armv7：stmb 不占用 pc
我有一个用 C 语言编写的库，与一些 ARM 程序集混合在一起。它曾经是为armv6编译的。现在我正在尝试将其升级到armv7。然而，有一个中断处理程序包含指令 stmdb sp!, {pc}，这在armv7中是不允许的。 armv7 上的等效指令是什么？我尝试了 str r15, [sp, #-4]! 但这不起作用。
I have a library written in C mixed mixed with some assembly for ARM. It used to be compiled for armv6. Now I am trying to upgrade it to armv7. However, there is an interrupt handler which has the instruction stmdb sp!, {pc} which is not allowed in armv7. What would be an equivalent instruction on armv7? I tried str r15, [sp, #-4]! but that doesn't work.
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PUSH和POP指令的寄存器列表中使用PC有具体限制，具体取决于操作模式，请参见：ARM指令集参考，
PUSH/POP具体来说，在 Thumb[2] 中，没有
push {pc}操作（这相当于没有stmfd sp!, {pc}操作 -push映射到stmfd sp!）。因此，如果您正在编译内核代码（如果不是内核代码，为什么您拥有/需要中断处理程序），请检查您是否正在编译 Thumb-2 内核。
也就是说，您是说您遇到了
stmfd sp!,{pc}指令 - 您确定这不是拼写错误？stmfd sp!,{lr}（及其同级，ldmfd sp!, {pc}- 这里存在PC）正常/完全合法且在 ARM 模式和 Thumb-2 模式下经常需要/遇到。但这实际上就是将程序计数器保存到堆栈的目的吗？人们可以用其他方法无法实现的事情来做什么呢？There's specific limitations regarding the use of
PCin the reg list forPUSHandPOPinstructions, depending on the operation mode, see:ARM Instruction Set Reference,
PUSH/POPSpecifically, in Thumb[2] there is no
push {pc}operation (which is the same as saying there's nostmfd sp!, {pc}operation -pushis mapped tostmfd sp!).So if you're compiling your kernel code (why else do you have/need an interrupt handler if it's not kernel code), check whether you're compiling a Thumb-2 kernel.
That said, you're saying you encountered a
stmfd sp!,{pc}instruction - you're sure that's not a typo ?stmfd sp!,{lr}(and its sibling,ldmfd sp!, {pc}- herePCis present) is normal / fully legal and often required / encountered in both ARM mode and Thumb-2 mode. But that actually is the purpose of saving the program counter to the stack ? What can one do with that that wouldn't be achievable in other ways ?“armv7”相当通用。你用的实际芯片是什么？您正在为 ARMv7-M 进行编译吗？然后尝试
PUSH {PC}。但我预计这不会是您遇到的唯一问题。我认为您应该发布一些片段并更详细地描述您要移植到的特定环境。"armv7" is rather generic. What's the actual chip you're using? Are you compiling for ARMv7-M? Try
PUSH {PC}then. Though I expect that won't be the only issue you will run into. I think you should post some snippets and describe in more details what specific environment you're porting to.