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Date: Sat,  4 Feb 2017 00:33:21 +0900
From: Hoeun Ryu <hoeun.ryu@...il.com>
To: Andrew Morton <akpm@...ux-foundation.org>,
	Michal Hocko <mhocko@...e.com>,
	Ingo Molnar <mingo@...nel.org>,
	Andy Lutomirski <luto@...nel.org>,
	Kees Cook <keescook@...omium.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Mateusz Guzik <mguzik@...hat.com>
Cc: linux-kernel@...r.kernel.org,
	kernel-hardening@...ts.openwall.com,
	Hoeun Ryu <hoeun.ryu@...il.com>
Subject: [PATCH 3/3] fork: allocate vmapped kernel stacks for cache when a cpu is up

when a cpu is up, predefined number of stacks are allocated and cached
immediately.

Signed-off-by: Hoeun Ryu <hoeun.ryu@...il.com>
---
 kernel/fork.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/kernel/fork.c b/kernel/fork.c
index 50de6cf..ee4067d 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -194,6 +194,21 @@ static int alloc_vm_stack_cache(unsigned int cpu)
 	vm_stack_cache->cur = 0;
 	vm_stack_cache->nr = 0;
 
+	for (i = 0; i < NR_CACHED_STACKS; i++) {
+		void *stack = __vmalloc_node_range(THREAD_SIZE, THREAD_SIZE,
+						VMALLOC_START, VMALLOC_END,
+						THREADINFO_GFP | __GFP_HIGHMEM,
+						PAGE_KERNEL,
+						0, cpu_to_node(cpu),
+						__builtin_return_address(0));
+		if (!stack)
+			return -ENOMEM;
+
+		vm_stacks[i] = find_vm_area(stack);
+		vm_stack_cache->cur++;
+		vm_stack_cache->nr++;
+	}
+
 	return 0;
 }
 
-- 
2.7.4

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