| Message ID | 20210119160723.116983-3-vladimir.murzin@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64: Support Enhanced PAN | expand |
On Tue, Jan 19, 2021 at 04:07:23PM +0000, Vladimir Murzin wrote: > With EPAN supported it might be handy to user know that PROT_EXEC > gives execute-only permission, so advertise it via HWCAPS2_EXECONLY I don't want to merge this without a concrete need for it in userspace. Kees -- do you see this being necessary? I'm having a hard time understanding what an application would do differently at runtime based on this hwcap. Will
diff --git a/arch/arm64/include/asm/hwcap.h b/arch/arm64/include/asm/hwcap.h index 9a5498c..5ee5bce 100644 --- a/arch/arm64/include/asm/hwcap.h +++ b/arch/arm64/include/asm/hwcap.h @@ -105,6 +105,7 @@ #define KERNEL_HWCAP_RNG __khwcap2_feature(RNG) #define KERNEL_HWCAP_BTI __khwcap2_feature(BTI) #define KERNEL_HWCAP_MTE __khwcap2_feature(MTE) +#define KERNEL_HWCAP_EXECONLY __khwcap2_feature(EXECONLY) /* * This yields a mask that user programs can use to figure out what diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h index 47e9fdc..135aa66 100644 --- a/arch/arm64/include/asm/sysreg.h +++ b/arch/arm64/include/asm/sysreg.h @@ -811,6 +811,7 @@ #define ID_AA64MMFR1_VMIDBITS_8 0 #define ID_AA64MMFR1_VMIDBITS_16 2 +#define ID_AA64MMFR1_EPAN 3 /* id_aa64mmfr2 */ #define ID_AA64MMFR2_E0PD_SHIFT 60 diff --git a/arch/arm64/include/uapi/asm/hwcap.h b/arch/arm64/include/uapi/asm/hwcap.h index b8f41aa..61471f4 100644 --- a/arch/arm64/include/uapi/asm/hwcap.h +++ b/arch/arm64/include/uapi/asm/hwcap.h @@ -75,5 +75,6 @@ #define HWCAP2_RNG (1 << 16) #define HWCAP2_BTI (1 << 17) #define HWCAP2_MTE (1 << 18) +#define HWCAP2_EXECONLY (1 << 19) #endif /* _UAPI__ASM_HWCAP_H */ diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index 9d85956..bc80cc2 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -2285,6 +2285,9 @@ static const struct arm64_cpu_capabilities arm64_elf_hwcaps[] = { #ifdef CONFIG_ARM64_MTE HWCAP_CAP(SYS_ID_AA64PFR1_EL1, ID_AA64PFR1_MTE_SHIFT, FTR_UNSIGNED, ID_AA64PFR1_MTE, CAP_HWCAP, KERNEL_HWCAP_MTE), #endif /* CONFIG_ARM64_MTE */ +#ifdef CONFIG_ARM64_EPAN + HWCAP_CAP(SYS_ID_AA64MMFR1_EL1, ID_AA64MMFR1_PAN_SHIFT, FTR_UNSIGNED, ID_AA64MMFR1_EPAN, CAP_HWCAP, KERNEL_HWCAP_EXECONLY), +#endif {}, }; diff --git a/arch/arm64/kernel/cpuinfo.c b/arch/arm64/kernel/cpuinfo.c index 77605ae..34c98d9 100644 --- a/arch/arm64/kernel/cpuinfo.c +++ b/arch/arm64/kernel/cpuinfo.c @@ -94,6 +94,7 @@ static const char *const hwcap_str[] = { [KERNEL_HWCAP_RNG] = "rng", [KERNEL_HWCAP_BTI] = "bti", [KERNEL_HWCAP_MTE] = "mte", + [KERNEL_HWCAP_EXECONLY] = "xo", }; #ifdef CONFIG_COMPAT
With EPAN supported it might be handy to user know that PROT_EXEC gives execute-only permission, so advertise it via HWCAPS2_EXECONLY Cc: Kees Cook <keescook@chromium.org> Cc: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com> --- arch/arm64/include/asm/hwcap.h | 1 + arch/arm64/include/asm/sysreg.h | 1 + arch/arm64/include/uapi/asm/hwcap.h | 1 + arch/arm64/kernel/cpufeature.c | 3 +++ arch/arm64/kernel/cpuinfo.c | 1 + 5 files changed, 7 insertions(+)