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powerpc64 gcc can generate code that offsets an address, to access part of an object in memory. If the address is a -mcmodel=medium toc pointer relative address then code like the following is possible. addis r9,r2,var@toc@ha ld r3,var@toc@l(r9) ld r4,(var+8)@toc@l(r9) This works fine so long as var is naturally aligned, *and* r2 is sufficiently aligned. If not, there is a possibility that the offset added to access var+8 wraps over a n*64k+32k boundary. Modules don't have any guarantee that r2 is sufficiently aligned. Moreover, code generated by older compilers generates a .toc section with 2**0 alignment, which can result in relocation failures at module load time even without the wrap problem. Thus, this patch links modules with an aligned .toc section (Makefile and module.lds changes), and forces alignment for out of tree modules or those without a .toc section (module_64.c changes). Signed-off-by: Alan Modra <amodra@gmail.com> [desnesn: updated patch to apply to powerpc-next kernel v4.15 ] Signed-off-by: Desnes A. Nunes do Rosario <desnesn@linux.vnet.ibm.com> [mpe: Fix out-of-tree build, swap -256 for ~0xff, reflow comment] Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.