[comboot] Add COMBOOT and COM32 support

src/arch/i386/interface/syslinux/com32_wrapper.S

@@ -0,0 +1,92 @@
+/*
+ * Copyright (C) 2008 Daniel Verkamp <daniel@drv.nu>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+	.text
+	.arch i386
+	.code32
+
+	.globl com32_farcall_wrapper
+com32_farcall_wrapper:
+
+	movl $com32_farcall, %eax
+	jmp com32_wrapper
+
+
+	.globl com32_cfarcall_wrapper
+com32_cfarcall_wrapper:
+
+	movl $com32_cfarcall, %eax
+	jmp com32_wrapper
+
+
+	.globl com32_intcall_wrapper
+com32_intcall_wrapper:
+
+	movl $com32_intcall, %eax
+	/*jmp com32_wrapper*/ /* fall through */
+
+com32_wrapper:
+
+	/* Switch to internal virtual address space */
+	call _phys_to_virt
+
+	mov %eax, (com32_helper_function)
+
+	/* Save external COM32 stack pointer */
+	movl %esp, (com32_external_esp)
+
+	/* Copy arguments to caller-save registers */
+	movl 12(%esp), %eax
+	movl 8(%esp), %ecx
+	movl 4(%esp), %edx
+
+	/* Switch to internal stack */
+	movl (com32_internal_esp), %esp
+
+	/* Copy arguments to internal stack */
+	pushl %eax
+	pushl %ecx
+	pushl %edx
+
+	call *(com32_helper_function)
+
+	/* Clean up stack */
+	addl $12, %esp
+
+	/* Save internal stack pointer and restore external stack pointer */
+	movl %esp, (com32_internal_esp)
+	movl (com32_external_esp), %esp
+
+	/* Switch to external flat physical address space */
+	call _virt_to_phys
+
+	ret
+
+
+	.data
+
+/* Internal gPXE virtual address space %esp */
+.globl com32_internal_esp
+.lcomm com32_internal_esp, 4
+
+/* External flat physical address space %esp */
+.globl com32_external_esp
+.lcomm com32_external_esp, 4
+
+/* Function pointer of helper to call */
+.lcomm com32_helper_function, 4