[metal] Ensure "/ape.com" reads as unmodified program image

ape/sections.internal.h

@@ -10,6 +10,10 @@ extern unsigned char _edata[];
 extern unsigned char _ezip[];
 extern unsigned char _end[];
 extern unsigned char _ereal[];
+extern unsigned char _tdata_start[];
+extern unsigned char _tdata_end[];
+extern unsigned char _tbss_start[];
+extern unsigned char _tbss_end[];
 extern unsigned char __privileged_start[];
 extern unsigned char __privileged_addr[];
 extern unsigned char __privileged_size[];

libc/calls/getfiledescriptorsize.c

@@ -18,6 +18,7 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
+#include "libc/calls/metalfile.internal.h"
 #include "libc/calls/struct/metastat.internal.h"
 #include "libc/calls/struct/stat.h"
 #include "libc/calls/syscall-sysv.internal.h"
@@ -60,7 +61,14 @@ ssize_t getfiledescriptorsize(int fd) {
       rc = -1;
     }
   } else if (IsMetal()) {
-    rc = -1;
+    if (fd < 0 || fd >= g_fds.n)
+      rc = ebadf();
+    else if (g_fds.p[fd].kind != kFdFile)
+      rc = eacces();
+    else {
+      struct MetalFile *state = (struct MetalFile *)g_fds.p[fd].handle;
+      rc = state->size;
+    }
   } else if (!IsWindows()) {
     if (!__sys_fstat(fd, &st)) {
       rc = METASTAT(st, st_size);

libc/calls/metalfile.c

@@ -0,0 +1,70 @@
+/*-*- 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│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ This is free and unencumbered software released into the public domain.      │
+│                                                                              │
+│ Anyone is free to copy, modify, publish, use, compile, sell, or              │
+│ distribute this software, either in source code form or as a compiled        │
+│ binary, for any purpose, commercial or non-commercial, and by any            │
+│ means.                                                                       │
+│                                                                              │
+│ In jurisdictions that recognize copyright laws, the author or authors        │
+│ of this software dedicate any and all copyright interest in the              │
+│ software to the public domain. We make this dedication for the benefit       │
+│ of the public at large and to the detriment of our heirs and                 │
+│ successors. We intend this dedication to be an overt act of                  │
+│ relinquishment in perpetuity of all present and future rights to this        │
+│ software under copyright law.                                                │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,              │
+│ EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF           │
+│ MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.       │
+│ IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR            │
+│ OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,        │
+│ ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR        │
+│ OTHER DEALINGS IN THE SOFTWARE.                                              │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "ape/relocations.h"
+#include "ape/sections.internal.h"
+#include "libc/assert.h"
+#include "libc/calls/internal.h"
+#include "libc/calls/metalfile.internal.h"
+#include "libc/intrin/weaken.h"
+#include "libc/macros.internal.h"
+#include "libc/mem/mem.h"
+#include "libc/runtime/directmap.internal.h"
+#include "libc/runtime/pc.internal.h"
+#include "libc/runtime/runtime.h"
+#include "libc/str/str.h"
+#include "libc/sysv/consts/at.h"
+#include "libc/sysv/consts/o.h"
+#include "libc/sysv/consts/prot.h"
+#include "libc/sysv/errfuns.h"
+
+#define MAP_ANONYMOUS_linux 0x00000020
+#define MAP_FIXED_linux     0x00000010
+#define MAP_SHARED_linux    0x00000001
+
+STATIC_YOINK("_init_metalfile");
+
+void *__ape_com_base;
+size_t __ape_com_size = 0;
+
+textstartup void InitializeMetalFile(void) {
+  if (IsMetal()) {
+    /*
+     * Copy out a pristine image of the program — before the program might
+     * decide to modify its own .data section.  Do this only if needed.
+     */
+    size_t size = ROUNDUP(_tdata_end - _base, 4096);
+    void *copied_base;
+    struct DirectMap dm;
+    dm = sys_mmap_metal(NULL, size, PROT_READ | PROT_WRITE,
+                        MAP_SHARED_linux | MAP_ANONYMOUS_linux, -1, 0);
+    copied_base = dm.addr;
+    _npassert(copied_base != (void *)-1);
+    memcpy(copied_base, (void *)(BANE + IMAGE_BASE_REAL), size);
+    __ape_com_base = copied_base;
+    __ape_com_size = size;
+  }
+}

libc/calls/metalfile.internal.h

@@ -9,9 +9,14 @@ struct MetalFile {
   size_t pos;
 };
 
+extern void *__ape_com_base;
+extern size_t __ape_com_size;
+
 COSMOPOLITAN_C_END_
 #endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */
 
-#define APE_COM_NAME "/ape.com"
+#define APE_COM_NAME     "/ape.com"
+#define APE_COM_ALT_NAME "/proc/self/exe"
+#define APE_COM_URI      "file:/proc/self/exe"
 
 #endif /* COSMOPOLITAN_LIBC_CALLS_METALFILE_INTERNAL_H_ */

libc/calls/metalfile_init.S

@@ -0,0 +1,38 @@
+/*-*- mode:unix-assembly; indent-tabs-mode:t; tab-width:8; coding:utf-8     -*-│
+│vi: set et ft=asm ts=8 tw=8 fenc=utf-8                                     :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ This is free and unencumbered software released into the public domain.      │
+│                                                                              │
+│ Anyone is free to copy, modify, publish, use, compile, sell, or              │
+│ distribute this software, either in source code form or as a compiled        │
+│ binary, for any purpose, commercial or non-commercial, and by any            │
+│ means.                                                                       │
+│                                                                              │
+│ In jurisdictions that recognize copyright laws, the author or authors        │
+│ of this software dedicate any and all copyright interest in the              │
+│ software to the public domain. We make this dedication for the benefit       │
+│ of the public at large and to the detriment of our heirs and                 │
+│ successors. We intend this dedication to be an overt act of                  │
+│ relinquishment in perpetuity of all present and future rights to this        │
+│ software under copyright law.                                                │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,              │
+│ EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF           │
+│ MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.       │
+│ IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR            │
+│ OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,        │
+│ ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR        │
+│ OTHER DEALINGS IN THE SOFTWARE.                                              │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/macros.internal.h"
+#include "libc/calls/metalfile.internal.h"
+
+	.init.start 101,_init_metalfile
+	push	%rdi
+	push	%rsi
+	call	InitializeMetalFile
+	pop	%rsi
+	pop	%rdi
+	.init.end 101,_init_metalfile
+APE_COM_URI:
+	.endobj	APE_COM_URI,globl,hidden

libc/calls/openat-metal.c

@@ -16,13 +16,16 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
+#include "ape/relocations.h"
 #include "ape/sections.internal.h"
+#include "libc/assert.h"
 #include "libc/calls/internal.h"
 #include "libc/calls/metalfile.internal.h"
 #include "libc/intrin/weaken.h"
 #include "libc/macros.internal.h"
 #include "libc/mem/mem.h"
 #include "libc/runtime/directmap.internal.h"
+#include "libc/runtime/pc.internal.h"
 #include "libc/runtime/runtime.h"
 #include "libc/str/str.h"
 #include "libc/sysv/consts/at.h"
@@ -30,12 +33,16 @@
 #include "libc/sysv/consts/o.h"
 #include "libc/sysv/consts/prot.h"
 #include "libc/sysv/errfuns.h"
+#include "libc/zipos/zipos.internal.h"
 
 int sys_openat_metal(int dirfd, const char *file, int flags, unsigned mode) {
   int fd;
   struct MetalFile *state;
-  if (dirfd != AT_FDCWD || strcmp(file, APE_COM_NAME)) return enoent();
+  if (dirfd != AT_FDCWD || (strcmp(file, APE_COM_NAME) &&
+                            strcmp(file, APE_COM_ALT_NAME))) return enoent();
   if (flags != O_RDONLY) return eacces();
+  if (!_weaken(__ape_com_base) || !_weaken(__ape_com_size))
+    return eopnotsupp();
   if ((fd = __reservefd(-1)) == -1) return -1;
   if (!_weaken(calloc) || !_weaken(free)) {
     struct DirectMap dm;
@@ -48,8 +55,8 @@ int sys_openat_metal(int dirfd, const char *file, int flags, unsigned mode) {
     state = _weaken(calloc)(1, sizeof(struct MetalFile));
     if (!state) return -1;
   }
-  state->base = (char *)_base;
+  state->base = (char *)__ape_com_base;
-  state->size = _end - _base;
+  state->size = __ape_com_size;
   g_fds.p[fd].kind = kFdFile;
   g_fds.p[fd].flags = flags;
   g_fds.p[fd].mode = mode;

libc/zipos/get.c

@@ -17,6 +17,7 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
+#include "libc/calls/metalfile.internal.h"
 #include "libc/intrin/cmpxchg.h"
 #include "libc/intrin/promises.internal.h"
 #include "libc/intrin/strace.internal.h"
@@ -29,6 +30,8 @@
 #include "libc/zip.h"
 #include "libc/zipos/zipos.internal.h"
 
+STATIC_YOINK(APE_COM_URI);
+
 static uint64_t __zipos_get_min_offset(const uint8_t *base,
                                        const uint8_t *cdir) {
   uint64_t i, n, c, r, o;