diff options
Diffstat (limited to 'Kernel')
| -rw-r--r-- | Kernel/Arch/x86/common/Boot/boot.S | 55 |
1 files changed, 39 insertions, 16 deletions
diff --git a/Kernel/Arch/x86/common/Boot/boot.S b/Kernel/Arch/x86/common/Boot/boot.S index 6e5f5fc779..c5e6f81081 100644 --- a/Kernel/Arch/x86/common/Boot/boot.S +++ b/Kernel/Arch/x86/common/Boot/boot.S @@ -118,6 +118,16 @@ start: */ print_and_halt: +/* from now on, we don't really care about booting because we are missing required CPU features such as PAE or long mode. + the flow from now is like so: + 1. Copy all necessary parts to low memory section in RAM + 2. Jump to that section + 3. In that section we do: + a. exit protected mode to pure 16 bit real mode + b. load the "<missing feature> is not supported" String, call the BIOS print to screen service + c. halt +*/ + .equ COPIED_STRING_LOCATION, 0x400 .equ GDT_REAL_MODE_LOCATION, 0x45000 .equ EXITING_PROTECTED_MODE_CODE_LOCATION, 0x10000 @@ -214,6 +224,9 @@ gdt_table_real_mode_end: no_long_mode_string: .asciz "Your computer does not support long mode (64-bit mode). Halting!" +no_pae_string: + .asciz "Your computer does not support PAE. Halting!" + kernel_image_too_big_string: .asciz "Error: Kernel Image too big for memory slot. Halting!" @@ -307,28 +320,32 @@ real_start: hlt kernel_not_too_large: - - -#if ARCH(X86_64) - /* test for long mode presence, save the most important registers from corruption */ + /* test for PAE presence, save the most important registers from corruption */ pushl %eax pushl %edx pushl %ebx + movl $0x1, %eax /* PAE presence is in CPUID input 0x1 */ + cpuid + testl $(1 << 6), %edx /* Test if the PAE-bit, which is bit 6, is set in the edx register. */ + jnz pae_supported /* If the bit is not set, there is no PAE capability. */ + + /* Since there is no PAE capability, halt with an error message */ + movl $(no_pae_string - KERNEL_BASE), %esi + pushl %esi + call print_and_halt + /* We should not return, but just in case, halt */ + hlt + + +#if ARCH(X86_64) +pae_supported: movl $0x80000001, %eax cpuid testl $(1 << 29), %edx /* Test if the LM-bit, which is bit 29, is set in the edx register. */ jnz long_mode_supported /* If LM-bit is not enabled, there is no long mode. */ - /* from now on, we don't really care about booting because we don't have long mode supported. - the flow from now is like so: - 1. Copy all necessary parts to low memory section in RAM - 2. Jump to that section - 3. In that section we do: - a. exit protected mode to pure 16 bit real mode - b. load the "Long mode is not supported" String, call the BIOS print to screen service - c. halt - */ + /* Since there is no long mode, halt with an error message */ movl $(no_long_mode_string - KERNEL_BASE), %esi pushl %esi call print_and_halt @@ -336,14 +353,21 @@ kernel_not_too_large: hlt -/* If long mode is supported, continue with booting the system */ +/* If both PAE and long mode is supported, continue with booting the system */ -.code32 long_mode_supported: /* restore the pushed registers and continue with booting */ popl %ebx popl %edx popl %eax +#else +/* If PAE is supported, continue with booting the system */ + +pae_supported: + /* restore the pushed registers and continue with booting */ + popl %ebx + popl %edx + popl %eax #endif /* We don't know where the bootloader might have put the command line. @@ -545,4 +569,3 @@ long_mode_supported: loop: hlt jmp loop - |