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Subject[PATCH 2/5] csky: Initial stack protector support
Date
From: Mao Han <han_mao@c-sky.com>

This is a basic -fstack-protector support without per-task canary
switching. The protector will report something like when stack
corruption is detected:

It's tested with strcpy local array overflow in sys_kill and get:
stack-protector: Kernel stack is corrupted in: sys_kill+0x23c/0x23c

TODO:
- Support task switch for different cannary

Signed-off-by: Mao Han <han_mao@c-sky.com>
Signed-off-by: Guo Ren <guoren@kernel.org>
---
arch/csky/Kconfig | 1 +
arch/csky/include/asm/stackprotector.h | 29 ++++++++++++++++++++++++++
arch/csky/kernel/process.c | 6 ++++++
3 files changed, 36 insertions(+)
create mode 100644 arch/csky/include/asm/stackprotector.h

diff --git a/arch/csky/Kconfig b/arch/csky/Kconfig
index 3973847b5f42..285234300740 100644
--- a/arch/csky/Kconfig
+++ b/arch/csky/Kconfig
@@ -48,6 +48,7 @@ config CSKY
select HAVE_PERF_USER_STACK_DUMP
select HAVE_DMA_API_DEBUG
select HAVE_DMA_CONTIGUOUS
+ select HAVE_STACKPROTECTOR
select HAVE_SYSCALL_TRACEPOINTS
select MAY_HAVE_SPARSE_IRQ
select MODULES_USE_ELF_RELA if MODULES
diff --git a/arch/csky/include/asm/stackprotector.h b/arch/csky/include/asm/stackprotector.h
new file mode 100644
index 000000000000..d7cd4e51edd9
--- /dev/null
+++ b/arch/csky/include/asm/stackprotector.h
@@ -0,0 +1,29 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_STACKPROTECTOR_H
+#define _ASM_STACKPROTECTOR_H 1
+
+#include <linux/random.h>
+#include <linux/version.h>
+
+extern unsigned long __stack_chk_guard;
+
+/*
+ * Initialize the stackprotector canary value.
+ *
+ * NOTE: this must only be called from functions that never return,
+ * and it must always be inlined.
+ */
+static __always_inline void boot_init_stack_canary(void)
+{
+ unsigned long canary;
+
+ /* Try to get a semi random initial value. */
+ get_random_bytes(&canary, sizeof(canary));
+ canary ^= LINUX_VERSION_CODE;
+ canary &= CANARY_MASK;
+
+ current->stack_canary = canary;
+ __stack_chk_guard = current->stack_canary;
+}
+
+#endif /* __ASM_SH_STACKPROTECTOR_H */
diff --git a/arch/csky/kernel/process.c b/arch/csky/kernel/process.c
index f320d9248a22..5349cd8c0f30 100644
--- a/arch/csky/kernel/process.c
+++ b/arch/csky/kernel/process.c
@@ -16,6 +16,12 @@

struct cpuinfo_csky cpu_data[NR_CPUS];

+#ifdef CONFIG_STACKPROTECTOR
+#include <linux/stackprotector.h>
+unsigned long __stack_chk_guard __read_mostly;
+EXPORT_SYMBOL(__stack_chk_guard);
+#endif
+
asmlinkage void ret_from_fork(void);
asmlinkage void ret_from_kernel_thread(void);

--
2.17.0
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