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authorPaul Burton <paul.burton@imgtec.com>2017-08-07 16:16:47 -0700
committerRalf Baechle <ralf@linux-mips.org>2017-08-08 14:00:50 +0200
commit5fc9484f5e41b239d1e7a123219e53f333e43ba5 (patch)
tree3c27069586db1d0939bcd6aca5b255f101c54d5a
parent527f10285bc3f700407bf3aab0ea7b3b9f9338da (diff)
downloadlinux-bcache-5fc9484f5e41b239d1e7a123219e53f333e43ba5.tar.zst
MIPS: Set ISA bit in entry-y for microMIPS kernels
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. 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. Signed-off-by: Paul Burton <paul.burton@imgtec.com> Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/16950/ Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
-rw-r--r--arch/mips/Makefile15
1 files changed, 14 insertions, 1 deletions
diff --git a/arch/mips/Makefile b/arch/mips/Makefile
index 04343625b929..bc2708c9ada4 100644
--- a/arch/mips/Makefile
+++ b/arch/mips/Makefile
@@ -243,8 +243,21 @@ 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/