It should just be renamed from fortify_panic -> fortify_error, including in arch/x86/boot/compressed/misc.c and arch/x86/boot/compressed/misc.c. It can use WARN instead of BUG by with a 'default n', !COMPILE_TEST option to use BUG again. Otherwise it needs to be patched downstream when that's wanted.
I don't think splitting it is the right approach to improving the runtime error handling. That only makes sense for the compile-time errors due to the limitations of __attribute__((error)). Can we think about that before changing it? Just make it use WARN for now. The best debugging experience would be passing along the sizes and having the fortify_error function convert that into nice error messages. For memcpy(p, q, n), n can be larger than both the detected sizes of p and q, not just either one. The error should just be saying the function name and printing the copy size and maximum sizes of p and q. That's going to increase the code size too but I think splitting it will be worse and it goes in the wrong direction in terms of complexity. It's going to make future extensions / optimization harder if it's split.
