memdisk: additional cleanups

Additional stylistic cleanups.  Rename "syscall" to "intcall" (we
can't call it __intcall without clashing with com32.h); use macros
instead of copying variables to different places with only the type
being different.

Also, only change the rm/pm jump instructions when actually relocating
the code.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

6 files changed, 87 insertions, 88 deletions

diff --git a/memdisk/conio.c b/memdisk/conio.c
index 0e75bd72..d1f0862c 100644
--- a/memdisk/conio.c
+++ b/memdisk/conio.c
@@ -30,7 +30,7 @@ int putchar(int ch)
     }
 
     regs.eax.w[0] = 0x0e00 | (ch & 0xff);
-    syscall(0x10, &regs, NULL);
+    intcall(0x10, &regs, NULL);
 
     return ch;
 }
diff --git a/memdisk/memdisk.h b/memdisk/memdisk.h
index 6bfeb903..b6b277a8 100644
--- a/memdisk/memdisk.h
+++ b/memdisk/memdisk.h
@@ -26,9 +26,55 @@
 
 #define __cdecl __attribute__((cdecl,regparm(0)))
 
-typedef void (*syscall_t) (uint8_t, com32sys_t *, com32sys_t *);
-extern __cdecl syscall_t syscall;
-extern void *sys_bounce;
+void __cdecl intcall(uint8_t, com32sys_t *, com32sys_t *);
+
+/* Structure passed in from the real-mode code */
+struct real_mode_args {
+    uint32_t rm_return;
+    uint32_t rm_intcall;
+    uint32_t rm_bounce;
+    uint32_t rm_base;
+    uint32_t rm_handle_interrupt;
+    uint32_t rm_gdt;
+    uint32_t rm_size;
+    uint32_t rm_pmjmp;
+    uint32_t rm_rmjmp;
+};
+extern struct real_mode_args rm_args;
+#define sys_bounce ((void *)rm_args.rm_bounce)
+
+/* This is the header in the boot sector/setup area */
+struct setup_header {
+    char cmdline[0x1f1];
+    uint8_t setup_secs;
+    uint16_t syssize;
+    uint16_t swap_dev;
+    uint16_t ram_size;
+    uint16_t vid_mode;
+    uint16_t root_dev;
+    uint16_t boot_flag;
+    uint16_t jump;
+    char header[4];
+    uint16_t version;
+    uint32_t realmode_swtch;
+    uint32_t start_sys;
+    uint8_t type_of_loader;
+    uint8_t loadflags;
+    uint16_t setup_move_size;
+    uint32_t code32_start;
+    uint32_t ramdisk_image;
+    uint32_t ramdisk_size;
+    uint32_t bootsect_kludge;
+    uint16_t head_end_ptr;
+    uint16_t pad1;
+    uint32_t cmd_line_ptr;
+    uint32_t initrd_addr_max;
+    uint32_t esdi;
+    uint32_t edx;
+    uint32_t sssp;
+    uint32_t csip;
+};
+#define shdr ((struct setup_header *)rm_args.rm_base)
 
 /* Standard routines */
 void *memcpy(void *, const void *, size_t);
diff --git a/memdisk/memdisk16.asm b/memdisk/memdisk16.asm
index 1a22ff6f..0c5b9973 100644
--- a/memdisk/memdisk16.asm
+++ b/memdisk/memdisk16.asm
@@ -562,17 +562,14 @@ call32_enter_pm:
 		mov [SavedSP],sp
 		cld
 		call enable_a20
-		lea eax,[ebp+.in_pm]
-		mov [.pm_jmp+2],eax	; Patch the PM jump
-		jmp .sync
-.sync:
 		mov byte [call32_gdt+8+5],89h	; Mark TSS unbusy
 		o32 lgdt [call32_gdt]	; Set up GDT
 		o32 lidt [call32_pmidt]	; Set up IDT
 		mov eax,cr0
 		or al,1
 		mov cr0,eax		; Enter protected mode
-.pm_jmp:	jmp 20h:strict dword 0
+		jmp 20h:strict dword .in_pm+CS_BASE
+.pm_jmp		equ $-6
 
 
 		bits 32
@@ -604,6 +601,8 @@ call32_call_start:
 		;
 		mov esp, (BOUNCE_SEG << 4) + 0x10000
 
+		push dword call32_enter_rm.rm_jmp+CS_BASE
+		push dword call32_enter_pm.pm_jmp+CS_BASE
 		push dword stack_end		; RM size
 		push dword call32_gdt+CS_BASE
 		push dword call32_handle_interrupt+CS_BASE
@@ -627,11 +626,6 @@ call32_enter_rm:
 		call .here
 .here:		pop ebp
 		sub ebp,.here
-		mov ecx,ebp
-		shr ecx,4
-		mov [ebp+.rm_jmp+3],cx	; Set segment
-		jmp .sync
-.sync:
 		o32 sidt [ebp+call32_pmidt]
 		cli
 		cld
@@ -652,14 +646,16 @@ call32_enter_rm:
 		mov eax,cr0
 		and al,~1
 		mov cr0,eax
-.rm_jmp:	jmp MY_CS:.in_rm
+		jmp MY_CS:.in_rm
+.rm_jmp		equ $-2
 
 .in_rm:					; Back in real mode
-		mov ds,cx
-		mov es,cx
-		mov fs,cx
-		mov gs,cx
-		mov ss,cx
+		mov ax,cs
+		mov ds,ax
+		mov es,ax
+		mov fs,ax
+		mov gs,ax
+		mov ss,ax
 		mov sp,[SavedSP]	; Restore stack
 		jmp bx			; Go to whereever we need to go...
 
diff --git a/memdisk/msetup.c b/memdisk/msetup.c
index 3674b288..f40a2c66 100644
--- a/memdisk/msetup.c
+++ b/memdisk/msetup.c
@@ -53,7 +53,7 @@ static inline int get_e820(void)
 	regs.edi.w[0] = OFFS(buf);
 	regs.es = SEG(buf);
 
-	syscall(0x15, &regs, &regs);
+	intcall(0x15, &regs, &regs);
 	copied = (regs.eflags.l & 1) ? 0 : regs.ecx.l;
 
 	if (regs.eax.l != 0x534d4150 || copied < 20)
@@ -76,7 +76,7 @@ static inline void get_dos_mem(void)
     com32sys_t regs;
 
     memset(&regs, 0, sizeof regs);
-    syscall(0x12, &regs, &regs);
+    intcall(0x12, &regs, &regs);
     insertrange(0, (uint64_t) ((uint32_t) regs.eax.w[0] << 10), 1);
     printf(" DOS: %d K\n", regs.eax.w[0]);
 }
@@ -89,7 +89,7 @@ static inline int get_e801(void)
     memset(&regs, 0, sizeof regs);
 
     regs.eax.w[0] = 0xe801;
-    syscall(0x15, &regs, &regs);
+    intcall(0x15, &regs, &regs);
 
     if (!(err = regs.eflags.l & 1)) {
 	if (regs.eax.w[0]) {
@@ -115,7 +115,7 @@ static inline int get_88(void)
     memset(&regs, 0, sizeof regs);
 
     regs.eax.b[1] = 0x88;
-    syscall(0x15, &regs, &regs);
+    intcall(0x15, &regs, &regs);
 
     if (!(err = regs.eflags.l & 1)) {
 	if (regs.eax.w[0]) {
diff --git a/memdisk/setup.c b/memdisk/setup.c
index 0a7c8c6b..98c4b69d 100644
--- a/memdisk/setup.c
+++ b/memdisk/setup.c
@@ -123,54 +123,6 @@ struct patch_area {
     struct edd_dpt edd_dpt;
 };
 
-/* This is the header in the boot sector/setup area */
-struct setup_header {
-    char cmdline[0x1f1];
-    uint8_t setup_secs;
-    uint16_t syssize;
-    uint16_t swap_dev;
-    uint16_t ram_size;
-    uint16_t vid_mode;
-    uint16_t root_dev;
-    uint16_t boot_flag;
-    uint16_t jump;
-    char header[4];
-    uint16_t version;
-    uint32_t realmode_swtch;
-    uint32_t start_sys;
-    uint8_t type_of_loader;
-    uint8_t loadflags;
-    uint16_t setup_move_size;
-    uint32_t code32_start;
-    uint32_t ramdisk_image;
-    uint32_t ramdisk_size;
-    uint32_t bootsect_kludge;
-    uint16_t head_end_ptr;
-    uint16_t pad1;
-    uint32_t cmd_line_ptr;
-    uint32_t initrd_addr_max;
-    uint32_t esdi;
-    uint32_t edx;
-    uint32_t sssp;
-    uint32_t csip;
-};
-struct setup_header *shdr;
-
-/* Structure passed in from the real-mode code */
-struct real_mode_args {
-    uint32_t rm_return;
-    uint32_t rm_syscall;
-    uint32_t rm_bounce;
-    uint32_t rm_base;
-    uint32_t rm_handle_interrupt;
-    uint32_t rm_gdt;
-    uint32_t rm_size;
-};
-struct real_mode_args rm_args;
-
-__cdecl syscall_t syscall;
-void *sys_bounce;
-
 /* Access to high memory */
 
 /* Access to objects in the zero page */
@@ -706,13 +658,6 @@ static uint32_t pnp_install_check(void)
     return 0;
 }
 
-static void update_global_vars(void)
-{
-    syscall = (__cdecl syscall_t) rm_args.rm_syscall;
-    sys_bounce = (void *)rm_args.rm_bounce;
-    shdr = (void *)rm_args.rm_base;
-}
-
 /*
  * Relocate the real-mode code to a new segment
  */
@@ -738,11 +683,12 @@ static void relocate_rm_code(uint32_t newbase)
     memmove((void *)newbase, (void *)oldbase, rm_args.rm_size);
 
     rm_args.rm_return  		+= delta;
-    rm_args.rm_syscall 		+= delta;
+    rm_args.rm_intcall 		+= delta;
     rm_args.rm_bounce  		+= delta;
     rm_args.rm_base    		+= delta;
     rm_args.rm_gdt              += delta;
-    rm_args.rm_handle_interrupt	+= delta;
+    rm_args.rm_pmjmp		+= delta;
+    rm_args.rm_rmjmp		+= delta;
 
     gdt_base = rm_args.rm_gdt;
 
@@ -753,13 +699,19 @@ static void relocate_rm_code(uint32_t newbase)
     set_seg_base(gdt_base, 0x18, rm_args.rm_base);
 
     asm volatile("lgdtl %0" : : "m" (*(char *)gdt_base));
-    sti();
 
-    update_global_vars();
+    *(uint32_t *)rm_args.rm_pmjmp += delta;
+    *(uint16_t *)rm_args.rm_rmjmp += delta >> 4;
+
+    rm_args.rm_handle_interrupt	+= delta;
+
+    sti();
 }
 
 #define STACK_NEEDED	512	/* Number of bytes of stack */
 
+struct real_mode_args rm_args;
+
 /*
  * Actual setup routine
  * Returns the drive number (which is then passed in %dl to the
@@ -791,9 +743,6 @@ void setup(const struct real_mode_args *rm_args_ptr)
     memcpy(&rm_args, rm_args_ptr, sizeof rm_args);
     sti();			/* ... then interrupts are safe */
 
-    /* Set up global variables */
-    update_global_vars();
-
     /* Show signs of life */
     printf("%s  %s\n", memdisk_version, copyright);
 
@@ -1021,7 +970,7 @@ void setup(const struct real_mode_args *rm_args_ptr)
 	regs.es = 0;
 	regs.eax.b[1] = 0x08;
 	regs.edx.b[0] = geometry->driveno & 0x80;
-	syscall(0x13, &regs, &regs);
+	intcall(0x13, &regs, &regs);
 
 	/* Note: per suggestion from the Interrupt List, consider
 	   INT 13 08 to have failed if the sector count in CL is zero. */
@@ -1151,7 +1100,7 @@ void setup(const struct real_mode_args *rm_args_ptr)
     if (getcmditem("pause") != CMD_NOTFOUND) {
 	puts("press any key to boot... ");
 	regs.eax.w[0] = 0;
-	syscall(0x16, &regs, NULL);
+	intcall(0x16, &regs, NULL);
     }
 
     puts("booting...\n");
diff --git a/memdisk/start32.S b/memdisk/start32.S
index 8fcebcc6..4fb05374 100644
--- a/memdisk/start32.S
+++ b/memdisk/start32.S
@@ -72,8 +72,16 @@ _start:
 	jmp	*(rm_args)		/* First argument is return */
 
 	.section ".text","ax"
+	.globl	intcall
+	.type	intcall, @function
+intcall:
+	jmp	*(rm_args+1*4)		/* Intcall is argument 1 */
+	.size	intcall, .-intcall
+
+	.type	handle_interrupt, @function
 handle_interrupt:
 	jmp	*(rm_args+4*4)		/* Interrupt pointer is argument 4 */
+	.size	handle_interrupt, .-handle_interrupt
 
 	.section ".rodata","a"
 idt_ptr: