From ea3752ba9685b47db4571ddaee39344cf2b0bf45 Mon Sep 17 00:00:00 2001 From: Mark Rutland Date: Tue, 30 May 2023 12:03:27 +0100 Subject: arm64: module: mandate MODULE_PLTS Contemporary kernels and modules can be relatively large, especially when common debug options are enabled. Using GCC 12.1.0, a v6.3-rc7 defconfig kernel is ~38M, and with PROVE_LOCKING + KASAN_INLINE enabled this expands to ~117M. Shanker reports [1] that the NVIDIA GPU driver alone can consume 110M of module space in some configurations. Both KASLR and ARM64_ERRATUM_843419 select MODULE_PLTS, so anyone wanting a kernel to have KASLR or run on Cortex-A53 will have MODULE_PLTS selected. This is the case in defconfig and distribution kernels (e.g. Debian, Android, etc). Practically speaking, this means we're very likely to need MODULE_PLTS and while it's almost guaranteed that MODULE_PLTS will be selected, it is possible to disable support, and we have to maintain some awkward special cases for such unusual configurations. This patch removes the MODULE_PLTS config option, with the support code always enabled if MODULES is selected. This results in a slight simplification, and will allow for further improvement in subsequent patches. For any config which currently selects MODULE_PLTS, there will be no functional change as a result of this patch. [1] https://lore.kernel.org/linux-arm-kernel/159ceeab-09af-3174-5058-445bc8dcf85b@nvidia.com/ Signed-off-by: Mark Rutland Reviewed-by: Ard Biesheuvel Cc: Shanker Donthineni Cc: Will Deacon Tested-by: Shanker Donthineni Link: https://lore.kernel.org/r/20230530110328.2213762-6-mark.rutland@arm.com Signed-off-by: Catalin Marinas --- arch/arm64/Kconfig | 28 +++------------------------- 1 file changed, 3 insertions(+), 25 deletions(-) (limited to 'arch/arm64/Kconfig') diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index b1201d25a8a4..a6002084f09c 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -207,6 +207,7 @@ config ARM64 select HAVE_IOREMAP_PROT select HAVE_IRQ_TIME_ACCOUNTING select HAVE_KVM + select HAVE_MOD_ARCH_SPECIFIC select HAVE_NMI select HAVE_PERF_EVENTS select HAVE_PERF_REGS @@ -577,7 +578,6 @@ config ARM64_ERRATUM_845719 config ARM64_ERRATUM_843419 bool "Cortex-A53: 843419: A load or store might access an incorrect address" default y - select ARM64_MODULE_PLTS if MODULES help This option links the kernel with '--fix-cortex-a53-843419' and enables PLT support to replace certain ADRP instructions, which can @@ -2107,26 +2107,6 @@ config ARM64_SME register state capable of holding two dimensional matrix tiles to enable various matrix operations. -config ARM64_MODULE_PLTS - bool "Use PLTs to allow module memory to spill over into vmalloc area" - depends on MODULES - 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). - config ARM64_PSEUDO_NMI bool "Support for NMI-like interrupts" select ARM_GIC_V3 @@ -2167,7 +2147,6 @@ config RELOCATABLE config RANDOMIZE_BASE bool "Randomize the address of the kernel image" - select ARM64_MODULE_PLTS if MODULES select RELOCATABLE help Randomizes the virtual address at which the kernel image is @@ -2198,9 +2177,8 @@ config RANDOMIZE_MODULE_REGION_FULL When this option is not set, the module region will be randomized over a limited range that contains the [_stext, _etext] interval of the core kernel, so branch relocations are almost always in range unless - ARM64_MODULE_PLTS is enabled and the region is exhausted. In this - particular case of region exhaustion, modules might be able to fall - back to a larger 2GB area. + the region is exhausted. In this particular case of region + exhaustion, modules might be able to fall back to a larger 2GB area. config CC_HAVE_STACKPROTECTOR_SYSREG def_bool $(cc-option,-mstack-protector-guard=sysreg -mstack-protector-guard-reg=sp_el0 -mstack-protector-guard-offset=0) -- cgit v1.2.3