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Subject[PATCH -next] powerpc: add support for syscall stack randomization
Date
Add support for adding a random offset to the stack while handling
syscalls. This patch uses mftb() instead of get_random_int() for better
performance.

Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
---
arch/powerpc/Kconfig | 1 +
arch/powerpc/kernel/interrupt.c | 3 +++
2 files changed, 4 insertions(+)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 5fc9153927ac..7e04c9f80cbc 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -192,6 +192,7 @@ config PPC
select HAVE_ARCH_KASAN if PPC32 && PPC_PAGE_SHIFT <= 14
select HAVE_ARCH_KASAN_VMALLOC if PPC32 && PPC_PAGE_SHIFT <= 14
select HAVE_ARCH_KFENCE if PPC_BOOK3S_32 || PPC_8xx || 40x
+ select HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
select HAVE_ARCH_KGDB
select HAVE_ARCH_MMAP_RND_BITS
select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT
diff --git a/arch/powerpc/kernel/interrupt.c b/arch/powerpc/kernel/interrupt.c
index 784ea3289c84..459385769721 100644
--- a/arch/powerpc/kernel/interrupt.c
+++ b/arch/powerpc/kernel/interrupt.c
@@ -4,6 +4,7 @@
#include <linux/err.h>
#include <linux/compat.h>
#include <linux/sched/debug.h> /* for show_regs */
+#include <linux/randomize_kstack.h>

#include <asm/kup.h>
#include <asm/cputime.h>
@@ -82,6 +83,7 @@ notrace long system_call_exception(long r3, long r4, long r5,

kuap_lock();

+ add_random_kstack_offset();
regs->orig_gpr3 = r3;

if (IS_ENABLED(CONFIG_PPC_IRQ_SOFT_MASK_DEBUG))
@@ -405,6 +407,7 @@ interrupt_exit_user_prepare_main(unsigned long ret, struct pt_regs *regs)

/* Restore user access locks last */
kuap_user_restore(regs);
+ choose_random_kstack_offset(mftb() & 0xFF);

return ret;
}
--
2.17.1
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