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Message-Id: <1486613040-30555-2-git-send-email-hoeun.ryu@gmail.com>
Date: Thu, 9 Feb 2017 13:03:47 +0900
From: Hoeun Ryu <hoeun.ryu@...il.com>
To: Kees Cook <keescook@...omium.org>,
Michal Marek <mmarek@...e.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Emese Revfy <re.emese@...il.com>,
Ingo Molnar <mingo@...nel.org>,
Mickaël Salaün <mic@...ikod.net>,
Nicholas Piggin <npiggin@...il.com>,
Andy Lutomirski <luto@...nel.org>,
Michal Hocko <mhocko@...e.com>,
"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 v2 2/2] fork: make number of cached stacks (vmapped) configurable using Kbuild
Introducing NR_VMAP_STACK_CACHE, the number of cached stacks for virtually
mapped kernel stack can be configurable using Kbuild system.
default value is 2.
Signed-off-by: Hoeun Ryu <hoeun.ryu@...il.com>
---
arch/Kconfig | 8 ++++++++
kernel/fork.c | 2 +-
2 files changed, 9 insertions(+), 1 deletion(-)
diff --git a/arch/Kconfig b/arch/Kconfig
index d49a8e6..066d111 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -849,6 +849,14 @@ config VMAP_STACK
the stack to map directly to the KASAN shadow map using a formula
that is incorrect if the stack is in vmalloc space.
+config NR_VMAP_STACK_CACHE
+ int "Number of cached stacks"
+ default "2"
+ depends on VMAP_STACK
+ help
+ This determines how many stacks can be cached for virtually
+ mapped kernel stacks.
+
config ARCH_WANT_RELAX_ORDER
bool
diff --git a/kernel/fork.c b/kernel/fork.c
index 7911ed2..73ba1da 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -166,7 +166,7 @@ void __weak arch_release_thread_stack(unsigned long *stack)
* vmalloc() is a bit slow, and calling vfree() enough times will force a TLB
* flush. Try to minimize the number of calls by caching stacks.
*/
-#define NR_CACHED_STACKS 2
+#define NR_CACHED_STACKS CONFIG_NR_VMAP_STACK_CACHE
static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]);
#endif
--
2.7.4
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