Hi Dongxu, As you can see, the arm_monitor_vector uses PC-relative addressing so that the code can be moved around in memory. I think ldr pc, =smc_handler breaks this. Also, please set the NS bit in SCR to 1 before returning. To reserve a memory region for the monitor-mode code and data, I suggest you modify the avail_p_regs[] in kernel/include/plat/imx6/plat/machine/hardware.h file. See the kernel/include/plat/tk1/plat/machine/hardware.h as an example. Regards, Yanyan ________________________________ From: Dongxu Ji <jidongxu1993@gmail.com> Sent: Wednesday, August 29, 2018 12:02 AM To: devel@sel4.systems; Shen, Yanyan (Data61, Kensington NSW) Subject: Fwd: [seL4] SMC in seL4 Hi Yanyan, 1. It doesn't set the NS bit to 1 in SCR(I just want it to return without do anything). The arm_monitor_vector and the smc_handler(): arm_monitor_vector: ldr pc, [pc, #28] ldr pc, [pc, #24] ldr pc, =smc_handler ldr pc, [pc, #16] ldr pc, [pc, #12] ldr pc, [pc, #8] ldr pc, [pc, #4] ldr pc, [pc, #0] smc_handler: movs pc, lr 2. I didn't do any extra work other than the boot log: .......... ELF-loader started on CPU: ARM Ltd. Cortex-A9 r2p10 paddr=[20000000..203fbfff] ELF-loading image 'kernel' paddr=[10000000..10026fff] vaddr=[e0000000..e0026fff] virt_entry=e0000000 ELF-loading image 'sel4test-driver' paddr=[10027000..10500fff] vaddr=[8000..4e1fff] virt_entry=25a6c Enabling MMU and paging Jumping to kernel-image entry point... 3. The initialization operations in platform_init.c: set sp: #define MONITOR_MODE (0x16) #define MON_VECTOR_START (0x11000000) #define VECTOR_BASE 0x11000000 #define STACK_TOP (VECTOR_BASE + (1 << 12) - 0x10) asm volatile ( "mrs r1, cpsr\n\t" "cps %0\n\t" "isb\n" "mov sp, %1\n\t" "msr cpsr, r1\n\t" ::"I"(MONITOR_MODE),"r"(STACK_TOP)); copy monitor mode vector to MON_VECTOR_START and write into MVBAR: uint32_t size = arm_monitor_vector_end - arm_monitor_vector; printf("Copy monitor mode vector from %x to %x size %x\n", (arm_monitor_vector), MON_VECTOR_START, size); memcpy((void *)MON_VECTOR_START, (void *)(arm_monitor_vector), size); asm volatile ("dmb\n isb\n"); asm volatile ("mcr p15, 0, %0, c12, c0, 1"::"r"(MON_VECTOR_START)); I enter into SVC mode by software interrupt and call the function smc(): asm (".arch_extension sec\n"); asm volatile ("stmfd sp!, {r3-r11, lr}\n\t" "dsb\n" "smc #0\n" "ldmfd sp!, {r3-r11, pc}"); and then the problem arises. Thank you, Dongxu Ji <Yanyan.Shen@data61.csiro.au<mailto:Yanyan.Shen@data61.csiro.au>> 于2018年8月28日周二 下午8:30写道： 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 <devel-bounces@sel4.systems> on behalf of 冀东旭 <jidongxu1993@gmail.com<mailto:jidongxu1993@gmail.com>> 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