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Date: Mon, 26 Mar 2018 14:03:21 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Kees Cook <keescook@...omium.org>
Cc: kernel-hardening@...ts.openwall.com,
Linus Torvalds <torvalds@...ux-foundation.org>,
linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH 1/4] task_struct: Allow randomized layout
On Mon, Mar 26, 2018 at 01:52:46PM +0200, Peter Zijlstra wrote:
> That now looks like:
>
> struct task_struct {
> struct thread_info thread_info; /* 0 16 */
> volatile long int state; /* 16 8 */
>
> /* XXX 40 bytes hole, try to pack */
>
> /* --- cacheline 1 boundary (64 bytes) --- */
> struct {
> void * stack; /* 64 8 */
> atomic_t usage; /* 72 4 */
> unsigned int flags; /* 76 4 */
> unsigned int ptrace; /* 80 4 */
> struct llist_node wake_entry; /* 88 8 */
>
>
> Can we please undo this crap?
The below gets rid of that nonsense.
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index e2c7f4369eff..767cf74d61f7 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -242,6 +242,15 @@
#if defined(RANDSTRUCT_PLUGIN) && !defined(__CHECKER__)
#define __randomize_layout __attribute__((randomize_layout))
#define __no_randomize_layout __attribute__((no_randomize_layout))
+/*
+ * RANDSTRUCT_PLUGIN wants to use an anonymous struct, but it is only
+ * possible since GCC 4.6. To provide as much build testing coverage
+ * as possible, this is used for all GCC 4.6+ builds, and not just on
+ * RANDSTRUCT_PLUGIN builds.
+ */
+#define randomized_struct_fields_start struct {
+#define randomized_struct_fields_end } __randomize_layout;
+
#endif
#endif /* GCC_VERSION >= 40500 */
@@ -256,15 +265,6 @@
*/
#define __visible __attribute__((externally_visible))
-/*
- * RANDSTRUCT_PLUGIN wants to use an anonymous struct, but it is only
- * possible since GCC 4.6. To provide as much build testing coverage
- * as possible, this is used for all GCC 4.6+ builds, and not just on
- * RANDSTRUCT_PLUGIN builds.
- */
-#define randomized_struct_fields_start struct {
-#define randomized_struct_fields_end } __randomize_layout;
-
#endif /* GCC_VERSION >= 40600 */
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