From: Marc Zyngier Date: Wed, 7 Jan 2026 18:07:00 +0000 (+0000) Subject: arm64: Unconditionally enable PAN support X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=018a231b0260ebd85eddca3fec85031b59f50117;p=thirdparty%2Fkernel%2Flinux.git arm64: Unconditionally enable PAN support FEAT_PAN has been around since ARMv8.1 (over 11 years ago), has no compiler dependency (we have our own accessors), and is a great security benefit. Drop CONFIG_ARM64_PAN, and make the support unconditionnal. Signed-off-by: Marc Zyngier Signed-off-by: Will Deacon --- diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index b6f57cc1e4df8..fcfb62ec4bae8 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -1680,7 +1680,6 @@ config MITIGATE_SPECTRE_BRANCH_HISTORY config ARM64_SW_TTBR0_PAN bool "Emulate Privileged Access Never using TTBR0_EL1 switching" depends on !KCSAN - select ARM64_PAN help Enabling this option prevents the kernel from accessing user-space memory directly by pointing TTBR0_EL1 to a reserved @@ -1859,20 +1858,6 @@ config ARM64_HW_AFDBM to work on pre-ARMv8.1 hardware and the performance impact is minimal. If unsure, say Y. -config ARM64_PAN - bool "Enable support for Privileged Access Never (PAN)" - default y - help - Privileged Access Never (PAN; part of the ARMv8.1 Extensions) - prevents the kernel or hypervisor from accessing user-space (EL0) - memory directly. - - Choosing this option will cause any unprotected (not using - copy_to_user et al) memory access to fail with a permission fault. - - The feature is detected at runtime, and will remain as a 'nop' - instruction if the cpu does not implement the feature. - endmenu # "ARMv8.1 architectural features" menu "ARMv8.2 architectural features" @@ -2109,7 +2094,6 @@ config ARM64_MTE depends on ARM64_AS_HAS_MTE && ARM64_TAGGED_ADDR_ABI depends on AS_HAS_ARMV8_5 # Required for tag checking in the uaccess routines - select ARM64_PAN select ARCH_HAS_SUBPAGE_FAULTS select ARCH_USES_HIGH_VMA_FLAGS select ARCH_USES_PG_ARCH_2 @@ -2141,7 +2125,6 @@ menu "ARMv8.7 architectural features" config ARM64_EPAN bool "Enable support for Enhanced Privileged Access Never (EPAN)" default y - depends on ARM64_PAN help Enhanced Privileged Access Never (EPAN) allows Privileged Access Never to be used with Execute-only mappings. diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h index 2c8029472ad45..177c691914f87 100644 --- a/arch/arm64/include/asm/cpucaps.h +++ b/arch/arm64/include/asm/cpucaps.h @@ -19,8 +19,6 @@ cpucap_is_possible(const unsigned int cap) "cap must be < ARM64_NCAPS"); switch (cap) { - case ARM64_HAS_PAN: - return IS_ENABLED(CONFIG_ARM64_PAN); case ARM64_HAS_EPAN: return IS_ENABLED(CONFIG_ARM64_EPAN); case ARM64_SVE: diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h index 6490930deef84..9810106a3f664 100644 --- a/arch/arm64/include/asm/uaccess.h +++ b/arch/arm64/include/asm/uaccess.h @@ -124,14 +124,12 @@ static inline bool uaccess_ttbr0_enable(void) static inline void __uaccess_disable_hw_pan(void) { - asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), ARM64_HAS_PAN, - CONFIG_ARM64_PAN)); + asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), ARM64_HAS_PAN)); } static inline void __uaccess_enable_hw_pan(void) { - asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_HAS_PAN, - CONFIG_ARM64_PAN)); + asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_HAS_PAN)); } static inline void uaccess_disable_privileged(void) diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index 547ccf28f2893..716440d147a2d 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -2164,7 +2164,6 @@ static bool has_bbml2_noabort(const struct arm64_cpu_capabilities *caps, int sco return cpu_supports_bbml2_noabort(); } -#ifdef CONFIG_ARM64_PAN static void cpu_enable_pan(const struct arm64_cpu_capabilities *__unused) { /* @@ -2176,7 +2175,6 @@ static void cpu_enable_pan(const struct arm64_cpu_capabilities *__unused) sysreg_clear_set(sctlr_el1, SCTLR_EL1_SPAN, 0); set_pstate_pan(1); } -#endif /* CONFIG_ARM64_PAN */ #ifdef CONFIG_ARM64_RAS_EXTN static void cpu_clear_disr(const struct arm64_cpu_capabilities *__unused) @@ -2541,7 +2539,6 @@ static const struct arm64_cpu_capabilities arm64_features[] = { .matches = has_cpuid_feature, ARM64_CPUID_FIELDS(ID_AA64MMFR0_EL1, ECV, CNTPOFF) }, -#ifdef CONFIG_ARM64_PAN { .desc = "Privileged Access Never", .capability = ARM64_HAS_PAN, @@ -2550,7 +2547,6 @@ static const struct arm64_cpu_capabilities arm64_features[] = { .cpu_enable = cpu_enable_pan, ARM64_CPUID_FIELDS(ID_AA64MMFR1_EL1, PAN, IMP) }, -#endif /* CONFIG_ARM64_PAN */ #ifdef CONFIG_ARM64_EPAN { .desc = "Enhanced Privileged Access Never", diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S index 9f4e8d68ab505..11a10d8f5beb2 100644 --- a/arch/arm64/kvm/hyp/entry.S +++ b/arch/arm64/kvm/hyp/entry.S @@ -126,7 +126,7 @@ SYM_INNER_LABEL(__guest_exit, SYM_L_GLOBAL) add x1, x1, #VCPU_CONTEXT - ALTERNATIVE(nop, SET_PSTATE_PAN(1), ARM64_HAS_PAN, CONFIG_ARM64_PAN) + ALTERNATIVE(nop, SET_PSTATE_PAN(1), ARM64_HAS_PAN) // Store the guest regs x2 and x3 stp x2, x3, [x1, #CPU_XREG_OFFSET(2)]