From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=217.140.110.172 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794248881; b=d7aC6W4U7ldNNkgmX5lStKHrG5Op9y8IhNRBWb2jiMx6tOSOCJ2UHIxlNbMTOJZCLmIy DdZ5WfnrHU7us+ABDRENC250d34pe91CqjS3WKkkO6ZcxOMg/2fjDo07NBoKMIek45EQh Du4W4drLfE/F110ecTZFYeu6LV5rAVJhsu6xTbWBjLi+xqSXcUUQoqOk9maPk30jzUS5z utU3RL4tfWYdX9LIlLYSVQ+2BVlnTnkEUUUJIBNn9srlB8yzJifh4JVv+7aBJMgnRnyEC AO6wORhmBlqNlEXBOukpfkxOHbWCnreOafqK1qaUoytOST4h3VfMgrY1G/AgkaEAuzw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794248881; h=DMARC-Filter:Received:Received:DKIM-Signature:From:To:Cc:Subject: Date:Message-ID:X-Mailer:In-Reply-To:References:MIME-Version: Content-Transfer-Encoding; bh=mDWFweHSaiLpPshCS+h0q+iQaBu+Lgc9eGDx2KfwrFI=; b=uVYwA4jaOr+z997c5TkRfoIiiImU+XgUDOr4uGAUAvnmImGVfKBnI7BRfZmzwqIK9hfQ gycc9cRq9FKi4fK+ynX73/Z5iNG3tUUOgVp4rsgreKyEiyk8YB11RTOnb1Aao9S3BrozO Ds32fBCx4ilFTkWB2RB4WxfTYSEAjh+KkaAG3q9uXdyLQoI50ldcvnwIF1d0krJCvjQhS 0TsYw+ZmFFF9BQSu0jwrHkSd/1ng9CWHJkhhZKyG4y8FmpQ2lARGCiMAJ98MWwyZ3Wnp7 YWmrRK4os6wALCemxxhEUoABdFy4mrCVbrIVibl8tr4Yt9RPlKD0GWMhfo7pU7DPZlg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass header.d=arm.com header.i=@arm.com header.a=rsa-sha256 header.s=foss header.b=YcqTCjTp; arc=none smtp.remote-ip=217.140.110.172 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 7E7E4606CC67; Mon, 9 Nov 2026 18:28:01 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 7E7E4606CC67 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.a=rsa-sha256 header.s=foss header.b=YcqTCjTp Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id E91191758; Mon, 9 Nov 2026 10:27:57 -0800 (PST) Received: from fedora (LJ9QCPV96V.austin.arm.com [10.118.150.23]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id D12233F882; Mon, 9 Nov 2026 10:28:00 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1794248880; bh=J7EaISQeGY9QzQfcJ7AujRJOKPOkfJhuRA/a7kt8pXY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=YcqTCjTpFZ8v6r5DSW9z3y4VFfKrCU486QOfw2utAPO7Lhg521/Zg0JVwjXE6iex7 DwNxAI8qtYwO86gLXzWJqinLT83xKK7mvVfoU8Nf2hr3n/T6WeL+U1GsA6jzJhvO5j 7FvCMN5ZkHFdu/UbWO3y3dbd3XI5/e1RP1ERV9Mc= From: Bill Roberts To: "H. Peter Anvin" , Borislav Petkov , Dave Hansen , Ingo Molnar , rick.p.edgecombe@intel.com, Shuah Khan , Thomas Gleixner , x86@kernel.org Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, Bill Roberts Subject: [PATCH v5 3/6] selftests/x86: add shadow stack lock test Date: Mon, 9 Nov 2026 12:27:55 -0600 Message-ID: <20261109182758.252223-4-bill.roberts@arm.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20261109182758.252223-1-bill.roberts@arm.com> References: <20261109182758.252223-1-bill.roberts@arm.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The shadow stack selftests do not currently verify that locking a feature prevents subsequent changes to its enabled state. Add a test that locks the WRSS feature while enabled and verifies that attempting to disable it fails with -EPERM. Despite WRSS being locked, this allows the existing code in main() to disable shadow stack before returning to prevent a SIGSEGV from a shadow stack underflow. This is why shadow stack enable is not locked. Signed-off-by: Bill Roberts --- .../testing/selftests/x86/test_shadow_stack.c | 38 +++++++++++++++++++ 1 file changed, 38 insertions(+) diff --git a/tools/testing/selftests/x86/test_shadow_stack.c b/tools/testing/selftests/x86/test_shadow_stack.c index b52c5420c137..e047f1ceae0a 100644 --- a/tools/testing/selftests/x86/test_shadow_stack.c +++ b/tools/testing/selftests/x86/test_shadow_stack.c @@ -1060,9 +1060,28 @@ int test_ptrace(void) return 1; } +static int test_locking(void) +{ + + if (ARCH_PRCTL(ARCH_SHSTK_LOCK, ARCH_SHSTK_WRSS)) { + printf("[FAIL]\tCould not lock Shadow stack write\n"); + return 1; + } + + if (ARCH_PRCTL(ARCH_SHSTK_DISABLE, ARCH_SHSTK_WRSS) != -EPERM) { + printf("[FAIL]\tCould change Shadow stack write after lock\n"); + return 1; + } + + printf("[OK]\tShadow stack locking\n"); + + return 0; +} + int main(int argc, char *argv[]) { int ret = 0; + unsigned long status = 0; if (ARCH_PRCTL(ARCH_SHSTK_ENABLE, ARCH_SHSTK_SHSTK)) { printf("[SKIP]\tCould not enable Shadow stack\n"); @@ -1079,12 +1098,31 @@ int main(int argc, char *argv[]) return 1; } + /* Note: test_shadow_stack_lock() needs write enabled */ if (ARCH_PRCTL(ARCH_SHSTK_ENABLE, ARCH_SHSTK_WRSS)) { printf("[SKIP]\tCould not enable WRSS\n"); ret = 1; goto out; } + if (ARCH_PRCTL(ARCH_SHSTK_STATUS, &status)) { + printf("[FAIL]\tCould not get Shadow stack status\n"); + ret = 1; + goto out; + } + + if (status != (ARCH_SHSTK_WRSS|ARCH_SHSTK_SHSTK)) { + printf("[FAIL]\tStatus not as expected, got 0x%lx status, wanted: 0x%llx\n", + status, (ARCH_SHSTK_WRSS|ARCH_SHSTK_SHSTK)); + ret = 1; + goto out; + } + + if (test_locking()) { + ret = 1; + goto out; + } + /* Should have succeeded if here, but this is a test, so double check. */ if (!get_ssp()) { printf("[FAIL]\tShadow stack disabled\n"); -- 2.55.0