| Date | Tue, 12 Mar 2024 09:15:58 +0200 | Subject | Re: [RFC 06/14] fork: zero vmap stack using clear_page() instead of memset() | From | Nikolay Borisov <> |
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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 <pasha.tatashin@soleen.com> > --- > 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;
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