linux-kernel - [PATCH 4/4] vmlinux.lds.h: Have ORC lookup cover entire _etext

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Date:   Wed, 13 Oct 2021 10:57:42 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Borislav Petkov <bp@...e.de>
Cc:     Kees Cook <keescook@...omium.org>,
        Kristen Carlson Accardi <kristen@...ux.intel.com>,
        Tony Luck <tony.luck@...el.com>,
        Alexander Lobakin <alexandr.lobakin@...el.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Arnd Bergmann <arnd@...db.de>, Joerg Roedel <jroedel@...e.de>,
        Arvind Sankar <nivedita@...m.mit.edu>,
        Jing Yangyang <jing.yangyang@....com.cn>,
        Abaci Robot <abaci@...ux.alibaba.com>,
        Jiapeng Chong <jiapeng.chong@...ux.alibaba.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Andrey Konovalov <andreyknvl@...il.com>,
        Miroslav Benes <mbenes@...e.cz>,
        "H. Nikolaus Schaller" <hns@...delico.com>,
        Fangrui Song <maskray@...gle.com>,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        linux-arch@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: [PATCH 4/4] vmlinux.lds.h: Have ORC lookup cover entire _etext - _stext

From: Kristen Carlson Accardi <kristen@...ux.intel.com>

When using -ffunction-sections to place each function in its own text
section (so it can be randomized at load time in the future FGKASLR
series), the linker will place most of the functions into separate .text.*
sections. SIZEOF(.text) won't work here for calculating the ORC lookup
table size, so the total text size must be calculated to include .text
AND all .text.* sections.

Signed-off-by: Kristen Carlson Accardi <kristen@...ux.intel.com>
Reviewed-by: Tony Luck <tony.luck@...el.com>
Tested-by: Tony Luck <tony.luck@...el.com>
Reviewed-by: Kees Cook <keescook@...omium.org>
[ alobakin: move it to vmlinux.lds.h and make arch-indep ]
Signed-off-by: Alexander Lobakin <alexandr.lobakin@...el.com>
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 include/asm-generic/vmlinux.lds.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index f2984af2b85b..e8234911dc18 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -869,10 +869,11 @@
 		KEEP(*(.orc_unwind))					\
 		__stop_orc_unwind = .;					\
 	}								\
+	text_size = _etext - _stext;					\
 	. = ALIGN(4);							\
 	.orc_lookup : AT(ADDR(.orc_lookup) - LOAD_OFFSET) {		\
 		orc_lookup = .;						\
-		. += (((SIZEOF(.text) + LOOKUP_BLOCK_SIZE - 1) /	\
+		. += (((text_size + LOOKUP_BLOCK_SIZE - 1) /		\
 			LOOKUP_BLOCK_SIZE) + 1) * 4;			\
 		orc_lookup_end = .;					\
 	}
-- 
2.30.2