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[109.217.237.144]) by smtp.gmail.com with ESMTPSA id n8sm9871745wmq.12.2021.04.29.07.52.19 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 29 Apr 2021 07:52:20 -0700 (PDT) Subject: Re: [PATCH v3 3/3] hw/core/loader: clear uninitialized ROM space To: Laurent Vivier , qemu-devel@nongnu.org References: <20210429141326.69245-1-laurent@vivier.eu> <20210429141326.69245-4-laurent@vivier.eu> From: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= Message-ID: <7dc74cc1-db14-ec34-274a-a23d6b44e793@redhat.com> Date: Thu, 29 Apr 2021 16:52:19 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <20210429141326.69245-4-laurent@vivier.eu> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=philmd@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=philmd@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.22, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Peter Maydell , Paolo Bonzini , Richard Henderson , Stefano Garzarella Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 4/29/21 4:13 PM, Laurent Vivier wrote: > As for "hw/elf_ops: clear uninitialized segment space" we need to > clear the uninitialized space when the ELF is set in ROM. > > Signed-off-by: Laurent Vivier > --- > hw/core/loader.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/hw/core/loader.c b/hw/core/loader.c > index d3e5f3b423f6..8146fdcbb7a0 100644 > --- a/hw/core/loader.c > +++ b/hw/core/loader.c > @@ -1146,9 +1146,13 @@ static void rom_reset(void *unused) > if (rom->mr) { > void *host = memory_region_get_ram_ptr(rom->mr); > memcpy(host, rom->data, rom->datasize); > + memset(host + rom->datasize, 0, rom->romsize - rom->datasize); > } else { > address_space_write_rom(rom->as, rom->addr, MEMTXATTRS_UNSPECIFIED, > rom->data, rom->datasize); > + address_space_set(rom->as, rom->addr + rom->datasize, 0, > + rom->romsize - rom->datasize, > + MEMTXATTRS_UNSPECIFIED); > } > if (rom->isrom) { > /* rom needs to be written only once */ > This is consistent with the comment from commit d60fa42e8ba ("Save memory allocation in the elf loader"): /* datasize is the amount of memory allocated in "data". If datasize is less * than romsize, it means that the area from datasize to romsize is filled * with zeros. */ Therefore: Reviewed-by: Philippe Mathieu-Daudé However depending on the underlying media, there might be cases where we want to fill with -1 instead. Just to keep in mind, if one day it bites us. Regards, Phil.