arm32: unwind: print_stack() should create a more complete state

Save general purpose registers and the frame pointer before starting
the unwind operation. Also, set PC to the begining of the print_stack
function since there's no point in going further.

Fixes: OP-TEE#1069
Signed-off-by: Jerome Forissier <jerome.forissier@linaro.org>

core/arch/arm/kernel/unwind_arm32.c

@@ -367,10 +367,11 @@ void print_stack(int level)
 {
 	struct unwind_state state;
 
-	memset(&state, 0, sizeof(state));
+	asm volatile("stmia %0, {r0-r12}" :: "r" (state.registers) : "memory");
+	state.registers[FP] = (uint32_t)__builtin_frame_address(0);
 	state.registers[SP] = read_sp();
 	state.registers[LR] = read_lr();
-	state.registers[PC] = read_pc();
+	state.registers[PC] = (uint32_t)print_stack;
 
 	do {
 		switch (level) {