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| author | Alan Modra <amodra@gmail.com> | 2017-12-06 17:12:28 -0200 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2017-12-11 13:03:35 +1100 |
| commit | 5c45b5280196a92c4437f5648209c5bd3f08e882 (patch) | |
| tree | 25ec5996a48e85c68e64440d99723c8bd6f7e9a4 /arch/powerpc/Makefile | |
| parent | acb1feab320e38588fccc568e3767761f494976f (diff) | |
| download | lwn-5c45b5280196a92c4437f5648209c5bd3f08e882.tar.gz lwn-5c45b5280196a92c4437f5648209c5bd3f08e882.zip | |
powerpc/modules: Fix alignment of .toc section in kernel modules
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>
Diffstat (limited to 'arch/powerpc/Makefile')
| -rw-r--r-- | arch/powerpc/Makefile | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile index 1381693a4a51..ccd2556bdb53 100644 --- a/arch/powerpc/Makefile +++ b/arch/powerpc/Makefile @@ -63,6 +63,7 @@ UTS_MACHINE := $(subst $(space),,$(machine-y)) ifdef CONFIG_PPC32 KBUILD_LDFLAGS_MODULE += arch/powerpc/lib/crtsavres.o else +KBUILD_LDFLAGS_MODULE += -T $(srctree)/arch/powerpc/kernel/module.lds ifeq ($(call ld-ifversion, -ge, 225000000, y),y) # Have the linker provide sfpr if possible. # There is a corresponding test in arch/powerpc/lib/Makefile |