262b5cae67
The .got.plt section contains the part of the GOT which is used by PLT entries, and which gets updated lazily by the dynamic loader when function calls are dispatched through those PLT entries. On fully linked binaries such as the kernel proper or the decompressor, this never happens, and so in practice, the .got.plt section consists only of the first 3 magic entries that are meant to point at the _DYNAMIC section and at the fixup routine in the loader. However, since we don't use a dynamic loader, those entries are never populated or used. This means that treating those entries like ordinary GOT entries, and updating their values based on the actual placement of the executable in memory is completely pointless, and we can just ignore the .got.plt section entirely, provided that it has no additional entries beyond the first 3 ones. So add an assertion in the linker script to ensure that this assumption holds, and move the contents out of the [_got, _egot) memory range that is modified by the GOT fixup routines. While at it, drop the KEEP(), since it has no effect on the contents of output sections that are created by the linker itself. Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu> Signed-off-by: Kees Cook <keescook@chromium.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Tested-by: Sedat Dilek <sedat.dilek@gmail.com> Tested-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Kees Cook <keescook@chromium.org> Acked-by: Arvind Sankar <nivedita@alum.mit.edu> Link: https://lore.kernel.org/r/20200731230820.1742553-2-keescook@chromium.org
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.