github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-05-27 00:22:00 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

arm64: Unconditionally enable PAN support

Browse Source 
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 <maz@kernel.org>
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Marc Zyngier 2026-01-07 18:07:00 +00:00 committed by Will Deacon
parent 6191b25d8b
commit 018a231b02
5 changed files with 3 additions and 28 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
arch/arm64/Kconfig
View File

@ -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.

2
arch/arm64/include/asm/cpucaps.h
View File

@ -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:

6
arch/arm64/include/asm/uaccess.h
View File

@ -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)

4
arch/arm64/kernel/cpufeature.c
View File

@ -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",

2
arch/arm64/kvm/hyp/entry.S
View File

@ -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)]