如何在 Linux 2.6.35 上从用户模式清除和无效 ARM v7 处理器缓存 [英] How clear and invalidate ARM v7 processor cache from User Mode on Linux 2.6.35

问题描述

我尝试为指令行清除和无效 ARM v7 处理器缓存，因为指令代码在执行过程中可能会发生变化.

I tried clear and invalidate ARM v7 processor cache for instruction line, because instruction codes can change in execution.

为了达到效果，我尝试了 2 个变体.他们在这里:

For reaching the effect, I tried 2 variants. Here they are:

1. 我使用了 GCC __clear_cache() 函数，但它没有给出所需的结果.缓存中的指令码没有改变.

1. I used GCC __clear_cache() function but it didn't give a required result. Instruction codes in cache didn't change.

我查找了 GCC 的源代码并找到了 uclinux-eabi.h 文件，我在其中找到了下一个用于清除缓存的代码:

I looked for a source codes for GCC and found the uclinux-eabi.h file where I found the next code for clearing cache:

/* Clear the instruction cache from `beg' to `end'.  This makes an
   inline system call to SYS_cacheflush.  */
#undef CLEAR_INSN_CACHE
#define CLEAR_INSN_CACHE(BEG, END)                                    
{                                                                     
    register unsigned long _beg __asm ("a1") = (unsigned long) (BEG); 
    register unsigned long _end __asm ("a2") = (unsigned long) (END); 
    register unsigned long _flg __asm ("a3") = 0;                     
    register unsigned long _scno __asm ("r7") = 0xf0002;              
    __asm __volatile                                                  
    (                                                                 
        "swi 0x0    @ sys_cacheflush"                                 
        : "=r" (_beg)                                                 
        : "0" (_beg), "r" (_end), "r" (_flg), "r" (_scno));           
}

这个变种也没有给出结果.

This variant didn't give the result too.

也许有人知道我做错了什么?

Maybe someone knows what I do wrong ?

推荐答案

我自己也遇到过类似的问题.__clear_cache() 有效，但前提是所讨论的内存区域是使用 mmap() 并设置了 PROT_EXEC 分配的.如果您为指令缓存提供来自常规 malloc() 内存的内存范围，Linux 将不会刷新指令缓存，即使处理器似乎很乐​​意从 malloc() 内存执行代码.

I had a similar problem myself. __clear_cache() works, but only if the memory area in question was allocated using mmap() with PROT_EXEC set. Linux will not flush the instruction cache if you provide it with a memory range that comes from regular malloc()ed memory, even if the processor seems to be happy to execute code from malloc()ed memory.

参见 https:///community.arm.com/groups/processors/blog/2010/02/17/caches-and-self-modifying-code 有关如何执行此操作的示例代码.

See https://community.arm.com/groups/processors/blog/2010/02/17/caches-and-self-modifying-code for example code on how to do this.

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