diff options
Diffstat (limited to 'documentation/GNU-efi')
| -rw-r--r-- | documentation/GNU-efi | 77 |
1 files changed, 74 insertions, 3 deletions
diff --git a/documentation/GNU-efi b/documentation/GNU-efi index 1efe81c..40cd91f 100644 --- a/documentation/GNU-efi +++ b/documentation/GNU-efi @@ -59,7 +59,18 @@ hello.so: $(OBJS) -j .dynsym -j .rel -j .rela -j .reloc \ --target=efi-app-$(ARCH) $^ $@ +----- +Now expanded version in git +Get ImageBase: + Run ./test.sh and then hello.efi...this prints ImageBase + +Get Offsets: + GDB + file hello.efi + -> get text and data offset + file + add-symbol-file hello.efi (ImageBase+text-off) -s .data (ImageBase+data-off) ################################################################################# @@ -210,12 +221,72 @@ you need to add ImageBase address to their offsets: * 3000 - ... is .text * * c00 - ... is .data * * (gdb) file || unload file * -* add-symbol-table hello.efi (ImageBase+text-off) -s .data (ImageBase+data-off) * +* add-symbol-file hello.efi (ImageBase+text-off) -s .data (ImageBase+data-off) * ********************************************************************************* +################################################################################# +# https://www.rodsbooks.com/efi-programming/hello.html # +################################################################################# - - +You should not normally include regular C header files, such as stdlib.h, +because most of these header files define data types and functions that are used +by the C library. This library is not available in EFI. + +************************************ +* efi.h and efilib.h always needed * +************************************ + +Entry point: efi_main() in GNU-efi + +CFLAGS: +* -fno-stack-protector: + Stack protection isn't suppoerted by EFI, so there's no point in + building a binary with this feature active. + +* -fpic: + EFI requires that code be position-independet, hence the use + of this option. + +* -fshort-wchar: + GCC defines the wchar_t type to be 32 bits by default, but EFI requires + it to be 16 bits for 16-bit strings to work correctly. + +* fmno-red-zone: + On x86-64 systems, the red zone is an area that follows the stack pointer + that can be used for temporary variables. The EFI may modify this area, + though, so it's not safe to use, and you must compile EFI binaries with + this option. + +* -Wall: + When developing EFI applications, you might want to pay extra attention to + compiler warnings, and this switch (which causes warnings to be treated as + errors) can help. + +* -DEFI_FUNCTION_WRAPPER: + This option is required on the x86_64 platform, but is not defined on the + 32-bit x86 platform. It relates to th calling conventions for EFI functions, + described on the Using EFI Services page. + +LDFLAGS: +* -nostdlib: + An EFI application should not be linked against standard libraries, and this + argument accomplishes this goal. + +* -nocombreloc: + This argument causes the linker to not combine relocation sections. + +* -T $(EFI_LDS): + To create an EFI binary, a non-standard linker script must be used, and this + option tells ld where to find it. + +* -shared: + Even with GNU-EFI's new linker script, ld can't create the final executable. + Instead, it creates a shared library, which is subsequently + turned into the final binary. + +* -Bsymbolic: + This option causes references to global symbols to be bound to the + definitions within the shared library. |