From 4274636cbe4cb33165fa57601de0cc75bb5b41d3 Mon Sep 17 00:00:00 2001
From: Sami Tolvanen <samitolvanen@google.com>
Date: Tue, 31 Mar 2020 14:32:27 -0700
Subject: [PATCH] ANDROID: kbuild: ensure __cfi_check is correctly aligned

On modules with no executable code, LLVM generates a __cfi_check stub,
but won't align it to page size as expected. This change ensures the
function is at the beginning of the .text section and correctly aligned
for the CFI shadow.

Bug: 148458318
Change-Id: I85ea31fa851bc23988f649b021b3ac7e9d9dcb38
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
---
 Makefile                                     |  2 +-
 scripts/Makefile                             |  2 ++
 scripts/{module-lto.lds => module-lto.lds.S} | 14 +++++++++++++-
 3 files changed, 16 insertions(+), 2 deletions(-)
 rename scripts/{module-lto.lds => module-lto.lds.S} (68%)

diff --git a/Makefile b/Makefile
index a35b848a075f..48aa90c5e6b7 100644
--- a/Makefile
+++ b/Makefile
@@ -880,7 +880,7 @@ LD_FLAGS_LTO_CLANG := -mllvm -import-instr-limit=5
 KBUILD_LDFLAGS += $(LD_FLAGS_LTO_CLANG)
 KBUILD_LDFLAGS_MODULE += $(LD_FLAGS_LTO_CLANG)
 
-KBUILD_LDS_MODULE += $(srctree)/scripts/module-lto.lds
+KBUILD_LDS_MODULE += scripts/module-lto.lds
 endif
 
 ifdef CONFIG_LTO
diff --git a/scripts/Makefile b/scripts/Makefile
index 3e86b300f5a1..543603e3a789 100644
--- a/scripts/Makefile
+++ b/scripts/Makefile
@@ -31,6 +31,8 @@ always		:= $(hostprogs-y) $(hostprogs-m)
 # The following hostprogs-y programs are only build on demand
 hostprogs-y += unifdef
 
+extra-$(CONFIG_LTO_CLANG)   += module-lto.lds
+
 subdir-$(CONFIG_GCC_PLUGINS) += gcc-plugins
 subdir-$(CONFIG_MODVERSIONS) += genksyms
 subdir-$(CONFIG_SECURITY_SELINUX) += selinux
diff --git a/scripts/module-lto.lds b/scripts/module-lto.lds.S
similarity index 68%
rename from scripts/module-lto.lds
rename to scripts/module-lto.lds.S
index 5ba0e9461e13..c0f4fdeb84a0 100644
--- a/scripts/module-lto.lds
+++ b/scripts/module-lto.lds.S
@@ -1,3 +1,6 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#include <asm/page.h>
+
 /*
  * With CONFIG_LTO_CLANG, LLD always enables -fdata-sections and
  * -ffunction-sections, which increases the size of the final module.
@@ -18,5 +21,14 @@ SECTIONS {
 	.rela.rodata : { *(.rela.rodata .rela.rodata.[0-9a-zA-Z_]*) }
 	.rela.text : { *(.rela.text .rela.text.[0-9a-zA-Z_]*) }
 	.rodata : { *(.rodata .rodata.[0-9a-zA-Z_]*) }
-	.text : { *(.text .text.[0-9a-zA-Z_]*) }
+
+	/*
+	 * With CFI_CLANG, ensure __cfi_check is at the beginning of the
+	 * .text section, and that the section is aligned to page size.
+	 */
+	.text : ALIGN(PAGE_SIZE) {
+		*(.text.__cfi_check)
+		*(.text .text.[0-9a-zA-Z_]* .text..L.cfi*)
+	}
+
 }