Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752650AbdLFMix (ORCPT ); Wed, 6 Dec 2017 07:38:53 -0500 Received: from foss.arm.com ([217.140.101.70]:34730 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752155AbdLFMgL (ORCPT ); Wed, 6 Dec 2017 07:36:11 -0500 From: Will Deacon To: linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org, catalin.marinas@arm.com, mark.rutland@arm.com, ard.biesheuvel@linaro.org, sboyd@codeaurora.org, dave.hansen@linux.intel.com, keescook@chromium.org, msalter@redhat.com, labbott@redhat.com, tglx@linutronix.de, Will Deacon Subject: [PATCH v3 10/20] arm64: entry: Add exception trampoline page for exceptions from EL0 Date: Wed, 6 Dec 2017 12:35:29 +0000 Message-Id: <1512563739-25239-11-git-send-email-will.deacon@arm.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1512563739-25239-1-git-send-email-will.deacon@arm.com> References: <1512563739-25239-1-git-send-email-will.deacon@arm.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4000 Lines: 162 To allow unmapping of the kernel whilst running at EL0, we need to point the exception vectors at an entry trampoline that can map/unmap the kernel on entry/exit respectively. This patch adds the trampoline page, although it is not yet plugged into the vector table and is therefore unused. Reviewed-by: Mark Rutland Signed-off-by: Will Deacon --- arch/arm64/kernel/entry.S | 86 +++++++++++++++++++++++++++++++++++++++++ arch/arm64/kernel/vmlinux.lds.S | 17 ++++++++ 2 files changed, 103 insertions(+) diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index d454d8ed45e4..716b5ef42e29 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -28,6 +28,8 @@ #include #include #include +#include +#include #include #include #include @@ -943,6 +945,90 @@ __ni_sys_trace: .popsection // .entry.text +#ifdef CONFIG_UNMAP_KERNEL_AT_EL0 +/* + * Exception vectors trampoline. + */ + .pushsection ".entry.tramp.text", "ax" + + .macro tramp_map_kernel, tmp + mrs \tmp, ttbr1_el1 + sub \tmp, \tmp, #(SWAPPER_DIR_SIZE + RESERVED_TTBR0_SIZE) + bic \tmp, \tmp, #USER_ASID_FLAG + msr ttbr1_el1, \tmp + .endm + + .macro tramp_unmap_kernel, tmp + mrs \tmp, ttbr1_el1 + add \tmp, \tmp, #(SWAPPER_DIR_SIZE + RESERVED_TTBR0_SIZE) + orr \tmp, \tmp, #USER_ASID_FLAG + msr ttbr1_el1, \tmp + /* + * We avoid running the post_ttbr_update_workaround here because the + * user and kernel ASIDs don't have conflicting mappings, so any + * "blessing" as described in: + * + * http://lkml.kernel.org/r/56BB848A.6060603@caviumnetworks.com + * + * will not hurt correctness. Whilst this may partially defeat the + * point of using split ASIDs in the first place, it avoids + * the hit of invalidating the entire I-cache on every return to + * userspace. + */ + .endm + + .macro tramp_ventry, regsize = 64 + .align 7 +1: + .if \regsize == 64 + msr tpidrro_el0, x30 // Restored in kernel_ventry + .endif + tramp_map_kernel x30 + ldr x30, =vectors + prfm plil1strm, [x30, #(1b - tramp_vectors)] + msr vbar_el1, x30 + add x30, x30, #(1b - tramp_vectors) + isb + br x30 + .endm + + .macro tramp_exit, regsize = 64 + adr x30, tramp_vectors + msr vbar_el1, x30 + tramp_unmap_kernel x30 + .if \regsize == 64 + mrs x30, far_el1 + .endif + eret + .endm + + .align 11 +ENTRY(tramp_vectors) + .space 0x400 + + tramp_ventry + tramp_ventry + tramp_ventry + tramp_ventry + + tramp_ventry 32 + tramp_ventry 32 + tramp_ventry 32 + tramp_ventry 32 +END(tramp_vectors) + +ENTRY(tramp_exit_native) + tramp_exit +END(tramp_exit_native) + +ENTRY(tramp_exit_compat) + tramp_exit 32 +END(tramp_exit_compat) + + .ltorg + .popsection // .entry.tramp.text +#endif /* CONFIG_UNMAP_KERNEL_AT_EL0 */ + /* * Special system call wrappers. */ diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S index 7da3e5c366a0..6b4260f22aab 100644 --- a/arch/arm64/kernel/vmlinux.lds.S +++ b/arch/arm64/kernel/vmlinux.lds.S @@ -57,6 +57,17 @@ jiffies = jiffies_64; #define HIBERNATE_TEXT #endif +#ifdef CONFIG_UNMAP_KERNEL_AT_EL0 +#define TRAMP_TEXT \ + . = ALIGN(PAGE_SIZE); \ + VMLINUX_SYMBOL(__entry_tramp_text_start) = .; \ + *(.entry.tramp.text) \ + . = ALIGN(PAGE_SIZE); \ + VMLINUX_SYMBOL(__entry_tramp_text_end) = .; +#else +#define TRAMP_TEXT +#endif + /* * The size of the PE/COFF section that covers the kernel image, which * runs from stext to _edata, must be a round multiple of the PE/COFF @@ -113,6 +124,7 @@ SECTIONS HYPERVISOR_TEXT IDMAP_TEXT HIBERNATE_TEXT + TRAMP_TEXT *(.fixup) *(.gnu.warning) . = ALIGN(16); @@ -214,6 +226,11 @@ SECTIONS . += RESERVED_TTBR0_SIZE; #endif +#ifdef CONFIG_UNMAP_KERNEL_AT_EL0 + tramp_pg_dir = .; + . += PAGE_SIZE; +#endif + __pecoff_data_size = ABSOLUTE(. - __initdata_begin); _end = .; -- 2.1.4