x86, oprom: ensure DF is always cleared

[coreboot.git] / src / devices / oprom / x86_asm.S

diff --git a/src/devices/oprom/x86_asm.S b/src/devices/oprom/x86_asm.S
index d5b5e1859ff7846492e54bcad803d044657a6265..56ebb3a885ec3789cafd88b4b5161954b11669bb 100644 (file)
--- a/src/devices/oprom/x86_asm.S
+++ b/src/devices/oprom/x86_asm.S
@@ -66,39 +66,45 @@ __registers = RELOCATED(.)
        .long 0 /* 16 - ESI */
        .long 0 /* 20 - EDI */
 
+/* 256 byte buffer, used by int10 */
+       .globl __buffer
+__buffer = RELOCATED(.)
+       .skip 256
+
        .code32
        .globl __realmode_call
 __realmode_call = RELOCATED(.)
        /* save all registers to the stack */
-       pushal
+       pusha
+       pushf
 
-       /* Move the protected mode stack to a safe place */
+       /* Move the protected mode stack pointer to a safe place */
        movl    %esp, __stack
-       movl    %esp, %ebp
+       movl    %esp, %ebp
 
-       /* This function is called with regparm=0 and we have
-        * to skip the 32 byte from pushal. Hence start at 36.
+       /* This function is called with regparm=0 and we have to
+        * skip the 36 byte from pushf+pusha. Hence start at 40.
         */
 
        /* entry point */
-       movl    36(%ebp), %eax
+       movl    40(%ebp), %eax
        mov     %ax, __lcall_instr + 1
        andl    $0xffff0000, %eax
        shrl    $4, %eax
        mov     %ax, __lcall_instr + 3
 
        /* initial register values */
-       movl    40(%ebp), %eax
-       movl    %eax, __registers +  0 /* eax */
        movl    44(%ebp), %eax
-       movl    %eax, __registers +  4 /* ebx */
+       movl    %eax, __registers +  0 /* eax */
        movl    48(%ebp), %eax
-       movl    %eax, __registers +  8 /* ecx */
+       movl    %eax, __registers +  4 /* ebx */
        movl    52(%ebp), %eax
-       movl    %eax, __registers + 12 /* edx */
+       movl    %eax, __registers +  8 /* ecx */
        movl    56(%ebp), %eax
-       movl    %eax, __registers + 16 /* esi */
+       movl    %eax, __registers + 12 /* edx */
        movl    60(%ebp), %eax
+       movl    %eax, __registers + 16 /* esi */
+       movl    64(%ebp), %eax
        movl    %eax, __registers + 20 /* edi */
 
        /* Activate the right segment descriptor real mode. */
@@ -188,41 +194,45 @@ __lcall_instr = RELOCATED(.)
        /* restore proper idt */
        lidt    idtarg
 
-       /* and exit */
+       /* restore stack pointer, eflags and register values */
        movl    __stack, %esp
-       popal
+       popf
+       popa
 
+       /* and exit */
        // TODO return AX from OPROM call
        ret
 
        .globl __realmode_interrupt
 __realmode_interrupt = RELOCATED(.)
        /* save all registers to the stack */
-       pushal
-       /* save the stack */
+       pusha
+       pushf
+
+       /* save the stack pointer */
        movl    %esp, __stack
-       movl    %esp, %ebp
+       movl    %esp, %ebp
 
-       /* This function is called with regparm=0 and we have
-        * to skip the 32 byte from pushal. Hence start at 36.
+       /* This function is called with regparm=0 and we have to
+        * skip the 36 byte from pushf+pusha. Hence start at 40.
         */
 
        /* prepare interrupt calling code */
-       movl    36(%ebp), %eax
+       movl    40(%ebp), %eax
        movb    %al, __intXX_instr + 1 /* intno */
 
        /* initial register values */
-       movl    40(%ebp), %eax
-       movl    %eax, __registers +  0 /* eax */
        movl    44(%ebp), %eax
-       movl    %eax, __registers +  4 /* ebx */
+       movl    %eax, __registers +  0 /* eax */
        movl    48(%ebp), %eax
-       movl    %eax, __registers +  8 /* ecx */
+       movl    %eax, __registers +  4 /* ebx */
        movl    52(%ebp), %eax
-       movl    %eax, __registers + 12 /* edx */
+       movl    %eax, __registers +  8 /* ecx */
        movl    56(%ebp), %eax
-       movl    %eax, __registers + 16 /* esi */
+       movl    %eax, __registers + 12 /* edx */
        movl    60(%ebp), %eax
+       movl    %eax, __registers + 16 /* esi */
+       movl    64(%ebp), %eax
        movl    %eax, __registers + 20 /* edi */
 
        /*  This configures CS properly for real mode. */
@@ -250,7 +260,7 @@ __realmode_interrupt = RELOCATED(.)
        data32 ljmp     $0, $RELOCATED(1f)
 1:
 
-       /* put the stack at the end of page zero.  That way we can easily 
+       /* put the stack at the end of page zero.  That way we can easily
         * share it between real mode and protected mode, because %esp and
         * %ss:%sp point to the same memory.
         */
@@ -304,9 +314,10 @@ __intXX_instr = RELOCATED(.)
        /* restore coreboot's 32-bit IDT */
        lidt    idtarg
 
-       /* Exit */
+       /* restore stack pointer, eflags and register values and exit */
        movl    __stack, %esp
-       popal
+       popf
+       popa
        ret
 
 /* This is the 16-bit interrupt entry point called by the IDT stub code.
@@ -322,6 +333,9 @@ __interrupt_handler_16bit = RELOCATED(.)
        push    %fs
        push    %gs
 
+       /* Clear DF to not break ABI assumptions */
+       cld
+
        /* Clean up the interrupt number. We could have done this in the stub,
         * but it would have cost 2 more bytes per stub entry.
         */