[SOLVED] What does the "%object" and "@object" mean in this inline assembly?

Issue

Below code is quoted from here line 453:

#define GEN_ABSOLUTE_SYM_KCONFIG(name, value)       \
    __asm__(".globl\t" #name                    \
        "\n\t.equ\t" #name "," #value       \
        "\n\t.type\t" #name ",%object")

For something like this:

GEN_ABSOLUTE_SYM_KCONFIG(CONFIG_I2C, 1); 

I think it should expand to:

 .globl      CONFIG_I2C
             .equ          CONFIG_I2C,1
             .type         CONFIG_I2C,%object

I can understand that the #name and #value are just Stringizing.

But what does the %object mean?

The object is not a formal parameter of the GEN_ABSOLUTE_SYM_KCONFIG macro.

Why is it here? And what does the % mean? It seems to be arm specific.

And in line 465, the %object changes to @object for x86.

#define GEN_ABSOLUTE_SYM_KCONFIG(name, value)       \
    __asm__(".globl\t" #name                    \
        "\n\t.equ\t" #name "," #value       \
        "\n\t.type\t" #name ",@object")

Solution

"%object"" is a GAS assembler directive specifying a symbol "type":

From the Binutils documentation:

https://sourceware.org/binutils/docs/as/Type.html

For ELF targets, the .type directive is used like this:

.type name , type description This sets the type of symbol name to be either a function symbol or an object symbol.

More generally:

https://community.arm.com/arm-community-blogs/b/architectures-and-processors-blog/posts/useful-assembler-directives-and-macros-for-the-gnu-assembler

The .type directive allows you to tell the assembler what type a symbol is. Most of the time we just use %function and %object.

Answered By - paulsm4