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Kernel: Stop booting and print if PAE is not supported by the processor

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We currently require PAE and not having it causes us to crash.
This turns that crash into an error message.
This commit is contained in:
Luke 2021-07-08 21:19:30 +01:00 • committed by Gunnar Beutner
parent 6531485251
commit c94b0e80e7
3 changed files with 50 additions and 16 deletions
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55
Kernel/Arch/x86/common/Boot/boot.S
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@ -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