| Message ID | 20201113152023.102855-3-vladimir.murzin@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64: Support Enhanced PAN | expand |
On Fri, Nov 13, 2020 at 03:20:23PM +0000, Vladimir Murzin wrote: > So user have a clue whether exec-only permissions will work. I do think we should tell user the PROT_EXEC actually gives execute-only permission. > --- 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_EPAN (1 << 19) However, I wonder whether EPAN is meaningful to the user. PAN is a kernel protection that doesn't say much from a user perspective. Maybe something like HWCAP2_EXECONLY? That said, we do have a precedent on 32-bit where we exposed HWCAP_LPAE to the user meaning that 64-bit atomics are available.
On 11/17/20 4:59 PM, Catalin Marinas wrote: > On Fri, Nov 13, 2020 at 03:20:23PM +0000, Vladimir Murzin wrote: >> So user have a clue whether exec-only permissions will work. > > I do think we should tell user the PROT_EXEC actually gives execute-only > permission. Ack. > >> --- 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_EPAN (1 << 19) > > However, I wonder whether EPAN is meaningful to the user. PAN is a > kernel protection that doesn't say much from a user perspective. Maybe > something like HWCAP2_EXECONLY? Works for me. > > That said, we do have a precedent on 32-bit where we exposed HWCAP_LPAE > to the user meaning that 64-bit atomics are available. > It doesn't mean we have to follow it :) Cheers Vladimir
diff --git a/arch/arm64/include/asm/hwcap.h b/arch/arm64/include/asm/hwcap.h index 9a5498c..6274c6c 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_EPAN __khwcap2_feature(EPAN) /* * 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 19147b6..e7bc373 100644 --- a/arch/arm64/include/asm/sysreg.h +++ b/arch/arm64/include/asm/sysreg.h @@ -796,6 +796,7 @@ #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..a99da14 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_EPAN (1 << 19) #endif /* _UAPI__ASM_HWCAP_H */ diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index 2033e0b..bb2016c 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -2275,6 +2275,9 @@ 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_EPAN), +#endif {}, }; diff --git a/arch/arm64/kernel/cpuinfo.c b/arch/arm64/kernel/cpuinfo.c index 77605ae..9b69b13 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_EPAN] = "epan", }; #ifdef CONFIG_COMPAT
So user have a clue whether exec-only permissions will work. 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(+)