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([2a10:bac0:b000:73a8:7285:c2ff:fedd:7e3a]) by smtp.gmail.com with ESMTPSA id h16-20020a1709067cd000b00a45f63d2959sm3538740ejp.210.2024.03.12.00.15.59 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 12 Mar 2024 00:16:01 -0700 (PDT) Message-ID: Date: Tue, 12 Mar 2024 09:15:58 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC 06/14] fork: zero vmap stack using clear_page() instead of memset() Content-Language: en-US To: Pasha Tatashin , linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, x86@kernel.org, bp@alien8.de, brauner@kernel.org, bristot@redhat.com, bsegall@google.com, dave.hansen@linux.intel.com, dianders@chromium.org, dietmar.eggemann@arm.com, eric.devolder@oracle.com, hca@linux.ibm.com, hch@infradead.org, hpa@zytor.com, jacob.jun.pan@linux.intel.com, jgg@ziepe.ca, jpoimboe@kernel.org, jroedel@suse.de, juri.lelli@redhat.com, kent.overstreet@linux.dev, kinseyho@google.com, kirill.shutemov@linux.intel.com, lstoakes@gmail.com, luto@kernel.org, mgorman@suse.de, mic@digikod.net, michael.christie@oracle.com, mingo@redhat.com, mjguzik@gmail.com, mst@redhat.com, npiggin@gmail.com, peterz@infradead.org, pmladek@suse.com, rick.p.edgecombe@intel.com, rostedt@goodmis.org, surenb@google.com, tglx@linutronix.de, urezki@gmail.com, vincent.guittot@linaro.org, vschneid@redhat.com References: <20240311164638.2015063-1-pasha.tatashin@soleen.com> <20240311164638.2015063-7-pasha.tatashin@soleen.com> From: Nikolay Borisov In-Reply-To: <20240311164638.2015063-7-pasha.tatashin@soleen.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspam-User: X-Stat-Signature: nzn4sukg636iiixapfi5wu7kokdxkh1w X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 5610540016 X-HE-Tag: 1710227763-355487 X-HE-Meta: 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 MuXk7beE h7Riqsbpp+TOe5+qnQsXPRYj0CHWqJHXbmFEkgmpA1NMFctFbbIodB32H+dwyEtXgnBbWdi9L69S59z7enmYPZBTvT2nYyd4H+qlpOm4hWqtxnMpvumY+CVtJ4yvDd0Ap5zwO+iL38FZiuYYkY/zRykS4Pv3RTJnvZMzx X-Bogosity: Ham, tests=bogofilter, spamicity=0.000075, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 11.03.24 г. 18:46 ч., Pasha Tatashin wrote: > In preporation for dynamic kernel stacks do not zero the whole span of > the stack, but instead only the pages that are part of the vm_area. > > This is because with dynamic stacks we might have only partially > populated stacks. > > Signed-off-by: Pasha Tatashin > --- > kernel/fork.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/kernel/fork.c b/kernel/fork.c > index 6a2f2c85e09f..41e0baee79d2 100644 > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -263,8 +263,8 @@ static int memcg_charge_kernel_stack(struct vm_struct *vm) > static int alloc_thread_stack_node(struct task_struct *tsk, int node) > { > struct vm_struct *vm_area; > + int i, j, nr_pages; > void *stack; > - int i; > > for (i = 0; i < NR_CACHED_STACKS; i++) { > vm_area = this_cpu_xchg(cached_stacks[i], NULL); > @@ -282,7 +282,9 @@ static int alloc_thread_stack_node(struct task_struct *tsk, int node) > stack = kasan_reset_tag(vm_area->addr); > > /* Clear stale pointers from reused stack. */ > - memset(stack, 0, THREAD_SIZE); > + nr_pages = vm_area->nr_pages; > + for (j = 0; j < nr_pages; j++) > + clear_page(page_address(vm_area->pages[j])); Can't this be memset(stack, 0, nr_pages*PAGE_SIZE) ? > > tsk->stack_vm_area = vm_area; > tsk->stack = stack;