linux-kernel - [PATCH 2/2] x86/mm/kaiser: Don't map the IRQ stack in user space

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Message-Id: <17ffd1c6e87772d110f96f8ff6c8e74f681258c8.1511842148.git.jpoimboe@redhat.com>
Date:   Mon, 27 Nov 2017 22:10:13 -0600
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>,
        Brian Gerst <brgerst@...il.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Rik van Riel <riel@...hat.com>, daniel.gruss@...k.tugraz.at,
        hughd@...gle.com, keescook@...gle.com, linux-mm@...ck.org,
        michael.schwarz@...k.tugraz.at, moritz.lipp@...k.tugraz.at,
        richard.fellner@...dent.tugraz.at
Subject: [PATCH 2/2] x86/mm/kaiser: Don't map the IRQ stack in user space

The '.data..percpu..first' section, which contains the IRQ software
stack, is included in the percpu user-mapped data area.

The IRQ stack is a software stack which is switched to *after* the CR3
switch, so it doesn't make sense to map it in user space.

Unmap it, and make sure the user-mapped area is page-aligned so it can
be mapped cleanly.

Fixes: 7d1b4c99a605 ("x86/mm/kaiser: Introduce user-mapped per-CPU areas")
Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
---
 include/asm-generic/vmlinux.lds.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 386f8846d9e9..45d2fbb081c6 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -826,9 +826,9 @@
  */
 #define PERCPU_INPUT(cacheline)						\
 	VMLINUX_SYMBOL(__per_cpu_start) = .;				\
-	VMLINUX_SYMBOL(__per_cpu_user_mapped_start) = .;		\
 	*(.data..percpu..first)						\
-	. = ALIGN(cacheline);						\
+	. = ALIGN(PAGE_SIZE);						\
+	VMLINUX_SYMBOL(__per_cpu_user_mapped_start) = .;		\
 	*(.data..percpu..user_mapped)					\
 	*(.data..percpu..user_mapped..shared_aligned)			\
 	VMLINUX_SYMBOL(__per_cpu_user_mapped_end) = .;			\
-- 
2.13.6