ios - "Invalid operand for instruction"arm64 架构错误

Question

尝试在 arm64 架构中运行以下内联汇编指令时出现编译错误。在 32 位架构下运行良好。

Store指令将堆栈指针(sp)存储到变量stack_ptr。

unsigned long stack_ptr = 0;

__asm__ __volatile__("str sp, %[stack_ptr]"
                     :[stack_ptr]"=m" (stack_ptr) //output operand list
                     );

Answer 1

在 64 位代码中，您不能使用 SP 作为 STR 指令中的操作数。引用 documentation :

You can only use SP as an operand in the following instructions:

• As the base register for loads and stores. In this case it must be quadword-aligned before adding any offset, or a stack alignment exception occurs.
• As a source or destination for arithmetic instructions, but it cannot be used as the destination in instructions that set the condition flags.
• In logical instructions, for example in order to align it.

你应该先将它复制到一个通用寄存器中，然后将它存储到内存中。

除非你需要一个真正精确的值，否则你可以只使用普通 C 并获取局部变量本身的地址来估计堆栈指针:

unsigned long stack_ptr = (unsigned long)&stack_ptr;