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arm64: Split kpti_install_ng_mappings()

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The arm64_cpu_capabilities::cpu_enable callbacks are intended for
cpu-local feature enablement (e.g. poking system registers). These get
called for each online CPU when boot/system cpucaps get finalized and
enabled, and get called whenever a CPU is subsequently onlined.

For KPTI with the ARM64_UNMAP_KERNEL_AT_EL0 cpucap, we use the
kpti_install_ng_mappings() function as the cpu_enable callback. This
does a mixture of cpu-local configuration (setting VBAR_EL1 to the
appropriate trampoline vectors) and some global configuration (rewriting
the swapper page tables to sue non-glboal mappings) that must happen at
most once.

This patch splits kpti_install_ng_mappings() into a cpu-local
cpu_enable_kpti() initialization function and a system-wide
kpti_install_ng_mappings() function. The cpu_enable_kpti() function is
responsible for selecting the necessary cpu-local vectors each time a
CPU is onlined, and the kpti_install_ng_mappings() function performs the
one-time rewrite of the translation tables too use non-global mappings.
Splitting the two makes the code a bit easier to follow and also allows
the page table rewriting code to be marked as __init such that it can be
freed after use.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Mark Rutland 2023-10-16 11:24:31 +01:00 committed by Catalin Marinas
parent 7f632d331d
commit 42c5a3b04b
1 changed files with 33 additions and 21 deletions
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54
arch/arm64/kernel/cpufeature.c
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@ -1754,16 +1754,15 @@ void create_kpti_ng_temp_pgd(pgd_t *pgdir, phys_addr_t phys, unsigned long virt,
phys_addr_t size, pgprot_t prot,
phys_addr_t (*pgtable_alloc)(int), int flags);
static phys_addr_t kpti_ng_temp_alloc;
static phys_addr_t __initdata kpti_ng_temp_alloc;
static phys_addr_t kpti_ng_pgd_alloc(int shift)
static phys_addr_t __init kpti_ng_pgd_alloc(int shift)
{
kpti_ng_temp_alloc -= PAGE_SIZE;
return kpti_ng_temp_alloc;
}
static void
kpti_install_ng_mappings(const struct arm64_cpu_capabilities *__unused)
static int __init __kpti_install_ng_mappings(void *__unused)
{
typedef void (kpti_remap_fn)(int, int, phys_addr_t, unsigned long);
extern kpti_remap_fn idmap_kpti_install_ng_mappings;
@ -1776,20 +1775,6 @@ kpti_install_ng_mappings(const struct arm64_cpu_capabilities *__unused)
pgd_t *kpti_ng_temp_pgd;
u64 alloc = 0;
if (__this_cpu_read(this_cpu_vector) == vectors) {
const char *v = arm64_get_bp_hardening_vector(EL1_VECTOR_KPTI);
__this_cpu_write(this_cpu_vector, v);
}
/*
* We don't need to rewrite the page-tables if either we've done
* it already or we have KASLR enabled and therefore have not
* created any global mappings at all.
*/
if (arm64_use_ng_mappings)
return;
remap_fn = (void *)__pa_symbol(idmap_kpti_install_ng_mappings);
if (!cpu) {
@ -1826,14 +1811,39 @@ kpti_install_ng_mappings(const struct arm64_cpu_capabilities *__unused)
free_pages(alloc, order);
arm64_use_ng_mappings = true;
}
return 0;
}
static void __init kpti_install_ng_mappings(void)
{
/*
* We don't need to rewrite the page-tables if either we've done
* it already or we have KASLR enabled and therefore have not
* created any global mappings at all.
*/
if (arm64_use_ng_mappings)
return;
stop_machine(__kpti_install_ng_mappings, NULL, cpu_online_mask);
}
#else
static void
kpti_install_ng_mappings(const struct arm64_cpu_capabilities *__unused)
static inline void kpti_install_ng_mappings(void)
{
}
#endif /* CONFIG_UNMAP_KERNEL_AT_EL0 */
static void cpu_enable_kpti(struct arm64_cpu_capabilities const *cap)
{
if (__this_cpu_read(this_cpu_vector) == vectors) {
const char *v = arm64_get_bp_hardening_vector(EL1_VECTOR_KPTI);
__this_cpu_write(this_cpu_vector, v);
}
}
static int __init parse_kpti(char *str)
{
bool enabled;
@ -2362,7 +2372,7 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
.desc = "Kernel page table isolation (KPTI)",
.capability = ARM64_UNMAP_KERNEL_AT_EL0,
.type = ARM64_CPUCAP_BOOT_RESTRICTED_CPU_LOCAL_FEATURE,
.cpu_enable = kpti_install_ng_mappings,
.cpu_enable = cpu_enable_kpti,
.matches = unmap_kernel_at_el0,
/*
* The ID feature fields below are used to indicate that
@ -3355,6 +3365,8 @@ void __init setup_system_features(void)
*/
enable_cpu_capabilities(SCOPE_ALL & ~SCOPE_BOOT_CPU);
kpti_install_ng_mappings();
sve_setup();
sme_setup();