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[2401:3900:2:1::2]) by mx.google.com with ESMTPS id j8si1591360pgq.542.2019.03.20.06.15.50 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 20 Mar 2019 06:15:51 -0700 (PDT) Received-SPF: neutral (google.com: 2401:3900:2:1::2 is neither permitted nor denied by best guess record for domain of mpe@ellerman.id.au) client-ip=2401:3900:2:1::2; Authentication-Results: mx.google.com; spf=neutral (google.com: 2401:3900:2:1::2 is neither permitted nor denied by best guess record for domain of mpe@ellerman.id.au) smtp.mailfrom=mpe@ellerman.id.au Received: from authenticated.ozlabs.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mail.ozlabs.org (Postfix) with ESMTPSA id 44PVm43NQyz9sNG; Thu, 21 Mar 2019 00:15:48 +1100 (AEDT) From: Michael Ellerman To: Catalin Marinas , Qian Cai Cc: akpm@linux-foundation.org, paulus@ozlabs.org, benh@kernel.crashing.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kvm-ppc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH v2] kmemleak: skip scanning holes in the .bss section In-Reply-To: <20190319115747.GB59586@arrakis.emea.arm.com> References: <20190313145717.46369-1-cai@lca.pw> <20190319115747.GB59586@arrakis.emea.arm.com> Date: Thu, 21 Mar 2019 00:15:46 +1100 Message-ID: <87lg19y9dp.fsf@concordia.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain X-Bogosity: Ham, tests=bogofilter, spamicity=0.000005, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Catalin Marinas writes: > Hi Qian, > > On Wed, Mar 13, 2019 at 10:57:17AM -0400, Qian Cai wrote: >> @@ -1531,7 +1547,14 @@ static void kmemleak_scan(void) >> >> /* data/bss scanning */ >> scan_large_block(_sdata, _edata); >> - scan_large_block(__bss_start, __bss_stop); >> + >> + if (bss_hole_start) { >> + scan_large_block(__bss_start, bss_hole_start); >> + scan_large_block(bss_hole_stop, __bss_stop); >> + } else { >> + scan_large_block(__bss_start, __bss_stop); >> + } >> + >> scan_large_block(__start_ro_after_init, __end_ro_after_init); > > I'm not a fan of this approach but I couldn't come up with anything > better. I was hoping we could check for PageReserved() in scan_block() > but on arm64 it ends up not scanning the .bss at all. > > Until another user appears, I'm ok with this patch. > > Acked-by: Catalin Marinas I actually would like to rework this kvm_tmp thing to not be in bss at all. It's a bit of a hack and is incompatible with strict RWX. If we size it a bit more conservatively we can hopefully just reserve some space in the text section for it. I'm not going to have time to work on that immediately though, so if people want this fixed now then this patch could go in as a temporary solution. cheers