From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AIpwx48Guuu523AIWHv568ncDW79/pDr89FNJ/zwb2z6gxBj2rA7FJzUhABTpSIhpuwk+nWwQGkV ARC-Seal: i=1; a=rsa-sha256; t=1523021712; cv=none; d=google.com; s=arc-20160816; b=kcbeTpr/p3E9+3m1JMpwBXBvDkwwtD23/11+VJGWO0nlx2yIM7/8uNaOcJLHROI/YC FkF+DX3dxqWd+0ngMZXuSKZe73diAVpPvycHd9MibyeTKmYT5UwGCwFYBUibCP2MI2BC ScXY0/8Ht3D1+PAXHk3Jw7bdYil2oBm7sh64sdHA2jLyO7oCCoG3GSAvU/7iPwwUriO6 e0o1NwbmHCWwWLoJVMvfO/9BTLBBd28BJ3dSR4cXCMavzjiBKv0bLoPL5dd7TT8Pk7vZ u9iCJn7LIpuY9bVDaiiciXEOZmK2pzmUglIgXNGTFmKgd/gD3KRM886Gd1xKZPqixosN lTCA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=mime-version:user-agent:references:in-reply-to:message-id:date :subject:cc:to:from:arc-authentication-results; bh=MiHc6sg8MSC/3KRj6KL7JP/WlYTVugo40LlCfJxGUco=; b=l0BSDS8b62uCom9ZpwCZUFgf1hr+TWI1tH5g3up10xyufca6usxLn1gTi8N8DezFH3 OCjwdyp0fcSktFMXp5NuflAp7pFBFvrQOFz7hbfAF2vZzLofEtdKYZLqhv5Vnmq2l2Ip luUj4I35hITiVJ+RIujTMOD7JvOknMqJLrJox/t76GL2P5yUI5FQ1AYNVX787etRORr4 cXNttikpA1jgPy0Z8t+hpc0lwAyeR4dEW0Gokkyx36XiBpD4e61cdIGEMDy/GqCdAc7j WWDXGAUoPLNd+cDZgRHKq4ZU2iUJadJ0Vf0tbm0gLgHRg0smpxKzHw2hP4oNWUzvm/wr WPCQ== ARC-Authentication-Results: i=1; mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 90.92.61.202 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 90.92.61.202 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Greg Kroah-Hartman , Mark Rutland , Laura Abbott , Shanker Donthineni , Will Deacon , Greg Hackmann , Alex Shi Subject: [PATCH 4.9 062/102] arm64: entry: Add fake CPU feature for unmapping the kernel at EL0 Date: Fri, 6 Apr 2018 15:23:43 +0200 Message-Id: <20180406084340.290236378@linuxfoundation.org> X-Mailer: git-send-email 2.17.0 In-Reply-To: <20180406084331.507038179@linuxfoundation.org> References: <20180406084331.507038179@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-LABELS: =?utf-8?b?IlxcU2VudCI=?= X-GMAIL-THRID: =?utf-8?q?1597004015892589296?= X-GMAIL-MSGID: =?utf-8?q?1597004015892589296?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Will Deacon commit ea1e3de85e94 upstream. Allow explicit disabling of the entry trampoline on the kernel command line (kpti=off) by adding a fake CPU feature (ARM64_UNMAP_KERNEL_AT_EL0) that can be used to toggle the alternative sequences in our entry code and avoid use of the trampoline altogether if desired. This also allows us to make use of a static key in arm64_kernel_unmapped_at_el0(). Reviewed-by: Mark Rutland Tested-by: Laura Abbott Tested-by: Shanker Donthineni Signed-off-by: Will Deacon [Alex: use first free cpucap number, use cpus_have_cap] Signed-off-by: Alex Shi [v4.9 backport] Signed-off-by: Mark Rutland [v4.9 backport] Tested-by: Will Deacon Tested-by: Greg Hackmann Signed-off-by: Greg Kroah-Hartman --- arch/arm64/include/asm/cpucaps.h | 3 +- arch/arm64/include/asm/mmu.h | 3 +- arch/arm64/kernel/cpufeature.c | 41 +++++++++++++++++++++++++++++++++++++++ arch/arm64/kernel/entry.S | 9 ++++---- 4 files changed, 50 insertions(+), 6 deletions(-) --- a/arch/arm64/include/asm/cpucaps.h +++ b/arch/arm64/include/asm/cpucaps.h @@ -34,7 +34,8 @@ #define ARM64_HAS_32BIT_EL0 13 #define ARM64_HYP_OFFSET_LOW 14 #define ARM64_MISMATCHED_CACHE_LINE_SIZE 15 +#define ARM64_UNMAP_KERNEL_AT_EL0 16 -#define ARM64_NCAPS 16 +#define ARM64_NCAPS 17 #endif /* __ASM_CPUCAPS_H */ --- a/arch/arm64/include/asm/mmu.h +++ b/arch/arm64/include/asm/mmu.h @@ -34,7 +34,8 @@ typedef struct { static inline bool arm64_kernel_unmapped_at_el0(void) { - return IS_ENABLED(CONFIG_UNMAP_KERNEL_AT_EL0); + return IS_ENABLED(CONFIG_UNMAP_KERNEL_AT_EL0) && + cpus_have_cap(ARM64_UNMAP_KERNEL_AT_EL0); } extern void paging_init(void); --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -746,6 +746,40 @@ static bool hyp_offset_low(const struct return idmap_addr > GENMASK(VA_BITS - 2, 0) && !is_kernel_in_hyp_mode(); } +#ifdef CONFIG_UNMAP_KERNEL_AT_EL0 +static int __kpti_forced; /* 0: not forced, >0: forced on, <0: forced off */ + +static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry, + int __unused) +{ + /* Forced on command line? */ + if (__kpti_forced) { + pr_info_once("kernel page table isolation forced %s by command line option\n", + __kpti_forced > 0 ? "ON" : "OFF"); + return __kpti_forced > 0; + } + + /* Useful for KASLR robustness */ + if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) + return true; + + return false; +} + +static int __init parse_kpti(char *str) +{ + bool enabled; + int ret = strtobool(str, &enabled); + + if (ret) + return ret; + + __kpti_forced = enabled ? 1 : -1; + return 0; +} +__setup("kpti=", parse_kpti); +#endif /* CONFIG_UNMAP_KERNEL_AT_EL0 */ + static const struct arm64_cpu_capabilities arm64_features[] = { { .desc = "GIC system register CPU interface", @@ -829,6 +863,13 @@ static const struct arm64_cpu_capabiliti .def_scope = SCOPE_SYSTEM, .matches = hyp_offset_low, }, +#ifdef CONFIG_UNMAP_KERNEL_AT_EL0 + { + .capability = ARM64_UNMAP_KERNEL_AT_EL0, + .def_scope = SCOPE_SYSTEM, + .matches = unmap_kernel_at_el0, + }, +#endif {}, }; --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -73,6 +73,7 @@ .macro kernel_ventry, el, label, regsize = 64 .align 7 #ifdef CONFIG_UNMAP_KERNEL_AT_EL0 +alternative_if ARM64_UNMAP_KERNEL_AT_EL0 .if \el == 0 .if \regsize == 64 mrs x30, tpidrro_el0 @@ -81,6 +82,7 @@ mov x30, xzr .endif .endif +alternative_else_nop_endif #endif sub sp, sp, #S_FRAME_SIZE @@ -208,10 +210,9 @@ alternative_else_nop_endif ldr lr, [sp, #S_LR] add sp, sp, #S_FRAME_SIZE // restore sp -#ifndef CONFIG_UNMAP_KERNEL_AT_EL0 - eret -#else .if \el == 0 +alternative_insn eret, nop, ARM64_UNMAP_KERNEL_AT_EL0 +#ifdef CONFIG_UNMAP_KERNEL_AT_EL0 bne 4f msr far_el1, x30 tramp_alias x30, tramp_exit_native @@ -219,10 +220,10 @@ alternative_else_nop_endif 4: tramp_alias x30, tramp_exit_compat br x30 +#endif .else eret .endif -#endif .endm .macro get_thread_info, rd