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I am writing a toy kernel for learning purposes, and I am having a bit of trouble with it. I have made a simple bootloader that loads a segment from a floppy disk (which is written in 32 bit code), then the bootloader enables the A20 gate and turns on protected mode. I can jump to the 32 bit code fine if I write it in assembler, but if I write it in C, I get a triple fault. When I disassemble the C code I can see that the first two instructions involve setting up a new stack frame. This is the key difference between the working ASM code and the failing C code. I am using NASM v2.10.05 for the ASM code, and GCC from the DJGPP 4.72 collection for the C code. This is the bootloader code: org 7c00h BITS 16 entry: mov [drive], dl ;Save the current drive cli mov ax,cs ; Setup segment registers mov ds,ax ; Make DS correct mov ss,ax ; Make SS correct mov bp,0fffeh mov sp,0fffeh ;Setup a temporary stack sti ;Set video mode to text ;=================== mov ah, 0 mov al, 3 int 10h ;=================== ;Set current page to 0 ;================== mov ah, 5 mov al, 0 int 10h ;================== ;Load the sector ;============= call load_image ;============= ;Clear interrupts ;============= cli ;============= ;Disable NMIs ;============ in ax, 70h and ax, 80h ;Set the high bit to 1 out 70h, ax ;============ ;Enable A20: ;=========== mov ax, 02401h int 15h ;=========== ;Load the GDT ;=========== lgdt [gdt_pointer] ;=========== ;Clear interrupts ;============= cli ;============= ;Enter protected mode ;================== mov eax, cr0 or eax, 1 ;Set the low bit to 1 mov cr0, eax ;================== jmp 08h:clear_pipe ;Far jump to clear the instruction queue ;====================================================== load_image: reset_drive: mov ah, 00h ; DL contains *this* drive, given to us by the BIOS int 13h jc reset_drive read_sectors: mov ah, 02h

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