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Message-ID: <20220120163826.bits6ffbnbal4yse@box.shutemov.name>
Date: Thu, 20 Jan 2022 19:38:26 +0300
From: "Kirill A. Shutemov" <kirill@...temov.name>
To: bp@...en8.de
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Subject: Re: [PATCH 2/3] x86/boot: Allow to hook up alternative port I/O
helpers
On Thu, Jan 20, 2022 at 05:15:43AM +0300, Kirill A. Shutemov wrote:
> diff --git a/arch/x86/boot/io.h b/arch/x86/boot/io.h
> new file mode 100644
> index 000000000000..640daa3925fb
> --- /dev/null
> +++ b/arch/x86/boot/io.h
> @@ -0,0 +1,30 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef BOOT_IO_H
> +#define BOOT_IO_H
> +
> +#include <asm/shared/io.h>
> +
> +struct port_io_ops {
> + unsigned char (*inb)(int port);
> + unsigned short (*inw)(int port);
> + unsigned int (*inl)(int port);
> + void (*outb)(unsigned char v, int port);
> + void (*outw)(unsigned short v, int port);
> + void (*outl)(unsigned int v, int port);
> +};
> +
> +extern struct port_io_ops pio_ops;
> +
> +static inline void init_io_ops(void)
> +{
> + pio_ops = (struct port_io_ops){
> + .inb = inb,
> + .inw = inw,
> + .inl = inl,
> + .outb = outb,
> + .outw = outw,
> + .outl = outl,
> + };
> +}
> +
> +#endif
It works fine on x86-64, but breaks on i386:
ld: Unexpected run-time relocations (.rel) detected!
I'll change it to
pio_ops.inb = inb;
pio_ops.inw = inw;
pio_ops.inl = inl;
pio_ops.outb = outb;
pio_ops.outw = outw;
pio_ops.outl = outl;
It works, but I hate that I don't really have control here. I have no clue
why compiler generate different code after the change. It is very fragile.
Do we really have no way to say compiler to avoid relactions here?
--
Kirill A. Shutemov
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