From: Florian Fainelli <f.fainelli@gmail.com>
To: linux-arm-kernel@lists.infradead.org
Cc: bcm-kernel-feedback-list@broadcom.com, ard.biesheuvel@linaro.org,
Florian Fainelli <f.fainelli@gmail.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
linux-kernel@vger.kernel.org (open list)
Subject: [PATCH v3] arm64: Allow user selection of ARM64_MODULE_PLTS
Date: Mon, 17 Jun 2019 15:29:59 -0700 [thread overview]
Message-ID: <20190617223000.11403-1-f.fainelli@gmail.com> (raw)
Make ARM64_MODULE_PLTS a selectable Kconfig symbol, since some people
might have very big modules spilling out of the dedicated module area
into vmalloc. Help text is copied from the ARM 32-bit counterpart and
modified to a mention of KASLR and specific ARM errata workaround(s).
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
---
Changes in v3:
- take out the part about "The modules will use slightly more memory, but after
rounding up to page size, the actual memory footprint is usually the same.
- take out the "If unusure say Y", since we would really prefer this to
be off by default for maximum performance
Changes in v2:
- added Ard's paragraph about KASLR
- added a paragraph about specific workarounds also requiring
ARM64_MODULE_PLTS
arch/arm64/Kconfig | 20 +++++++++++++++++++-
1 file changed, 19 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 697ea0510729..9206feaeff07 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -1418,8 +1418,26 @@ config ARM64_SVE
KVM in the same kernel image.
config ARM64_MODULE_PLTS
- bool
+ bool "Use PLTs to allow module memory to spill over into vmalloc area"
select HAVE_MOD_ARCH_SPECIFIC
+ help
+ Allocate PLTs when loading modules so that jumps and calls whose
+ targets are too far away for their relative offsets to be encoded
+ in the instructions themselves can be bounced via veneers in the
+ module's PLT. This allows modules to be allocated in the generic
+ vmalloc area after the dedicated module memory area has been
+ exhausted.
+
+ When running with address space randomization (KASLR), the module
+ region itself may be too far away for ordinary relative jumps and
+ calls, and so in that case, module PLTs are required and cannot be
+ disabled.
+
+ Specific errata workaround(s) might also force module PLTs to be
+ enabled (ARM64_ERRATUM_843419).
+
+ Disabling this is usually safe for small single-platform
+ configurations.
config ARM64_PSEUDO_NMI
bool "Support for NMI-like interrupts"
--
2.17.1
next reply other threads:[~2019-06-17 22:30 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-17 22:29 Florian Fainelli [this message]
2019-06-18 9:29 ` [PATCH v3] arm64: Allow user selection of ARM64_MODULE_PLTS Will Deacon
2019-06-25 8:29 ` Catalin Marinas
2019-06-26 17:05 ` Florian Fainelli
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