panic on linux at rust/library/std/src/sys/random/linux.rs:107: out of range for slice of length 16

[cathaysia]

rust/library/std/src/sys/random/linux.rs

Line 107 in ba7e63b

bytes = &mut bytes[ret as usize..];

[ChrisDenton]

Can you give any context? How do you reproduce this panic? What versions of rust are affected? Is there anything special about your environment?

[cathaysia]

Hi there. I apologize for opening an issue with such limited information; I am still actively investigating this problem. The only details I currently have are that the software's architecture is MIPS64 (Big-Endian), and the execution environment is MIPS64o32. I suspect that the issue does not lie with Rust itself; however, I noticed that no bounds checking is being performed at this specific location. That is why I created this issue. Or perhaps this behavior was intentionally designed this way?

[SpriteOvO]

however, I noticed that no bounds checking is being performed at this specific location. That is why I created this issue. Or perhaps this behavior was intentionally designed this way?

In fact, there is a boundary check here that is implicitly generated by the compiler to prevent further undefined behaviors, and that is why you can see this panic message.

According to the doc of getrandom, it should not return a value greater than the buffer length. Therefore, not performing explicit boundary checks here and converting to recoverable errors also sounds reasonable.

I would suggest narrowing the problem down by creating a reproducible code snippet, and then we can further investigate the cause together.

[cathaysia]

I need to see if I can obtain some more detailed information tomorrow. This issue was discovered by someone else, and I don't have any further details on my end at the moment.

[mathisbot]

89 is precisely the errno for ENOSYS on MIPS, so its probably an ABI problem/mismatch

[taiki-e]

the execution environment is MIPS64o32

o32 is for MIPS32, MIPS64's 32-bit ABI is called n32.

The syscall numbers for MIPS64 differ between 32-bit and 64-bit, and Rust supports only 64-bit targets. Unless you are using a properly patched version of std/libc, you are likely calling system calls with the wrong syscall numbers.

[cathaysia]

I used readelf to compare the binaries compiled by C and Rust, and I found that the only difference between the two is that the C version uses software floating-point, whereas the Rust version uses hardware floating-point.

Finally, I found this: https://github.com/cross-rs/cross/pull/974/changes#diff-7cc1fad371267909f6300d179a976517c3a665756cb675f4d72aad0fdb6071b5

Due to linker-related issues, I was unable to create a soft-float MIPS64 program; therefore, I have recreated a Docker image: cross-rs/cross#1773

This allows me to create a MIPS64 big-endian program using soft float; however, unfortunately, my testing environment is currently unavailable, so I am unable to verify whether this resolves the issue.

[cathaysia]

I am closing this issue due to a lack of further progress.