On Sun, Sep 06, 2020 at 11:16:17PM +0100, André Przywara wrote: > 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.igles...@xilinx.com> > >> > >> Mention the requirement of 4K aligned load addresses in the > >> help section for the POSITION_INDEPENDENT option. > >> > >> Suggested-by: Michal Simek <michal.si...@xilinx.com> > >> Signed-off-by: Edgar E. Iglesias <edgar.igles...@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 a > >> + 4K 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" >
That sounds good to me. Thanks, Edgar
