linux-kernel - [PATCH AUTOSEL 5.4 103/175] MIPS: Truncate link address into 32bit for 32bit kernel

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Date:   Mon,  8 Jun 2020 19:17:36 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     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>, linux-mips@...r.kernel.org,
        clang-built-linux@...glegroups.com
Subject: [PATCH AUTOSEL 5.4 103/175] 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 cdc09b71febe..5403a91ce098 100644
--- a/arch/mips/Makefile
+++ b/arch/mips/Makefile
@@ -285,12 +285,23 @@ 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)" \
 		  ITS_INPUTS="$(its-y)"
diff --git a/arch/mips/boot/compressed/Makefile b/arch/mips/boot/compressed/Makefile
index d859f079b771..378cbfb31ee7 100644
--- a/arch/mips/boot/compressed/Makefile
+++ b/arch/mips/boot/compressed/Makefile
@@ -90,7 +90,7 @@ ifneq ($(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
 UIMAGE_LOADADDR = $(VMLINUZ_LOAD_ADDRESS)
 
diff --git a/arch/mips/kernel/vmlinux.lds.S b/arch/mips/kernel/vmlinux.lds.S
index 33ee0d18fb0a..eb9d7af93836 100644
--- a/arch/mips/kernel/vmlinux.lds.S
+++ b/arch/mips/kernel/vmlinux.lds.S
@@ -50,7 +50,7 @@ SECTIONS
 	/* . = 0xa800000000300000; */
 	. = 0xffffffff80300000;
 #endif
-	. = VMLINUX_LOAD_ADDRESS;
+	. = LINKER_LOAD_ADDRESS;
 	/* read-only */
 	_text = .;	/* Text and read-only data */
 	.text : {
-- 
2.25.1