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riscv: drop the use of XIP_OFFSET in XIP_FIXUP_FLASH_OFFSET

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XIP_OFFSET is the hard-coded offset of writable data section within the
kernel.

By hard-coding this value, the read-only section of the kernel (which is
placed before the writable data section) is restricted in size.

As a preparation to remove this hard-coded macro XIP_OFFSET entirely, stop
using XIP_OFFSET in XIP_FIXUP_FLASH_OFFSET. Instead, use __data_loc and
_sdata to do the same thing.

While at it, also add a description for XIP_FIXUP_FLASH_OFFSET.

Signed-off-by: Nam Cao <namcao@linutronix.de>
Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Link: https://lore.kernel.org/r/7b3319657edd1822f3457e7e7c07aaa326cc2f87.1717789719.git.namcao@linutronix.de
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
This commit is contained in:
Nam Cao 2024-06-07 22:22:10 +02:00 committed by Palmer Dabbelt
parent e4eac34fed
commit 23311f57ee
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1 changed files with 12 additions and 4 deletions
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16
arch/riscv/include/asm/xip_fixup.h
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@ -24,13 +24,21 @@
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
REG_L t1, _xip_phys_offset
sub \reg, \reg, t1
add \reg, \reg, t0
.endm
_xip_phys_offset: .dword CONFIG_XIP_PHYS_ADDR + XIP_OFFSET
#else
.macro XIP_FIXUP_OFFSET reg
.endm