如何在 Linux 2.6.35 上从用户模式清除和使 ARM v7 处理器缓存无效
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How clear and invalidate ARM v7 processor cache from User Mode on Linux 2.6.35
提问by Alex Kolesnyk
I tried clear and invalidate ARM v7 processor cache for instruction line, because instruction codes can change in execution.
我尝试清除指令行的 ARM v7 处理器缓存并使之无效，因为指令代码可以在执行中更改。
For reaching the effect, I tried 2 variants. Here they are:
为了达到效果，我尝试了 2 个变体。他们来了：
I used GCC __clear_cache()function but it didn't give a required result. Instruction codes in cache didn't change.
I looked for a source codes for GCC and found the uclinux-eabi.h filewhere 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)); \ }
我使用了 GCC __clear_cache()函数，但它没有给出所需的结果。缓存中的指令代码没有改变。
我寻找 GCC 的源代码并找到了uclinux-eabi.h 文件，我在其中找到了下一个清除缓存的代码：
/* 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)); \ }
This variant didn't give the result too.
这个变体也没有给出结果。
Maybe someone knows what I do wrong ?
也许有人知道我做错了什么？
回答by Rune
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.
我自己也有类似的问题。__clear_cache() 有效，但前提是有问题的内存区域是使用带有 PROT_EXEC 设置的 mmap() 分配的。如果您为它提供来自常规 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。
See https://community.arm.com/groups/processors/blog/2010/02/17/caches-and-self-modifying-codefor example code on how to do this.
有关如何执行此操作的示例代码，请参阅https://community.arm.com/groups/processors/blog/2010/02/17/caches-and-self-modifying-code。
