diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/arch/i386/prefix/romprefix.S | 3 | ||||
| -rw-r--r-- | src/arch/i386/transitions/librm.S | 40 |
2 files changed, 38 insertions, 5 deletions
diff --git a/src/arch/i386/prefix/romprefix.S b/src/arch/i386/prefix/romprefix.S index 69f35f78c..ae18f05d0 100644 --- a/src/arch/i386/prefix/romprefix.S +++ b/src/arch/i386/prefix/romprefix.S @@ -754,6 +754,9 @@ exec: /* Set %ds = %cs */ call prot_call popl %eax /* discard */ + /* Set up flat real mode for return to BIOS */ + call flatten_real_mode + /* Uninstall iPXE */ call uninstall diff --git a/src/arch/i386/transitions/librm.S b/src/arch/i386/transitions/librm.S index 02d25b22c..b5affdb89 100644 --- a/src/arch/i386/transitions/librm.S +++ b/src/arch/i386/transitions/librm.S @@ -66,15 +66,15 @@ physical_ds: /* 32 bit protected mode data segment, physical addresses */ .byte 0, 0x93, 0xcf, 0 .org gdt + REAL_CS, 0 -real_cs: /* 16 bit flat real mode code segment */ +real_cs: /* 16 bit real mode code segment */ .word 0xffff, 0 - .byte 0, 0x9b, 0x8f, 0 + .byte 0, 0x9b, 0x00, 0 .org gdt + REAL_DS -real_ds: /* 16 bit flat real mode data segment */ +real_ds: /* 16 bit real mode data segment */ .word 0xffff, 0 - .byte 0, 0x93, 0x8f, 0 - + .byte 0, 0x93, 0x00, 0 + gdt_end: .equ gdt_length, gdt_end - gdt @@ -507,6 +507,36 @@ real_call: rc_function: .word 0, 0 /**************************************************************************** + * flatten_real_mode (real-mode near call) + * + * Switch to flat real mode + * + **************************************************************************** + */ + .section ".text16", "ax", @progbits + .code16 + .globl flatten_real_mode +flatten_real_mode: + /* Modify GDT to use flat real mode */ + movb $0x8f, real_cs + 6 + movb $0x8f, real_ds + 6 + /* Call dummy protected-mode function */ + pushl $flatten_dummy + pushw %cs + call prot_call + addw $4, %sp + /* Restore GDT */ + movb $0x00, real_cs + 6 + movb $0x00, real_ds + 6 + /* Return */ + ret + + .section ".text", "ax", @progbits + .code32 +flatten_dummy: + ret + +/**************************************************************************** * Stored real-mode and protected-mode stack pointers * * The real-mode stack pointer is stored here whenever real_to_prot |