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[PATCH] make PowerPC64 default to nonexecutable stack
- From: Ryan Arnold <rsa at us dot ibm dot com>
- To: libc-alpha at sourceware dot org
- Date: Wed, 15 Dec 2010 19:43:26 -0600
- Subject: [PATCH] make PowerPC64 default to nonexecutable stack
- Reply-to: rsa at us dot ibm dot com
The inlined patch defaults powerpc64 to no-exec and does so by defining
the default permissions (DEFAULT_STACK_PERMS) in a platform specific
header file, namely stackinfo.h.
The patch follows the suggestions given on 11/03/2011 regarding my RFC
patch of the same title.
The check-execstack test-case silently succeeds if PF_X is not set.
One odd necessity is that the elf/Makefile check-execstack: rule needed
to be updated to search the sysdeps directories for the correct header.
Ryan S. Arnold
IBM Linux Technology Center
2010-12-15 Ryan S. Arnold <rsa@us.ibm.com>
* elf/Makefile: (check-execstack): Replace $(native-compile) with a
similar rule which adds the sysdep directories to the header search in
order to pick up the correct platform stackinfo.h.
* elf/check-execstack.c (main): Check DEFAULT_STACK_PERMS for PF_X and
perform test if it is, otherwise return successfully without testing.
* elf/dl-load.c (_dl_map_object_from_fd): Source stack_flags from
DEFAULT_STACK_PERMS define in stackinfo.h.
* elf/dl-support.c (_dl_stack_flags): Source from DEFAULT_STACK_PERMS
defined in stackinfo.h.
* elf/rtld.c (_dl_starting_up): Source ._dl_stack_flags from
DEFAULT_STACK_PERMS defined in stackinfo.h.
* sysdeps/i386/stackinfo.h: Define DEFAULT_STACK_PERMS with PF_X.
* sysdeps/ia64/stackinfo.h: Likewise.
* sysdeps/s390/stackinfo.h: Likewise.
* sysdeps/sh/stackinfo.h: Likewise.
* sysdeps/sparc/stackinfo.h: Likewise.
* sysdeps/x86_64/stackinfo.h: Likewise.
* sysdeps/powerpc/stackinfo.h: Define DEFAULT_STACK_PERMS without
PF_X for powerpc64. Retain PF_X for powerpc32.
diff --git a/elf/Makefile b/elf/Makefile
index b0420f5..bba6493 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -899,8 +899,14 @@ $(objpfx)check-textrel: check-textrel.c
$(native-compile)
check-execstack-CFLAGS = -O -Wall -D_XOPEN_SOURCE=600 -D_BSD_SOURCE -std=gnu99
+# Perform the same operation as $(native-compile) but add the sysdeps
+# directories as header search locations.
$(objpfx)check-execstack: check-execstack.c
- $(native-compile)
+ $(make-target-directory)
+ $(patsubst %/,cd % &&,$(objpfx)) \
+ $(BUILD_CC) $($(basename $(<F))-CFLAGS) $(ALL_BUILD_CFLAGS) \
+ $(addprefix -I$(shell pwd)/,$(sysdirs)) -I$(shell pwd) \
+ $(firstword $(filter /%,$< $(shell pwd)/$<)) -o $(@F)
check-localplt-CFLAGS = -O -Wall -D_GNU_SOURCE -std=gnu99
$(objpfx)check-localplt: check-localplt.c
diff --git a/elf/check-execstack.c b/elf/check-execstack.c
index 55cf487..60aa6d6 100644
--- a/elf/check-execstack.c
+++ b/elf/check-execstack.c
@@ -1,5 +1,5 @@
/* Check for executable stacks in DSOs.
- Copyright (C) 2009 Free Software Foundation, Inc.
+ Copyright (C) 2009, 2010 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contribute by Ulrich Drepper <drepper@redhat.com>. 2009.
@@ -26,6 +26,7 @@
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
+#include <stackinfo.h>
#ifdef BITS
@@ -150,9 +151,13 @@ main (int argc, char *argv[])
int cnt;
int result = 0;
- for (cnt = 1; cnt < argc; ++cnt)
- result |= handle_file (argv[cnt]);
-
+ /* We can return successfully, i.e., not fail, if PF_X isn't present. If it
+ * is present then check for the GNU_STACK header. */
+ if (DEFAULT_STACK_PERMS & PF_X)
+ {
+ for (cnt = 1; cnt < argc; ++cnt)
+ result |= handle_file (argv[cnt]);
+ }
return result;
}
#endif
diff --git a/elf/dl-load.c b/elf/dl-load.c
index 4c14f08..41b5ce7 100644
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -984,8 +984,10 @@ _dl_map_object_from_fd (const char *name, int fd, struct filebuf *fbp,
}
}
- /* Presumed absent PT_GNU_STACK. */
- uint_fast16_t stack_flags = PF_R|PF_W|PF_X;
+ /* On most platforms presume that PT_GNU_STACK is absent and the stack is
+ * executable. Other platforms default to a nonexecutable stack and don't
+ * need PT_GNU_STACK to do so. */
+ uint_fast16_t stack_flags = DEFAULT_STACK_PERMS;
{
/* Scan the program header table, collecting its load commands. */
diff --git a/elf/dl-support.c b/elf/dl-support.c
index 5897b32..1b128c3 100644
--- a/elf/dl-support.c
+++ b/elf/dl-support.c
@@ -32,6 +32,7 @@
#include <dl-procinfo.h>
#include <unsecvars.h>
#include <hp-timing.h>
+#include <stackinfo.h>
extern char *__progname;
char **_dl_argv = &__progname; /* This is checked for some error messages. */
@@ -134,8 +135,9 @@ uint64_t _dl_hwcap __attribute__ ((nocommon));
setting _dl_hwcap nonzero below, but we do anyway. */
uint64_t _dl_hwcap_mask __attribute__ ((nocommon));
-/* Prevailing state of the stack, PF_X indicating it's executable. */
-ElfW(Word) _dl_stack_flags = PF_R|PF_W|PF_X;
+/* Prevailing state of the stack. Generally this includes PF_X, indicating it's
+ * executable but this isn't true for all platforms. */
+ElfW(Word) _dl_stack_flags = DEFAULT_STACK_PERMS;
/* If loading a shared object requires that we make the stack executable
when it was not, we do it by calling this function.
diff --git a/elf/rtld.c b/elf/rtld.c
index d53730f..8510380 100644
--- a/elf/rtld.c
+++ b/elf/rtld.c
@@ -40,6 +40,7 @@
#include <dl-osinfo.h>
#include <dl-procinfo.h>
#include <tls.h>
+#include <stackinfo.h>
#include <assert.h>
@@ -122,8 +123,9 @@ INTVARDEF(_dl_starting_up)
(except those which cannot be added for some reason). */
struct rtld_global _rtld_global =
{
- /* Default presumption without further information is executable stack. */
- ._dl_stack_flags = PF_R|PF_W|PF_X,
+ /* Generally the default presumption without further information is an
+ * executable stack but this is not true for all platforms. */
+ ._dl_stack_flags = DEFAULT_STACK_PERMS,
#ifdef _LIBC_REENTRANT
._dl_load_lock = _RTLD_LOCK_RECURSIVE_INITIALIZER,
._dl_load_write_lock = _RTLD_LOCK_RECURSIVE_INITIALIZER,
diff --git a/sysdeps/i386/stackinfo.h b/sysdeps/i386/stackinfo.h
index 2530ea7..166c1d1 100644
--- a/sysdeps/i386/stackinfo.h
+++ b/sysdeps/i386/stackinfo.h
@@ -1,4 +1,4 @@
-/* Copyright (C) 1999, 2009 Free Software Foundation, Inc.
+/* Copyright (C) 1999, 2009, 2010 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
@@ -22,9 +22,15 @@
#ifndef _STACKINFO_H
#define _STACKINFO_H 1
+#include <elf.h>
+
/* On x86 the stack grows down. */
#define _STACK_GROWS_DOWN 1
+/* Default to an executable stack. PF_X can be overridden if PT_GNU_STACK is
+ * present, but it is presumed absent. */
+#define DEFAULT_STACK_PERMS (PF_R|PF_W|PF_X)
+
/* Access to the stack pointer. The macros are used in alloca_account
for which they need to act as barriers as well, hence the additional
(unnecessary) parameters. */
diff --git a/sysdeps/ia64/stackinfo.h b/sysdeps/ia64/stackinfo.h
index b7dc5d9..a7446e6 100644
--- a/sysdeps/ia64/stackinfo.h
+++ b/sysdeps/ia64/stackinfo.h
@@ -1,4 +1,4 @@
-/* Copyright (C) 2001 Free Software Foundation, Inc.
+/* Copyright (C) 2001, 2010 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
@@ -22,8 +22,14 @@
#ifndef _STACKINFO_H
#define _STACKINFO_H 1
+#include <elf.h>
+
/* On IA-64 the stack grows down. The register stack is of no concern
here. */
#define _STACK_GROWS_DOWN 1
+/* Default to an executable stack. PF_X can be overridden if PT_GNU_STACK is
+ * present, but it is presumed absent. */
+#define DEFAULT_STACK_PERMS (PF_R|PF_W|PF_X)
+
#endif /* stackinfo.h */
diff --git a/sysdeps/powerpc/stackinfo.h b/sysdeps/powerpc/stackinfo.h
index 839758a..aac86a4 100644
--- a/sysdeps/powerpc/stackinfo.h
+++ b/sysdeps/powerpc/stackinfo.h
@@ -1,4 +1,4 @@
-/* Copyright (C) 1999 Free Software Foundation, Inc.
+/* Copyright (C) 1999, 2010 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
@@ -22,7 +22,18 @@
#ifndef _STACKINFO_H
#define _STACKINFO_H 1
+#include <elf.h>
+
/* On PPC the stack grows down. */
#define _STACK_GROWS_DOWN 1
+#if __WORDSIZE == 64
+/* PPC64 doesn't need an executable stack and doesn't need PT_GNU_STACK
+ * to make the stack nonexecutable. */
+# define DEFAULT_STACK_PERMS (PF_R|PF_W)
+#else
+/* PF_X can be overridden if PT_GNU_STACK is present but is presumed absent. */
+# define DEFAULT_STACK_PERMS (PF_R|PF_W|PF_X)
+#endif
+
#endif /* stackinfo.h */
diff --git a/sysdeps/s390/stackinfo.h b/sysdeps/s390/stackinfo.h
index 7e09c85..058dff6 100644
--- a/sysdeps/s390/stackinfo.h
+++ b/sysdeps/s390/stackinfo.h
@@ -1,4 +1,4 @@
-/* Copyright (C) 2000 Free Software Foundation, Inc.
+/* Copyright (C) 2000, 2010 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
@@ -22,7 +22,13 @@
#ifndef _STACKINFO_H
#define _STACKINFO_H 1
+#include <elf.h>
+
/* On s390 the stack grows down. */
#define _STACK_GROWS_DOWN 1
+/* Default to an executable stack. PF_X can be overridden if PT_GNU_STACK is
+ * present, but it is presumed absent. */
+#define DEFAULT_STACK_PERMS (PF_R|PF_W|PF_X)
+
#endif /* stackinfo.h */
diff --git a/sysdeps/sh/stackinfo.h b/sysdeps/sh/stackinfo.h
index e65338f..f1c0977 100644
--- a/sysdeps/sh/stackinfo.h
+++ b/sysdeps/sh/stackinfo.h
@@ -1,4 +1,4 @@
-/* Copyright (C) 2001 Free Software Foundation, Inc.
+/* Copyright (C) 2001, 2010 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
@@ -22,7 +22,13 @@
#ifndef _STACKINFO_H
#define _STACKINFO_H 1
+#include <elf.h>
+
/* On SH the stack grows down. */
#define _STACK_GROWS_DOWN 1
+/* Default to an executable stack. PF_X can be overridden if PT_GNU_STACK is
+ * present, but it is presumed absent. */
+#define DEFAULT_STACK_PERMS (PF_R|PF_W|PF_X)
+
#endif /* stackinfo.h */
diff --git a/sysdeps/sparc/stackinfo.h b/sysdeps/sparc/stackinfo.h
index fd34e2d..189e4b6 100644
--- a/sysdeps/sparc/stackinfo.h
+++ b/sysdeps/sparc/stackinfo.h
@@ -1,4 +1,4 @@
-/* Copyright (C) 2001 Free Software Foundation, Inc.
+/* Copyright (C) 2001, 2010 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
@@ -22,7 +22,13 @@
#ifndef _STACKINFO_H
#define _STACKINFO_H 1
+#include <elf.h>
+
/* On sparc the stack grows down. */
#define _STACK_GROWS_DOWN 1
+/* Default to an executable stack. PF_X can be overridden if PT_GNU_STACK is
+ * present, but it is presumed absent. */
+#define DEFAULT_STACK_PERMS (PF_R|PF_W|PF_X)
+
#endif /* stackinfo.h */
diff --git a/sysdeps/x86_64/stackinfo.h b/sysdeps/x86_64/stackinfo.h
index b11849d..d4fc25f 100644
--- a/sysdeps/x86_64/stackinfo.h
+++ b/sysdeps/x86_64/stackinfo.h
@@ -1,4 +1,4 @@
-/* Copyright (C) 2001, 2009 Free Software Foundation, Inc.
+/* Copyright (C) 2001, 2009, 2010 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
@@ -22,9 +22,15 @@
#ifndef _STACKINFO_H
#define _STACKINFO_H 1
+#include <elf.h>
+
/* On x86_64 the stack grows down. */
#define _STACK_GROWS_DOWN 1
+/* Default to an executable stack. PF_X can be overridden if PT_GNU_STACK is
+ * present, but it is presumed absent. */
+#define DEFAULT_STACK_PERMS (PF_R|PF_W|PF_X)
+
/* Access to the stack pointer. The macros are used in alloca_account
for which they need to act as barriers as well, hence the additional
(unnecessary) parameters. */