[memdisk] Saner handling of the values returned to the real-mode code.

2 files changed, 18 insertions, 17 deletions

diff --git a/memdisk/memdisk16.asm b/memdisk/memdisk16.asm
index ebcfe7e8..87c088fd 100644
--- a/memdisk/memdisk16.asm
+++ b/memdisk/memdisk16.asm
@@ -70,6 +70,13 @@ pad1		dw 0
 cmd_line_ptr	dd 0			; Command line
 ramdisk_max	dd 0xffffffff		; Highest allowed ramdisk address
 
+;
+; These fields aren't real setup fields, they're poked in by the
+; 32-bit code.
+;
+b_esdi		dd 0			; ES:DI for boot sector invocation
+b_edx		dd 0			; EDX for boot sector invocation
+
 		section .rodata
 memdisk_version:
 		db "MEMDISK ", VERSION, " ", DATE, 0
@@ -131,14 +138,13 @@ copy_cmdline:
 		call init32
 ;
 ; When init32 returns, we have been set up, the new boot sector loaded,
-; and we should go and and run the newly loaded boot sector
+; and we should go and and run the newly loaded boot sector.
 ;
-; The setup function returns (in DX) the drive number, and
-; the value for ES:DI in AX
+; The setup function will have poked values into the setup area.
 ;
-		movzx edi,ax
-		shr eax,16
-		mov es,ax
+		movzx edi,word [cs:b_esdi]
+		mov es,word [cs:b_esdi+2]
+		mov edx,[cs:b_edx]
 
 		cli
 		xor esi,esi		; No partition table involved
diff --git a/memdisk/setup.c b/memdisk/setup.c
index fe8023b1..745cfe4a 100644
--- a/memdisk/setup.c
+++ b/memdisk/setup.c
@@ -123,9 +123,11 @@ struct setup_header {
   uint16_t pad1;
   uint32_t cmd_line_ptr;
   uint32_t initrd_addr_max;
+  uint32_t esdi;
+  uint32_t edx;
 };
 
-const struct setup_header * const shdr = (struct setup_header *)(LOW_SEG << 4);
+struct setup_header * const shdr = (struct setup_header *)(LOW_SEG << 4);
 
 /* Access to high memory */
 
@@ -535,12 +537,7 @@ static uint32_t pnp_install_check(void)
 syscall_t syscall;
 void *sys_bounce;
 
-struct setup_return {
-  uint32_t es;			/* ES:DI -> $PnP structure */
-  uint32_t dx;			/* DL -> boot device */
-};
-
-struct setup_return setup(syscall_t cs_syscall, void *cs_bounce)
+void setup(syscall_t cs_syscall, void *cs_bounce)
 {
   unsigned int bin_size = (int) &_binary_memdisk_bin_size;
   struct memdisk_header *hptr;
@@ -553,7 +550,6 @@ struct setup_return setup(syscall_t cs_syscall, void *cs_bounce)
   int total_size, cmdlinelen;
   com32sys_t regs;
   uint32_t ramdisk_image, ramdisk_size;
-  struct setup_return sr;
 
   /* Set up global variables */
   syscall = cs_syscall;
@@ -809,7 +805,6 @@ struct setup_return setup(syscall_t cs_syscall, void *cs_bounce)
   puts("booting...\n");
 
   /* On return the assembly code will jump to the boot vector */
-  sr.esdi = pnp_install_check();
-  sr.dx = geometry->driveno;
-  return sr;
+  shdr->esdi = pnp_install_check();
+  shdr->edx  = geometry->driveno;
 }