Messages in this thread | | | From | Ard Biesheuvel <> | Date | Fri, 3 Nov 2017 20:09:42 +0000 | Subject | Re: [PATCH 13/15] arm64: add a workaround for GNU gold with ARM64_MODULE_PLTS |
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On 3 November 2017 at 17:12, Sami Tolvanen <samitolvanen@google.com> wrote: > CONFIG_CLANG_LTO depends on GNU gold and due to a known bug, the > linker crashes when ARM64_MODULE_PLTS is enabled: > > https://sourceware.org/bugzilla/show_bug.cgi?id=14592 > > To work around the problem, this change: > > 1) Enables ARM64_MODULE_PLTS only when it's needed, i.e. when > RANDOMIZE_MODULE_REGION_FULL is selected, >
This is not true. Even when RANDOMIZE_MODULE_REGION_FULL is not enabled, we may need module PLTs.
When the module region is randomized, it shares its chunk of vmalloc space with other users, and so there is a [low] probability that the module region we choose is used up by vmalloc/vmap/ioremap allocations, and so we need to be able to fall back to the general vmalloc space.
> 2) and disables RANDOMIZE_MODULE_REGION_FULL with clang LTO. > > Signed-off-by: Sami Tolvanen <samitolvanen@google.com> > --- > arch/arm64/Kconfig | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > index 43ccddb7c8ec..a301fdc90319 100644 > --- a/arch/arm64/Kconfig > +++ b/arch/arm64/Kconfig > @@ -997,8 +997,8 @@ config RELOCATABLE > > config RANDOMIZE_BASE > bool "Randomize the address of the kernel image" > - select ARM64_MODULE_PLTS if MODULES > select RELOCATABLE > + select ARM64_MODULE_PLTS if RANDOMIZE_MODULE_REGION_FULL > help > Randomizes the virtual address at which the kernel image is > loaded, as a security feature that deters exploit attempts > @@ -1016,7 +1016,7 @@ config RANDOMIZE_BASE > > config RANDOMIZE_MODULE_REGION_FULL > bool "Randomize the module region independently from the core kernel" > - depends on RANDOMIZE_BASE > + depends on RANDOMIZE_BASE && !CLANG_LTO > default y > help > Randomizes the location of the module region without considering the > -- > 2.15.0.403.gc27cc4dac6-goog > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
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