Hi, The smc_handle() in monitor.S, it does nothing but "movs pc, lr". Does it set the NS bit to 1 in SCR? Also, what did you do to ensure that 0x11000000 is not used by the kernel? Could you share the code (if possible) so that I could better understand the problem. Regards, Yanyan ________________________________ From: Devel on behalf of 冀东旭 Sent: Tuesday, August 28, 2018 1:02 PM To: devel@sel4.systems Subject: [seL4] SMC in seL4 Hello, I'm porting sel4 to imx6q sabrelite as the trusted OS in trustzone. I initialize the monitor mode by setting the sp to STACK_TOP and copying arm_monitor_vector to MON_VECTOR_START according to the functions "install_monitor_hook()" and "switch_to_mon_mode()" in "platform_init.c". #define VECTOR_BASE 0x11000000(addr is not used by the seL4 kernel) #define STACK_TOP (VECTOR_BASE + (1 << 12) - 0x10) #define MON_VECTOR_START 0x11000000(The VECTOR_BASE is the same as MON_VECTOR_START) The smc_handle() in monitor.S, it does nothing but "movs pc, lr". After calling smc in SVC mode, it hangs without any log. If I comment the "smc #0", it can return the caller successfully in usr mode. stmfd sp!, {r3-r11, lr} dsb smc #0 ldmfd sp!, {r3-r11, pc} Is the sp in monitor mode appropriate? Or I need to do something else in initialization operations? What's wrong with it? Do you have any ideas? Thank you! Dongxu Ji