In order to fetch the correct entry point with the ISA bit included, for
use by non-ELF boot loaders, parse the output of `objdump -f' for the
start address recorded in the kernel executable itself, rather than
using `nm' to get the value of the `kernel_entry' symbol.
Sign-extend the address retrieved if 32-bit, so that execution is
correctly started on 64-bit processors as well. The tool always prints
the entry point using either 8 or 16 hexadecimal digits, matching the
address width (aka class) of the ELF file, even in the presence of
leading zeros.
Signed-off-by: Maciej W. Rozycki <macro@xxxxxxxx>
---
Changes in v3:
- renamed from "MIPS: Set ISA bit in entry-y for microMIPS kernels", to
avoid confusion with commit 5fc9484f5e41,
- fixed the `sed' program to correctly pass through 64-bit values.
Changes in v2:
- rebased.
We still handle the load address wrong in the presence of the
CONFIG_PHYSICAL_START option, e.g.:
make -f ./scripts/Makefile.build obj=arch/mips/boot VMLINUX=vmlinux \
VMLINUX_LOAD_ADDRESS=0x84000000 VMLINUX_ENTRY_ADDRESS=0xffffffff8463c870 PLATFORM="mti-malta/" ITS_INPUTS="vmlinux.its.S" ADDR_BITS=32 arch/mips/boot/vmlinux.srec
which again will be an issue with a 32-bit image and a 64-bit processor.
But that's a matter for a separate fix.
Maciej
---
arch/mips/Makefile | 20 ++++++--------------
1 file changed, 6 insertions(+), 14 deletions(-)
linux-mips-start-address.diff
Index: linux-jhogan-test/arch/mips/Makefile
===================================================================
--- linux-jhogan-test.orig/arch/mips/Makefile 2018-03-21 17:22:12.000000000 +0000
+++ linux-jhogan-test/arch/mips/Makefile 2018-03-21 17:29:53.524879000 +0000
@@ -249,20 +249,12 @@ ifdef CONFIG_PHYSICAL_START
load-y = $(CONFIG_PHYSICAL_START)
endif
-entry-noisa-y = 0x$(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
+# Sign-extend the entry point to 64 bits if retrieved as a 32-bit number.
+entry-y = $(shell $(OBJDUMP) -f vmlinux 2>/dev/null \
+ | sed -n '/^start address / { \
+ s/^.* //; \
+ s/0x\([0-7].......\)$$/0x00000000\1/; \
+ s/0x\(........\)$$/0xffffffff\1/; p }')
cflags-y += -I$(srctree)/arch/mips/include/asm/mach-generic
drivers-$(CONFIG_PCI) += arch/mips/pci/
