On Thu, 15 Dec 2022 at 13:40, Evgeniy Baskov <baskov@xxxxxxxxx> wrote: > > Doing it that way allows setting up stricter memory attributes, > simplifies boot code path and removes potential relocation > of kernel image. > > Wire up required interfaces and minimally initialize zero page > fields needed for it to function correctly. > > Tested-by: Peter Jones <pjones@xxxxxxxxxx> > Signed-off-by: Evgeniy Baskov <baskov@xxxxxxxxx> > --- > arch/x86/boot/compressed/head_32.S | 50 ++++- > arch/x86/boot/compressed/head_64.S | 58 ++++- > drivers/firmware/efi/Kconfig | 2 + > drivers/firmware/efi/libstub/Makefile | 2 +- > .../firmware/efi/libstub/x86-extract-direct.c | 208 ++++++++++++++++++ > drivers/firmware/efi/libstub/x86-stub.c | 119 +--------- > drivers/firmware/efi/libstub/x86-stub.h | 14 ++ > 7 files changed, 338 insertions(+), 115 deletions(-) > create mode 100644 drivers/firmware/efi/libstub/x86-extract-direct.c > create mode 100644 drivers/firmware/efi/libstub/x86-stub.h > > diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S > index ead6007df1e5..0be75e5072ae 100644 > --- a/arch/x86/boot/compressed/head_32.S > +++ b/arch/x86/boot/compressed/head_32.S > @@ -152,11 +152,57 @@ SYM_FUNC_END(startup_32) > > #ifdef CONFIG_EFI_STUB > SYM_FUNC_START(efi32_stub_entry) > +/* > + * Calculate the delta between where we were compiled to run > + * at and where we were actually loaded at. This can only be done > + * with a short local call on x86. Nothing else will tell us what > + * address we are running at. The reserved chunk of the real-mode > + * data at 0x1e4 (defined as a scratch field) are used as the stack > + * for this calculation. Only 4 bytes are needed. > + */ Please drop this comment > + call 1f > +1: popl %ebx > + addl $_GLOBAL_OFFSET_TABLE_+(.-1b), %ebx Please drop this and ... > + > + /* Clear BSS */ > + xorl %eax, %eax > + leal _bss@GOTOFF(%ebx), %edi > + leal _ebss@GOTOFF(%ebx), %ecx just use (_bss - 1b) here (etc) > + subl %edi, %ecx > + shrl $2, %ecx > + rep stosl > + > add $0x4, %esp > movl 8(%esp), %esi /* save boot_params pointer */ > + movl %edx, %edi /* save GOT address */ What does this do? > call efi_main > - /* efi_main returns the possibly relocated address of startup_32 */ > - jmp *%eax > + movl %eax, %ecx > + > + /* > + * efi_main returns the possibly > + * relocated address of extracted kernel entry point. > + */ > + > + cli > + > + /* Load new GDT */ > + leal gdt@GOTOFF(%ebx), %eax > + movl %eax, 2(%eax) > + lgdt (%eax) > + > + /* Load segment registers with our descriptors */ > + movl $__BOOT_DS, %eax > + movl %eax, %ds > + movl %eax, %es > + movl %eax, %fs > + movl %eax, %gs > + movl %eax, %ss > + > + /* Zero EFLAGS */ > + pushl $0 > + popfl > + > + jmp *%ecx > SYM_FUNC_END(efi32_stub_entry) > SYM_FUNC_ALIAS(efi_stub_entry, efi32_stub_entry) > #endif ...
