From 40d1a07b333ef1f7fce11ee20b8f4281d1a75fb9 Mon Sep 17 00:00:00 2001 From: Max Filippov Date: Mon, 27 Mar 2017 02:44:47 -0700 Subject: xtensa: enable stack protector The implementation is adopted from the ARM arch. GCC 7.3, 8 or newer is required for building the xtensa kernel with SSP. Signed-off-by: Max Filippov --- arch/xtensa/include/asm/stackprotector.h | 40 ++++++++++++++++++++++++++++++++ 1 file changed, 40 insertions(+) create mode 100644 arch/xtensa/include/asm/stackprotector.h (limited to 'arch/xtensa/include') diff --git a/arch/xtensa/include/asm/stackprotector.h b/arch/xtensa/include/asm/stackprotector.h new file mode 100644 index 000000000000..e368f94fd2af --- /dev/null +++ b/arch/xtensa/include/asm/stackprotector.h @@ -0,0 +1,40 @@ +/* + * GCC stack protector support. + * + * (This is directly adopted from the ARM implementation) + * + * Stack protector works by putting predefined pattern at the start of + * the stack frame and verifying that it hasn't been overwritten when + * returning from the function. The pattern is called stack canary + * and gcc expects it to be defined by a global variable called + * "__stack_chk_guard" on Xtensa. This unfortunately means that on SMP + * we cannot have a different canary value per task. + */ + +#ifndef _ASM_STACKPROTECTOR_H +#define _ASM_STACKPROTECTOR_H 1 + +#include +#include + +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; + + current->stack_canary = canary; + __stack_chk_guard = current->stack_canary; +} + +#endif /* _ASM_STACKPROTECTOR_H */ -- cgit v1.2.3