diff options
| author | Kevin Wolf <mail@kevin-wolf.de> | 2013-06-23 22:07:45 +0200 |
|---|---|---|
| committer | Anthony Liguori <aliguori@us.ibm.com> | 2013-06-28 14:01:52 -0500 |
| commit | 26a8ec07616df8eeb7ae5e76a4eade6809c426e3 (patch) | |
| tree | 23953b1d7a5120432ce1d446d9ea63b4971a54c7 /pc-bios/optionrom/multiboot.S | |
| parent | 390fb6b47144adbad453cdf95c130854728c56f8 (diff) | |
multiboot: Calculate upper_mem in the ROM
The upper_mem field of the Multiboot information struct doesn't really
contain the RAM size - 1 MB like we used to calculate it, but only the
memory from 1 MB up to the first (upper) memory hole.
In order to correctly retrieve this information, the multiboot ROM now
looks at the mmap it creates anyway and tries to find the size of
contiguous usable memory from 1 MB.
Drop the multiboot.c definition of lower_mem and upper_mem because both
are queried at runtime now.
Signed-off-by: Kevin Wolf <mail@kevin-wolf.de>
Reviewed-by: Anthony Liguori <aliguori@us.ibm.com>
Message-id: 1372018066-21822-3-git-send-email-mail@kevin-wolf.de
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Diffstat (limited to 'pc-bios/optionrom/multiboot.S')
| -rw-r--r-- | pc-bios/optionrom/multiboot.S | 40 |
1 files changed, 40 insertions, 0 deletions
diff --git a/pc-bios/optionrom/multiboot.S b/pc-bios/optionrom/multiboot.S index a0f3602956..b7efe4de34 100644 --- a/pc-bios/optionrom/multiboot.S +++ b/pc-bios/optionrom/multiboot.S @@ -123,6 +123,46 @@ mmap_store_entry: jnz mmap_loop mmap_done: + /* Calculate upper_mem field: The amount of memory between 1 MB and + the first upper memory hole. Get it from the mmap. */ + xor %di, %di + mov $0x100000, %edx +upper_mem_entry: + cmp %fs:0x2c, %di + je upper_mem_done + add $4, %di + + /* Skip if type != 1 */ + cmpl $1, %es:16(%di) + jne upper_mem_next + + /* Skip if > 4 GB */ + movl %es:4(%di), %eax + test %eax, %eax + jnz upper_mem_next + + /* Check for contiguous extension (base <= %edx < base + length) */ + movl %es:(%di), %eax + cmp %eax, %edx + jb upper_mem_next + addl %es:8(%di), %eax + cmp %eax, %edx + jae upper_mem_next + + /* If so, update %edx, and restart the search (mmap isn't ordered) */ + mov %eax, %edx + xor %di, %di + jmp upper_mem_entry + +upper_mem_next: + addl %es:-4(%di), %edi + jmp upper_mem_entry + +upper_mem_done: + sub $0x100000, %edx + shr $10, %edx + mov %edx, %fs:0x8 + real_to_prot: /* Load the GDT before going into protected mode */ lgdt: |