Messages in this thread |  | | Date | Thu, 13 Dec 2012 18:15:54 -0800 | Subject | Re: [PATCH v6 19/27] x86, boot: update comments about entries for 64bit image | From | Yinghai Lu <> |
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On Thu, Dec 13, 2012 at 3:27 PM, H. Peter Anvin <hpa@zytor.com> wrote: > if we depend on other > things we should make that explicit, not just here but in boot.txt.
please check lines for boot.txt
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**** 64-bit BOOT PROTOCOL
For machine with 64bit cpus and 64bit kernel, we could use 64bit bootloader We need a 64-bit boot protocol.
In 64-bit boot protocol, the first step in loading a Linux kernel should be to setup the boot parameters (struct boot_params, traditionally known as "zero page"). The memory for struct boot_params should be allocated under or above 4G and initialized to all zero. Then the setup header from offset 0x01f1 of kernel image on should be loaded into struct boot_params and examined. The end of setup header can be calculated as follow:
0x0202 + byte value at offset 0x0201
In addition to read/modify/write the setup header of the struct boot_params as that of 16-bit boot protocol, the boot loader should also fill the additional fields of the struct boot_params as that described in zero-page.txt.
After setting up the struct boot_params, the boot loader can load the 64-bit kernel in the same way as that of 16-bit boot protocol, but kernel could be above 4G.
In 64-bit boot protocol, the kernel is started by jumping to the 64-bit kernel entry point, which is the start address of loaded 64-bit kernel plus 0x200.
At entry, the CPU must be in 64-bit mode with paging enabled. The range with setup_header.init_size from start address of loaded kernel and zero page and command line buffer get ident mapping; a GDT must be loaded with the descriptors for selectors __BOOT_CS(0x10) and __BOOT_DS(0x18); both descriptors must be 4G flat segment; __BOOT_CS must have execute/read permission, and __BOOT_DS must have read/write permission; CS must be __BOOT_CS and DS, ES, SS must be __BOOT_DS; interrupt must be disabled; %rsi must hold the base address of the struct boot_params. ---
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