On Wed, 2015-03-25 at 18:56 +0100, Mason wrote:
> Hello everyone,
>
> AFAIU, functions only used at system init are tagged __init to have
> the linker store them in a separate .init.text section, so memory can
> be reclaimed once initialization is complete. Is that correct?
>
> The corresponding tag for data is __initdata (section .init.data)
>
> I started wondering if the string literals used in an __init functions
> were automatically marked __initdata.
>
> Looking at the objdump output, I see that the string literals are,
> in fact, stored in the .rodata section. I suppose that .rodata is NOT
> reclaimed after init?
>
> This way seems to work:
>
> static char XyZa[] __initdata = KERN_ALERT "foo";
> static const char XyZb[] __initconst = KERN_ALERT "bar";
> void __init XyZc(void) { printk(XyZa); printk(XyZb); }
>
> $ arm-linux-gnueabihf-objdump -xd arch/arm/mach-tangox/time.o | grep XyZ
> 00000000 l O .init.data 00000006 XyZa
> 00000000 l O .init.rodata 00000006 XyZb
> 00000000 g F .init.text 00000028 XyZc
> 00000000 <XyZc>:
>
> $ arm-linux-gnueabihf-objdump -xd vmlinux | grep XyZ
> c021e360 l O .init.data 00000006 XyZa
> c0220090 l O .init.data 00000006 XyZb
> c020d928 g F .init.text 00000028 XyZc
> c020d928 <XyZc>:
>
> c020d928 <XyZc>:
> c020d928: e1a0c00d mov ip, sp
> c020d92c: e92dd800 push {fp, ip, lr, pc}
> c020d930: e24cb004 sub fp, ip, #4
> c020d934: e30e0360 movw r0, #58208 ; 0xe360
> c020d938: e34c0021 movt r0, #49185 ; 0xc021
> c020d93c: ebfe00c9 bl c018dc68 <printk>
> c020d940: e3000090 movw r0, #144 ; 0x90
> c020d944: e34c0022 movt r0, #49186 ; 0xc022
> c020d948: ebfe00c6 bl c018dc68 <printk>
> c020d94c: e89da800 ldm sp, {fp, sp, pc}
>
> Did I miss something in init.h?
> Or should it be done like above to reclaim string literals?
No, you didn't miss anything.
One proposal:
https://lkml.org/lkml/2014/8/21/255
> Regards.
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