Sync pseudo-reloc.c with cygwin/lib/

winsup/mingw/ChangeLog

@@ -1,3 +1,20 @@
+2009-10-23  Charles Wilson  <mingw@cwilson.fastmail.fm>
+
+	Sync pseudo-reloc.c with cygwin/lib/
+	* pseudo-reloc.c [CYGWIN]: Added comments throughout and various
+	whitespace fixes. Exploit cygwin_internal(CW_EXIT_PROCESS,...)
+	for fatal error handling that is consistent with cygwin process
+	life-cycle. Ensure state variable (in _pei386_runtime_relocator)
+	is unique to each address space, across fork().
+	[CYGWIN] (__print_reloc_error): New function for reporting
+	errors in a manner supported by cygwin at this early stage of
+	the process life-cycle.
+	[CYGWIN] (_pei386_runtime_relocator): Ensure relocations
+	performed only once for each address space, but are repeated
+	after fork() in the new address space.
+	[MINGW] (__write_memory): Ensure that b is always initialized
+	by call to VirtualQuery, even if -DNDEBUG.
+
 2009-09-29  Keith Marshall  <keithmarshall@users.sourceforge.net>
 
 	Make MinGW printf() "%p" format compatible with MSVCRT scanf().

winsup/mingw/pseudo-reloc.c

@@ -21,15 +21,39 @@
 #include <string.h>
 #include <assert.h>
 
- extern char __RUNTIME_PSEUDO_RELOC_LIST__;
+#if defined(__CYGWIN__)
- extern char __RUNTIME_PSEUDO_RELOC_LIST_END__;
+#include <wchar.h>
- extern char _image_base__;
+#include <ntdef.h>
+#include <stdarg.h>
+#include <sys/cygwin.h>
+/* copied from winsup.h */
+# define NO_COPY __attribute__((nocommon)) __attribute__((section(".data_cygwin_nocopy")))
+/* custom status code: */
+#define STATUS_ILLEGAL_DLL_PSEUDO_RELOCATION ((NTSTATUS) 0xe0000269)
+#else
+# define NO_COPY
+#endif
 
+extern char __RUNTIME_PSEUDO_RELOC_LIST__;
+extern char __RUNTIME_PSEUDO_RELOC_LIST_END__;
+extern char _image_base__;
+
+/* v1 relocation is basically:
+ *   *(base + .target) += .addend
+ * where (base + .target) is always assumed to point
+ * to a DWORD (4 bytes).
+ */
 typedef struct {
   DWORD addend;
   DWORD target;
 } runtime_pseudo_reloc_item_v1;
 
+/* v2 relocation is more complex. In effect, it is
+ *    *(base + .target) += *(base + .sym) - (base + .sym)
+ * with care taken in both reading, sign extension, and writing
+ * because .flags may indicate that (base + .target) may point
+ * to a BYTE, WORD, DWORD, or QWORD (w64).
+ */
 typedef struct {
   DWORD sym;
   DWORD target;
@@ -42,19 +66,107 @@ typedef struct {
   DWORD version;
 } runtime_pseudo_reloc_v2;
 
+#if defined(__CYGWIN__)
+#define SHORT_MSG_BUF_SZ 128
+/* This function is used to print short error messages
+ * to stderr, which may occur during DLL initialization
+ * while fixing up 'pseudo' relocations. This early, we
+ * may not be able to use cygwin stdio functions, so we
+ * use the win32 WriteFile api. This should work with both
+ * normal win32 console IO handles, redirected ones, and
+ * cygwin ptys.
+ */
+static BOOL
+__print_reloc_error (const char *fmt, ...)
+{
+  char buf[SHORT_MSG_BUF_SZ];
+  wchar_t module[MAX_PATH];
+  char * posix_module = NULL;
+  BOOL rVal = FALSE;
+  static const char * UNKNOWN_MODULE = "<unknown module>: ";
+  DWORD len;
+  DWORD done;
+  va_list args;
+  HANDLE errh = GetStdHandle (STD_ERROR_HANDLE);
+  ssize_t modulelen = GetModuleFileNameW (NULL, module, sizeof (module));
+
+  if (errh == INVALID_HANDLE_VALUE)
+    return FALSE;
+
+  if (modulelen > 0)
+    posix_module = cygwin_create_path (CCP_WIN_W_TO_POSIX, module);
+
+  va_start (args, fmt);
+  len = (DWORD) vsnprintf (buf, SHORT_MSG_BUF_SZ, fmt, args);
+  va_end (args);
+  buf[SHORT_MSG_BUF_SZ-1] = '\0'; /* paranoia */
+
+  if (posix_module)
+    {
+      rVal = WriteFile (errh, (PCVOID)posix_module,
+                        strlen(posix_module), &done, NULL) &&
+             WriteFile (errh, (PCVOID)": ", 2, &done, NULL) &&
+             WriteFile (errh, (PCVOID)buf, len, &done, NULL);
+      free (posix_module);
+    }
+  else
+    {
+      rVal = WriteFile (errh, (PCVOID)UNKNOWN_MODULE,
+                        sizeof(UNKNOWN_MODULE), &done, NULL) &&
+             WriteFile (errh, (PCVOID)buf, len, &done, NULL);
+    }
+  return rVal;
+}
+#endif /* __CYGWIN__ */
+
+/* This function temporarily marks the page containing addr
+ * writable, before copying len bytes from *src to *addr, and
+ * then restores the original protection settings to the page.
+ *
+ * Using this function eliminates the requirement with older
+ * pseudo-reloc implementations, that sections containing
+ * pseudo-relocs (such as .text and .rdata) be permanently
+ * marked writable. This older behavior sabotaged any memory
+ * savings achieved by shared libraries on win32 -- and was
+ * slower, too.  However, on cygwin as of binutils 2.20 the
+ * .text section is still marked writable, and the .rdata section
+ * is folded into the (writable) .data when --enable-auto-import.
+ */
 static void
 __write_memory (void *addr,const void *src,size_t len)
 {
   MEMORY_BASIC_INFORMATION b;
   DWORD oldprot;
+  SIZE_T memsz;
+
   if (!len)
     return;
-  assert (VirtualQuery (addr, &b, sizeof(b)));
+
+  memsz = VirtualQuery (addr, &b, sizeof(b));
+
+#if defined(__CYGWIN__)
+  /* CYGWIN: If error, print error message and die. */
+  if (memsz == 0)
+    {
+      __print_reloc_error (
+        "error while loading shared libraries: bad address specified 0x%08x.\n",
+        addr);
+      cygwin_internal (CW_EXIT_PROCESS,
+                       STATUS_ILLEGAL_DLL_PSEUDO_RELOCATION,
+                       1);
+    }
+#else
+  /* MINGW: If error, die. assert() may print error message when !NDEBUG */
+  assert (memsz);
+#endif
+
   /* Temporarily allow write access to read-only protected memory.  */
   if (b.Protect != PAGE_EXECUTE_READWRITE && b.Protect != PAGE_READWRITE)
     VirtualProtect (b.BaseAddress, b.RegionSize, PAGE_EXECUTE_READWRITE,
 		  &oldprot);
+  /* write the data. */
   memcpy (addr, src, len);
+  /* Restore original protection. */
   if (b.Protect != PAGE_EXECUTE_READWRITE && b.Protect != PAGE_READWRITE)
     VirtualProtect (b.BaseAddress, b.RegionSize, oldprot, &oldprot);
 }
@@ -70,15 +182,52 @@ do_pseudo_reloc (void * start, void * end, void * base)
   runtime_pseudo_reloc_v2 *v2_hdr = (runtime_pseudo_reloc_v2 *) start;
   runtime_pseudo_reloc_item_v2 *r;
 
+  /* A valid relocation list will contain at least one entry, and
+   * one v1 data structure (the smallest one) requires two DWORDs.
+   * So, if the relocation list is smaller than 8 bytes, bail.
+   */
   if (reloc_target < 8)
     return;
-  /* Check if this is old version pseudo relocation version.  */
+
+  /* Check if this is the old pseudo relocation version.  */
+  /* There are two kinds of v1 relocation lists:
+   *   1) With a (v2-style) version header. In this case, the
+   *      first entry in the list is a 3-DWORD structure, with
+   *      value:
+   *         { 0, 0, RP_VERSION_V1 }
+   *      In this case, we skip to the next entry in the list,
+   *      knowing that all elements after the head item can
+   *      be cast to runtime_pseudo_reloc_item_v1.
+   *   2) Without a (v2-style) version header. In this case, the
+   *      first element in the list IS an actual v1 relocation
+   *      record, which is two DWORDs.  Because there will never
+   *      be a case where a v1 relocation record has both
+   *      addend == 0 and target == 0, this case will not be
+   *      confused with the prior one.
+   * All current binutils, when generating a v1 relocation list,
+   * use the second (e.g. original) form -- that is, without the
+   * v2-style version header.
+   */
   if (reloc_target >= 12
       && v2_hdr->magic1 == 0 && v2_hdr->magic2 == 0
       && v2_hdr->version == RP_VERSION_V1)
+    {
+      /* We have a list header item indicating that the rest
+       * of the list contains v1 entries.  Move the pointer to
+       * the first true v1 relocation record.  By definition,
+       * that v1 element will not have both addend == 0 and
+       * target == 0 (and thus, when interpreted as a
+       * runtime_pseudo_reloc_v2, it will not have both
+       * magic1 == 0 and magic2 == 0).
+       */
       v2_hdr++;
+    }
+
   if (v2_hdr->magic1 != 0 || v2_hdr->magic2 != 0)
     {
+      /*************************
+       * Handle v1 relocations *
+       *************************/
       runtime_pseudo_reloc_item_v1 * o;
       for (o = (runtime_pseudo_reloc_item_v1 *) v2_hdr;
 	   o < (runtime_pseudo_reloc_item_v1 *)end;
@@ -92,26 +241,54 @@ do_pseudo_reloc (void * start, void * end, void * base)
       return;
     }
 
+  /* If we got this far, then we have relocations of version 2 or newer */
+
   /* Check if this is a known version.  */
   if (v2_hdr->version != RP_VERSION_V2)
     {
-#ifdef DEBUG
+#if defined(__CYGWIN__)
+      /* CYGWIN: Print error message and die, even when !DEBUGGING */
+      __print_reloc_error (
+        "error while loading shared libraries: invalid pseudo_reloc version %d.\n",
+        (int) v2_hdr->version);
+      cygwin_internal (CW_EXIT_PROCESS,
+                       STATUS_ILLEGAL_DLL_PSEUDO_RELOCATION,
+                       1);
+#else
+# if defined(DEBUG)
+      /* MINGW: Don't die; just return to caller. If DEBUG, print error message. */
       fprintf (stderr, "internal mingw runtime error:"
 	       "psuedo_reloc version %d is unknown to this runtime.\n",
 	       (int) v2_hdr->version);
+# endif
 #endif
       return;
     }
 
+  /*************************
+   * Handle v2 relocations *
+   *************************/
+
   /* Walk over header. */
   r = (runtime_pseudo_reloc_item_v2 *) &v2_hdr[1];
 
   for (; r < (runtime_pseudo_reloc_item_v2 *) end; r++)
     {
+      /* location where new address will be written */
       reloc_target = (ptrdiff_t) base + r->target;
+
+      /* get sym pointer. It points either to the iat entry
+       * of the referenced element, or to the stub function.
+       */
       addr_imp = (ptrdiff_t) base + r->sym;
       addr_imp = *((ptrdiff_t *) addr_imp);
 
+      /* read existing relocation value from image, casting to the
+       * bitsize indicated by the 8 LSBs of flags. If the value is
+       * negative, manually sign-extend to ptrdiff_t width. Raise an
+       * error if the bitsize indicated by the 8 LSBs of flags is not
+       * supported.
+       */
       switch ((r->flags & 0xff))
         {
           case 8:
@@ -138,15 +315,30 @@ do_pseudo_reloc (void * start, void * end, void * base)
 #endif
 	  default:
 	    reldata=0;
-#ifdef DEBUG
+#if defined(__CYGWIN__)
+            /* Print error message and die, even when !DEBUGGING */
+            __print_reloc_error (
+              "error while loading shared libraries: unknown pseudo_reloc bit size %d.\n",
+              (int) (r->flags & 0xff));
+            cygwin_internal (CW_EXIT_PROCESS,
+                             STATUS_ILLEGAL_DLL_PSEUDO_RELOCATION,
+                             1);
+#else
+# ifdef DEBUG
+            /* MINGW: If error, don't die; just print message if DEBUG */
 	    fprintf(stderr, "internal mingw runtime error: "
 		    "unknown pseudo_reloc bit size %d\n",
 		    (int) (r->flags & 0xff));
+# endif
 #endif
 	    break;
         }
+
+      /* Adjust the relocation value */
       reldata -= ((ptrdiff_t) base + r->sym);
       reldata += addr_imp;
+
+      /* Write the new relocation value back to *reloc_target */
       switch ((r->flags & 0xff))
         {
          case 8:
@@ -168,9 +360,9 @@ do_pseudo_reloc (void * start, void * end, void * base)
  }
 
 void
- _pei386_runtime_relocator ()
+_pei386_runtime_relocator ()
 {
-  static int was_init = 0;
+  static NO_COPY int was_init = 0;
   if (was_init)
     return;
   ++was_init;