diff options
| -rw-r--r-- | OvmfPkg/Library/LoadLinuxLib/X64/JumpToKernel.S | 43 | ||||
| -rw-r--r-- | OvmfPkg/Library/LoadLinuxLib/X64/JumpToKernel.asm | 45 |
2 files changed, 82 insertions, 6 deletions
diff --git a/OvmfPkg/Library/LoadLinuxLib/X64/JumpToKernel.S b/OvmfPkg/Library/LoadLinuxLib/X64/JumpToKernel.S index 9ae755b067..d9b991b703 100644 --- a/OvmfPkg/Library/LoadLinuxLib/X64/JumpToKernel.S +++ b/OvmfPkg/Library/LoadLinuxLib/X64/JumpToKernel.S @@ -23,8 +23,47 @@ ASM_GLOBAL ASM_PFX(JumpToKernel) # );
#------------------------------------------------------------------------------
ASM_PFX(JumpToKernel):
+
+ // Set up for executing kernel. BP in %esi, entry point on the stack
+ // (64-bit when the 'ret' will use it as 32-bit, but we're little-endian)
movq %rdx, %rsi
- addq $0x200, %rcx
- callq %rcx
+ pushq %rcx
+
+ // Jump into the compatibility mode CS
+ pushq $0x10
+ leaq 1f, %rax
+ pushq %rax
+ retfq
+
+1: // Now in compatibility mode
+.code32
+ movl $0x18, %eax
+ movl %eax, %ds
+ movl %eax, %es
+ movl %eax, %fs
+ movl %eax, %gs
+ movl %eax, %ss
+
+ // Disable paging
+ movl %cr0, %eax
+ btcl $31, %eax
+ movl %eax, %cr0
+
+ // Disable long mode in EFER
+ movl $0x0c0000080, %ecx
+ rdmsr
+ btcl $8, %eax
+ wrmsr
+
+ // Disable PAE
+ movl %cr4, %eax
+ btcl $5, %eax
+ movl %eax, %cr4
+
+ // Zero registers and 'return' to kernel
+ xorl %ebp, %ebp
+ xorl %edi, %edi
+ xorl %ebx, %ebx
ret
+.code64
diff --git a/OvmfPkg/Library/LoadLinuxLib/X64/JumpToKernel.asm b/OvmfPkg/Library/LoadLinuxLib/X64/JumpToKernel.asm index ed53321c23..4df9c723aa 100644 --- a/OvmfPkg/Library/LoadLinuxLib/X64/JumpToKernel.asm +++ b/OvmfPkg/Library/LoadLinuxLib/X64/JumpToKernel.asm @@ -24,10 +24,47 @@ ;------------------------------------------------------------------------------
JumpToKernel PROC
- mov rsi, rdx
- add rcx, 200h
- call rcx
- ret
+ ; Set up for executing kernel. BP in %esi, entry point on the stack
+ ; (64-bit when the 'ret' will use it as 32-bit, but we're little-endian)
+ mov rsi, rdx
+ push rcx
+
+ ; Jump into the compatibility mode CS
+ push 10h
+ lea rax, @F
+ push rax
+ DB 048h, 0cbh ; retfq
+
+@@:
+ ; Now in compatibility mode.
+
+ DB 0b8h, 018h, 000h, 000h, 000h ; movl $0x18, %eax
+ DB 08eh, 0d8h ; movl %eax, %ds
+ DB 08eh, 0c0h ; movl %eax, %es
+ DB 08eh, 0e0h ; movl %eax, %fs
+ DB 08eh, 0e8h ; movl %eax, %gs
+ DB 08eh, 0d0h ; movl %eax, %ss
+
+ ; Disable paging
+ DB 00fh, 020h, 0c0h ; movl %cr0, %eax
+ DB 00fh, 0bah, 0f8h, 01fh ; btcl $31, %eax
+ DB 00fh, 022h, 0c0h ; movl %eax, %cr0
+
+ ; Disable long mode in EFER
+ DB 0b9h, 080h, 000h, 000h, 0c0h ; movl $0x0c0000080, %ecx
+ DB 00fh, 032h ; rdmsr
+ DB 00fh, 0bah, 0f8h, 008h ; btcl $8, %eax
+ DB 00fh, 030h ; wrmsr
+
+ ; Disable PAE
+ DB 00fh, 020h, 0e0h ; movl %cr4, %eax
+ DB 00fh, 0bah, 0f8h, 005h ; btcl $5, %eax
+ DB 00fh, 022h, 0e0h ; movl %eax, %cr4
+
+ DB 031h, 0edh ; xor %ebp, %ebp
+ DB 031h, 0ffh ; xor %edi, %edi
+ DB 031h, 0dbh ; xor %ebx, %ebx
+ DB 0c3h ; ret
JumpToKernel ENDP
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