Drop down to real mode for PXE call

src/main.c

@@ -21,6 +21,15 @@ outb(uint16_t port, uint8_t data)
 extern void bios_write(const char *msg);
 extern void *bios_getmap(void *buffer);
 
+void
+debug_write(const char *msg)
+{
+	for (const char *c = msg; *c; c++) {
+		outb(0xE9, *c);
+	}
+	bios_write(msg);
+}
+
 extern BOOTBOOT bootboot;
 
 #define E820_TYPE_FREE        0x1
@@ -93,6 +102,20 @@ display_string(uint16_t attr, const char *str)
 	bios_func(0x10, reg);
 }
 
+void
+debug_write_uint(unsigned v)
+{
+	char buf[20], *p = buf + sizeof buf;
+	p--;
+	*p = 0;
+	do {
+		p--;
+		*p = (v % 10) + '0';
+		v /= 10;
+	} while (v);
+	debug_write(p);
+}
+
 #define PG_PRESENT 0x001
 #define PG_WRITE   0x002
 #define PG_USER    0x004
@@ -136,27 +159,51 @@ struct exPXE {
 	uint32_t pmentry;
 };
 
-//extern uint32_t pxe_call(uint16_t func, offset, segment);
+extern uint32_t pxe_entry;
+extern uint32_t pxe_call(uint16_t func, uint16_t segment, uint16_t offset);
 
+extern unsigned char pxe_cmd_buf[512];
 extern struct PXENV *PXENV;
 extern struct exPXE *exPXE;
 
+#define PXENV_GET_CACHED 0x0071
+#define PXENV_TFTP_OPEN  0x0020
+
+typedef struct __attribute__((packed)) s_PXENV_GET_CACHED {
+	uint16_t      status;
+	uint16_t      packet_type;
+	uint16_t      buffer_size;
+	uint16_t      buffer_offset;
+	uint16_t      buffer_seg;
+	uint16_t      buffer_limit;
+} t_PXENV_GET_CACHED;
+
+typedef struct __attribute__((packed)) s_PXENV_TFTP_OPEN {
+	uint16_t      status;
+	uint32_t      server_ip;
+	uint32_t      gateway_ip;
+	unsigned char filename[128];
+	uint16_t      tftp_port;
+	uint16_t      packet_size;
+} t_PXENV_TFTP_OPEN;
+
 void
 main()
 {
 	blank_screen(0x10);
 	move_cursor(0, 0);
 	//display_string(0x14, "Netboot via fernlader v2 ...\r\n");
-	bios_write("Going well ...\r\n");
+	debug_write("Going well ...\r\n");
 
 	if (memcmp(PXENV->signature, "PXENV+", 6) != 0) {
-		bios_write("missing PXENV+ signature\r\n");
+		debug_write("missing PXENV+ signature\r\n");
 	}
 	if (PXENV->version >= 0x0201) {
-		bios_write("!PXE version\r\n");
+		debug_write("!PXE version\r\n");
 		if (memcmp(exPXE->signature, "!PXE", 4) != 0) {
-			bios_write("missing !PXE signature\r\n");
+			debug_write("missing !PXE signature\r\n");
 		}
+		pxe_entry = exPXE->rmentry;
 	}
 
 	memcpy(bootboot.magic, BOOTBOOT_MAGIC, sizeof bootboot.magic);
@@ -172,11 +219,38 @@ main()
 		char buf[2];
 		buf[0] = memmap[i].type < 10 ? memmap[i].type + '0' : '?';
 		buf[1] = 0;
-		bios_write(buf);
+		debug_write(buf);
 	}
 
 	pg_setup();
 
+#if 0
+	t_PXENV_TFTP_OPEN *t_open = (void *)pxe_cmd_buf;
+	t_open->status = 0;
+	t_open->server_ip = 0x0100000Au;
+	t_open->gateway_ip = 0;
+	memcpy(t_open->filename, "/initrd", 8);
+	t_open->tftp_port = 69 << 8;
+	t_open->packet_size = 512;
+#endif
+
+#if 1
+	t_PXENV_GET_CACHED *t_get = (void *)pxe_cmd_buf;
+	t_get->status = 0;
+	t_get->packet_type = 2;
+	t_get->buffer_size = 0;
+	t_get->buffer_offset = 0;
+	t_get->buffer_seg = 0;
+	t_get->buffer_limit = 0xFFFFu;
+	debug_write("Performing PXE call\r\n");
+	unsigned ret = pxe_call(PXENV_GET_CACHED, (uint16_t)(uintptr_t)pxe_cmd_buf, 0x0000);
+	debug_write("Still alive!\r\n");
+	debug_write("ret=");
+	debug_write_uint(ret);
+	debug_write("\r\nstatus=");
+	debug_write_uint(t_get->status);
+#endif
+
 #if 0
 	uint32_t reg[7];
 	reg[0] = (0x0E << 8) + 'J';
@@ -188,7 +262,7 @@ main()
 	reg[6] = 0;
 	bios_func(0x10, reg);
 
-	bios_write("what?\r\n");
+	debug_write("what?\r\n");
 #endif
 
 	for (;;) {

src/nbp.S

@@ -13,6 +13,9 @@ _start:     cli
             mov         %ss, %ax
             mov         %ax, %cs:real_ss
 
+            mov         %es, %ax
+            mov         %ax, %cs:real_es
+
             xor         %eax, %eax
             mov         %es, %ax
             shl         $4, %eax
@@ -71,6 +74,12 @@ exPXE:      .long       0
             .global     real_ss
 real_ss:    .word       0
 
+            .global     real_es
+real_es:    .word       0
+
+            .global     pxe_cmd_buf
+pxe_cmd_buf:.space      512, 0
+
             .global     GDT
 GDT:        // entry 0: null descriptor
             .space      8, 0

src/pxe.S

@@ -4,21 +4,42 @@
 
             .data
 
-pxe_entry:  .word       0
+            .global     pxe_entry
+pxe_entry:  .long       0
+pxe_retval: .word       0
 
             .text
             .global     pxe_call
             .code32
 pxe_call:   push        %ebp
             mov         %esp, %ebp
+            push        %ebx
+
+            mov         0x08(%ebp), %ebx # op
+            mov         0x0C(%ebp), %ecx # off
+            mov         0x10(%ebp), %edx # seg
 
             PROT16
+            REAL
 
-            call        (pxe_entry)
+            mov         %cs:(real_es), %ax
-            push        %eax
+            mov         %ax, %es
 
+            push        %dx
+            push        %cx
+            push        %bx
+
+            lcall       *(pxe_entry)
+            mov         %ax, pxe_retval
+
+            add         $6, %sp
+
+            PROT
             PROT32
 
-            pop         %eax
+            mov         pxe_retval, %ax
+            movzwl      %ax, %eax
+
+            pop         %ebx
             leave
             ret

src/std.h

@@ -24,6 +24,8 @@ typedef unsigned short     uint16_t;
 typedef unsigned int       uint32_t;
 typedef unsigned long long uint64_t;
 
+typedef unsigned int       uintptr_t;
+
 // stdbool.h
 
 #define true  ((_Bool)1)