ILINK register is accessible from userspace #154
Description
Hi,
ARCv2 documentation contains the following: "The ILINK register is not accessible in user mode. Illegal accesses from user mode to ILINK raise a Privilege Violation exception". But QEMU allows ILINK access form user mode.
Examples are based on Zephyr.
The following is executed in userspace:
uint32_t rd_ilink = 0;
__asm__ volatile("mov %%[ilink], 0xaaaaaaaa\n"::);
__asm__ volatile("mov %0, %%[ilink]\n": "=r"(rd_ilink) : );
printf("Ilink was set in %s to 0x%x but we got no crashes\n",
k_is_user_context() ? "UserSpace!" : "privileged mode." , rd_ilink);
Expected behavior - raising exception
*** Booting Zephyr OS build v3.3.0-rc3-59-gf1b662ae17b5 ***
Hello World from UserSpace! (nsim)
E: ***** Exception vector: 0x7, cause code: 0x0, parameter 0x0
E: Address 0xe6
E: EV_PrivilegeV
E: Privilege violation
E: r0: 0x1 r1: 0x2 r2: 0x600 r3: 0x857c
E: r4: 0x0 r5: 0x0 r6: 0x176 r7: 0x0
E: r8: 0x0 r9: 0x0 r10: 0x0 r11: 0x0
E: r12: 0x43 r13: 0x0 pc: 0xe6
E: blink: 0xb6 status32: 0x80182282
E: lp_end: 0x0 lp_start: 0x0 lp_count: 0x0
E: >>> ZEPHYR FATAL ERROR 0: CPU exception on CPU 0
E: Current thread: 0x80000000 (unknown)
E: Halting system
Current behavior - continuing execution
*** Booting Zephyr OS build v3.3.0-rc3-59-gf1b662ae17b5 ***
Hello World from UserSpace! (qemu_arc)
Ilink was set in UserSpace! to 0xaaaaaaaa but we got no crashes
How to reproduce
Download example and run it on recent version of qemu
qemu-system-arc -cpu archs -m 8M -nographic -no-reboot -monitor none -global cpu.firq=false -global cpu.num-irqlevels=15 -global cpu.num-irq=25 -global cpu.ext-irq=20 -global cpu.freq_hz=10000000 -global cpu.timer0=true -global cpu.timer1=true -global cpu.has-mpu=true -global cpu.mpu-numreg=16 -net none -pidfile qemu.pid -chardev stdio,id=con,mux=on -serial chardev:con -mon chardev=con,mode=readline -icount shift=6,align=off,sleep=off -rtc clock=vm -kernel <PATH_TO_ZEPHYR_ELF>
Routine that contains example code with ILINK access is user_function()