From patchwork Wed Sep 16 15:08:26 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Madhavan T. Venkataraman" X-Patchwork-Id: 11780425 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 409BF92C for ; Wed, 16 Sep 2020 18:30:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1C47F206D4 for ; Wed, 16 Sep 2020 18:30:39 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b="Ujz+S1Oq" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728071AbgIPSag (ORCPT ); Wed, 16 Sep 2020 14:30:36 -0400 Received: from linux.microsoft.com ([13.77.154.182]:37872 "EHLO linux.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728094AbgIPSaE (ORCPT ); Wed, 16 Sep 2020 14:30:04 -0400 Received: from localhost.localdomain (unknown [47.187.206.220]) by linux.microsoft.com (Postfix) with ESMTPSA id 169662074C90; Wed, 16 Sep 2020 08:08:37 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 169662074C90 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1600268917; bh=b+dZfSYt921SZbqVi9d6jmG8B2GKXdUDhoo8NhJxV+k=; h=From:To:Subject:Date:In-Reply-To:References:From; b=Ujz+S1OqtosPp/8L9N3unu6wuJGss69KS6W/GHWBWqM4qfdWcRG/EKRgUKJbOEORc x+qd/TTcA8Trl1XdmvODaLvWIGzELcQgFeVjLlgZi8uYhTVxlKm7dCUF532grSOPqk Po96nXGPIm2UK+uUyzCR1OmHS74BMY4y3GHpUvus= From: madvenka@linux.microsoft.com To: kernel-hardening@lists.openwall.com, linux-api@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, oleg@redhat.com, x86@kernel.org, madvenka@linux.microsoft.com Subject: [PATCH v2 4/4] [RFC] arm/trampfd: Provide support for the trampoline file descriptor Date: Wed, 16 Sep 2020 10:08:26 -0500 Message-Id: <20200916150826.5990-5-madvenka@linux.microsoft.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20200916150826.5990-1-madvenka@linux.microsoft.com> References: <210d7cd762d5307c2aa1676705b392bd445f1baa> <20200916150826.5990-1-madvenka@linux.microsoft.com> Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: From: "Madhavan T. Venkataraman" - Define architecture specific register names - Architecture specific functions for: - system call init - code descriptor check - data descriptor check - Fill a page with a trampoline table, Signed-off-by: Madhavan T. Venkataraman --- arch/arm/include/uapi/asm/ptrace.h | 21 +++++ arch/arm/kernel/Makefile | 1 + arch/arm/kernel/trampfd.c | 124 +++++++++++++++++++++++++++++ arch/arm/tools/syscall.tbl | 1 + 4 files changed, 147 insertions(+) create mode 100644 arch/arm/kernel/trampfd.c diff --git a/arch/arm/include/uapi/asm/ptrace.h b/arch/arm/include/uapi/asm/ptrace.h index e61c65b4018d..598047768f9b 100644 --- a/arch/arm/include/uapi/asm/ptrace.h +++ b/arch/arm/include/uapi/asm/ptrace.h @@ -151,6 +151,27 @@ struct pt_regs { #define ARM_r0 uregs[0] #define ARM_ORIG_r0 uregs[17] +/* + * These register names are to be used by 32-bit applications. + */ +enum reg_32_name { + arm_min, + arm_r0 = arm_min, + arm_r1, + arm_r2, + arm_r3, + arm_r4, + arm_r5, + arm_r6, + arm_r7, + arm_r8, + arm_r9, + arm_r10, + arm_r11, + arm_r12, + arm_max, +}; + /* * The size of the user-visible VFP state as seen by PTRACE_GET/SETVFPREGS * and core dumps. diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile index 89e5d864e923..652c54c2f19a 100644 --- a/arch/arm/kernel/Makefile +++ b/arch/arm/kernel/Makefile @@ -105,5 +105,6 @@ obj-$(CONFIG_SMP) += psci_smp.o endif obj-$(CONFIG_HAVE_ARM_SMCCC) += smccc-call.o +obj-$(CONFIG_TRAMPFD) += trampfd.o extra-y := $(head-y) vmlinux.lds diff --git a/arch/arm/kernel/trampfd.c b/arch/arm/kernel/trampfd.c new file mode 100644 index 000000000000..45146ed489e8 --- /dev/null +++ b/arch/arm/kernel/trampfd.c @@ -0,0 +1,124 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Trampoline FD - ARM support. + * + * Author: Madhavan T. Venkataraman (madvenka@linux.microsoft.com) + * + * Copyright (c) 2020, Microsoft Corporation. + */ + +#include +#include + +#define TRAMPFD_CODE_SIZE 28 + +/* + * trampfd syscall. + */ +void trampfd_arch(struct trampfd_info *info) +{ + info->code_size = TRAMPFD_CODE_SIZE; + info->ntrampolines = PAGE_SIZE / info->code_size; + info->code_offset = TRAMPFD_CODE_PGOFF << PAGE_SHIFT; + info->reserved = 0; +} + +/* + * trampfd code descriptor check. + */ +int trampfd_code_arch(struct trampfd_code *code) +{ + int ntrampolines; + int min, max; + + min = arm_min; + max = arm_max; + ntrampolines = PAGE_SIZE / TRAMPFD_CODE_SIZE; + + if (code->reg < min || code->reg >= max) + return -EINVAL; + + if (!code->ntrampolines || code->ntrampolines > ntrampolines) + return -EINVAL; + return 0; +} + +/* + * trampfd data descriptor check. + */ +int trampfd_data_arch(struct trampfd_data *data) +{ + int min, max; + + min = arm_min; + max = arm_max; + + if (data->reg < min || data->reg >= max) + return -EINVAL; + return 0; +} + +#define MOVW(ins, reg, imm32) \ +{ \ + u16 *_imm16 = (u16 *) &(imm32); /* little endian */ \ + int _hw, _opcode; \ + \ + for (_hw = 0; _hw < 2; _hw++) { \ + /* movw or movt */ \ + _opcode = _hw ? 0xe3400000 : 0xe3000000; \ + *ins++ = _opcode | (_imm16[_hw] >> 12) << 16 | \ + (reg) << 12 | (_imm16[_hw] & 0xFFF); \ + } \ +} + +#define LDR(ins, reg) \ +{ \ + *ins++ = 0xe5900000 | (reg) << 16 | (reg) << 12; \ +} + +#define BX(ins, reg) \ +{ \ + *ins++ = 0xe12fff10 | (reg); \ +} + +void trampfd_code_fill(struct trampfd *trampfd, char *addr) +{ + char *eaddr = addr + PAGE_SIZE; + int creg = trampfd->code_reg - arm_min; + int dreg = trampfd->data_reg - arm_min; + u32 *code = trampfd->code; + u32 *data = trampfd->data; + u32 *instruction = (u32 *) addr; + int i; + + for (i = 0; i < trampfd->ntrampolines; i++, code++, data++) { + /* + * movw creg, code & 0xFFFF + * movt creg, code >> 16 + */ + MOVW(instruction, creg, code); + + /* + * ldr creg, [creg] + */ + LDR(instruction, creg); + + /* + * movw dreg, data & 0xFFFF + * movt dreg, data >> 16 + */ + MOVW(instruction, dreg, data); + + /* + * ldr dreg, [dreg] + */ + LDR(instruction, dreg); + + /* + * bx creg + */ + BX(instruction, creg); + } + addr = (char *) instruction; + memset(addr, 0, eaddr - addr); +} diff --git a/arch/arm/tools/syscall.tbl b/arch/arm/tools/syscall.tbl index d5cae5ffede0..85dcbc9e08ee 100644 --- a/arch/arm/tools/syscall.tbl +++ b/arch/arm/tools/syscall.tbl @@ -452,3 +452,4 @@ 437 common openat2 sys_openat2 438 common pidfd_getfd sys_pidfd_getfd 439 common faccessat2 sys_faccessat2 +440 common trampfd sys_trampfd