaining program pages into memory which have not yet
+//	Reads any remaining program & data sectors into memory which have not
-//	been read by the boot sector.
+//	yet been read by the boot sector.
 //
-//	@clob	eax, ecx, dx, esi, edi, bp
+//	@return	ebp physical address after end of loaded sectors
-loadhi:	mov	$v_ape_highsectors,%bp
+//	@clob	eax, ecx, dx, esi, edi
-	test	%bp,%bp
+loadhi:
-	jz	9f
+#define	SEG 0x79000
+	mov	$IMAGE_BASE_PHYSICAL+v_ape_maxrealbytes-SEG,%edi
+	sub	$v_ape_maxrealsectors,%bp
+	jbe	9f
 	mov	$mm+"struct mman::pc_drive",%si
 	cld
 	lodsb	//← pc_drive
@@ -1565,8 +1576,6 @@ loadhi:	mov	$v_ape_highsectors,%bp
 	xchg	%ax,%cx
 	mov	(%si),%dh #← pc_drive_next_head
 	push	%es
-#define	SEG 0x79000
-	mov	$IMAGE_BASE_PHYSICAL+v_ape_realbytes-SEG,%edi
 	push	$SEG>>4
 	pop	%es
 0:	call	pcread
@@ -1584,7 +1593,8 @@ loadhi:	mov	$v_ape_highsectors,%bp
 	dec	%bp
 	jnz	0b
 	pop	%es
-9:	ret
+9:	lea	SEG(%edi),%ebp
+	ret
 
 //	Initializes long mode paging.
 pinit:	push	%ds
@@ -1638,6 +1648,8 @@ golong:	cli
 	.endfn	golong
 
 //	Long mode is long.
+//
+//	@param	ebp physical address after end of loaded sectors
 	.code64
 long:	movabs	$BANE+PHYSICAL(0f),%rax
 	jmp	*%rax
@@ -1653,12 +1665,12 @@ long:	movabs	$BANE+PHYSICAL(0f),%rax
 	xor	%r13d,%r13d
 	xor	%r14d,%r14d
 	xor	%r15d,%r15d
-	xor	%ebx,%ebx
-	xor	%ebp,%ebp
 	mov	$mm,%rdi
 	mov	%cr3,%rsi
 	mov	$IMAGE_BASE_PHYSICAL,%edx
-	lea	v_ape_allbytes(%rdx),%ecx
+	mov	%ebp,%ecx
+	xor	%ebx,%ebx
+	xor	%ebp,%ebp
 	call	__map_phdrs
 	push	$0x037f
 	fldcw	(%rsp)
@@ -1792,9 +1804,9 @@ kernel:	movabs	$ape_stack_vaddr,%rsp
 	.endm
 	.ldsvar	_end
 	.ldsvar	_etext
-	.ldsvar	v_ape_realsectors
+	.ldsvar	v_ape_maxrealsectors
-	.ldsvar	v_ape_realbytes
+	.ldsvar	v_ape_maxrealbytes
-	.ldsvar	v_ape_highsectors
+	.ldsvar	v_ape_allsectors
 	.ldsvar	ape_idata_ro
 	.ldsvar	ape_piro
 	.ldsvar	ape_piro_end

ape/ape.lds

@@ -436,7 +436,6 @@ SECTIONS {
 /*END: NT FORK COPYING */
     _edata = .;
     PROVIDE(edata = .);
-    _ezip = .; /* <-- very deprecated */
   } :Ram
 
   . = ALIGN(CONSTANT(COMMONPAGESIZE));
@@ -632,12 +631,10 @@ APE_DECLARE_FIXED_DECIMAL(IDENTITY, blink_xnu_aarch64_size);
 #endif /* APE_IS_SHELL_SCRIPT */
 
 #if SupportsMetal()
-v_ape_realsectors = MIN(0x70000 - IMAGE_BASE_REAL, ROUNDUP(RVA(_ezip), 512)) / 512;
+v_ape_maxrealbytes = ROUNDUP(0x70000 - IMAGE_BASE_REAL, 512);
-v_ape_realbytes = v_ape_realsectors * 512;
+v_ape_maxrealsectors = v_ape_maxrealbytes / 512;
-v_ape_realdwords = v_ape_realsectors * (512 / 4);
+v_ape_allbytes = ROUNDUP(_edata - __executable_start, 512);
-v_ape_allsectors = ROUNDUP(RVA(_ezip), 512) / 512;
+v_ape_allsectors = v_ape_allbytes / 512;
-v_ape_allbytes = v_ape_allsectors * 512;
-v_ape_highsectors = MIN(0xffff, v_ape_allsectors - v_ape_realsectors);
 TSSDESCSTUB2(_tss, _tss, _tss_end ? _tss_end - _tss - 1 : 0);
 #endif
 

ape/sections.internal.h

@@ -9,7 +9,6 @@ extern unsigned char __privileged_start[] __attribute__((__weak__));
 extern unsigned char _ehead[] __attribute__((__weak__));
 extern unsigned char _etext[] __attribute__((__weak__));
 extern unsigned char _edata[] __attribute__((__weak__));
-extern unsigned char _ezip[] __attribute__((__weak__));
 extern unsigned char _end[] __attribute__((__weak__));
 extern unsigned char _ereal[] __attribute__((__weak__));
 extern unsigned char _tdata_start[] __attribute__((__weak__));

libc/calls/fstat-metal.c

@@ -17,14 +17,17 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/internal.h"
+#include "libc/calls/metalfile.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 sys_fstat_metal(int fd, struct stat *st) {
-  if (fd < 0) return einval();
+  struct MetalFile *file;
-  if (fd < g_fds.n && g_fds.p[fd].kind == kFdSerial) {
+  if (fd < 0 || fd >= g_fds.n) return einval();
+  switch (g_fds.p[fd].kind) {
+    case kFdSerial:
       bzero(st, sizeof(*st));
       st->st_dev = g_fds.p[fd].handle;
       st->st_rdev = g_fds.p[fd].handle;
@@ -32,7 +35,15 @@ int sys_fstat_metal(int fd, struct stat *st) {
       st->st_mode = S_IFCHR | 0600;
       st->st_blksize = 1;
       return 0;
-  } else {
+    case kFdFile:
+      file = (struct MetalFile *)g_fds.p[fd].handle;
+      bzero(st, sizeof(*st));
+      st->st_nlink = 1;
+      st->st_size = file->size;
+      st->st_mode = S_IFREG | 0600;
+      st->st_blksize = 1;
+      return 0;
+    default:
       return ebadf();
   }
 }

libc/calls/internal.h

@@ -43,6 +43,7 @@ forceinline bool __isfdkind(int fd, int kind) {
 int _check_interrupts(int);
 int sys_close_nt(struct Fd *, int);
 int sys_openat_metal(int, const char *, int, unsigned);
+int64_t sys_lseek_metal(struct Fd *, int64_t, int);
 
 COSMOPOLITAN_C_END_
 #endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */

libc/calls/lseek-metal.c

@@ -0,0 +1,50 @@
+/*-*- 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 2020 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/calls.h"
+#include "libc/calls/internal.h"
+#include "libc/calls/metalfile.internal.h"
+#include "libc/calls/struct/fd.internal.h"
+#include "libc/sysv/errfuns.h"
+
+int64_t sys_lseek_metal(struct Fd *fd, int64_t offset, int whence) {
+  size_t new_pos;
+  struct MetalFile *file;
+  switch (fd->kind) {
+    case kFdFile:
+      file = (struct MetalFile *)fd->handle;
+      switch (whence) {
+        case SEEK_SET:
+          new_pos = offset;
+          break;
+        case SEEK_CUR:
+          new_pos = file->pos + offset;
+          break;
+        case SEEK_END:
+          new_pos = file->size + offset;
+          break;
+        default:
+          return einval();
+      }
+      if (new_pos > file->size) return einval();
+      file->pos = new_pos;
+      return new_pos;
+    default:
+      return ebadf();
+  }
+}

libc/calls/lseek.c

@@ -77,9 +77,11 @@
  */
 int64_t lseek(int fd, int64_t offset, int whence) {
   int64_t rc;
-  if (fd < g_fds.n && g_fds.p[fd].kind == kFdZip) {
+  if (fd >= 0 && fd < g_fds.n && g_fds.p[fd].kind == kFdZip) {
     rc = _weaken(__zipos_seek)(
         (struct ZiposHandle *)(intptr_t)g_fds.p[fd].handle, offset, whence);
+  } else if (fd >= 0 && fd < g_fds.n && IsMetal()) {
+    rc = sys_lseek_metal(g_fds.p + fd, offset, whence);
   } else if (IsLinux() || IsXnu() || IsFreebsd() || IsOpenbsd()) {
     rc = sys_lseek(fd, offset, whence, 0);
   } else if (IsNetbsd()) {

libc/calls/metalfile.c

@@ -53,7 +53,7 @@ void *__ape_com_base;
 size_t __ape_com_size = 0;
 
 textstartup dontasan void InitializeMetalFile(void) {
-  if (IsMetal()) {
+  if (IsMetal() && _weaken(__ape_com_sectors)) {
     /*
      * Copy out a pristine image of the program — before the program might
      * decide to modify its own .data section.
@@ -63,8 +63,7 @@ textstartup dontasan void InitializeMetalFile(void) {
      * The zipos code will automatically arrange to do this.  Alternatively,
      * user code can __static_yoink this symbol.
      */
-    size_t size = ROUNDUP(_ezip - __executable_start, 4096);
+    size_t size = ROUNDUP((size_t)__ape_com_sectors * 512, 4096);
-    // TODO(jart): Restore support for ZIPOS on metal.
     void *copied_base;
     struct DirectMap dm;
     dm = sys_mmap_metal(NULL, size, PROT_READ | PROT_WRITE,

libc/calls/metalfile.internal.h

@@ -11,6 +11,7 @@ struct MetalFile {
 
 extern void *__ape_com_base;
 extern size_t __ape_com_size;
+extern uint16_t __ape_com_sectors;  // ape/ape.S
 
 COSMOPOLITAN_C_END_
 #endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */

libc/intrin/directmap-metal.c

@@ -16,6 +16,7 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/assert.h"
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
 #include "libc/calls/metalfile.internal.h"
@@ -46,6 +47,10 @@ dontasan struct DirectMap sys_mmap_metal(void *vaddr, size_t size, int prot,
   struct mman *mm;
   struct DirectMap res;
   uint64_t addr, faddr = 0, page, e, *pte, *fdpte, *pml4t;
+  if ((uintptr_t)BANE + size < (uintptr_t)BANE) {
+    assert(false);
+    return bad_mmap();
+  }
   mm = __get_mm();
   pml4t = __get_pml4t();
   size = ROUNDUP(size, 4096);
@@ -69,11 +74,14 @@ dontasan struct DirectMap sys_mmap_metal(void *vaddr, size_t size, int prot,
     } else {
       addr = ROUNDUP(addr, 4096);
     }
-    for (i = 0; i < size; i += 4096) {
+    i = 0;
+    while (i < size) {
       pte = __get_virtual(mm, pml4t, addr + i, false);
       if (pte && (*pte & (PAGE_V | PAGE_RSRV))) {
         addr = MAX(addr, sys_mmap_metal_break) + i + 4096;
         i = 0;
+      } else {
+        i += 4096;
       }
     }
     sys_mmap_metal_break = MAX(addr + size, sys_mmap_metal_break);

libc/intrin/interrupts.S

@@ -25,6 +25,7 @@
 │ OTHER DEALINGS IN THE SOFTWARE.                                              │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/dce.h"
+#include "libc/intrin/kprintf.h"
 #include "libc/macros.internal.h"
 #include "libc/runtime/pc.internal.h"
 

tool/build/zipcopy.c

@@ -23,11 +23,15 @@
 #include "libc/elf/struct/shdr.h"
 #include "libc/errno.h"
 #include "libc/fmt/magnumstrs.internal.h"
+#include "libc/intrin/newbie.h"
 #include "libc/limits.h"
+#include "libc/nt/struct/imagedosheader.internal.h"
+#include "libc/runtime/pc.internal.h"
 #include "libc/runtime/runtime.h"
 #include "libc/stdio/stdio.h"
 #include "libc/str/str.h"
 #include "libc/sysv/consts/map.h"
+#include "libc/sysv/consts/msync.h"
 #include "libc/sysv/consts/o.h"
 #include "libc/sysv/consts/prot.h"
 #include "libc/zip.internal.h"
@@ -109,6 +113,25 @@ static void GetOpts(int argc, char *argv[]) {
   outpath = argv[optind + 1];
 }
 
+static void BiosZipFix(unsigned long cdest) {
+  struct NtImageDosHeader head;
+  size_t hd_sz = sizeof(head);
+  size_t e_oemid = offsetof(struct NtImageDosHeader, e_oemid);
+  size_t e_oeminfo = offsetof(struct NtImageDosHeader, e_oeminfo);
+  if (outsize < hd_sz) return;
+  if (pread(outfd, &head, hd_sz, 0) != hd_sz) return;
+  if (READ64LE((uint8_t *)&head) != READ64LE("MZqFpD='") &&
+      READ64LE((uint8_t *)&head) != READ64LE("jartsr='")) return;
+  if (le16toh(head.e_oemid) != READ16LE("JT") ||
+      le16toh(head.e_oeminfo) != 1) return;
+  // patch executable head so that it will load the right count of sectors
+  // when run as a legacy BIOS disk image
+  head.e_res2[0] = htole16(ROUNDUP(cdest, 0x200) / 0x200);
+  if (pwrite(outfd, &head, hd_sz, 0) != hd_sz) {
+    SysDie(outpath, "head pwrite");
+  }
+}
+
 static void CopyZip(void) {
   char *secstrs;
   int rela, recs;
@@ -176,7 +199,7 @@ static void CopyZip(void) {
   }
 
   // write output
-  if ((outfd = open(outpath, O_WRONLY | O_CREAT, 0644)) == -1) {
+  if ((outfd = open(outpath, O_RDWR | O_CREAT, 0644)) == -1) {
     SysDie(outpath, "open");
   }
   if ((outsize = lseek(outfd, 0, SEEK_END)) == -1) {
@@ -205,6 +228,7 @@ static void CopyZip(void) {
   if (pwrite(outfd, eocd, length, cdest) != length) {
     SysDie(outpath, "eocd pwrite");
   }
+  BiosZipFix(cdest);
   if (close(outfd)) {
     SysDie(outpath, "close");
   }