linux-kernel - [RFC 11/17] x86/asm: Add task_top_of_stack() to find the top of a task's stack

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Message-Id: <f23201bd4340b0bd0dd1cbe41aa778a9c7640c66.1504733277.git.luto@kernel.org>
Date:   Wed,  6 Sep 2017 14:36:56 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     x86@...nel.org
Cc:     linux-kernel@...r.kernel.org, Borislav Petkov <bp@...en8.de>,
        Brian Gerst <brgerst@...il.com>,
        Andrew Cooper <andrew.cooper3@...rix.com>,
        Juergen Gross <jgross@...e.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Kees Cook <keescook@...omium.org>,
        Andy Lutomirski <luto@...nel.org>
Subject: [RFC 11/17] x86/asm: Add task_top_of_stack() to find the top of a task's stack

This will let us get rid of a few places that hardcode accesses to
thread.sp0.

Signed-off-by: Andy Lutomirski <luto@...nel.org>
---
 arch/x86/include/asm/processor.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 85ddfc1a9bb5..f83fbf1b6dd9 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -788,6 +788,8 @@ static inline void spin_lock_prefetch(const void *x)
 #define TOP_OF_INIT_STACK ((unsigned long)&init_stack + sizeof(init_stack) - \
 			   TOP_OF_KERNEL_STACK_PADDING)
 
+#define task_top_of_stack(task) ((unsigned long)(task_pt_regs(task) + 1))
+
 #ifdef CONFIG_X86_32
 /*
  * User space process size: 3GB (default).
-- 
2.13.5