On Tue, 17 Feb 2026 at 10:46, Heinrich Schuchardt <[email protected]> wrote: > > On 2/17/26 09:18, Ilias Apalodimas wrote: > > Hi Heinrich, > > > > On Tue, 17 Feb 2026 at 09:47, Heinrich Schuchardt > > <[email protected]> wrote: > >> > >> The UEFI specification requires at least 128 KiB stack space. Consider this > >> value as a prerequisite for CONFIG_EFI_LOADER. > >> > >> Mention the requirement in the CONFIG_STACK_SPACE description and decribe > >> that the UEFI sub-system uses CONFIG_STACK_SPACE when defining the memory > >> map. > >> > >> Signed-off-by: Heinrich Schuchardt <[email protected]> > >> --- > >> Kconfig | 8 +++++--- > >> lib/efi_loader/Kconfig | 2 ++ > >> 2 files changed, 7 insertions(+), 3 deletions(-) > >> > >> diff --git a/Kconfig b/Kconfig > >> index ce25ea24a60..99b3cd62526 100644 > >> --- a/Kconfig > >> +++ b/Kconfig > >> @@ -615,9 +615,11 @@ config STACK_SIZE > >> default 0x4000 if ARCH_STM32 > >> default 0x1000000 > >> help > >> - Define Max stack size that can be used by U-Boot. This value is > >> used > >> - by the UEFI sub-system. On some boards initrd_high is calculated > >> as > >> - base stack pointer minus this stack size. > >> + Define Max stack size that can be used by U-Boot. The UEFI > >> sub-system > >> + considers this value when setting up the memory map. The UEFI > >> + specification requires 128 KiB or more of available stack space. > >> On > >> + some boards initrd_high is calculated as base stack pointer > >> minus this > >> + stack size. > >> > >> config SYS_MEM_TOP_HIDE > >> hex "Exclude some memory from U-Boot / OS information" > >> diff --git a/lib/efi_loader/Kconfig b/lib/efi_loader/Kconfig > >> index 13e44be1d06..450ffa61c0a 100644 > >> --- a/lib/efi_loader/Kconfig > >> +++ b/lib/efi_loader/Kconfig > >> @@ -15,6 +15,8 @@ config EFI_LOADER > >> # We need EFI_STUB_32BIT to be set on x86_32 with EFI_STUB > >> depends on !EFI_STUB || !X86 || X86_64 || EFI_STUB_32BIT > >> depends on !EFI_APP > >> + # The EFI specification requires 128 KiB or more of stack space > >> + depends on STACK_SIZE >= 0x20000 > > > > Won't this disable EFI for ARCH_STM32 devices? Those define the > > default stack size as 0x4000. > > The UEFI specification explicitly requires an enabled MMU. > The ARMv7-M architecture does not offer it.
There was a discussion about this earlier and we decided to keep it alive though. IIRC Mark explained why we can keep it enabled. Thanks /Ilias > > Best regards > > Heinrich > > > > > Thanks > > /Ilias > >> default y if !ARM || SYS_CPU = armv7 || SYS_CPU = armv8 > >> select EFI > >> select CHARSET > >> -- > >> 2.51.0 > >> >
