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korg/linux

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MIPS: Use a custom elf-entry program to find kernel entry point For a long time arch/mips/Makefile used nm to discover the kernel entry point by looking for the address of the kernel_entry symbol. This doesn't work for systems which make use of bit 0 of the PC to reflect the ISA mode - ie. microMIPS (and MIPS16, but we don't support building kernels that target MIPS16 anyway). So for a while with commit 5fc9484f5e41 ("MIPS: Set ISA bit in entry-y for microMIPS kernels") we manually modified the last nibble of the output from nm, which worked but wasn't particularly pretty. Commit 27c524d17430 ("MIPS: Use the entry point from the ELF file header") then cleaned this up by using objdump to print the ELF entry point which includes the ISA bit, rather than using nm to print the address of the kernel_entry symbol which doesn't. That removed the ugly replacement of the last nibble, but added its own ugliness by needing to manually sign extend in the 32 bit case. Unfortunately it has been pointed out that objdump's output is localised, and therefore grepping for its "start address" output doesn't work when the user's language settings are such that objdump doesn't print in English. We could simply revert commit 27c524d17430 ("MIPS: Use the entry point from the ELF file header") and return to the manual replacement of the last nibble of entry-y, but it seems that was found sufficiently unpalatable to avoid. We could attempt to force the language used by objdump by setting an environment variable such as LC_ALL, but that seems fragile. Instead we add a small tool named elf-entry which simply prints out the entry point of the kernel in the format we require. Signed-off-by: Paul Burton <paul.burton@mips.com> Reported-by: Philippe Reynes <philippe.reynes@softathome.com> Tested-by: Philippe Reynes <philippe.reynes@softathome.com> Fixes: 27c524d17430 ("MIPS: Use the entry point from the ELF file header") Patchwork: https://patchwork.linux-mips.org/patch/20322/ Cc: James Hogan <jhogan@kernel.org> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: linux-mips@linux-mips.org

2018-08-30 02:01:30 +08:00

elf-entry