Segment based referencing in c

[thomasloven]

Some xv6 code mirrors have the following line:

Code: Select all

extern struct cpu *cpu asm("%gs:0");

[github]

This is a hack using the assembly label attribute available in some compilers which works by accident rather than by design - if at all.

However, having a simple way of automatically referencing an offset from fs/gs is damn convenient, and having it be a variable rather than a function carries a measure of elegance.

Can the same thing somehow be be done The Right Way™?

[Octocontrabass]

Yes, using GCC's Named Address Spaces extensions.

[thomasloven]

Works like a charm! Thank you!