linux-kernel - [PATCH 02/29] powerpc: Remove PT

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Date:   Thu, 26 Sep 2019 10:55:35 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Kees Cook <keescook@...omium.org>,
        Rick Edgecombe <rick.p.edgecombe@...el.com>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Arnd Bergmann <arnd@...db.de>, linux-arch@...r.kernel.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 02/29] powerpc: Remove PT_NOTE workaround

The kernel requires gcc 4.6 now, so this PT_NOTE workaround can be
removed in preparation for moving NOTES into RO_DATA.

Signed-off-by: Kees Cook <keescook@...omium.org>
---
 arch/powerpc/kernel/vmlinux.lds.S | 24 ++----------------------
 1 file changed, 2 insertions(+), 22 deletions(-)

diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S
index 81e672654789..a3c8492b2b19 100644
--- a/arch/powerpc/kernel/vmlinux.lds.S
+++ b/arch/powerpc/kernel/vmlinux.lds.S
@@ -20,20 +20,6 @@ ENTRY(_stext)
 PHDRS {
 	kernel PT_LOAD FLAGS(7); /* RWX */
 	note PT_NOTE FLAGS(0);
-	dummy PT_NOTE FLAGS(0);
-
-	/* binutils < 2.18 has a bug that makes it misbehave when taking an
-	   ELF file with all segments at load address 0 as input.  This
-	   happens when running "strip" on vmlinux, because of the AT() magic
-	   in this linker script.  People using GCC >= 4.2 won't run into
-	   this problem, because the "build-id" support will put some data
-	   into the "notes" segment (at a non-zero load address).
-
-	   To work around this, we force some data into both the "dummy"
-	   segment and the kernel segment, so the dummy segment will get a
-	   non-zero load address.  It's not enough to always create the
-	   "notes" segment, since if nothing gets assigned to it, its load
-	   address will be zero.  */
 }
 
 #ifdef CONFIG_PPC64
@@ -178,14 +164,8 @@ SECTIONS
 	EXCEPTION_TABLE(0)
 
 	NOTES :kernel :note
-
-	/* The dummy segment contents for the bug workaround mentioned above
-	   near PHDRS.  */
-	.dummy : AT(ADDR(.dummy) - LOAD_OFFSET) {
-		LONG(0)
-		LONG(0)
-		LONG(0)
-	} :kernel :dummy
+	/* Restore program header away from PT_NOTE. */
+	.dummy : { *(.dummy) } :kernel
 
 /*
  * Init sections discarded at runtime
-- 
2.17.1