@@ -1418,8 +1418,28 @@ 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. The modules will use slightly more memory, but after
+ rounding up to page size, the actual memory footprint is usually
+ the same.
+
+ 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. If unsure, say y.
config ARM64_PSEUDO_NMI
bool "Support for NMI-like interrupts"
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 v2: - added Ard's paragraph about KASLR - added a paragraph about specific workarounds also requiring ARM64_MODULE_PLTS arch/arm64/Kconfig | 22 +++++++++++++++++++++- 1 file changed, 21 insertions(+), 1 deletion(-)