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[217.140.101.70]) by mx.google.com with ESMTP id gr21si721835ejb.81.2019.03.22.08.52.38 for ; Fri, 22 Mar 2019 08:52:39 -0700 (PDT) Received-SPF: pass (google.com: domain of catalin.marinas@arm.com designates 217.140.101.70 as permitted sender) client-ip=217.140.101.70; Authentication-Results: mx.google.com; spf=pass (google.com: domain of catalin.marinas@arm.com designates 217.140.101.70 as permitted sender) smtp.mailfrom=catalin.marinas@arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id D22BEA78; Fri, 22 Mar 2019 08:52:37 -0700 (PDT) Received: from arrakis.emea.arm.com (arrakis.cambridge.arm.com [10.1.196.78]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 211443F59C; Fri, 22 Mar 2019 08:52:29 -0700 (PDT) Date: Fri, 22 Mar 2019 15:52:27 +0000 From: Catalin Marinas To: Andrey Konovalov Cc: Will Deacon , Mark Rutland , Robin Murphy , Kees Cook , Kate Stewart , Greg Kroah-Hartman , Andrew Morton , Ingo Molnar , "Kirill A . Shutemov" , Shuah Khan , Vincenzo Frascino , Eric Dumazet , "David S. Miller" , Alexei Starovoitov , Daniel Borkmann , Steven Rostedt , Ingo Molnar , Peter Zijlstra , Arnaldo Carvalho de Melo , Alex Deucher , Christian =?iso-8859-1?Q?K=F6nig?= , "David (ChunMing) Zhou" , Yishai Hadas , Mauro Carvalho Chehab , Jens Wiklander , Alex Williamson , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, netdev@vger.kernel.org, bpf@vger.kernel.org, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-rdma@vger.kernel.org, linux-media@vger.kernel.org, kvm@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Dmitry Vyukov , Kostya Serebryany , Evgeniy Stepanov , Lee Smith , Ramana Radhakrishnan , Jacob Bramley , Ruben Ayrapetyan , Chintan Pandya , Luc Van Oostenryck , Dave Martin , Kevin Brodsky , Szabolcs Nagy Subject: Re: [PATCH v13 13/20] bpf, arm64: untag user pointers in stack_map_get_build_id_offset Message-ID: <20190322155227.GS13384@arrakis.emea.arm.com> References: <09d6b8e5c8275de85c7aba716578fbcb3cbce924.1553093421.git.andreyknvl@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <09d6b8e5c8275de85c7aba716578fbcb3cbce924.1553093421.git.andreyknvl@google.com> User-Agent: Mutt/1.10.1 (2018-07-13) 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 Wed, Mar 20, 2019 at 03:51:27PM +0100, Andrey Konovalov wrote: > This patch is a part of a series that extends arm64 kernel ABI to allow to > pass tagged user pointers (with the top byte set to something else other > than 0x00) as syscall arguments. > > stack_map_get_build_id_offset() uses provided user pointers for vma > lookups, which can only by done with untagged pointers. > > Untag user pointers in this function for doing the lookup and > calculating the offset, but save as is in the bpf_stack_build_id > struct. > > Signed-off-by: Andrey Konovalov > --- > kernel/bpf/stackmap.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c > index 950ab2f28922..bb89341d3faf 100644 > --- a/kernel/bpf/stackmap.c > +++ b/kernel/bpf/stackmap.c > @@ -320,7 +320,9 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs, > } > > for (i = 0; i < trace_nr; i++) { > - vma = find_vma(current->mm, ips[i]); > + u64 untagged_ip = untagged_addr(ips[i]); > + > + vma = find_vma(current->mm, untagged_ip); > if (!vma || stack_map_get_build_id(vma, id_offs[i].build_id)) { > /* per entry fall back to ips */ > id_offs[i].status = BPF_STACK_BUILD_ID_IP; > @@ -328,7 +330,7 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs, > memset(id_offs[i].build_id, 0, BPF_BUILD_ID_SIZE); > continue; > } > - id_offs[i].offset = (vma->vm_pgoff << PAGE_SHIFT) + ips[i] > + id_offs[i].offset = (vma->vm_pgoff << PAGE_SHIFT) + untagged_ip > - vma->vm_start; > id_offs[i].status = BPF_STACK_BUILD_ID_VALID; > } Can the ips[*] here ever be tagged? -- Catalin