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arm: relocate: Introduce data-only relocation mode

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Introduce new mode of relocation which relocates only data, not code.
This is mainly meant to relocate data to read-write portion of the RAM,
while the code remains in read-only portion of the RAM from which it is
allowed to execute. This split configuration is present on various secure
cores.

The result of the relocation is U-Boot running at its original address,
data relocated to the end of DRAM, but with added read-write area offset.
The U-Boot binary area is not reserved from the end of the DRAM in this
relocation mode, because U-Boot itself is not relocated.

Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
This commit is contained in:
Marek Vasut 2026-03-16 00:54:05 +01:00 committed by Tom Rini
parent e204058607
commit d9eee3d178
4 changed files with 47 additions and 1 deletions
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17
Kconfig
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@ -474,6 +474,23 @@ config SKIP_RELOCATE
Skips relocation of U-Boot allowing for systems that have extremely
limited RAM to run U-Boot.
config SKIP_RELOCATE_CODE
bool "Skips relocation of U-Boot code to end of RAM"
help
Skips relocation of U-Boot code to the end of RAM, but still does
relocate data to the end of RAM. This is mainly meant to relocate
data to read-write portion of the RAM, while the code remains in
read-only portion of the RAM from which it is allowed to execute.
This split configuration is present on various secure cores.
config SKIP_RELOCATE_CODE_DATA_OFFSET
hex "Offset of read-write data memory from read-only text memory"
default 0x0
depends on SKIP_RELOCATE_CODE
help
Offset of the read-write memory which contains data, from read-only
memory which contains executable text.
endif # EXPERT
config PHYS_64BIT

4
arch/arm/lib/crt0.S
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@ -157,7 +157,11 @@ ENTRY(_main)
orr lr, #1 /* As required by Thumb-only */
#endif
ldr r0, [r9, #GD_RELOCADDR] /* r0 = gd->relocaddr */
#if defined(CONFIG_SKIP_RELOCATE_CODE)
bl relocate_code
#else
b relocate_code
#endif
here:
/*
* now relocate vectors

25
arch/arm/lib/relocate.S
View File

@ -79,6 +79,15 @@ ENDPROC(relocate_vectors)
ENTRY(relocate_code)
relocate_base:
adr r3, relocate_base
#ifdef CONFIG_SKIP_RELOCATE_CODE
mov r4, #CONFIG_SKIP_RELOCATE_CODE_DATA_OFFSET
ldr r1, _data_start_ofs
add r5, r1, r3 /* r5 <- Run &__data_start */
ldr r1, _data_end_ofs
add r6, r1, r3 /* r6 <- Run &__data_end */
#else
ldr r1, _image_copy_start_ofs
add r1, r3 /* r1 <- Run &__image_copy_start */
subs r4, r0, r1 /* r4 <- Run to copy offset */
@ -90,6 +99,7 @@ copy_loop:
stmia r0!, {r10-r11} /* copy to target address [r0] */
cmp r1, r2 /* until source end address [r2] */
blo copy_loop
#endif
/*
* fix .rel.dyn relocations
@ -107,6 +117,15 @@ fixloop:
/* relative fix: increase location by offset */
add r0, r0, r4
ldr r1, [r0]
#ifdef CONFIG_SKIP_RELOCATE_CODE
/* Test whether this is data, if not, do not relocate. */
cmp r1, r5
blt fixnext
cmp r1, r6
bgt fixnext
#endif
add r1, r1, r4
str r1, [r0]
fixnext:
@ -126,3 +145,9 @@ _rel_dyn_start_ofs:
.word __rel_dyn_start - relocate_code
_rel_dyn_end_ofs:
.word __rel_dyn_end - relocate_code
#ifdef CONFIG_SKIP_RELOCATE_CODE
_data_start_ofs:
.word __data_start - relocate_code
_data_end_ofs:
.word __data_end - relocate_code
#endif

2
common/board_f.c
View File

@ -462,7 +462,7 @@ static int reserve_uboot(void)
if (CONFIG_IS_ENABLED(SKIP_RELOCATE))
gd->flags |= GD_FLG_SKIP_RELOC;
if (!(gd->flags & GD_FLG_SKIP_RELOC)) {
if (!(gd->flags & GD_FLG_SKIP_RELOC) && !CONFIG_IS_ENABLED(SKIP_RELOCATE_CODE)) {
/*
* reserve memory for U-Boot code, data & bss
* round down to next 4 kB limit