fiq debugger: rockchip: fix crash because of invalid sp_el0

(1) use cpu id from bl31 delivers;
(2) sp_el0 should point to kernel address in EL1 mode.

On ARM64, kernel uses sp_el0 to store current_thread_info(),
we see a problem: when fiq occurs, cpu is EL1 mode but sp_el0
point to userspace address. At this moment, if we read
'current_thread_info()->cpu' or other, it leads an error.

We find above situation happens when save/restore cpu context
between system mode and user mode under heavy load.
Like 'ret_fast_syscall()', kernel restore context of user mode,
but fiq occurs before the instruction 'eret', so this causes the
above situation.

Assembly code:

ffffff80080826c8 <ret_fast_syscall>:

...skipping...

ffffff80080826fc:       d503201f        nop
ffffff8008082700:       d5384100        mrs     x0, sp_el0
ffffff8008082704:       f9400c00        ldr     x0, [x0,torvalds#24]
ffffff8008082708:       d5182000        msr     ttbr0_el1, x0
ffffff800808270c:       d5033fdf        isb
ffffff8008082710:       f9407ff7        ldr     x23, [sp,torvalds#248]
ffffff8008082714:       d5184117        msr     sp_el0, x23
ffffff8008082718:       d503201f        nop
ffffff800808271c:       d503201f        nop
ffffff8008082720:       d5184035        msr     elr_el1, x21
ffffff8008082724:       d5184016        msr     spsr_el1, x22
ffffff8008082728:       a94007e0        ldp     x0, x1, [sp]
ffffff800808272c:       a9410fe2        ldp     x2, x3, [sp,torvalds#16]
ffffff8008082730:       a94217e4        ldp     x4, x5, [sp,torvalds#32]
ffffff8008082734:       a9431fe6        ldp     x6, x7, [sp,torvalds#48]
ffffff8008082738:       a94427e8        ldp     x8, x9, [sp,torvalds#64]
ffffff800808273c:       a9452fea        ldp     x10, x11, [sp,torvalds#80]
ffffff8008082740:       a94637ec        ldp     x12, x13, [sp,torvalds#96]
ffffff8008082744:       a9473fee        ldp     x14, x15, [sp,torvalds#112]
ffffff8008082748:       a94847f0        ldp     x16, x17, [sp,torvalds#128]
ffffff800808274c:       a9494ff2        ldp     x18, x19, [sp,torvalds#144]
ffffff8008082750:       a94a57f4        ldp     x20, x21, [sp,torvalds#160]
ffffff8008082754:       a94b5ff6        ldp     x22, x23, [sp,torvalds#176]
ffffff8008082758:       a94c67f8        ldp     x24, x25, [sp,torvalds#192]
ffffff800808275c:       a94d6ffa        ldp     x26, x27, [sp,torvalds#208]
ffffff8008082760:       a94e77fc        ldp     x28, x29, [sp,torvalds#224]
ffffff8008082764:       f9407bfe        ldr     x30, [sp,torvalds#240]
ffffff8008082768:       9104c3ff        add     sp, sp, #0x130
ffffff800808276c:       d69f03e0        eret

Change-Id: I071e899f8a407764e166ca0403199c9d87d6ce78
Signed-off-by: chenjh <chenjh@rock-chips.com>

drivers/staging/android/fiq_debugger/fiq_debugger.c

@@ -583,7 +583,13 @@ static bool fiq_debugger_fiq_exec(struct fiq_debugger_state *state,
 			void *svc_sp)
 {
 	bool signal_helper = false;
+	unsigned long va_start;
 
+#ifdef CONFIG_ARM64
+	va_start = VA_START;
+#else
+	va_start = PAGE_OFFSET;
+#endif
 	if (!strcmp(cmd, "help") || !strcmp(cmd, "?")) {
 		fiq_debugger_help(state);
 	} else if (!strcmp(cmd, "pc")) {
@@ -593,11 +599,14 @@ static bool fiq_debugger_fiq_exec(struct fiq_debugger_state *state,
 	} else if (!strcmp(cmd, "allregs")) {
 		fiq_debugger_dump_allregs(&state->output, regs);
 	} else if (!strcmp(cmd, "bt")) {
-		if (!user_mode((struct pt_regs *)regs))
+		if (user_mode((struct pt_regs *)regs) ||
+		    ((unsigned long)svc_sp < va_start) ||
+		    ((unsigned long)svc_sp > -256UL))
+			fiq_debugger_printf(&state->output, "User mode\n");
+		else
 			fiq_debugger_dump_stacktrace(&state->output, regs,
 						     100, svc_sp);
-		else
-			fiq_debugger_printf(&state->output, "User mode\n");
+
 	} else if (!strncmp(cmd, "reset", 5)) {
 		cmd += 5;
 		while (*cmd == ' ')
@@ -1022,13 +1031,8 @@ void fiq_debugger_fiq(void *regs, u32 cpu)
 	if (!state)
 		return;
 
-	if (!user_mode((struct pt_regs *)regs))
-		need_irq = fiq_debugger_handle_uart_interrupt(state,
-						smp_processor_id(),
-						regs, current_thread_info());
-	else
-		need_irq = fiq_debugger_handle_uart_interrupt(state, cpu,
-						regs, current_thread_info());
+	need_irq = fiq_debugger_handle_uart_interrupt(state, cpu, regs,
+						      current_thread_info());
 	if (need_irq)
 		fiq_debugger_force_irq(state);
 }