On Mon, Aug 21, 2017 at 09:20:38PM +0100, Maciej W. Rozycki wrote:
> 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@xxxxxxxxxx>
> ---
> Ralf,
>
> As you requested, here's v2 rebased as a replacement for 5fc9484f5e41,
> with the heading reused.
>
> Please apply.
>
> Maciej
>
> ---
> arch/mips/Makefile | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> linux-mips-start-address.diff
> Index: linux-sfr-usead/arch/mips/Makefile
> ===================================================================
> --- linux-sfr-usead.orig/arch/mips/Makefile 2017-08-21 20:48:38.000000000 +0100
> +++ linux-sfr-usead/arch/mips/Makefile 2017-08-21 17:47:16.802753000 +0100
> @@ -243,8 +243,12 @@ include arch/mips/Kbuild.platforms
> ifdef CONFIG_PHYSICAL_START
> load-y = $(CONFIG_PHYSICAL_START)
> endif
> -entry-y = 0x$(shell $(NM) vmlinux 2>/dev/null \
> - | grep "\bkernel_entry\b" | cut -f1 -d \ )
> +
> +# 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/^.*0x\([0-7].......\)$$/0x00000000\1/; \
> + s/^.*0x\(........\)$$/0xffffffff\1/; p }')
This leaves the "start address " on the beginning if the address is
already 64 bits wide, e.g.:
VMLINUX_LOAD_ADDRESS=0xffffffff80100000 VMLINUX_ENTRY_ADDRESS=start address 0xffffffff80832720 ...
The following seems to work, to drop the "start address " first then
work purely on the hex value (i.e. no need for .* at the front of the
sign extension regexes any more):
+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 }')
Look reasonable? Is there a cleaner way?
Cheers
James
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