diff options
| -rw-r--r-- | pc-bios/optionrom/multiboot.S | 35 |
1 files changed, 17 insertions, 18 deletions
diff --git a/pc-bios/optionrom/multiboot.S b/pc-bios/optionrom/multiboot.S index 003bcfb49f..a0f3602956 100644 --- a/pc-bios/optionrom/multiboot.S +++ b/pc-bios/optionrom/multiboot.S @@ -89,17 +89,14 @@ run_multiboot: /* Initialize multiboot mmap structs using int 0x15(e820) */ xor %ebx, %ebx - /* mmap start after first size */ - movl $4, %edi + /* Start storing mmap data at %es:0 */ + xor %edi, %edi mmap_loop: + /* The multiboot entry size has offset -4, so leave some space */ + add $4, %di /* entry size (mmap struct) & max buffer size (int15) */ movl $20, %ecx - /* store entry size */ - /* old as(1) doesn't like this insn so emit the bytes instead: - movl %ecx, %es:-4(%edi) - */ - .dc.b 0x26,0x67,0x66,0x89,0x4f,0xfc /* e820 */ movl $0x0000e820, %eax /* 'SMAP' magic */ @@ -107,21 +104,23 @@ mmap_loop: int $0x15 mmap_check_entry: - /* last entry? then we're done */ + /* Error or last entry already done? */ jb mmap_done - and %bx, %bx - jz mmap_done - /* valid entry, so let's loop on */ mmap_store_entry: - /* %ax = entry_number * 24 */ - mov $24, %ax - mul %bx - mov %ax, %di + /* store entry size */ + /* old as(1) doesn't like this insn so emit the bytes instead: + movl %ecx, %es:-4(%edi) + */ + .dc.b 0x26,0x67,0x66,0x89,0x4f,0xfc + + /* %edi += entry_size, store as mbs_mmap_length */ + add %ecx, %edi movw %di, %fs:0x2c - /* %di = 4 + (entry_number * 24) */ - add $4, %di - jmp mmap_loop + + /* Continuation value 0 means last entry */ + test %ebx, %ebx + jnz mmap_loop mmap_done: real_to_prot: |