From: Ard Biesheuvel ardb@kernel.org
commit c4e792d1acce31c2eb7b9193ab06ab94de05bf42 upstream.
The LLVM ld.lld linker uses a different symbol type for __bss_start, resulting in the calculation of KBSS_SZ to be thrown off. Up until now, this has gone unnoticed as it only affects the appended DTB case, but pending changes for ARM in the way the decompressed kernel is cleaned from the caches has uncovered this problem.
On a ld.lld build:
$ nm vmlinux |grep bss_ c1c22034 D __bss_start c1c86e98 B __bss_stop
resulting in
$ readelf -s arch/arm/boot/compressed/vmlinux | grep bss_size 433: c1c86e98 0 NOTYPE GLOBAL DEFAULT ABS _kernel_bss_size
which is obviously incorrect, and may cause the cache clean to access unmapped memory, or cause the size calculation to wrap, resulting in no cache clean to be performed at all.
Fix this by updating the sed regex to take D type symbols into account.
Link: https://lore.kernel.org/linux-arm-kernel/6c65bcef-d4e7-25fa-43cf-2c435bb61bb... Link: https://lore.kernel.org/linux-arm-kernel/20210205085220.31232-1-ardb@kernel....
Cc: stable@vger.kernel.org # v4.19+ Reviewed-by: Nick Desaulniers ndesaulniers@google.com Tested-by: Nick Desaulniers ndesaulniers@google.com Reported-by: Guillaume Tucker guillaume.tucker@collabora.com Reported-by: "kernelci.org bot" bot@kernelci.org Signed-off-by: Ard Biesheuvel ardb@kernel.org Signed-off-by: Russell King rmk+kernel@armlinux.org.uk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/arm/boot/compressed/Makefile | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/arch/arm/boot/compressed/Makefile +++ b/arch/arm/boot/compressed/Makefile @@ -115,8 +115,8 @@ asflags-y := -DZIMAGE
# Supply kernel BSS size to the decompressor via a linker symbol. KBSS_SZ = $(shell echo $$(($$($(NM) $(obj)/../../../../vmlinux | \ - sed -n -e 's/^([^ ]*) [AB] __bss_start$$/-0x\1/p' \ - -e 's/^([^ ]*) [AB] __bss_stop$$/+0x\1/p') )) ) + sed -n -e 's/^([^ ]*) [ABD] __bss_start$$/-0x\1/p' \ + -e 's/^([^ ]*) [ABD] __bss_stop$$/+0x\1/p') )) ) LDFLAGS_vmlinux = --defsym _kernel_bss_size=$(KBSS_SZ) # Supply ZRELADDR to the decompressor via a linker symbol. ifneq ($(CONFIG_AUTO_ZRELADDR),y)