diff options
Diffstat (limited to 'arch/riscv/include/asm/xip_fixup.h')
| -rw-r--r-- | arch/riscv/include/asm/xip_fixup.h | 49 |
1 files changed, 49 insertions, 0 deletions
diff --git a/arch/riscv/include/asm/xip_fixup.h b/arch/riscv/include/asm/xip_fixup.h new file mode 100644 index 000000000000..f3d56299bc22 --- /dev/null +++ b/arch/riscv/include/asm/xip_fixup.h @@ -0,0 +1,49 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * XIP fixup macros, only useful in assembly. + */ +#ifndef _ASM_RISCV_XIP_FIXUP_H +#define _ASM_RISCV_XIP_FIXUP_H + +#include <linux/pgtable.h> + +#ifdef CONFIG_XIP_KERNEL +.macro XIP_FIXUP_OFFSET reg + /* Fix-up address in Flash into address in RAM early during boot before + * MMU is up. Because generated code "thinks" data is in Flash, but it + * is actually in RAM (actually data is also in Flash, but Flash is + * read-only, thus we need to use the data residing in RAM). + * + * The start of data in Flash is _sdata and the start of data in RAM is + * CONFIG_PHYS_RAM_BASE. So this fix-up essentially does this: + * reg += CONFIG_PHYS_RAM_BASE - _start + */ + li t0, CONFIG_PHYS_RAM_BASE + add \reg, \reg, t0 + la t0, _sdata + sub \reg, \reg, t0 +.endm +.macro XIP_FIXUP_FLASH_OFFSET reg + /* In linker script, at the transition from read-only section to + * writable section, the VMA is increased while LMA remains the same. + * (See in linker script how _sdata, __data_loc and LOAD_OFFSET is + * changed) + * + * Consequently, early during boot before MMU is up, the generated code + * reads the "writable" section at wrong addresses, because VMA is used + * by compiler to generate code, but the data is located in Flash using + * LMA. + */ + la t0, _sdata + sub \reg, \reg, t0 + la t0, __data_loc + add \reg, \reg, t0 +.endm +#else +.macro XIP_FIXUP_OFFSET reg +.endm +.macro XIP_FIXUP_FLASH_OFFSET reg +.endm +#endif /* CONFIG_XIP_KERNEL */ + +#endif |