[x86i386-20030821] Fix i386 on x86-64 threads

[Andrew Cagney <ac131313 at redhat dot com>]

Hello,

This patch gets GDB working with i386 executables on the x86-64.  Note 
that you'll also need a really really really recent glibc.

I've checked it into my cagney_x86i386-20030821-branch.

Andrew
2003-08-21  Andrew Cagney  <cagney@redhat.com>

	* x86-64-linux-nat.c (ps_get_thread_area): When architecture is
	i386 use PTRACE_GET_THREAD_AREA.  Suggested by Roland McGrath.

Index: ./gdb/x86-64-linux-nat.c
===================================================================
RCS file: /cvs/src/src/gdb/x86-64-linux-nat.c,v
retrieving revision 1.26.2.1
diff -u -r1.26.2.1 x86-64-linux-nat.c
--- ./gdb/x86-64-linux-nat.c	21 Aug 2003 20:37:30 -0000	1.26.2.1
+++ ./gdb/x86-64-linux-nat.c	26 Aug 2003 16:02:07 -0000
@@ -314,34 +314,74 @@
   return x86_64_linux_dr_get (DR_STATUS);
 }
 
+/* This function is called by libthread_db as part of its handling of
+   a request for a thread's local storage address.  */
+
 extern ps_err_e
 ps_get_thread_area (const struct ps_prochandle *ph,
                     lwpid_t lwpid, int idx, void **base)
 {
 
-/* This definition comes from prctl.h, but some kernels may not have it.  */
+  switch (TARGET_ARCHITECTURE->mach)
+    {
+    case bfd_mach_i386_i386:
+    case bfd_mach_i386_i386_intel_syntax:
+      {
+	/* The full structure is found in <asm-i386/ldt.h>.  The
+	   second integer is the LDT's base_address and that is used
+	   to locate the thread's local storage.  See i386-linux-nat.c
+	   more info.  */
+	unsigned int desc[4];
+
+	/* This code assumes that "int" is 32 bits and that
+           GET_THREAD_AREA returns no more than 4 int values.  */
+	gdb_assert (sizeof (int) == 4);	
+#ifndef PTRACE_GET_THREAD_AREA
+#define PTRACE_GET_THREAD_AREA 25
+#endif
+	if  (ptrace (PTRACE_GET_THREAD_AREA, 
+		     lwpid, (void *) (long) idx, (unsigned long) &desc) < 0)
+	  return PS_ERR;
+      
+	/* Extend the value to 64 bits.  Here it's assumed that a
+           "long" and a "void *" are the same.  */
+	(*base) = (void *) (long) desc[1];
+	return PS_OK;
+      }
+
+    case bfd_mach_x86_64:
+    case bfd_mach_x86_64_intel_syntax:
+
+      /* This definition comes from prctl.h, but some kernels may not
+         have it.  */
 #ifndef PTRACE_ARCH_PRCTL
 #define PTRACE_ARCH_PRCTL      30
 #endif
 
-  /* FIXME: ezannoni-2003-07-09 see comment above about include file order.
-     We could be getting bogus values for these two.  */
-  gdb_assert (FS < ELF_NGREG);
-  gdb_assert (GS < ELF_NGREG);
-  switch (idx)
-    {
-    case FS:
-      if (ptrace (PTRACE_ARCH_PRCTL, lwpid, base, ARCH_GET_FS) == 0)
-       return PS_OK;
-      break;
-    case GS:
-      if (ptrace (PTRACE_ARCH_PRCTL, lwpid, base, ARCH_GET_GS) == 0)
-       return PS_OK;
-      break;
-    default:                   /* Should not happen.  */
-      return PS_BADADDR;
+      /* FIXME: ezannoni-2003-07-09 see comment above about include
+	 file order.  We could be getting bogus values for these two.  */
+      gdb_assert (FS < ELF_NGREG);
+      gdb_assert (GS < ELF_NGREG);
+      switch (idx)
+	{
+	case FS:
+	  if (ptrace (PTRACE_ARCH_PRCTL, lwpid, base, ARCH_GET_FS) == 0)
+	    return PS_OK;
+	  break;
+	case GS:
+	  if (ptrace (PTRACE_ARCH_PRCTL, lwpid, base, ARCH_GET_GS) == 0)
+	    return PS_OK;
+	  break;
+	default:                   /* Should not happen.  */
+	  return PS_BADADDR;
+	}
+      return PS_ERR;               /* ptrace failed.  */
+      
+    case bfd_mach_i386_i8086:
+      internal_error (__FILE__, __LINE__, "bad i8086 machine");
+    default:
+      internal_error (__FILE__, __LINE__, "bad_switch");
     }
-  return PS_ERR;               /* ptrace failed.  */
 }
 
 void