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From:   Christophe Leroy <christophe.leroy@csgroup.eu>
To:     Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Andrew Morton <akpm@linux-foundation.org>,
        "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>,
        Helge Deller <deller@gmx.de>, Arnd Bergmann <arnd@arndb.de>,
        Kees Cook <keescook@chromium.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc:     Christophe Leroy <christophe.leroy@csgroup.eu>,
        linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
        linux-ia64@vger.kernel.org, linux-parisc@vger.kernel.org,
        linux-arch@vger.kernel.org, linux-mm@kvack.org
Subject: [PATCH v4 10/13] lkdtm: Force do_nothing() out of line
Date:   Tue, 15 Feb 2022 13:41:05 +0100
Message-Id: <a5dcf4d2088e6aca47ab3b4c6d5c0f7fa064e25a.1644928018.git.christophe.leroy@csgroup.eu>
In-Reply-To: <cover.1644928018.git.christophe.leroy@csgroup.eu>
References: <cover.1644928018.git.christophe.leroy@csgroup.eu>
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LKDTM tests display that the run do_nothing() at a given
address, but in reality do_nothing() is inlined into the
caller.

Force it out of line so that it really runs text at the
displayed address.

Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 drivers/misc/lkdtm/perms.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
index 2dede2ef658f..60b3b2fe929d 100644
--- a/drivers/misc/lkdtm/perms.c
+++ b/drivers/misc/lkdtm/perms.c
@@ -21,7 +21,7 @@
 /* This is non-const, so it will end up in the .data section. */
 static u8 data_area[EXEC_SIZE];
 
-/* This is cost, so it will end up in the .rodata section. */
+/* This is const, so it will end up in the .rodata section. */
 static const unsigned long rodata = 0xAA55AA55;
 
 /* This is marked __ro_after_init, so it should ultimately be .rodata. */
@@ -31,7 +31,7 @@ static unsigned long ro_after_init __ro_after_init = 0x55AA5500;
  * This just returns to the caller. It is designed to be copied into
  * non-executable memory regions.
  */
-static void do_nothing(void)
+static noinline void do_nothing(void)
 {
 	return;
 }
-- 
2.34.1