2003-09-23 Roland McGrath <roland@redhat.com>

	* sysdeps/generic/ldsodefs.h (struct rtld_global): Add _dl_stack_flags
	and _dl_make_stack_executable_hook.  Declare _dl_make_stack_executable.
	* elf/rtld.c (_rtld_global): Add initializer for _dl_stack_flags.
	(dl_main): Reset _dl_stack_flags according to PT_GNU_STACK phdr.
	Initialize _dl_make_stack_executable_hook.
	* elf/dl-support.c: Define those new variables.
	(_dl_non_dynamic_init): Scan phdrs for PT_GNU_STACK.
	(_dl_phdr): Fix type.
	* elf/dl-load.c (_dl_map_object_from_fd): Grok PT_GNU_STACK phdr and
	enable execute permission for the stack if necessary.
	* sysdeps/generic/dl-execstack.c: New file.
	* elf/Makefile (dl-routines): Add it.
	* elf/Versions (ld: GLIBC_PRIVATE): Add _dl_make_stack_executable.
	* sysdeps/unix/sysv/linux/dl-execstack.c: New file.

3 files changed, 160 insertions, 0 deletions

diff --git a/sysdeps/generic/dl-execstack.c b/sysdeps/generic/dl-execstack.c
new file mode 100644
index 0000000000..04f87cf519
--- /dev/null
+++ b/sysdeps/generic/dl-execstack.c
@@ -0,0 +1,32 @@
+/* Stack executability handling for GNU dynamic linker.  Stub version.
+   Copyright (C) 2003 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, write to the Free
+   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+   02111-1307 USA.  */
+
+#include <ldsodefs.h>
+#include <errno.h>
+
+/* There is no portable way to know the bounds of the initial thread's stack
+   so as to mprotect it.  */
+
+int
+internal_function
+_dl_make_stack_executable (void)
+{
+  return ENOSYS;
+}
+rtld_hidden_def (_dl_make_stack_executable)
diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h
index 58dfc15ca3..afb192925a 100644
--- a/sysdeps/generic/ldsodefs.h
+++ b/sysdeps/generic/ldsodefs.h
@@ -355,6 +355,14 @@ struct rtld_global
   EXTERN void (*_dl_rtld_unlock_recursive) (void *);
 #endif
 
+  /* Prevailing state of the stack, PF_X indicating it's executable.  */
+  EXTERN ElfW(Word) _dl_stack_flags;
+
+  /* If loading a shared object requires that we make the stack executable
+     when it was not, we do it by calling this function.
+     It returns an errno code or zero on success.  */
+  EXTERN int (*_dl_make_stack_executable_hook) (void) internal_function;
+
   /* Keep the conditional TLS members at the end so the layout of the
      structure used by !USE_TLS code matches the prefix of the layout in
      the USE_TLS rtld.  Note that `struct link_map' is conditionally
@@ -438,6 +446,11 @@ extern void **_dl_initial_error_catch_tsd (void) __attribute__ ((const))
      attribute_hidden;
 #endif
 
+/* This is the initial value of GL(dl_make_stack_executable_hook).
+   A threads library can change it.  */
+extern int _dl_make_stack_executable (void) internal_function;
+rtld_hidden_proto (_dl_make_stack_executable)
+
 /* Parameters passed to the dynamic linker.  */
 extern int _dl_argc attribute_hidden;
 extern char **_dl_argv;
diff --git a/sysdeps/unix/sysv/linux/dl-execstack.c b/sysdeps/unix/sysv/linux/dl-execstack.c
new file mode 100644
index 0000000000..42300b0f4d
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/dl-execstack.c
@@ -0,0 +1,115 @@
+/* Stack executability handling for GNU dynamic linker.  Linux version.
+   Copyright (C) 2003 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, write to the Free
+   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+   02111-1307 USA.  */
+
+#include <ldsodefs.h>
+#include <sys/mman.h>
+#include <errno.h>
+#include <stdbool.h>
+#include <stackinfo.h>
+
+extern void *__libc_stack_end;
+
+int
+internal_function
+_dl_make_stack_executable (void)
+{
+  if (__libc_stack_end == 0)
+    /* XXX for a DT_NEEDED library that requires the change,
+       this is not initialized yet!
+    */
+    return ENOSYS;
+
+#if _STACK_GROWS_DOWN
+  /* This gives us the highest page that needs to be changed.  */
+  uintptr_t page = (uintptr_t) __libc_stack_end & -(intptr_t) GL(dl_pagesize);
+
+  /* There is always a hole in the address space below the bottom of the
+     stack.  So when we make an mprotect call that starts below the bottom
+     of the stack, it will include the hole and fail with ENOMEM.
+
+     We start with a random guess at how deep the stack might have gotten
+     so as to have extended the GROWSDOWN mapping to lower pages.  */
+
+  size_t size = GL(dl_pagesize) * 8;
+  page = page + GL(dl_pagesize) - size;
+  while (1)
+    {
+      if (__mprotect ((void *) page, size,
+		      PROT_READ|PROT_WRITE|PROT_EXEC) == 0)
+	/* We got this chunk changed; loop to do another chunk below.  */
+	page -= size;
+      else
+	{
+	  if (errno != ENOMEM)	/* Unexpected failure mode.  */
+	    return errno;
+
+	  if (size == GL(dl_pagesize))
+	    /* We just tried to mprotect the top hole page and failed.
+	       We are done.  */
+	    break;
+
+	  /* Our mprotect call failed because it started below the lowest
+	     stack page.  Try again on just the top half of that region.  */
+	  size /= 2;
+	  page += size;
+	}
+    }
+
+#elif _STACK_GROWS_UP
+
+  /* This gives us the lowest page that needs to be changed.  */
+  uintptr_t page = (uintptr_t) __libc_stack_end & -(intptr_t) GL(dl_pagesize);
+
+  /* There is always a hole in the address space above the top of the
+     stack.  So when we make an mprotect call that spans past the top
+     of the stack, it will include the hole and fail with ENOMEM.
+
+     We start with a random guess at how deep the stack might have gotten
+     so as to have extended the GROWSUP mapping to higher pages.  */
+
+  size_t size = GL(dl_pagesize) * 8;
+  while (1)
+    {
+      if (__mprotect ((void *) page, size,
+		      PROT_READ|PROT_WRITE|PROT_EXEC) == 0)
+	/* We got this chunk changed; loop to do another chunk below.  */
+	page += size;
+      else
+	{
+	  if (errno != ENOMEM)	/* Unexpected failure mode.  */
+	    return errno;
+
+	  if (size == GL(dl_pagesize))
+	    /* We just tried to mprotect the lowest hole page and failed.
+	       We are done.  */
+	    break;
+
+	  /* Our mprotect call failed because it extended past the highest
+	     stack page.  Try again on just the bottom half of that region.  */
+	  size /= 2;
+	}
+    }
+
+#else
+# error "Define either _STACK_GROWS_DOWN or _STACK_GROWS_UP"
+#endif
+
+  return 0;
+}
+rtld_hidden_def (_dl_make_stack_executable)