PM function called by prot_call() should be allowed to modifying

registers returned to RM code.

diff --git a/src/arch/i386/transitions/librm.S b/src/arch/i386/transitions/librm.S
index 6dc6b4fd861853934d5fc3f9cef9ce0266e2f08e..5299841c9fee9f6d0cebd2af3b2808c6e0f52487 100644 (file)
--- a/src/arch/i386/transitions/librm.S
+++ b/src/arch/i386/transitions/librm.S
@@ -496,8 +496,10 @@ EXPORT(prot_call):
        movl    $SIZEOF_REAL_MODE_REGS, %ecx
        subl    %ecx, %esp
        movl    %esp, %edi
+       pushl   %esi
        cld
-       rep     movsb
+       rep movsb
+       popl    %edi            /* %edi = phys addr of RM copy of rm_regs */
        
        /* Switch to virtual addresses. */
        call    1f
@@ -522,7 +524,18 @@ EXPORT(prot_call):
 
        /* Switch to physical addresses, discard PM register store */
        lcall   $VIRTUAL_CS, $_virt_to_phys
-       addl    $SIZEOF_REAL_MODE_REGS+4, %esp /* also discard lcall seg */
+       popl    %eax /* discard */
+
+       /* Copy rm_regs from PM stack to RM stack, and remove rm_regs
+        * from PM stack.  (%edi still contains physical address of
+        * rm_regs on RM stack from earlier, since C code preserves
+        * %edi).
+        */
+       movl    %esp, %esi
+       movl    $SIZEOF_REAL_MODE_REGS, %ecx
+       cld
+       rep movsb
+       movl    %esi, %esp      /* remove rm_regs from PM stack */
 
        /* Switch to real mode */
        call    prot_to_real