linux-kernel - [RFC PATCH 1/8] thread_info: include <current.h> for THREAD_INFO_IN

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Date:   Thu, 15 Sep 2016 14:49:02 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     akpm@...ux-foundation.org, ard.biesheuvel@...aro.org,
        catalin.marinas@....com, james.morse@....com,
        keescook@...omium.org, linux-kernel@...r.kernel.org,
        lorenzo.pieralisi@....com, luto@...nel.org, mark.rutland@....com,
        suzuki.poulose@....com, takahiro.akashi@...aro.org,
        will.deacon@....com, kernel-hardening@...ts.openwall.com
Subject: [RFC PATCH 1/8] thread_info: include <current.h> for THREAD_INFO_IN_TASK

When CONFIG_THREAD_INFO_IN_TASK is selected, the current_thread_info()
macro relies on current having been defined prior to its use. However,
not all users of current_thread_info() include <asm/current.h>, and thus
current is not guaranteed to be defined.

When CONFIG_THREAD_INFO_IN_TASK is not selected, it's possible that
get_current() / current are based upon current_thread_info(), and
<asm/current.h> includes <asm/thread_info.h>. Thus always including
<asm/current.h> would result in circular dependences on some platforms.

To ensure both cases work, this patch includes <asm/current.h>, but only
when CONFIG_THREAD_INFO_IN_TASK is selected.

Signed-off-by: Mark Rutland <mark.rutland@....com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Kees Cook <keescook@...omium.org>
Cc: Will Deacon <will.deacon@....com>
Cc: linux-kernel@...r.kernel.org
---
 include/linux/thread_info.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h
index cb0ed34..d9622f7 100644
--- a/include/linux/thread_info.h
+++ b/include/linux/thread_info.h
@@ -25,6 +25,7 @@ struct thread_info {
 #endif

 #ifdef CONFIG_THREAD_INFO_IN_TASK
+#include <asm/current.h>
 #define current_thread_info() ((struct thread_info *)current)
 #endif

-- 
1.9.1