From 269e2358492b674c50160553d037702e916b9f1b Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Thu, 11 Dec 2014 02:17:03 +0100 Subject: [PATCH] linuxboot: fix loading old kernels Old kernels that used high memory only allowed the initrd to be in the first 896MB of memory. If you load the initrd above, they complain that "initrd extends beyond end of memory". In order to fix this, while not breaking machines with small amounts of memory fixed by cdebec5 (linuxboot: compute initrd loading address, 2014-10-06), we need to distinguish two cases. If pc.c placed the initrd at end of memory, use the new algorithm based on the e801 memory map. If instead pc.c placed the initrd at the maximum address specified by the bzImage, leave it there. The only interesting part is that the low-memory info block is now loaded very early, in real mode, and thus the 32-bit address has to be converted into a real mode segment. The initrd address is also patched in the info block before entering real mode, it is simpler that way. This fixes booting the RHEL4.8 32-bit installation image with 1GB of RAM. Cc: qemu-stable@nongnu.org Cc: mst@redhat.com Cc: jsnow@redhat.com Signed-off-by: Paolo Bonzini --- pc-bios/linuxboot.bin | Bin 1024 -> 1024 bytes pc-bios/optionrom/linuxboot.S | 37 +++++++++++++++++++++++++--------- 2 files changed, 27 insertions(+), 10 deletions(-) diff --git a/pc-bios/linuxboot.bin b/pc-bios/linuxboot.bin index 130103fb739228a6869aaf1b174b9d20c13378fc..923d1796fbc58f1a836c160be533d1cf697b7511 100644 GIT binary patch delta 142 zcmZqRXyBNj#iGKj$vjbStpET3 delta 89 zcmV-f0H*(d2!IHXDg?v=$pVossgsWZS(EMo83L>VlL-PJ0%li}!2uqVMgp}0xE7KA v9R$Z_iNlfnG8kuOkAoNj003sV000004= 0x203 + jae 1f // have initrd_max + movl $0x37ffffff, %es:0x22c // else assume 0x37ffffff +1: + + /* Check if using kernel-specified initrd address */ + read_fw FW_CFG_INITRD_ADDR + mov %eax, %edi // (load_kernel wants it in %edi) + read_fw FW_CFG_INITRD_SIZE // find end of initrd + add %edi, %eax + xor %es:0x22c, %eax // if it matches es:0x22c + and $-4096, %eax // (apart from padding for page) + jz load_kernel // then initrd is not at top + // of memory + + /* pc.c placed the initrd at end of memory. Compute a better + * initrd address based on e801 data. + */ mov $0xe801, %ax xor %cx, %cx xor %dx, %dx @@ -107,7 +131,9 @@ copy_kernel: read_fw FW_CFG_INITRD_SIZE subl %eax, %edi andl $-4096, %edi /* EDI = start of initrd */ + movl %edi, %es:0x218 /* put it in the header */ +load_kernel: /* 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. */ @@ -139,19 +165,10 @@ 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_CMDLINE) - 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 mov %eax, %cr0