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 <mark.rutland@arm.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Cc: Shanker Donthineni <sdonthineni@nvidia.com>
Cc: Will Deacon <will@kernel.org>
Tested-by: Shanker Donthineni <sdonthineni@nvidia.com>
Link: https://lore.kernel.org/r/20230530110328.2213762-6-mark.rutland@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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
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
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
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
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 $(cc-option,-mstack-protector-guard=sysreg -mstack-protector-guard-reg=sp_el0 -mstack-protector-guard-offset=0)
#include <asm-generic/module.h>
-#ifdef CONFIG_ARM64_MODULE_PLTS
struct mod_plt_sec {
int plt_shndx;
int plt_num_entries;
/* for CONFIG_DYNAMIC_FTRACE */
struct plt_entry *ftrace_trampolines;
};
-#endif
u64 module_emit_plt_entry(struct module *mod, Elf64_Shdr *sechdrs,
void *loc, const Elf64_Rela *rela,
SECTIONS {
-#ifdef CONFIG_ARM64_MODULE_PLTS
.plt 0 : { BYTE(0) }
.init.plt 0 : { BYTE(0) }
.text.ftrace_trampoline 0 : { BYTE(0) }
-#endif
#ifdef CONFIG_KASAN_SW_TAGS
/*
obj-$(CONFIG_COMPAT_ALIGNMENT_FIXUPS) += compat_alignment.o
obj-$(CONFIG_KUSER_HELPERS) += kuser32.o
obj-$(CONFIG_FUNCTION_TRACER) += ftrace.o entry-ftrace.o
-obj-$(CONFIG_MODULES) += module.o
-obj-$(CONFIG_ARM64_MODULE_PLTS) += module-plts.o
+obj-$(CONFIG_MODULES) += module.o module-plts.o
obj-$(CONFIG_PERF_EVENTS) += perf_regs.o perf_callchain.o
obj-$(CONFIG_HAVE_HW_BREAKPOINT) += hw_breakpoint.o
obj-$(CONFIG_CPU_PM) += sleep.o suspend.o
static struct plt_entry *get_ftrace_plt(struct module *mod)
{
-#ifdef CONFIG_ARM64_MODULE_PLTS
+#ifdef CONFIG_MODULES
struct plt_entry *plt = mod->arch.ftrace_trampolines;
return &plt[FTRACE_PLT_IDX];
* must use a PLT to reach it. We can only place PLTs for modules, and
* only when module PLT support is built-in.
*/
- if (!IS_ENABLED(CONFIG_ARM64_MODULE_PLTS))
+ if (!IS_ENABLED(CONFIG_MODULES))
return false;
/*
*
* Note: 'mod' is only set at module load time.
*/
- if (!IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_ARGS) &&
- IS_ENABLED(CONFIG_ARM64_MODULE_PLTS) && mod) {
+ if (!IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_ARGS) && mod)
return aarch64_insn_patch_text_nosync((void *)pc, new);
- }
if (!ftrace_find_callable_addr(rec, mod, &addr))
return -EINVAL;
void *module_alloc(unsigned long size)
{
u64 module_alloc_end = module_alloc_base + MODULES_VSIZE;
- gfp_t gfp_mask = GFP_KERNEL;
void *p;
- /* Silence the initial allocation */
- if (IS_ENABLED(CONFIG_ARM64_MODULE_PLTS))
- gfp_mask |= __GFP_NOWARN;
-
+ /*
+ * Where possible, prefer to allocate within direct branch range of the
+ * kernel such that no PLTs are necessary. This may fail, so we pass
+ * __GFP_NOWARN to silence the resulting warning.
+ */
p = __vmalloc_node_range(size, MODULE_ALIGN, module_alloc_base,
- module_alloc_end, gfp_mask, PAGE_KERNEL, 0,
- NUMA_NO_NODE, __builtin_return_address(0));
+ module_alloc_end, GFP_KERNEL | __GFP_NOWARN,
+ PAGE_KERNEL, 0, NUMA_NO_NODE,
+ __builtin_return_address(0));
- if (!p && IS_ENABLED(CONFIG_ARM64_MODULE_PLTS)) {
+ if (!p) {
p = __vmalloc_node_range(size, MODULE_ALIGN, module_alloc_base,
module_alloc_base + SZ_2G, GFP_KERNEL,
PAGE_KERNEL, 0, NUMA_NO_NODE,
__builtin_return_address(0));
}
- if (p && (kasan_alloc_module_shadow(p, size, gfp_mask) < 0)) {
+ if (p && (kasan_alloc_module_shadow(p, size, GFP_KERNEL) < 0)) {
vfree(p);
return NULL;
}
case R_AARCH64_CALL26:
ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 2, 26,
AARCH64_INSN_IMM_26);
-
- if (IS_ENABLED(CONFIG_ARM64_MODULE_PLTS) &&
- ovf == -ERANGE) {
+ if (ovf == -ERANGE) {
val = module_emit_plt_entry(me, sechdrs, loc, &rel[i], sym);
if (!val)
return -ENOEXEC;
const Elf_Shdr *sechdrs,
struct module *mod)
{
-#if defined(CONFIG_ARM64_MODULE_PLTS) && defined(CONFIG_DYNAMIC_FTRACE)
+#if defined(CONFIG_DYNAMIC_FTRACE)
const Elf_Shdr *s;
struct plt_entry *plts;
projects / platform / kernel / linux-starfive.git / commitdiff