Linkage problems when adding S file to Linux kernel

Question

After a previous question got answered: Adding a .S file to the linux kernel code I was able to add a .S file to the Linux kernel make files. However, my .S file includes several sections that replace functions that were written in C. I commented out these functions, and declared the replacement functions as globals, but when I try to link the kernel (using make) I get the following error:

arch/x86/kernel/vmlinux.lds:XXX: non constant or forward reference address expression for section .YYY

The original functions that I replaced were declared using: __attribute__ ((unused, __section__("YYY"))) notrace

The asm sections are declared using:

.text
.globl YYY

I also tried adding:

.type YYY,@function

I probably missed some declaration somewhere, but I'm not sure where to look.

Any ideas?

Answer 1

If you want to place assembly functions into section YYY, rather than .text, you need to replace

.text

with

.section YYY,"ax"

Answer 2

This code:

.text
.globl YYY

tells the assembler that you are going to write things in the "text" section, and that "YYY" is a global within that section. Your .type adds that "YYY" is the name of a function. That's not what you want: you want the section to be named "YYY", not the function itself. To select a section with a specific name, use a .section directive (.text is just a shortcut for a .section which designates the "text" section).