diff options
Diffstat (limited to 'arch/x86/boot/compressed/head_64.S')
| -rw-r--r-- | arch/x86/boot/compressed/head_64.S | 48 |
1 files changed, 28 insertions, 20 deletions
diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S index f5d1aaa..c1d383d 100644 --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -37,6 +37,12 @@ __HEAD .code32 ENTRY(startup_32) + /* + * 32bit entry is 0 and it is ABI so immutable! + * If we come here directly from a bootloader, + * kernel(text+data+bss+brk) ramdisk, zero_page, command line + * all need to be under the 4G limit. + */ cld /* * Test KEEP_SEGMENTS flag to see if the bootloader is asking @@ -154,6 +160,12 @@ ENTRY(startup_32) btsl $_EFER_LME, %eax wrmsr + /* After gdt is loaded */ + xorl %eax, %eax + lldt %ax + movl $0x20, %eax + ltr %ax + /* * Setup for the jump to 64bit mode * @@ -176,28 +188,18 @@ ENTRY(startup_32) lret ENDPROC(startup_32) -no_longmode: - /* This isn't an x86-64 CPU so hang */ -1: - hlt - jmp 1b - -#include "../../kernel/verify_cpu.S" - - /* - * Be careful here startup_64 needs to be at a predictable - * address so I can export it in an ELF header. Bootloaders - * should look at the ELF header to find this address, as - * it may change in the future. - */ .code64 .org 0x200 ENTRY(startup_64) /* + * 64bit entry is 0x200 and it is ABI so immutable! * We come here either from startup_32 or directly from a - * 64bit bootloader. If we come here from a bootloader we depend on - * an identity mapped page table being provied that maps our - * entire text+data+bss and hopefully all of memory. + * 64bit bootloader. + * If we come here from a bootloader, kernel(text+data+bss+brk), + * ramdisk, zero_page, command line could be above 4G. + * We depend on an identity mapped page table being provided + * that maps our entire kernel(text+data+bss+brk), zero page + * and command line. */ #ifdef CONFIG_EFI_STUB /* @@ -247,9 +249,6 @@ preferred_addr: movl %eax, %ss movl %eax, %fs movl %eax, %gs - lldt %ax - movl $0x20, %eax - ltr %ax /* * Compute the decompressed kernel start address. It is where @@ -349,6 +348,15 @@ relocated: */ jmp *%rbp + .code32 +no_longmode: + /* This isn't an x86-64 CPU so hang */ +1: + hlt + jmp 1b + +#include "../../kernel/verify_cpu.S" + .data gdt: .word gdt_end - gdt |