On 3/18/26 7:59 AM, Ilias Apalodimas wrote:
Hello Ilias,
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.
We should mention at some point in the commit message that this is for v7 only.
I actually do use this on V8M .
[...]
+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.
+
Similar concerns with Tom for limiting the Kconfig selection. Do we
need a depends on the armv7 arch for now ?
No, because I use it on V8M.
@@ -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
Where are these defined? __data_[start|end] only seem to exist for x86
and microblaze
Currently, I have to use own linker script, the data section looks like
this:
"
. = ALIGN(4);
.data : {
__data_start = .;
*(.data*)
__data_end = .;
}
"
Any system which will use this will have to patch the start/end in their
data section too, or ideally if they use generic linker script, patch
that generic linker script to emit those symbols. Maybe we should patch
at least arch/arm/cpu/u-boot.lds ?
[...]
Overall this seems to be needed, I am a little concerned about test
coverage, since this will be fragile when changing asm and/or linker
scripts. But OTOH I dont have any bright ideas on how to test it
Maybe QEMU can be extended with Cortex-M support ?
