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authorWill Deacon <will@kernel.org>2020-05-28 18:00:51 +0100
committerWill Deacon <will@kernel.org>2020-05-28 18:00:51 +0100
commitd27865279f12035c730818aa1a0280fada866a37 (patch)
tree5c4462885c2a6d7453b34ceb51d39b390030a2a6 /arch/arm64/kernel/cpufeature.c
parent342403bcb4dfe41324a0f6f4cb5a8d324f31c725 (diff)
parenta4eb355a3fdad85d16e4b098e8d56bb28b812ce0 (diff)
downloadlwn-d27865279f12035c730818aa1a0280fada866a37.tar.gz
lwn-d27865279f12035c730818aa1a0280fada866a37.zip
Merge branch 'for-next/bti' into for-next/core
Support for Branch Target Identification (BTI) in user and kernel (Mark Brown and others) * for-next/bti: (39 commits) arm64: vdso: Fix CFI directives in sigreturn trampoline arm64: vdso: Don't prefix sigreturn trampoline with a BTI C instruction arm64: bti: Fix support for userspace only BTI arm64: kconfig: Update and comment GCC version check for kernel BTI arm64: vdso: Map the vDSO text with guarded pages when built for BTI arm64: vdso: Force the vDSO to be linked as BTI when built for BTI arm64: vdso: Annotate for BTI arm64: asm: Provide a mechanism for generating ELF note for BTI arm64: bti: Provide Kconfig for kernel mode BTI arm64: mm: Mark executable text as guarded pages arm64: bpf: Annotate JITed code for BTI arm64: Set GP bit in kernel page tables to enable BTI for the kernel arm64: asm: Override SYM_FUNC_START when building the kernel with BTI arm64: bti: Support building kernel C code using BTI arm64: Document why we enable PAC support for leaf functions arm64: insn: Report PAC and BTI instructions as skippable arm64: insn: Don't assume unrecognized HINTs are skippable arm64: insn: Provide a better name for aarch64_insn_is_nop() arm64: insn: Add constants for new HINT instruction decode arm64: Disable old style assembly annotations ...
Diffstat (limited to 'arch/arm64/kernel/cpufeature.c')
-rw-r--r--arch/arm64/kernel/cpufeature.c37
1 files changed, 37 insertions, 0 deletions
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index b3202a99e559..4ae41670c2e6 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -241,6 +241,8 @@ static const struct arm64_ftr_bits ftr_id_aa64pfr1[] = {
ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR1_MPAMFRAC_SHIFT, 4, 0),
ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR1_RASFRAC_SHIFT, 4, 0),
ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR1_SSBS_SHIFT, 4, ID_AA64PFR1_SSBS_PSTATE_NI),
+ ARM64_FTR_BITS(FTR_VISIBLE_IF_IS_ENABLED(CONFIG_ARM64_BTI),
+ FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR1_BT_SHIFT, 4, 0),
ARM64_FTR_END,
};
@@ -1638,6 +1640,21 @@ static bool can_use_gic_priorities(const struct arm64_cpu_capabilities *entry,
}
#endif
+#ifdef CONFIG_ARM64_BTI
+static void bti_enable(const struct arm64_cpu_capabilities *__unused)
+{
+ /*
+ * Use of X16/X17 for tail-calls and trampolines that jump to
+ * function entry points using BR is a requirement for
+ * marking binaries with GNU_PROPERTY_AARCH64_FEATURE_1_BTI.
+ * So, be strict and forbid other BRs using other registers to
+ * jump onto a PACIxSP instruction:
+ */
+ sysreg_clear_set(sctlr_el1, 0, SCTLR_EL1_BT0 | SCTLR_EL1_BT1);
+ isb();
+}
+#endif /* CONFIG_ARM64_BTI */
+
/* Internal helper functions to match cpu capability type */
static bool
cpucap_late_cpu_optional(const struct arm64_cpu_capabilities *cap)
@@ -2020,6 +2037,23 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
.min_field_value = 1,
},
#endif
+#ifdef CONFIG_ARM64_BTI
+ {
+ .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,
+ .field_pos = ID_AA64PFR1_BT_SHIFT,
+ .min_field_value = ID_AA64PFR1_BT_BTI,
+ .sign = FTR_UNSIGNED,
+ },
+#endif
{},
};
@@ -2129,6 +2163,9 @@ static const struct arm64_cpu_capabilities arm64_elf_hwcaps[] = {
HWCAP_CAP(SYS_ID_AA64ZFR0_EL1, ID_AA64ZFR0_F64MM_SHIFT, FTR_UNSIGNED, ID_AA64ZFR0_F64MM, CAP_HWCAP, KERNEL_HWCAP_SVEF64MM),
#endif
HWCAP_CAP(SYS_ID_AA64PFR1_EL1, ID_AA64PFR1_SSBS_SHIFT, FTR_UNSIGNED, ID_AA64PFR1_SSBS_PSTATE_INSNS, CAP_HWCAP, KERNEL_HWCAP_SSBS),
+#ifdef CONFIG_ARM64_BTI
+ HWCAP_CAP(SYS_ID_AA64PFR1_EL1, ID_AA64PFR1_BT_SHIFT, FTR_UNSIGNED, ID_AA64PFR1_BT_BTI, CAP_HWCAP, KERNEL_HWCAP_BTI),
+#endif
#ifdef CONFIG_ARM64_PTR_AUTH
HWCAP_MULTI_CAP(ptr_auth_hwcap_addr_matches, CAP_HWCAP, KERNEL_HWCAP_PACA),
HWCAP_MULTI_CAP(ptr_auth_hwcap_gen_matches, CAP_HWCAP, KERNEL_HWCAP_PACG),