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commit ff69279a44e9ba876466b7d3ab84d6dbd31cac92
parent af3a5fe4ddfe3d426eb025d4c3afd176efea658e
Author: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Date:   Wed, 29 Aug 2018 08:47:53 +0200

powerpc: disable support for relative ksymtab references

The newly added code that emits ksymtab entries as pairs of 32-bit
relative references interacts poorly with the way powerpc lays out its
address space: when a module exports a per-CPU variable, the primary
module region covering the ksymtab entry -and thus the 32-bit relative
reference- is too far away from the actual per-CPU variable's base
address (to which the per-CPU offsets are applied to obtain the
respective address of each CPU's copy), resulting in corruption when the
module loader attempts to resolve symbol references of modules that are
loaded on top and link to the exported per-CPU symbol.

So let's disable this feature on powerpc.  Even though it implements
CONFIG_RELOCATABLE, it does not implement CONFIG_RANDOMIZE_BASE and so
KASLR kernels (which are the main target of the feature) do not exist on
powerpc anyway.

Reported-by: Andreas Schwab <schwab@linux-m68k.org>
Suggested-by: Nicholas Piggin <nicholas.piggin@gmail.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Diffstat:
March/powerpc/Kconfig | 1-
1 file changed, 0 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig @@ -177,7 +177,6 @@ config PPC select HAVE_ARCH_KGDB select HAVE_ARCH_MMAP_RND_BITS select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT - select HAVE_ARCH_PREL32_RELOCATIONS select HAVE_ARCH_SECCOMP_FILTER select HAVE_ARCH_TRACEHOOK select HAVE_CBPF_JIT if !PPC64