On 04/09/2020 19:42, Stephen Warren wrote:
On 9/4/20 3:07 AM, Edgar E. Iglesias wrote:
From: "Edgar E. Iglesias" edgar.iglesias@xilinx.com
Mention the requirement of 4K aligned load addresses in the help section for the POSITION_INDEPENDENT option.
Suggested-by: Michal Simek michal.simek@xilinx.com Signed-off-by: Edgar E. Iglesias edgar.iglesias@xilinx.com
arch/arm/Kconfig | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index f30c2639ec..c144c08612 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -21,6 +21,9 @@ config POSITION_INDEPENDENT information that is embedded in the binary to support U-Boot relocating itself to the top-of-RAM later during execution.
When this option is enabled, U-Boot needs to be loaded at a4K aligned address.I don't believe this restriction should be documented as part of POSITION_INDEPENDENT; the restriction always exists at least for 64-bit ARM, since arch/arm/lib/relocate_64.S relocate_code uses the same assembly sequence that imposes this restriction, and IIUC that code is unconditionally used.
While this is true, the difference is that without POSITION_INDEPENDENT the alignment is easily determined by the hardcoded load address. So we should actually have a build time check on this.
With POSITION_INDEPENDENT, however, the load address is only known at runtime (somewhat under the user's control, if you like). So a warning or hint here might be useful. But maybe it should be noted as a general restriction in the paragraph above: " ... from almost any address" => "from almost any 4K aligned address"
Cheers, Andre.