linux-kernel - [PATCH 4.9 079/128] MIPS: Truncate link address into 32bit for 32bit kernel

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Message-Id: <20200619141624.346641028@linuxfoundation.org>
Date:   Fri, 19 Jun 2020 16:32:53 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Jiaxun Yang <jiaxun.yang@...goat.com>,
        Fangrui Song <maskray@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Nathan Chancellor <natechancellor@...il.com>,
        "Maciej W. Rozycki" <macro@...ux-mips.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.9 079/128] MIPS: Truncate link address into 32bit for 32bit kernel

From: Jiaxun Yang <jiaxun.yang@...goat.com>

[ Upstream commit ff487d41036035376e47972c7c522490b839ab37 ]

LLD failed to link vmlinux with 64bit load address for 32bit ELF
while bfd will strip 64bit address into 32bit silently.
To fix LLD build, we should truncate load address provided by platform
into 32bit for 32bit kernel.

Signed-off-by: Jiaxun Yang <jiaxun.yang@...goat.com>
Link: https://github.com/ClangBuiltLinux/linux/issues/786
Link: https://sourceware.org/bugzilla/show_bug.cgi?id=25784
Reviewed-by: Fangrui Song <maskray@...gle.com>
Reviewed-by: Kees Cook <keescook@...omium.org>
Tested-by: Nathan Chancellor <natechancellor@...il.com>
Cc: Maciej W. Rozycki <macro@...ux-mips.org>
Tested-by: Nick Desaulniers <ndesaulniers@...gle.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/mips/Makefile                 | 13 ++++++++++++-
 arch/mips/boot/compressed/Makefile |  2 +-
 arch/mips/kernel/vmlinux.lds.S     |  2 +-
 3 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/arch/mips/Makefile b/arch/mips/Makefile
index 1a6bac7b076f..25f3bfef9b39 100644
--- a/arch/mips/Makefile
+++ b/arch/mips/Makefile
@@ -256,12 +256,23 @@ ifdef CONFIG_64BIT
   endif
 endif
 
+# When linking a 32-bit executable the LLVM linker cannot cope with a
+# 32-bit load address that has been sign-extended to 64 bits.  Simply
+# remove the upper 32 bits then, as it is safe to do so with other
+# linkers.
+ifdef CONFIG_64BIT
+	load-ld			= $(load-y)
+else
+	load-ld			= $(subst 0xffffffff,0x,$(load-y))
+endif
+
 KBUILD_AFLAGS	+= $(cflags-y)
 KBUILD_CFLAGS	+= $(cflags-y)
-KBUILD_CPPFLAGS += -DVMLINUX_LOAD_ADDRESS=$(load-y)
+KBUILD_CPPFLAGS += -DVMLINUX_LOAD_ADDRESS=$(load-y) -DLINKER_LOAD_ADDRESS=$(load-ld)
 KBUILD_CPPFLAGS += -DDATAOFFSET=$(if $(dataoffset-y),$(dataoffset-y),0)
 
 bootvars-y	= VMLINUX_LOAD_ADDRESS=$(load-y) \
+		  LINKER_LOAD_ADDRESS=$(load-ld) \
 		  VMLINUX_ENTRY_ADDRESS=$(entry-y) \
 		  PLATFORM="$(platform-y)"
 ifdef CONFIG_32BIT
diff --git a/arch/mips/boot/compressed/Makefile b/arch/mips/boot/compressed/Makefile
index 2f77e250b91d..0fa91c981658 100644
--- a/arch/mips/boot/compressed/Makefile
+++ b/arch/mips/boot/compressed/Makefile
@@ -87,7 +87,7 @@ ifneq ($(zload-y),)
 VMLINUZ_LOAD_ADDRESS := $(zload-y)
 else
 VMLINUZ_LOAD_ADDRESS = $(shell $(obj)/calc_vmlinuz_load_addr \
-		$(obj)/vmlinux.bin $(VMLINUX_LOAD_ADDRESS))
+		$(obj)/vmlinux.bin $(LINKER_LOAD_ADDRESS))
 endif
 
 vmlinuzobjs-y += $(obj)/piggy.o
diff --git a/arch/mips/kernel/vmlinux.lds.S b/arch/mips/kernel/vmlinux.lds.S
index 2d965d91fee4..612b2b301280 100644
--- a/arch/mips/kernel/vmlinux.lds.S
+++ b/arch/mips/kernel/vmlinux.lds.S
@@ -49,7 +49,7 @@ SECTIONS
 	/* . = 0xa800000000300000; */
 	. = 0xffffffff80300000;
 #endif
-	. = VMLINUX_LOAD_ADDRESS;
+	. = LINKER_LOAD_ADDRESS;
 	/* read-only */
 	_text = .;	/* Text and read-only data */
 	.text : {
-- 
2.25.1