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SubjectRe: x86 embedded - Problem getting past 'move compressed kernel before decompression'
On 02/20/2010 06:03 PM, Graeme Russ wrote:
>
> The following is something I have hacked together to jump into the 32-bit
> start address of the Linux Kernel:
>
> struct boot_params boot_params __attribute__((aligned(16)));
> struct setup_header *hdr = (struct setup_header *)(0x90000 + 0x1f1);
>
> void boot_zimage(void *setup_base)
> {
> memset(&boot_params, 0x00, sizeof boot_params);
> memcpy(&boot_params.hdr, hdr, sizeof (*hdr));
>
> boot_params.alt_mem_k = 128 * 1024;
> boot_params.e820_entries = 1;
> boot_params.e820_map[0].addr = 0x00000000;
> boot_params.e820_map[0].size = 128 * 1024;
> boot_params.e820_map[0].type = 1;
>
> asm( "movw $0x18, %%cx\n" \
> "movl %%ecx, %%ds\n" \
> "movl %%ecx, %%es\n" \
> "movl %%ecx, %%fs\n" \
> "movl %%ecx, %%gs\n" \
> "movl %%ecx, %%ss\n" \
> "xorl %%ebp, %%ebp\n" \
> "xorl %%edi, %%edi\n" \
> "xorl %%ebx, %%ebx\n" \
> "movl %0, %%esi\n"
^^
> "movl $0x100000, %%eax\n" \
> "jmpl *%%eax" : : "r"(&boot_params));
^

At this point you have probably clobbered the register that you have
your boot_params in.

Instead, do something like:

asm volatile(
"movl %0, %%ds\n" \
"movl %0, %%es\n" \
"movl %0, %%fs\n" \
"movl %0, %%gs\n" \
"movl %0, %%ss\n" \
"xorl %ebp, %ebp\n" \
"xorl %ebx, %ebx\n" \
"movl $0x100000, %%eax\n" \
"ljmpl $0x10,$0x100000"
: : "S" (&boot_params), "D" (0), "c" (0x18));
-hpa

--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.



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