When building a kernel for the microMIPS ISA, ensure that the ISA bit (ie. bit 0) in the entry address is set. Otherwise we may include an entry address in images which bootloaders will jump to as MIPS32 code. Signed-off-by: Paul Burton <paul.burton@xxxxxxxxxx> Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx> Cc: linux-mips@xxxxxxxxxxxxxx --- I originally tried using "objdump -f" to obtain the entry address, which works for microMIPS but it always outputs a 32 bit address for a 32 bit ELF whilst nm will sign extend to 64 bit. That matters for systems where we might want to run a MIPS32 kernel on a MIPS64 CPU & load it with a MIPS64 bootloader, which would then jump to a non-canonical (non-sign-extended) address. This works in all cases as it only changes the behaviour for microMIPS kernels, but isn't the prettiest solution. A possible alternative would be to write a custom tool to just extract, sign extend & print the entry point of an ELF executable. I'm open to feedback if that would be preferred. --- arch/mips/Makefile | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/arch/mips/Makefile b/arch/mips/Makefile index 876394554274..d78d615cd395 100644 --- a/arch/mips/Makefile +++ b/arch/mips/Makefile @@ -242,8 +242,21 @@ include arch/mips/Kbuild.platforms ifdef CONFIG_PHYSICAL_START load-y = $(CONFIG_PHYSICAL_START) endif -entry-y = 0x$(shell $(NM) vmlinux 2>/dev/null \ + +entry-noisa-y = 0x$(shell $(NM) vmlinux 2>/dev/null \ | grep "\bkernel_entry\b" | cut -f1 -d \ ) +ifdef CONFIG_CPU_MICROMIPS + # + # Set the ISA bit, since the kernel_entry symbol in the ELF will have it + # clear which would lead to images containing addresses which bootloaders may + # jump to as MIPS32 code. + # + entry-y = $(patsubst %0,%1,$(patsubst %2,%3,$(patsubst %4,%5, \ + $(patsubst %6,%7,$(patsubst %8,%9,$(patsubst %a,%b, \ + $(patsubst %c,%d,$(patsubst %e,%f,$(entry-noisa-y))))))))) +else + entry-y = $(entry-noisa-y) +endif cflags-y += -I$(srctree)/arch/mips/include/asm/mach-generic drivers-$(CONFIG_PCI) += arch/mips/pci/ -- 2.14.0
