Writing an OS in Rust: Advanced Paging

Re:Writing an OS in Rust: Advanced Paging by pjmlp on Monday January 28, 2019 @03:32PM (#19020799)

Memory safety in kernels is also welcomed and is very present in mainframe OSes and high integrity systems where human lives are at stake.

Yes, there are a couple of areas where unsafety is required, there isn't any other way.

However 100% of the kernel source code doesn't need to be unsafe.

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Re:Writing an OS in Rust: Advanced Paging by zaarn on Monday January 28, 2019 @04:56PM (#19021474)

There is two types of memory safety that you talk about there, I think.

One is the memory safety that the rust compiler wants to hold and the other is the memory safety you program into a system.

Those can be entirely different with incompatible guarantees, depending on the mission statement of the software.

Some things a kernel must do are unsafe for the rust compiler. Dereferencing a null pointer, for example, is basically a crash in most operating system's userland.

In kernel space a null pointer may be valid memory that points to real data you need to use.

Setting the page tables is unsafe as well; it's almost impossible to guarantee that the following instructions can run in a static manner. You have to validate the page tables you're about to load at runtime and even then the result could be a process crashing.

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