diff options
| author | Paolo Bonzini <pbonzini@redhat.com> | 2014-10-06 16:49:57 +0200 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2014-10-09 15:36:15 +0200 |
| commit | cdebec5e40bd0af82da0659f37af85ee2aa2c9d1 (patch) | |
| tree | 7e355ce31516dbd959a49639e6f2ed15f6cb6e6f /pc-bios/optionrom/linuxboot.S | |
| parent | fc02086b5ab8de50ce8234cf8f42b254de9e5d91 (diff) | |
linuxboot: compute initrd loading address
Even though hw/i386/pc.c tries to compute a valid loading address for the
initrd, close to the top of RAM, this does not take into account other
data that is malloced into that memory by SeaBIOS.
Luckily we can easily look at the memory map to find out how much memory is
used up there. This patch places the initrd in the first four gigabytes,
below the first hole (as returned by INT 15h, AX=e801h).
Without this patch:
[ 0.000000] init_memory_mapping: [mem 0x07000000-0x07fdffff]
[ 0.000000] RAMDISK: [mem 0x0710a000-0x07fd7fff]
With this patch:
[ 0.000000] init_memory_mapping: [mem 0x07000000-0x07fdffff]
[ 0.000000] RAMDISK: [mem 0x07112000-0x07fdffff]
So linuxboot is able to use the 64k that were added as padding for
QEMU <= 2.1.
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'pc-bios/optionrom/linuxboot.S')
| -rw-r--r-- | pc-bios/optionrom/linuxboot.S | 47 |
1 files changed, 43 insertions, 4 deletions
diff --git a/pc-bios/optionrom/linuxboot.S b/pc-bios/optionrom/linuxboot.S index 748c831160..5bc0af08e0 100644 --- a/pc-bios/optionrom/linuxboot.S +++ b/pc-bios/optionrom/linuxboot.S @@ -76,14 +76,45 @@ boot_kernel: copy_kernel: + /* Compute initrd address */ + mov $0xe801, %ax + xor %cx, %cx + xor %dx, %dx + int $0x15 + + /* Output could be in AX/BX or CX/DX */ + or %cx, %cx + jnz 1f + or %dx, %dx + jnz 1f + mov %ax, %cx + mov %bx, %dx +1: + + or %dx, %dx + jnz 2f + addw $1024, %cx /* add 1 MB */ + movzwl %cx, %edi + shll $10, %edi /* convert to bytes */ + jmp 3f + +2: + addw $16777216 >> 16, %dx /* add 16 MB */ + movzwl %dx, %edi + shll $16, %edi /* convert to bytes */ + +3: + read_fw FW_CFG_INITRD_SIZE + subl %eax, %edi + andl $-4096, %edi /* EDI = start of initrd */ /* We need to load the kernel into memory we can't access in 16 bit mode, so let's get into 32 bit mode, write the kernel and jump back again. */ /* Reserve space on the stack for our GDT descriptor. */ - mov %esp, %ebp - sub $16, %esp + mov %esp, %ebp + sub $16, %esp /* Now create the GDT descriptor */ movw $((3 * 8) - 1), -16(%bp) @@ -108,10 +139,18 @@ copy_kernel: /* We're now running in 16-bit CS, but 32-bit ES! */ /* Load kernel and initrd */ + pushl %edi + read_fw_blob_addr32_edi(FW_CFG_INITRD) read_fw_blob_addr32(FW_CFG_KERNEL) - read_fw_blob_addr32(FW_CFG_INITRD) read_fw_blob_addr32(FW_CFG_CMDLINE) - read_fw_blob_addr32(FW_CFG_SETUP) + + read_fw FW_CFG_SETUP_ADDR + mov %eax, %edi + mov %eax, %ebx + read_fw_blob_addr32_edi(FW_CFG_SETUP) + + /* Update the header with the initrd address we chose above */ + popl %es:0x218(%ebx) /* And now jump into Linux! */ mov $0, %eax |