mirror of https://gitee.com/openkylin/linux.git
927185c124
The kernel uses the OUTPUT_FORMAT linker script command in it's linker
scripts. Most of the time, the -m option is passed to the linker with
correct architecture, but sometimes (at least for x86_64) the -m option
contradicts the OUTPUT_FORMAT directive.
Specifically, arch/x86/boot and arch/x86/realmode/rm produce i386 object
files, but are linked with the -m elf_x86_64 linker flag when building
for x86_64.
The GNU linker manpage doesn't explicitly state any tie-breakers between
-m and OUTPUT_FORMAT. But with BFD and Gold linkers, OUTPUT_FORMAT
overrides the emulation value specified with the -m option.
LLVM lld has a different behavior, however. When supplied with
contradicting -m and OUTPUT_FORMAT values it fails with the following
error message:
ld.lld: error: arch/x86/realmode/rm/header.o is incompatible with elf_x86_64
Therefore, just add the correct -m after the incorrect one (it overrides
it), so the linker invocation looks like this:
ld -m elf_x86_64 -z max-page-size=0x200000 -m elf_i386 --emit-relocs -T \
realmode.lds header.o trampoline_64.o stack.o reboot.o -o realmode.elf
This is not a functional change for GNU ld, because (although not
explicitly documented) OUTPUT_FORMAT overrides -m EMULATION.
Tested by building x86_64 kernel with GNU gcc/ld toolchain and booting
it in QEMU.
[ bp: massage and clarify text. ]
Suggested-by: Dmitry Golovin <dima@golovin.in>
Signed-off-by: George Rimar <grimar@accesssoftek.com>
Signed-off-by: Tri Vo <trong@android.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Tested-by: Tri Vo <trong@android.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Michael Matz <matz@suse.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: morbo@google.com
Cc: ndesaulniers@google.com
Cc: ruiu@google.com
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20190111201012.71210-1-trong@android.com
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| Documentation | ||
| LICENSES | ||
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| drivers | ||
| firmware | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
README
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.