linux-kernel - [PATCH v2 07/29] x86: Restore "text" Program Header with dummy section

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Message-Id: <20191011000609.29728-8-keescook@chromium.org>
Date:   Thu, 10 Oct 2019 17:05:47 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Kees Cook <keescook@...omium.org>,
        Rick Edgecombe <rick.p.edgecombe@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Michael Ellerman <mpe@...erman.id.au>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Will Deacon <will@...nel.org>, linux-arch@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linuxppc-dev@...ts.ozlabs.org, linux-alpha@...r.kernel.org,
        linux-ia64@...r.kernel.org, linux-s390@...r.kernel.org,
        linux-c6x-dev@...ux-c6x.org,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Michal Simek <monstr@...str.eu>, linux-parisc@...r.kernel.org,
        linux-xtensa@...ux-xtensa.org, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 07/29] x86: Restore "text" Program Header with dummy section

In a linker script, if once places a section in one or more segments using
":PHDR", then the linker will place all subsequent allocatable sections,
which do not specify ":PHDR", into the same segments. In order to have
the NOTES section in both PT_LOAD (":text") and PT_NOTE (":note"), both
segments are marked, and the only way to to undo this to keep subsequent
sections out of PT_NOTE is to mark the following section with just the
single desired PT_LOAD (":text").

In preparation for having a common NOTES macro, perform the segment
assignment use a dummy section (as done by other architectures).

Signed-off-by: Kees Cook <keescook@...omium.org>
---
 arch/x86/kernel/vmlinux.lds.S | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index e2feacf921a0..788e78978030 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -147,8 +147,9 @@ SECTIONS
 	} :text = 0x9090
 
 	NOTES :text :note
+	.dummy : { *(.dummy) } :text
 
-	EXCEPTION_TABLE(16) :text = 0x9090
+	EXCEPTION_TABLE(16)
 
 	/* .text should occupy whole number of pages */
 	. = ALIGN(PAGE_SIZE);
-- 
2.17.1