2004-01-15 Roland McGrath <roland@frob.com>

	* priv.h (struct execdata.info.elf): Add `execstack' flag.
	* exec.c (check_elf_phdr): Set it according to PT_GNU_STACK's PF_X
	flag bit.  If no PT_GNU_STACK, default to set.
	(do_exec): If flag is clear, remove execute permission from stack.

2 files changed, 23 insertions, 2 deletions

diff --git a/exec/exec.c b/exec/exec.c
index d96ce8e9..6ffacbde 100644
--- a/exec/exec.c
+++ b/exec/exec.c
@@ -1,5 +1,5 @@
 /* GNU Hurd standard exec server.
-   Copyright (C) 1992,93,94,95,96,98,99,2000,01,02
+   Copyright (C) 1992,93,94,95,96,98,99,2000,01,02,04
    	Free Software Foundation, Inc.
    Written by Roland McGrath.
 
@@ -902,6 +902,12 @@ check_elf_phdr (struct execdata *e, const ElfW(Phdr) *mapped_phdr,
   memcpy (e->info.elf.phdr, mapped_phdr,
 	  e->info.elf.phnum * sizeof (ElfW(Phdr)));
 
+  /* Default state if we do not see PT_GNU_STACK telling us what to do.
+     Executable stack is the compatible default.
+     (XXX should be machine-dependent??)
+  */
+  e->info.elf.execstack = 1;
+
   for (phdr = e->info.elf.phdr;
        phdr < &e->info.elf.phdr[e->info.elf.phnum];
        ++phdr)
@@ -922,6 +928,9 @@ check_elf_phdr (struct execdata *e, const ElfW(Phdr) *mapped_phdr,
 				     phdr->p_filesz))
 	  e->error = ENOEXEC;
 	break;
+      case PT_GNU_STACK:
+	e->info.elf.execstack = phdr->p_flags & PF_X;
+	break;
       }
 }
 
@@ -1822,6 +1831,17 @@ do_exec (file_t file,
 			       &boot->stack_base, &boot->stack_size);
   if (e.error)
     goto out;
+#ifdef BFD
+  if (!e.bfd)
+#endif
+    {
+      /* It would probably be better to change mach_setup_thread so
+	 it does a vm_map with the right permissions to start with.  */
+      if (!e.info.elf.execstack)
+	e.error = vm_protect (newtask, boot->stack_base, boot->stack_size,
+			      0, VM_PROT_READ | VM_PROT_WRITE);
+    }
+
 
   if (oldtask != newtask && oldtask != MACH_PORT_NULL)
     {
diff --git a/exec/priv.h b/exec/priv.h
index 46cc919e..625ea477 100644
--- a/exec/priv.h
+++ b/exec/priv.h
@@ -1,5 +1,5 @@
 /* GNU Hurd standard exec server, private declarations.
-   Copyright (C) 1992,93,94,95,96,99,2000,02 Free Software Foundation, Inc.
+   Copyright (C) 1992,93,94,95,96,99,2000,02, 04 Free Software Foundation, Inc.
    Written by Roland McGrath.
 
 This file is part of the GNU Hurd.
@@ -151,6 +151,7 @@ struct execdata
 	    ElfW(Word) phnum;	/* Number of program header table elements.  */
 	    int anywhere;	/* Nonzero if image can go anywhere.  */
 	    vm_address_t loadbase; /* Actual mapping location.  */
+	    int execstack;	/* Zero if stack can be nonexecutable.  */
 	  } elf;
       } info;
   };