xip_fixup.h

 1/* SPDX-License-Identifier: GPL-2.0-only */
 2/*
 3 * XIP fixup macros, only useful in assembly.
 4 */
 5#ifndef _ASM_RISCV_XIP_FIXUP_H
 6#define _ASM_RISCV_XIP_FIXUP_H
 7
 8#include <linux/pgtable.h>
 9
10#ifdef CONFIG_XIP_KERNEL
11.macro XIP_FIXUP_OFFSET reg
12	/* Fix-up address in Flash into address in RAM early during boot before
13	 * MMU is up. Because generated code "thinks" data is in Flash, but it
14	 * is actually in RAM (actually data is also in Flash, but Flash is
15	 * read-only, thus we need to use the data residing in RAM).
16	 *
17	 * The start of data in Flash is _sdata and the start of data in RAM is
18	 * CONFIG_PHYS_RAM_BASE. So this fix-up essentially does this:
19	 * reg += CONFIG_PHYS_RAM_BASE - _start
20	 */
21	li t0, CONFIG_PHYS_RAM_BASE
22        add \reg, \reg, t0
23	la t0, _sdata
24	sub \reg, \reg, t0
25.endm
26.macro XIP_FIXUP_FLASH_OFFSET reg
27	/* In linker script, at the transition from read-only section to
28	 * writable section, the VMA is increased while LMA remains the same.
29	 * (See in linker script how _sdata, __data_loc and LOAD_OFFSET is
30	 * changed)
31	 *
32	 * Consequently, early during boot before MMU is up, the generated code
33	 * reads the "writable" section at wrong addresses, because VMA is used
34	 * by compiler to generate code, but the data is located in Flash using
35	 * LMA.
36	 */
37	la t0, _sdata
38	sub \reg, \reg, t0
39	la t0, __data_loc
40	add \reg, \reg, t0
41.endm
42#else
43.macro XIP_FIXUP_OFFSET reg
44.endm
45.macro XIP_FIXUP_FLASH_OFFSET reg
46.endm
47#endif /* CONFIG_XIP_KERNEL */
48
49#endif