#ifndef __ASSEMBLY__
+#include <asm/cpufeature.h>
#include <asm/pgtable-types.h>
extern bool arm64_use_ng_mappings;
#define PTE_MAYBE_NG (arm64_use_ng_mappings ? PTE_NG : 0)
#define PMD_MAYBE_NG (arm64_use_ng_mappings ? PMD_SECT_NG : 0)
+#define PTE_MAYBE_GP (system_supports_bti() ? PTE_GP : 0)
+
#define PROT_DEFAULT (_PROT_DEFAULT | PTE_MAYBE_NG)
#define PROT_SECT_DEFAULT (_PROT_SECT_DEFAULT | PMD_MAYBE_NG)
{
.desc = "Branch Target Identification",
.capability = ARM64_BTI,
+#ifdef CONFIG_ARM64_BTI_KERNEL
+ .type = ARM64_CPUCAP_STRICT_BOOT_CPU_FEATURE,
+#else
.type = ARM64_CPUCAP_SYSTEM_FEATURE,
+#endif
.matches = has_cpuid_feature,
.cpu_enable = bti_enable,
.sys_reg = SYS_ID_AA64PFR1_EL1,
#endif
/*
+ * Open coded check for BTI, only for use to determine configuration
+ * for early mappings for before the cpufeature code has run.
+ */
+static bool arm64_early_this_cpu_has_bti(void)
+{
+ u64 pfr1;
+
+ if (!IS_ENABLED(CONFIG_ARM64_BTI_KERNEL))
+ return false;
+
+ pfr1 = read_sysreg_s(SYS_ID_AA64PFR1_EL1);
+ return cpuid_feature_extract_unsigned_field(pfr1,
+ ID_AA64PFR1_BT_SHIFT);
+}
+
+/*
* Create fine-grained mappings for the kernel.
*/
static void __init map_kernel(pgd_t *pgdp)
pgprot_t text_prot = rodata_enabled ? PAGE_KERNEL_ROX : PAGE_KERNEL_EXEC;
/*
+ * If we have a CPU that supports BTI and a kernel built for
+ * BTI then mark the kernel executable text as guarded pages
+ * now so we don't have to rewrite the page tables later.
+ */
+ if (arm64_early_this_cpu_has_bti())
+ text_prot = __pgprot_modify(text_prot, PTE_GP, PTE_GP);
+
+ /*
* Only rodata will be remapped with different permissions later on,
* all other segments are allowed to use contiguous mappings.
*/