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ANDROID: scs: use vmapped shadow stacks by default

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Enable CONFIG_SHADOW_CALL_STACK_VMAP by default, and as we allocate
a full page for the stack, allow the kernel use all of it.

Bug: 169781940
Change-Id: Ie8eaa7f24e9bf10ff28a302ac98ad843b71c9c2a
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
This commit is contained in:
Sami Tolvanen 2020-10-14 13:24:28 -07:00
parent b494bbca7a
commit 1eb128820e
2 changed files with 6 additions and 0 deletions
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1
arch/Kconfig
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@ -549,6 +549,7 @@ config SHADOW_CALL_STACK
config SHADOW_CALL_STACK_VMAP
bool "Use virtually mapped shadow call stacks"
depends on SHADOW_CALL_STACK
default y
help
Use virtually mapped shadow call stacks. Selecting this option
provides better stack exhaustion protection, but increases per-thread

5
include/linux/scs.h
View File

@ -14,12 +14,17 @@
#ifdef CONFIG_SHADOW_CALL_STACK
#ifdef CONFIG_SHADOW_CALL_STACK_VMAP
#define SCS_SIZE PAGE_SIZE
#else
/*
* In testing, 1 KiB shadow stack size (i.e. 128 stack frames on a 64-bit
* architecture) provided ~40% safety margin on stack usage while keeping
* memory allocation overhead reasonable.
*/
#define SCS_SIZE 1024UL
#endif
#define GFP_SCS (GFP_KERNEL | __GFP_ZERO)
/*