Asan minimalism

1. Physical memory is limited , Virtual memory unlimited .
2. ASAN Took over the application malloc technological process
3. Every time memory is allocated , Be sure to use a new virtual address , And add page protection at both ends of the address

OVER

The main points of ： Because the virtual memory resource is “ Infinite ” Of , So you can waste a lot . Waste is reflected in two aspects ：

• Allocated address space , Even if free After that , It will not be assigned to users again . What users feel is that the memory address allocated by the memory allocator is always higher than the last time .
  • already free The memory area that has been used is called Dead Zone
• Every time a piece of memory is allocated , Always reserve a page at both ends , And make these two pages read and write protected .
  • The pages reserved at both ends are called Red Zone
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Based on this mechanism ,ASAN Just track the stack for each memory allocation , When something goes wrong, you can accurately report the problem point . Memory problems that can be detected ：

• The visit has free Used memory , Trigger Dead Zone Call the police
• Memory access out of bounds , Trigger Red Zone Call the police
• Some wild pointer problems , Trigger Dead Zone / Red Zone Call the police

What's the problem? ASAN It can't be solved ？

• Some wild pointer problems （ I just wrote that I haven't “Dead” The memory area of , No alarm will be triggered ）