c - Unrecognised emulation mode: elf_i386 on MinGW32 -

i'm trying make kernel, , cannot link c output assembly. ld. i'm getting error:

unrecognized emulation mode: elf_i386

i'm using windows 10 professional mingw32 , msys. code using:

link.ld

/* *  link.ld */ output_format(elf32-i386) entry(start) sections  {    . = 0x100000;    .text : { *(.text) }    .data : { *(.data) }    .bss  : { *(.bss)  }  } 

kernel.c

/* *  kernel.c */ void kmain(void) {     const char *str = "my first kernel";     char *vidptr = (char*)0xb8000;  //video mem begins here.     unsigned int = 0;     unsigned int j = 0;      /* loops clears screen     * there 25 lines each of 80 columns; each element takes 2 bytes */     while(j < 80 * 25 * 2) {         /* blank character */         vidptr[j] = ' ';         /* attribute-byte - light grey on black screen */         vidptr[j+1] = 0x07;                  j = j + 2;     }      j = 0;      /* loop writes string video memory */     while(str[j] != '\0') {         /* character's ascii */         vidptr[i] = str[j];         /* attribute-byte: give character black bg , light grey fg */         vidptr[i+1] = 0x07;         ++j;         = + 2;     }     return; } 

kernel.asm

;;kernel.asm bits 32         ;nasm directive - 32 bit section .text  global start extern kmain            ;kmain defined in c file  start:   cli           ;block interrupts   mov esp, stack_space  ;set stack pointer   call kmain   hlt           ;halt cpu  section .bss resb 8192       ;8kb stack stack_space: 

to compile , link use:

nasm -f elf32 kernel.asm -o kasm.o gcc -m32 -c kernel.c -o kc.o ld -m elf_i386 -t link.ld -o kernel kasm.o kc.o 

i'm using:

• gcc 4.8.1
• ld 2.25.1
• nasm 2.11.09rc1

why getting error, , how can fix it?

the standard mingw/32 ld linker doesn't output elf binaries. preferably using i686 cross-compiler, if you're not may able away tips below.

it appears using arjun's let's write kernel tutorial. if following tutorial have missed step make kernel.asm compatible grub boot loader , qemu's -kernel option. before start should read rest of tutorial. following code adds multiboot header kernel.asm make grub compatible:

;;kernel.asm bits 32         ;nasm directive - 32 bit global entry extern _kmain            ;kmain defined in c file  section .text entry:  jmp start          ;multiboot spec         align 4         dd 0x1badb002            ;magic         dd 0x00                  ;flags         dd -(0x1badb002 + 0x00)  ;checksum. m+f+c should 0  start:         cli           ;block interrupts         mov esp, stack_space  ;set stack pointer         call _kmain         hlt           ;halt cpu  section .bss resb 8192       ;8kb stack stack_space: 

besides adding header i've put entry label in file , jmp start jump on multiboot header. i've done make easy set breakpoint @ 0x100000 in future if start debugging.

one other change on mingw, gcc adds underscore function names default. i've changed references c function kmain _kmain. differs linux convention.

since entry point of our code entry instead of start i've modified link.ld be:

/* *  link.ld */ output_format(pei-i386)     entry(entry)  sections  {    . = 0x100000;    .text : { *(.text) }    .data : { *(.data) }    .bss  : { *(.bss)  }  } 

another important change in file above usage of output_format(pei-i386) . output portable executable image (32-bit) rather elf (which isn't supported).

in order build kernel , produce elf image pei-i386 can use these commands:

nasm -f elf32 kernel.asm -o kasm.o gcc -m32 -c kernel.c -o kc.o -ffreestanding -nostdlib -nostdinc ld -t link.ld -o kernel kasm.o kc.o -build-id=none objcopy -o elf32-i386 kernel kernel.elf 

the ld command has been modified not write out build-id executable avoid multiboot header being shifted outside first 8k of executable. gcc options have been modified produce freestanding code (without standard library , includes) using options -ffreestanding -nostdlib -nostdinc. use objcopy convert pei-i386 file (kernel) elf32 image called kernel.elf. want using kernel.elf grub and/or qemu.