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Wed, 07 May 2025 05:46:36 -0700 (PDT) From: Linus Walleij Date: Wed, 07 May 2025 14:46:31 +0200 Subject: [PATCH v2 5/5] fork: zero vmap stack using clear_page() instead of memset() MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20250507-fork-fixes-v2-5-82ab1e42cde3@linaro.org> References: <20250507-fork-fixes-v2-0-82ab1e42cde3@linaro.org> In-Reply-To: <20250507-fork-fixes-v2-0-82ab1e42cde3@linaro.org> To: Andrew Morton , linux-mm@kvack.org, Pasha Tatashin Cc: Linus Walleij X-Mailer: b4 0.14.2 X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: DAE5D14000B X-Stat-Signature: c9fa7n6zj4ikk7iyj1dunkxjm3ei5c6d X-Rspam-User: X-HE-Tag: 1746621998-659564 X-HE-Meta: U2FsdGVkX18O8XKN5wF1JSXC5RdUNlpaYblsIFkjoO2EIbIxLEJPaX1J7vETF1qEg/Z6AioQFkfJ31jL/GGi8jJJpFWjP2fzlOOBslw7GeQv+WcSX8oa30xtLrQsB1GWP8OcUKF4fQCajpFRAO5AgDt3mzMzw8Dsa8TMldElvwEOnSe4y9tCnPuO+JQLLiKGGPNdr2nm1UBWSLkSCMrEza0kGDeZZDM3aP3cs73w6pqyW19RacF0a8fX5L/3+ki5UcKXf2S3MTBlzg+BYWVSL/s03n9gs3+PPj0KetAnFEPOSD+Og4U2YIj3JKC4w+VPTWWY53IW+n/00T79oku2EEItlclUg0exk4lwPVY7guldakNMRehpH1aRBQc8eQ5eXtky+Tu715Sv15wMd57t9oIaqFaZFqJT0Gv8anxvMW38NG87II3xdyycoufWBaIevb4n5iyan5kGmWBFeZSHrwteC1v34cKRU5w89lbGaCBWf8VbLuDtUbZ6uddOw+gJTaYbMBj7g55REVGqdAFd5izPZEg4LnIInU6B1VC1awPAHn8QS4ZUWS6EM7cW/OPgUnbNtZHWLGferGdf+JqjbTd2/oXYH8bMWR43VD41UHxccPh5BI/obMNdLGl7jsfw+hIXKy1G6Sxm7JPETRwX/5B8KGt0f6RIfog+3s/HhzSpSIhBop/dZ5GGYMr3iXWtH9L5o3kwceT7dCWhtYer3+rwhKA4QZt/WPpfr6REs800anox3v4MxaYJDc9ktcVGdjJ5yklFYvK3j5Y1PWhL2kYx95G62peKLIHI9lABi4rvHUud/EiZeqCcSy2B32ciGTHUA+fXBMephM44BcHd9zUB0Q9PCt0LZHSkwsZSxXWhJva0Id64XQa1FTRjHOHdq2mi9Z/r7FPfsBdRUG97S/aUZt6sllM/c4mluzBcxibKkN8Dixa4hBtEm0GirNBxJ9TXmdJ0srAs+bK9nkZ ilZ66rjg 1Yyr/+osXBrKnN2YOW+UyDdaob4cFBcyGRV7ENinWenSUC8sjzigh/75H1Xo6CEoFgkIzQ6U2Doo1PCgn9TomtSRod7AMTw+DVIyGrYXIvTJtPolFnxsiDdYBnIqSTaax+aTOKAd9orEJfEqhwCLjY5Fe0B0/rzgJw8n7RmZUYV2zkszqU6kxp5CbVgH2EJilMI3jOxZS0C3Bdv6v5CIxRz+rEWGruRTyDHWe7omLVi8CjzAUYadjap/R41eguqXcGMVeNglCBh5Xapitku5MO3vx1pzYMY1t0/D4FiETh8XSf4M4bZjZrKIQ5DQ1AgkwtNRRG6KWvJSt7EsVXPsosnWKK1Kfg12iJVV1PTF8/r/zFwbWfWUA28D6H9p6B4JdBmW2LTdLKb7eAv89JH7S1twtFfDcZFLXgnZqD4GUep5p8xlddnbIDxrUc/gWDFHJ51Sz1MXECL/h4e1/72LwKFh81w== 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: List-Subscribe: List-Unsubscribe: From: Pasha Tatashin Do not zero the whole span of the stack, but instead only the pages that are part of the vm_area. As several architectures have optimized implementations of clear_page(), this will give the architecture a clear idea of what is going on and will speed up the clearing operation. Signed-off-by: Pasha Tatashin Link: https://lore.kernel.org/20240311164638.2015063-7-pasha.tatashin@soleen.com [linus.walleij@linaro.org: Rebased] Signed-off-by: Linus Walleij --- kernel/fork.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/kernel/fork.c b/kernel/fork.c index 6ac4674fdf04081fbcbf1eb99167a4c990a58506..d3f000b846c634221c7dafe6e64185a276c5a08b 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -271,13 +271,15 @@ static int memcg_charge_kernel_stack(struct vm_struct *vm_area) static int alloc_thread_stack_node(struct task_struct *tsk, int node) { struct vm_struct *vm_area; + int nr_pages; void *stack; - int i; + int i, j; for (i = 0; i < NR_CACHED_STACKS; i++) { vm_area = this_cpu_xchg(cached_stacks[i], NULL); if (!vm_area) continue; + nr_pages = vm_area->nr_pages; if (memcg_charge_kernel_stack(vm_area)) { vfree(vm_area->addr); @@ -290,7 +292,8 @@ 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); + for (j = 0; j < nr_pages; j++) + clear_page(page_address(vm_area->pages[j])); tsk->stack_vm_area = vm_area; tsk->stack = stack; -- 2.49.0