From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 45A8EC04A94 for ; Fri, 11 Aug 2023 16:26:15 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 8A8656B0074; Fri, 11 Aug 2023 12:26:14 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 858666B0078; Fri, 11 Aug 2023 12:26:14 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 71FA66B007B; Fri, 11 Aug 2023 12:26:14 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 5FEB46B0074 for ; Fri, 11 Aug 2023 12:26:14 -0400 (EDT) Received: from smtpin26.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 2A3231A08A0 for ; Fri, 11 Aug 2023 16:26:14 +0000 (UTC) X-FDA: 81112351068.26.39682CE Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by imf11.hostedemail.com (Postfix) with ESMTP id 7DABE40020 for ; Fri, 11 Aug 2023 16:26:12 +0000 (UTC) Authentication-Results: imf11.hostedemail.com; dkim=none; spf=pass (imf11.hostedemail.com: domain of cmarinas@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=cmarinas@kernel.org; dmarc=fail reason="SPF not aligned (relaxed), No valid DKIM" header.from=arm.com (policy=none) ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1691771172; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=8fjANWOstaIzcYa5Cg1g7lz2w2/b4n6P/2JqHwTYBtE=; b=o/G2PVrDWUjmqAe0GKdkd3nEdIhm4psY/CRsPd1cawyL5eL/mE3IwpSyLLW0Ks23TX3CzL 1zXoyzPW1T6DbWcdSF6jIdWJf1h/L/lJcCk9QhCB5IqduSnDOIqZTCDaS/JpY508RHSXhM lZ8aKiDgiADlTOmaF5KFGj3Bc0+jYso= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1691771172; a=rsa-sha256; cv=none; b=0OZPCmsYeuHx3HxqEhvKFx4HcR+gJgPDaTNG1T/qF5ZXL5lA276fgPYXCgljSCRwdwDl7H 0sLOloLqQBscaPU0jxhsichABsp5xgXGmBBXfWrTI2+0p1ikWmUN5I7CCr8/AHcIScCsH9 Em6pZT+cYkqVOM8zjzQf63rRyMnf9J8= ARC-Authentication-Results: i=1; imf11.hostedemail.com; dkim=none; spf=pass (imf11.hostedemail.com: domain of cmarinas@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=cmarinas@kernel.org; dmarc=fail reason="SPF not aligned (relaxed), No valid DKIM" header.from=arm.com (policy=none) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 8541864B18; Fri, 11 Aug 2023 16:26:11 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2AFF3C433C7; Fri, 11 Aug 2023 16:26:05 +0000 (UTC) Date: Fri, 11 Aug 2023 17:26:03 +0100 From: Catalin Marinas To: Mark Brown Cc: Will Deacon , Jonathan Corbet , Andrew Morton , Marc Zyngier , Oliver Upton , James Morse , Suzuki K Poulose , Arnd Bergmann , Oleg Nesterov , Eric Biederman , Kees Cook , Shuah Khan , "Rick P. Edgecombe" , Deepak Gupta , Ard Biesheuvel , Szabolcs Nagy , "H.J. Lu" , Paul Walmsley , Palmer Dabbelt , Albert Ou , linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, kvmarm@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org Subject: Re: [PATCH v4 19/36] arm64/gcs: Allocate a new GCS for threads with GCS enabled Message-ID: References: <20230807-arm64-gcs-v4-0-68cfa37f9069@kernel.org> <20230807-arm64-gcs-v4-19-68cfa37f9069@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230807-arm64-gcs-v4-19-68cfa37f9069@kernel.org> X-Stat-Signature: 1yua6syyjkrguongcfbtkxmzja9uscmk X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 7DABE40020 X-Rspam-User: X-HE-Tag: 1691771172-711451 X-HE-Meta: U2FsdGVkX1+VeIeLOc3Y5ZC82dtQHbY3uSoXsFO+XSnnXYW9pmecDCMbqtbOnat2CQXCloF+WTlRvJ1AZEjazI8TwVzmuDQKZLUiWtFTWyMG0LcJo4F9zgZEdYUG5UsQHEMvWd3CpnKsWaGQogEx1JQH+ZDAlwLRiM2PYLIlaNDNiKLpnCyvvT9vgEaxOqF4jIXCD4AKokZweDHW1Ifzh8ZKh10h+NnWPozaR+e4jnxWjDDMhAA7ZVjJ/tzvKsOehdZQkM4T2cR1IAcPpYX3rJHu4Hr6mZ7UXuXyloJSsAw96pNUv1QOX94Gbj1Xd1JldTGVkJCT4KvKZYeKgMwiBq08ehWtwWgl9pOV6H7IUJBKB2aHWlwqXHuwnL9u18vtiWMTpUejXQIQLfDCnp0cFZXEOWQUGboFSvWDOsfFg03RPSs2UQzWQMkMX9pgQPXmkUUxtq4TSNm/IVUAGn8fcg92KLFukk/E8gGrwGI7yIApY7C70COhBDuMV+lIZSDftfpuTxqg1mH9JdbUKZABvGJfGx8UhoUCIQoUuBtzp/KIJqGlnkC3cu8mq7MXaN1WzVo0fO+mLWfA9wovDE3eFS+TutgyhnuHDJ12SDbnGAbxlYY4QEtaJFm7dXR5ND0n4SRfe8m6vXgmTFge9ijyVcfKzt84RBKfzmF9k3aw+oq1cyCe4EBD086KU/mkuW34MQivVLUwoQOsSGVOj79OCvVafvalck20Cg7P2caPsOCWXZY9iP7xncnoQmE4hUBpaVwUMRdJuHKuKmINij3nAwodLwM2S8RKhiA+vjaxivBFHR+x8EZbbLLe39Sl/UKE6MATdPKvBWZDtCwTK0LO7xrg9ivDWDgKMwWjQsjeI5BE7s1fDeHQFTW9yjEpYv1V1z3jIKMrJIHgP+j1a3+ZKFPpdRVPrOuxZW0PmbHIkLW8tFFudTyOjz4rgn5HXwd84QzPdJV3alQlat2157z B99QhAK5 cQES2M3jThXa0pUjAR7kpuTZsSgwcOap0PGFniOZgYoa268WsFKvo7UVZPjch1JkCE7l21BGpDDtwExv8CdbMDIcGvT2d3FVzzX1cfY6SXQSSGbtFAgQh4LpP5lAOGY9zansOaG+ugmwPXfzpAJb/8dacFTlOAC5c9wa3v5MGgGuzdXbGrbys+1km8eQg/yGxt29nwWZTxBmfdzxLKYlD6IpZjhme4WpeyEFH81v9Q5YlMRNkxfJHKOBpLUBCCdftwb/+gfD/4XeKKjVo+KOg4uhv2ZQ2lqKQxnx4gFaqfqlxnqdob0vOPBsfsvqa69Hu1tQzaO4gKxLpPHVRCS8mQfS6k74R23UlL+C9fH3X4AbHG9otzRD2j9MFCYfktcxhekESfpLRDf8ngTWdbye/pWppHIsQiEL46F5zcLhXvgYteXGRXgiKiZlmIz26Ejl02EV0oH61l+5R2kZT4M+eNTRzCKr2qkkPiRL0q9iUmP4Mcxw= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Aug 07, 2023 at 11:00:24PM +0100, Mark Brown wrote: > diff --git a/arch/arm64/mm/gcs.c b/arch/arm64/mm/gcs.c > index b0a67efc522b..1e059c37088d 100644 > --- a/arch/arm64/mm/gcs.c > +++ b/arch/arm64/mm/gcs.c > @@ -8,6 +8,62 @@ > #include > #include > > +static unsigned long alloc_gcs(unsigned long addr, unsigned long size, > + unsigned long token_offset, bool set_res_tok) > +{ > + int flags = MAP_ANONYMOUS | MAP_PRIVATE; > + struct mm_struct *mm = current->mm; > + unsigned long mapped_addr, unused; > + > + if (addr) > + flags |= MAP_FIXED_NOREPLACE; > + > + mmap_write_lock(mm); > + mapped_addr = do_mmap(NULL, addr, size, PROT_READ, flags, > + VM_SHADOW_STACK | VM_WRITE, 0, &unused, NULL); Why not PROT_WRITE as well? I guess I need to check the x86 patches since the do_mmap() called here has a different prototype than what's in mainline. This gets confusing since currently the VM_* flags are derived from the PROT_* flags passed to mmap(). But you skip the PROT_WRITE in favour of adding VM_WRITE directly. I haven't followed the x86 discussion but did we run out of PROT_* bits for a PROT_SHADOW_STACK? > + mmap_write_unlock(mm); > + > + return mapped_addr; > +} > + > +static unsigned long gcs_size(unsigned long size) > +{ > + if (size) > + return PAGE_ALIGN(size); > + > + /* Allocate RLIMIT_STACK with limits of PAGE_SIZE..4G */ > + size = PAGE_ALIGN(min_t(unsigned long long, > + rlimit(RLIMIT_STACK), SZ_4G)); > + return max(PAGE_SIZE, size); > +} I saw Szabolcs commenting on the default size as well. Maybe we should go for RLIMIT_STACK/2 but let's see how the other sub-thread is going. > + > +unsigned long gcs_alloc_thread_stack(struct task_struct *tsk, > + unsigned long clone_flags, size_t size) > +{ > + unsigned long addr; > + > + if (!system_supports_gcs()) > + return 0; > + > + if (!task_gcs_el0_enabled(tsk)) > + return 0; > + > + if ((clone_flags & (CLONE_VFORK | CLONE_VM)) != CLONE_VM) > + return 0; Is it safe for CLONE_VFORK not to get a new shadow stack? A syscall for exec could push something to the stack. I guess the GCS pointer in the parent stays the same, so it wouldn't matter. That said, I think this check should be somewhere higher up in the caller of gcs_alloc_thread_stack(). The copy_thread_gcs() function already does most of the above checks. Is the GCS allocation called from elsewhere as well? -- Catalin