arch/x86/lib/bios.c - filogic/uboot - Gitiles

 // SPDX-License-Identifier: GPL-2.0
 /*
  * From Coreboot file device/oprom/realmode/x86.c
  *
  * Copyright (C) 2007 Advanced Micro Devices, Inc.
  * Copyright (C) 2009-2010 coresystems GmbH
  */
 #include <common.h>
 #include <compiler.h>
 #include <bios_emul.h>
 #include <irq_func.h>
 #include <log.h>
 #include <vesa.h>
 #include <linux/linkage.h>
 #include <asm/cache.h>
 #include <asm/processor.h>
 #include <asm/i8259.h>
 #include <asm/io.h>
 #include <asm/post.h>
 #include "bios.h"

 /* Interrupt handlers for each interrupt the ROM can call */
 static int (*int_handler[256])(void);

 /* to have a common register file for interrupt handlers */
 #if !CONFIG_IS_ENABLED(BIOSEMU)
 X86EMU_sysEnv _X86EMU_env;
 #endif

 asmlinkage void (*realmode_call)(u32 addr, u32 eax, u32 ebx, u32 ecx, u32 edx,
 				 u32 esi, u32 edi);

 asmlinkage void (*realmode_interrupt)(u32 intno, u32 eax, u32 ebx, u32 ecx,
 				      u32 edx, u32 esi, u32 edi);

 static void setup_realmode_code(void)
 {
 	memcpy((void *)REALMODE_BASE, &asm_realmode_code,
 	       asm_realmode_code_size);

 	/* Ensure the global pointers are relocated properly. */
 	realmode_call = PTR_TO_REAL_MODE(asm_realmode_call);
 	realmode_interrupt = PTR_TO_REAL_MODE(__realmode_interrupt);

 	debug("Real mode stub @%x: %d bytes\n", REALMODE_BASE,
 	      asm_realmode_code_size);
 }

 static void setup_rombios(void)
 {
 	const char date[] = "06/11/99";
 	memcpy((void *)0xffff5, &date, 8);

 	const char ident[] = "PCI_ISA";
 	memcpy((void *)0xfffd9, &ident, 7);

 	/* system model: IBM-AT */
 	writeb(0xfc, 0xffffe);
 }

 static int int_exception_handler(void)
 {
 	/* compatibility shim */
 	struct eregs reg_info = {
 		.eax = M.x86.R_EAX,
 		.ecx = M.x86.R_ECX,
 		.edx = M.x86.R_EDX,
 		.ebx = M.x86.R_EBX,
 		.esp = M.x86.R_ESP,
 		.ebp = M.x86.R_EBP,
 		.esi = M.x86.R_ESI,
 		.edi = M.x86.R_EDI,
 		.vector = M.x86.intno,
 		.error_code = 0,
 		.eip = M.x86.R_EIP,
 		.cs = M.x86.R_CS,
 		.eflags = M.x86.R_EFLG
 	};
 	struct eregs *regs = &reg_info;

 	log_err("Exception %d while executing option rom\n", regs->vector);
 	cpu_hlt();

 	return 0;
 }

 static int int_unknown_handler(void)
 {
 	debug("Unsupported software interrupt #0x%x eax 0x%x\n",
 	      M.x86.intno, M.x86.R_EAX);

 	return -1;
 }

 /* setup interrupt handlers for mainboard */
 void bios_set_interrupt_handler(int intnum, int (*int_func)(void))
 {
 	int_handler[intnum] = int_func;
 }

 static void setup_interrupt_handlers(void)
 {
 	int i;

 	/*
 	 * The first 16 int_handler functions are not BIOS services,
 	 * but the CPU-generated exceptions ("hardware interrupts")
 	 */
 	for (i = 0; i < 0x10; i++)
 		int_handler[i] = &int_exception_handler;

 	/* Mark all other int_handler calls as unknown first */
 	for (i = 0x10; i < 0x100; i++) {
 		/* Skip if bios_set_interrupt_handler() isn't called first */
 		if (int_handler[i])
 			continue;

 		 /*
 		  * Now set the default functions that are actually needed
 		  * to initialize the option roms. The board may override
 		  * these with bios_set_interrupt_handler()
 		 */
 		switch (i) {
 		case 0x10:
 			int_handler[0x10] = &int10_handler;
 			break;
 		case 0x12:
 			int_handler[0x12] = &int12_handler;
 			break;
 		case 0x16:
 			int_handler[0x16] = &int16_handler;
 			break;
 		case 0x1a:
 			int_handler[0x1a] = &int1a_handler;
 			break;
 		default:
 			int_handler[i] = &int_unknown_handler;
 			break;
 		}
 	}
 }

 static void write_idt_stub(void *target, u8 intnum)
 {
 	unsigned char *codeptr;

 	codeptr = (unsigned char *)target;
 	memcpy(codeptr, &__idt_handler, __idt_handler_size);
 	codeptr[3] = intnum; /* modify int# in the code stub. */
 }

 static void setup_realmode_idt(void)
 {
 	struct realmode_idt *idts = NULL;
 	int i;

 	/*
 	 * Copy IDT stub code for each interrupt. This might seem wasteful
 	 * but it is really simple
 	 */
 	 for (i = 0; i < 256; i++) {
 		idts[i].cs = 0;
 		idts[i].offset = 0x1000 + (i * __idt_handler_size);
 		write_idt_stub((void *)((ulong)idts[i].offset), i);
 	}

 	/*
 	 * Many option ROMs use the hard coded interrupt entry points in the
 	 * system bios. So install them at the known locations.
 	 */

 	/* int42 is the relocated int10 */
 	write_idt_stub((void *)0xff065, 0x42);
 	/* BIOS Int 11 Handler F000:F84D */
 	write_idt_stub((void *)0xff84d, 0x11);
 	/* BIOS Int 12 Handler F000:F841 */
 	write_idt_stub((void *)0xff841, 0x12);
 	/* BIOS Int 13 Handler F000:EC59 */
 	write_idt_stub((void *)0xfec59, 0x13);
 	/* BIOS Int 14 Handler F000:E739 */
 	write_idt_stub((void *)0xfe739, 0x14);
 	/* BIOS Int 15 Handler F000:F859 */
 	write_idt_stub((void *)0xff859, 0x15);
 	/* BIOS Int 16 Handler F000:E82E */
 	write_idt_stub((void *)0xfe82e, 0x16);
 	/* BIOS Int 17 Handler F000:EFD2 */
 	write_idt_stub((void *)0xfefd2, 0x17);
 	/* ROM BIOS Int 1A Handler F000:FE6E */
 	write_idt_stub((void *)0xffe6e, 0x1a);
 }

 #ifdef CONFIG_FRAMEBUFFER_SET_VESA_MODE
 static u8 vbe_get_mode_info(struct vesa_state *mi)
 {
 	u16 buffer_seg;
 	u16 buffer_adr;
 	char *buffer;

 	debug("VBE: Getting information about VESA mode %04x\n",
 	      mi->video_mode);
 	buffer = PTR_TO_REAL_MODE(asm_realmode_buffer);
 	buffer_seg = (((unsigned long)buffer) >> 4) & 0xff00;
 	buffer_adr = ((unsigned long)buffer) & 0xffff;

 	realmode_interrupt(0x10, VESA_GET_MODE_INFO, 0x0000, mi->video_mode,
 			   0x0000, buffer_seg, buffer_adr);
 	memcpy(mi->mode_info_block, buffer, sizeof(struct vesa_state));
 	mi->valid = true;

 	return 0;
 }

 static u8 vbe_set_mode(struct vesa_state *mi)
 {
 	int video_mode = mi->video_mode;

 	debug("VBE: Setting VESA mode %#04x\n", video_mode);
 	/* request linear framebuffer mode */
 	video_mode |= (1 << 14);
 	/* don't clear the framebuffer, we do that later */
 	video_mode |= (1 << 15);
 	realmode_interrupt(0x10, VESA_SET_MODE, video_mode,
 			   0x0000, 0x0000, 0x0000, 0x0000);

 	return 0;
 }

 static void vbe_set_graphics(int vesa_mode, struct vesa_state *mode_info)
 {
 	unsigned char *framebuffer;

 	mode_info->video_mode = (1 << 14) | vesa_mode;
 	vbe_get_mode_info(mode_info);

 	framebuffer = (unsigned char *)(ulong)mode_info->vesa.phys_base_ptr;
 	debug("VBE: resolution:  %dx%d@%d\n",
 	      le16_to_cpu(mode_info->vesa.x_resolution),
 	      le16_to_cpu(mode_info->vesa.y_resolution),
 	      mode_info->vesa.bits_per_pixel);
 	debug("VBE: framebuffer: %p\n", framebuffer);
 	if (!framebuffer) {
 		debug("VBE: Mode does not support linear framebuffer\n");
 		return;
 	}

 	mode_info->video_mode &= 0x3ff;
 	vbe_set_mode(mode_info);
 }
 #endif /* CONFIG_FRAMEBUFFER_SET_VESA_MODE */

 void bios_run_on_x86(struct udevice *dev, unsigned long addr, int vesa_mode,
 		     struct vesa_state *mode_info)
 {
 	pci_dev_t pcidev = dm_pci_get_bdf(dev);
 	u32 num_dev;

 	num_dev = PCI_BUS(pcidev) << 8 | PCI_DEV(pcidev) << 3 |
 			PCI_FUNC(pcidev);

 	/* Needed to avoid exceptions in some ROMs */
 	interrupt_init();

 	/* Set up some legacy information in the F segment */
 	setup_rombios();

 	/* Set up C interrupt handlers */
 	setup_interrupt_handlers();

 	/* Set up real-mode IDT */
 	setup_realmode_idt();

 	/* Make sure the code is placed. */
 	setup_realmode_code();

 	debug("Calling Option ROM at %lx, pci device %#x...", addr, num_dev);

 	/* Option ROM entry point is at OPROM start + 3 */
 	realmode_call(addr + 0x0003, num_dev, 0xffff, 0x0000, 0xffff, 0x0,
 		      0x0);
 	debug("done\n");

 #ifdef CONFIG_FRAMEBUFFER_SET_VESA_MODE
 	if (vesa_mode != -1)
 		vbe_set_graphics(vesa_mode, mode_info);
 #endif
 }

 asmlinkage int interrupt_handler(u32 intnumber, u32 gsfs, u32 dses,
 				 u32 edi, u32 esi, u32 ebp, u32 esp,
 				 u32 ebx, u32 edx, u32 ecx, u32 eax,
 				 u32 cs_ip, u16 stackflags)
 {
 	u32 ip;
 	u32 cs;
 	u32 flags;
 	int ret = 0;

 	ip = cs_ip & 0xffff;
 	cs = cs_ip >> 16;
 	flags = stackflags;

 #ifdef CONFIG_REALMODE_DEBUG
 	debug("oprom: INT# 0x%x\n", intnumber);
 	debug("oprom: eax: %08x ebx: %08x ecx: %08x edx: %08x\n",
 	      eax, ebx, ecx, edx);
 	debug("oprom: ebp: %08x esp: %08x edi: %08x esi: %08x\n",
 	      ebp, esp, edi, esi);
 	debug("oprom:  ip: %04x      cs: %04x   flags: %08x\n",
 	      ip, cs, flags);
 	debug("oprom: stackflags = %04x\n", stackflags);
 #endif

 	/*
 	 * Fetch arguments from the stack and put them to a place
 	 * suitable for the interrupt handlers
 	 */
 	M.x86.R_EAX = eax;
 	M.x86.R_ECX = ecx;
 	M.x86.R_EDX = edx;
 	M.x86.R_EBX = ebx;
 	M.x86.R_ESP = esp;
 	M.x86.R_EBP = ebp;
 	M.x86.R_ESI = esi;
 	M.x86.R_EDI = edi;
 	M.x86.intno = intnumber;
 	M.x86.R_EIP = ip;
 	M.x86.R_CS = cs;
 	M.x86.R_EFLG = flags;

 	/* Call the interrupt handler for this interrupt number */
 	ret = int_handler[intnumber]();

 	/*
 	 * This code is quite strange...
 	 *
 	 * Put registers back on the stack. The assembler code will pop them
 	 * later. We force (volatile!) changing the values of the parameters
 	 * of this function. We know that they stay alive on the stack after
 	 * we leave this function.
 	 */
 	*(volatile u32 *)&eax = M.x86.R_EAX;
 	*(volatile u32 *)&ecx = M.x86.R_ECX;
 	*(volatile u32 *)&edx = M.x86.R_EDX;
 	*(volatile u32 *)&ebx = M.x86.R_EBX;
 	*(volatile u32 *)&esi = M.x86.R_ESI;
 	*(volatile u32 *)&edi = M.x86.R_EDI;
 	flags = M.x86.R_EFLG;

 	/* Pass success or error back to our caller via the CARRY flag */
 	if (ret) {
 		flags &= ~1; /* no error: clear carry */
 	} else {
 		debug("int%02x call returned error\n", intnumber);
 		flags |= 1;  /* error: set carry */
 	}
 	*(volatile u16 *)&stackflags = flags;

 	return ret;
 }
	// SPDX-License-Identifier: GPL-2.0
	/*
	* From Coreboot file device/oprom/realmode/x86.c
	*
	* Copyright (C) 2007 Advanced Micro Devices, Inc.
	* Copyright (C) 2009-2010 coresystems GmbH
	*/
	#include <common.h>
	#include <compiler.h>
	#include <bios_emul.h>
	#include <irq_func.h>
	#include <log.h>
	#include <vesa.h>
	#include <linux/linkage.h>
	#include <asm/cache.h>
	#include <asm/processor.h>
	#include <asm/i8259.h>
	#include <asm/io.h>
	#include <asm/post.h>
	#include "bios.h"

	/* Interrupt handlers for each interrupt the ROM can call */
	static int (*int_handler[256])(void);

	/* to have a common register file for interrupt handlers */
	#if !CONFIG_IS_ENABLED(BIOSEMU)
	X86EMU_sysEnv _X86EMU_env;
	#endif

	asmlinkage void (*realmode_call)(u32 addr, u32 eax, u32 ebx, u32 ecx, u32 edx,
	u32 esi, u32 edi);

	asmlinkage void (*realmode_interrupt)(u32 intno, u32 eax, u32 ebx, u32 ecx,
	u32 edx, u32 esi, u32 edi);

	static void setup_realmode_code(void)
	{
	memcpy((void *)REALMODE_BASE, &asm_realmode_code,
	asm_realmode_code_size);

	/* Ensure the global pointers are relocated properly. */
	realmode_call = PTR_TO_REAL_MODE(asm_realmode_call);
	realmode_interrupt = PTR_TO_REAL_MODE(__realmode_interrupt);

	debug("Real mode stub @%x: %d bytes\n", REALMODE_BASE,
	asm_realmode_code_size);
	}

	static void setup_rombios(void)
	{
	const char date[] = "06/11/99";
	memcpy((void *)0xffff5, &date, 8);

	const char ident[] = "PCI_ISA";
	memcpy((void *)0xfffd9, &ident, 7);

	/* system model: IBM-AT */
	writeb(0xfc, 0xffffe);
	}

	static int int_exception_handler(void)
	{
	/* compatibility shim */
	struct eregs reg_info = {
	.eax = M.x86.R_EAX,
	.ecx = M.x86.R_ECX,
	.edx = M.x86.R_EDX,
	.ebx = M.x86.R_EBX,
	.esp = M.x86.R_ESP,
	.ebp = M.x86.R_EBP,
	.esi = M.x86.R_ESI,
	.edi = M.x86.R_EDI,
	.vector = M.x86.intno,
	.error_code = 0,
	.eip = M.x86.R_EIP,
	.cs = M.x86.R_CS,
	.eflags = M.x86.R_EFLG
	};
	struct eregs *regs = &reg_info;

	log_err("Exception %d while executing option rom\n", regs->vector);
	cpu_hlt();

	return 0;
	}

	static int int_unknown_handler(void)
	{
	debug("Unsupported software interrupt #0x%x eax 0x%x\n",
	M.x86.intno, M.x86.R_EAX);

	return -1;
	}

	/* setup interrupt handlers for mainboard */
	void bios_set_interrupt_handler(int intnum, int (*int_func)(void))
	{
	int_handler[intnum] = int_func;
	}

	static void setup_interrupt_handlers(void)
	{
	int i;

	/*
	* The first 16 int_handler functions are not BIOS services,
	* but the CPU-generated exceptions ("hardware interrupts")
	*/
	for (i = 0; i < 0x10; i++)
	int_handler[i] = &int_exception_handler;

	/* Mark all other int_handler calls as unknown first */
	for (i = 0x10; i < 0x100; i++) {
	/* Skip if bios_set_interrupt_handler() isn't called first */
	if (int_handler[i])
	continue;

	/*
	* Now set the default functions that are actually needed
	* to initialize the option roms. The board may override
	* these with bios_set_interrupt_handler()
	*/
	switch (i) {
	case 0x10:
	int_handler[0x10] = &int10_handler;
	break;
	case 0x12:
	int_handler[0x12] = &int12_handler;
	break;
	case 0x16:
	int_handler[0x16] = &int16_handler;
	break;
	case 0x1a:
	int_handler[0x1a] = &int1a_handler;
	break;
	default:
	int_handler[i] = &int_unknown_handler;
	break;
	}
	}
	}

	static void write_idt_stub(void *target, u8 intnum)
	{
	unsigned char *codeptr;

	codeptr = (unsigned char *)target;
	memcpy(codeptr, &__idt_handler, __idt_handler_size);
	codeptr[3] = intnum; /* modify int# in the code stub. */
	}

	static void setup_realmode_idt(void)
	{
	struct realmode_idt *idts = NULL;
	int i;

	/*
	* Copy IDT stub code for each interrupt. This might seem wasteful
	* but it is really simple
	*/
	for (i = 0; i < 256; i++) {
	idts[i].cs = 0;
	idts[i].offset = 0x1000 + (i * __idt_handler_size);
	write_idt_stub((void *)((ulong)idts[i].offset), i);
	}

	/*
	* Many option ROMs use the hard coded interrupt entry points in the
	* system bios. So install them at the known locations.
	*/

	/* int42 is the relocated int10 */
	write_idt_stub((void *)0xff065, 0x42);
	/* BIOS Int 11 Handler F000:F84D */
	write_idt_stub((void *)0xff84d, 0x11);
	/* BIOS Int 12 Handler F000:F841 */
	write_idt_stub((void *)0xff841, 0x12);
	/* BIOS Int 13 Handler F000:EC59 */
	write_idt_stub((void *)0xfec59, 0x13);
	/* BIOS Int 14 Handler F000:E739 */
	write_idt_stub((void *)0xfe739, 0x14);
	/* BIOS Int 15 Handler F000:F859 */
	write_idt_stub((void *)0xff859, 0x15);
	/* BIOS Int 16 Handler F000:E82E */
	write_idt_stub((void *)0xfe82e, 0x16);
	/* BIOS Int 17 Handler F000:EFD2 */
	write_idt_stub((void *)0xfefd2, 0x17);
	/* ROM BIOS Int 1A Handler F000:FE6E */
	write_idt_stub((void *)0xffe6e, 0x1a);
	}

	#ifdef CONFIG_FRAMEBUFFER_SET_VESA_MODE
	static u8 vbe_get_mode_info(struct vesa_state *mi)
	{
	u16 buffer_seg;
	u16 buffer_adr;
	char *buffer;

	debug("VBE: Getting information about VESA mode %04x\n",
	mi->video_mode);
	buffer = PTR_TO_REAL_MODE(asm_realmode_buffer);
	buffer_seg = (((unsigned long)buffer) >> 4) & 0xff00;
	buffer_adr = ((unsigned long)buffer) & 0xffff;

	realmode_interrupt(0x10, VESA_GET_MODE_INFO, 0x0000, mi->video_mode,
	0x0000, buffer_seg, buffer_adr);
	memcpy(mi->mode_info_block, buffer, sizeof(struct vesa_state));
	mi->valid = true;

	return 0;
	}

	static u8 vbe_set_mode(struct vesa_state *mi)
	{
	int video_mode = mi->video_mode;

	debug("VBE: Setting VESA mode %#04x\n", video_mode);
	/* request linear framebuffer mode */
	video_mode \|= (1 << 14);
	/* don't clear the framebuffer, we do that later */
	video_mode \|= (1 << 15);
	realmode_interrupt(0x10, VESA_SET_MODE, video_mode,
	0x0000, 0x0000, 0x0000, 0x0000);

	return 0;
	}

	static void vbe_set_graphics(int vesa_mode, struct vesa_state *mode_info)
	{
	unsigned char *framebuffer;

	mode_info->video_mode = (1 << 14) \| vesa_mode;
	vbe_get_mode_info(mode_info);

	framebuffer = (unsigned char *)(ulong)mode_info->vesa.phys_base_ptr;
	debug("VBE: resolution: %dx%d@%d\n",
	le16_to_cpu(mode_info->vesa.x_resolution),
	le16_to_cpu(mode_info->vesa.y_resolution),
	mode_info->vesa.bits_per_pixel);
	debug("VBE: framebuffer: %p\n", framebuffer);
	if (!framebuffer) {
	debug("VBE: Mode does not support linear framebuffer\n");
	return;
	}

	mode_info->video_mode &= 0x3ff;
	vbe_set_mode(mode_info);
	}
	#endif /* CONFIG_FRAMEBUFFER_SET_VESA_MODE */

	void bios_run_on_x86(struct udevice *dev, unsigned long addr, int vesa_mode,
	struct vesa_state *mode_info)
	{
	pci_dev_t pcidev = dm_pci_get_bdf(dev);
	u32 num_dev;

	num_dev = PCI_BUS(pcidev) << 8 \| PCI_DEV(pcidev) << 3 \|
	PCI_FUNC(pcidev);

	/* Needed to avoid exceptions in some ROMs */
	interrupt_init();

	/* Set up some legacy information in the F segment */
	setup_rombios();

	/* Set up C interrupt handlers */
	setup_interrupt_handlers();

	/* Set up real-mode IDT */
	setup_realmode_idt();

	/* Make sure the code is placed. */
	setup_realmode_code();

	debug("Calling Option ROM at %lx, pci device %#x...", addr, num_dev);

	/* Option ROM entry point is at OPROM start + 3 */
	realmode_call(addr + 0x0003, num_dev, 0xffff, 0x0000, 0xffff, 0x0,
	0x0);
	debug("done\n");

	#ifdef CONFIG_FRAMEBUFFER_SET_VESA_MODE
	if (vesa_mode != -1)
	vbe_set_graphics(vesa_mode, mode_info);
	#endif
	}

	asmlinkage int interrupt_handler(u32 intnumber, u32 gsfs, u32 dses,
	u32 edi, u32 esi, u32 ebp, u32 esp,
	u32 ebx, u32 edx, u32 ecx, u32 eax,
	u32 cs_ip, u16 stackflags)
	{
	u32 ip;
	u32 cs;
	u32 flags;
	int ret = 0;

	ip = cs_ip & 0xffff;
	cs = cs_ip >> 16;
	flags = stackflags;

	#ifdef CONFIG_REALMODE_DEBUG
	debug("oprom: INT# 0x%x\n", intnumber);
	debug("oprom: eax: %08x ebx: %08x ecx: %08x edx: %08x\n",
	eax, ebx, ecx, edx);
	debug("oprom: ebp: %08x esp: %08x edi: %08x esi: %08x\n",
	ebp, esp, edi, esi);
	debug("oprom: ip: %04x cs: %04x flags: %08x\n",
	ip, cs, flags);
	debug("oprom: stackflags = %04x\n", stackflags);
	#endif

	/*
	* Fetch arguments from the stack and put them to a place
	* suitable for the interrupt handlers
	*/
	M.x86.R_EAX = eax;
	M.x86.R_ECX = ecx;
	M.x86.R_EDX = edx;
	M.x86.R_EBX = ebx;
	M.x86.R_ESP = esp;
	M.x86.R_EBP = ebp;
	M.x86.R_ESI = esi;
	M.x86.R_EDI = edi;
	M.x86.intno = intnumber;
	M.x86.R_EIP = ip;
	M.x86.R_CS = cs;
	M.x86.R_EFLG = flags;

	/* Call the interrupt handler for this interrupt number */
	ret = int_handler[intnumber]();

	/*
	* This code is quite strange...
	*
	* Put registers back on the stack. The assembler code will pop them
	* later. We force (volatile!) changing the values of the parameters
	* of this function. We know that they stay alive on the stack after
	* we leave this function.
	*/
	(volatile u32 )&eax = M.x86.R_EAX;
	(volatile u32 )&ecx = M.x86.R_ECX;
	(volatile u32 )&edx = M.x86.R_EDX;
	(volatile u32 )&ebx = M.x86.R_EBX;
	(volatile u32 )&esi = M.x86.R_ESI;
	(volatile u32 )&edi = M.x86.R_EDI;
	flags = M.x86.R_EFLG;

	/* Pass success or error back to our caller via the CARRY flag */
	if (ret) {
	flags &= ~1; /* no error: clear carry */
	} else {
	debug("int%02x call returned error\n", intnumber);
	flags \|= 1; /* error: set carry */
	}
	(volatile u16 )&stackflags = flags;

	return ret;
	}