From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-lf1-f52.google.com (mail-lf1-f52.google.com [209.85.167.52]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F254112C80A for ; Thu, 7 Mar 2024 14:22:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.167.52 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709821338; cv=none; b=DqzuRw8+jp7IoCvzUGvigeiKYd6OHZLkSBKdlVaJzuq2LCC4ScKef/b7LW/HKeKSVOmqr+rT/VX5eZP65/mGfGqtKmuXkamwYXZx5JqkQh2q7RR4SlSNRCPYfvfO20HxBAdVkQiUUbV9zRhG3a0E5LLaSs+Hskyxz3Zb791Oo3s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709821338; c=relaxed/simple; bh=F66H3GtO1vPo4dQ+jNE2W9m971kNiLoxFo7yvvrYRxQ=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=CTJhjYkm1gRETCaKzfkexSctUND6entE26xckZL00ej3YGBKsynFv1e7BMJGExOHA1IehoBDnS5xTHafPCrnlDvEhkwqSl0cmXnSjuQvh15k9/rtvga0GagCTBmOF2qzQQfZCycpANUZtk8UHpCeuqxGIkxvnUPSFibN/csyEa4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linaro.org; spf=pass smtp.mailfrom=linaro.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b=K+8HhZxF; arc=none smtp.client-ip=209.85.167.52 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linaro.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linaro.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="K+8HhZxF" Received: by mail-lf1-f52.google.com with SMTP id 2adb3069b0e04-51320ca689aso972411e87.2 for ; Thu, 07 Mar 2024 06:22:16 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; t=1709821335; x=1710426135; darn=lists.linux.dev; h=cc:to:in-reply-to:references:message-id:content-transfer-encoding :mime-version:subject:date:from:from:to:cc:subject:date:message-id :reply-to; bh=gA8ZxFrx9Z5SRPo+jVn81u04sn9IDPwgcfATkPUWIfU=; b=K+8HhZxFl8BQgWlMD716YVT3Yvlm83nysO4Lz7u1xBnh8CEfh/ASCxEkzkayxl+994 cK6IgjEyoHQ4NxeI5Fl5YZbI/Nkq0t3xS0aSKT9yB5Eetw12w0gsJ76ltj4oxcZYId1F cnzVsouILCVyFX1BpP4MFwA4SHNll8vdt/sLEDbS202OJNpyTdWhjvc6WgMVZSf8q77X y751SCiESPyg7YYzdAAxt/Vkmws6MoMXMtqVTen0eVcIm+61s3Uf16JnUTsWzekIrHNm iplquv/ghNrT6AGRJ330XjN7OP/0UDOK272w6t2PvWZXXR5fS65kDlziaf++zDo4E6XC yazw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1709821335; x=1710426135; h=cc:to:in-reply-to:references:message-id:content-transfer-encoding :mime-version:subject:date:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=gA8ZxFrx9Z5SRPo+jVn81u04sn9IDPwgcfATkPUWIfU=; b=e7+QgVN9JJtC9X+9BqgbAt4LaY+p4t8vRLzT6G0j4dw8VnNAJu56S19wm5XuR9CpEm iGG3rrNnHQAXE3aTnOBf2Mkh5jO7fQQGeEfvgdvnnGfAkloP3vRTnqfC9vQCUlD1liMt yduYIsWP30kvRijmj3EABqNJB/9kLEbcgk9bRIssiUvgi4DPJaXGU9BuA+eGeCDJne+N XxHz2KD4VQh5/gLWcuR6kMvT1OEXuULM7O8+4eYSE7jh2+/GTkgxR+oHwZ2+E0YgWXPj NFXU9lIs1P4MntoArNdGf4z1wERZDBzR0QQyHsab63zOSnmIYG7zOxCeUOYSnX/REzot 06Dg== X-Forwarded-Encrypted: i=1; AJvYcCVL3eJXCgD2F5GfUVfErbLmSw4HQIw4HqyRji+Wlu4s1VPGlqKCJIypi3LdXXYw5k9AYgxVjhtXdXtcA0yYmoobI7pVDw== X-Gm-Message-State: AOJu0YxjKiZ5FSMiWLBTFWL6ipbifpsVk2oXoiPmSqkChCKP3wliJKdj Tq2QGiFDZwkldFGdCK2pjDmmZ2MW0iXQ/+Fz6lMUYQ0Qv8MRNLfONZgEacExktQ= X-Google-Smtp-Source: AGHT+IFJ0RWu6nZugPa5qOJDHSREvOJkqmv9RWJNmGCystSvavUS9gLkmUCT0/awji5M89TB64nTNw== X-Received: by 2002:a05:6512:2216:b0:513:4a0c:b83d with SMTP id h22-20020a056512221600b005134a0cb83dmr1652946lfu.46.1709821335171; Thu, 07 Mar 2024 06:22:15 -0800 (PST) Received: from [127.0.1.1] ([85.235.12.238]) by smtp.gmail.com with ESMTPSA id x11-20020a19e00b000000b005133b381a5csm2417137lfg.90.2024.03.07.06.22.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 07 Mar 2024 06:22:14 -0800 (PST) From: Linus Walleij Date: Thu, 07 Mar 2024 15:22:08 +0100 Subject: [PATCH v2 9/9] ARM: KCFI: Allow permissive CFI mode Precedence: bulk X-Mailing-List: llvm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20240307-arm32-cfi-v2-9-cc74ea0306b3@linaro.org> References: <20240307-arm32-cfi-v2-0-cc74ea0306b3@linaro.org> In-Reply-To: <20240307-arm32-cfi-v2-0-cc74ea0306b3@linaro.org> To: Russell King , Sami Tolvanen , Kees Cook , Nathan Chancellor , Nick Desaulniers , Ard Biesheuvel , Arnd Bergmann Cc: linux-arm-kernel@lists.infradead.org, llvm@lists.linux.dev, Linus Walleij X-Mailer: b4 0.12.4 This registers a breakpoint handler for the new breakpoint type (0x03) inserted by LLVM CLANG for CFI breakpoints. If we are in permissive mode, just print a backtrace and continue. Example with CONFIG_CFI_PERMISSIVE enabled: root@Vexpress:/ echo CFI_FORWARD_PROTO > /sys/kernel/debug/provoke-crash/DIRECT lkdtm: Performing direct entry CFI_FORWARD_PROTO lkdtm: Calling matched prototype ... lkdtm: Calling mismatched prototype ... hw-breakpoint: Permissive CFI breakpoint CPU: 0 PID: 114 Comm: sh Not tainted 6.8.0-rc1+ #111 Hardware name: ARM-Versatile Express unwind_backtrace from show_stack+0x28/0x30 (...) lkdtm: FAIL: survived mismatched prototype function call! lkdtm: Unexpected! This kernel (6.8.0-rc1+ armv7l) was built with CONFIG_CFI_CLANG=y As you can see the LKDTM test fails, but I expect that this would be expected behaviour in the permissive mode. Signed-off-by: Linus Walleij --- arch/arm/include/asm/hw_breakpoint.h | 1 + arch/arm/kernel/hw_breakpoint.c | 10 ++++++++++ 2 files changed, 11 insertions(+) diff --git a/arch/arm/include/asm/hw_breakpoint.h b/arch/arm/include/asm/hw_breakpoint.h index 62358d3ca0a8..e7f9961c53b2 100644 --- a/arch/arm/include/asm/hw_breakpoint.h +++ b/arch/arm/include/asm/hw_breakpoint.h @@ -84,6 +84,7 @@ static inline void decode_ctrl_reg(u32 reg, #define ARM_DSCR_MOE(x) ((x >> 2) & 0xf) #define ARM_ENTRY_BREAKPOINT 0x1 #define ARM_ENTRY_ASYNC_WATCHPOINT 0x2 +#define ARM_ENTRY_CFI_BREAKPOINT 0x3 #define ARM_ENTRY_SYNC_WATCHPOINT 0xa /* DSCR monitor/halting bits. */ diff --git a/arch/arm/kernel/hw_breakpoint.c b/arch/arm/kernel/hw_breakpoint.c index dc0fb7a81371..256146684813 100644 --- a/arch/arm/kernel/hw_breakpoint.c +++ b/arch/arm/kernel/hw_breakpoint.c @@ -932,6 +932,16 @@ static int hw_breakpoint_pending(unsigned long addr, unsigned int fsr, case ARM_ENTRY_SYNC_WATCHPOINT: watchpoint_handler(addr, fsr, regs); break; + case ARM_ENTRY_CFI_BREAKPOINT: + if (IS_ENABLED(CONFIG_CFI_PERMISSIVE)) { + pr_err("Permissive CFI breakpoint\n"); + dump_stack(); + /* Skip the breaking instruction */ + instruction_pointer(regs) += 4; + } else { + die("Oops - CFI", regs, 0); + } + break; default: ret = 1; /* Unhandled fault. */ } -- 2.34.1