mirror of
https://github.com/ipxe/ipxe
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a4023e02e8
COM32 binaries generally expect to run with interrupts
enabled. Syslinux does so, and COM32 programs will execute cli/sti
pairs when running a critical section, to provide mutual exclusion
against BIOS interrupt handlers. Previously, under iPXE, the IDT was
not valid, so any interrupt (e.g. a timer tick) would generally cause
the machine to triple fault.
This change introduces code to:
- Create a valid IDT at the same location that syslinux uses
- Create an "interrupt jump buffer", which contains small pieces of
code that simply record the vector number and jump to a common
handler
- Thunk down to real mode and execute the BIOS's interrupt handler
whenever an interrupt is received in a COM32 program
- Switch IDTs and enable/disable interrupts when context switching to
and from COM32 binaries
Testing done:
- Booted VMware ESX using a COM32 multiboot loader (mboot.c32)
- Built with GDBSERIAL enabled, and tested breakpoints on int22 and
com32_irq
- Put the following code in a COM32 program:
asm volatile ( "sti" );
while ( 1 );
Before this change, the machine would triple fault
immediately. After this change, it hangs as expected. Under Bochs,
it is possible to see the interrupt handler run, and the current
time in the BIOS data area gets incremented.
Signed-off-by: Stefan Hajnoczi <stefanha@gmail.com>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
181 lines
4.8 KiB
C
181 lines
4.8 KiB
C
#ifndef COMBOOT_H
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#define COMBOOT_H
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/**
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* @file
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*
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* SYSLINUX COMBOOT
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*/
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FILE_LICENCE ( GPL2_OR_LATER );
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#include <stdint.h>
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#include <setjmp.h>
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#include <ipxe/in.h>
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/** Descriptor in a 32-bit IDT */
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struct idt_descriptor {
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uint16_t offset_low;
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uint16_t selector;
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uint16_t flags;
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uint16_t offset_high;
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} __attribute__ (( packed ));
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/** Operand for the LIDT instruction */
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struct idt_register {
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uint16_t limit;
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uint32_t base;
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} __attribute__ (( packed ));
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/** Entry in the interrupt jump buffer */
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struct ijb_entry {
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uint8_t pusha_instruction;
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uint8_t mov_instruction;
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uint8_t mov_value;
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uint8_t jump_instruction;
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uint32_t jump_destination;
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} __attribute__ (( packed ));
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/** The x86 opcode for "pushal" */
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#define IJB_PUSHA 0x60
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/** The x86 opcode for "movb $imm8,%al" */
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#define IJB_MOV_AL_IMM8 0xB0
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/** The x86 opcode for "jmp rel32" */
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#define IJB_JMP_REL32 0xE9
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/** Flags that specify a 32-bit interrupt gate with DPL=0 */
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#define IDT_INTERRUPT_GATE_FLAGS 0x8E00
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/** Address of COM32 interrupt descriptor table */
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#define COM32_IDT 0x100000
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/** Number of entries in a fully populated IDT */
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#define COM32_NUM_IDT_ENTRIES 256
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/** Address of COM32 interrupt jump buffer */
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#define COM32_IJB 0x100800
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/** Segment used for COMBOOT PSP and image */
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#define COMBOOT_PSP_SEG 0x07C0
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/** Entry point address of COM32 images */
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#define COM32_START_PHYS 0x101000
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/** COM32 bounce buffer segment */
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#define COM32_BOUNCE_SEG 0x07C0
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/** Size of SYSLINUX file block in bytes */
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#define COMBOOT_FILE_BLOCKSZ 512
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/** COMBOOT feature flags (INT 22h AX=15h) */
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#define COMBOOT_FEATURE_LOCAL_BOOT (1 << 0)
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#define COMBOOT_FEATURE_IDLE_LOOP (1 << 1)
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/** Maximum number of shuffle descriptors for
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* shuffle and boot functions
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* (INT 22h AX=0012h, 001Ah, 001Bh)
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*/
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#define COMBOOT_MAX_SHUFFLE_DESCRIPTORS 682
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typedef union {
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uint32_t l;
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uint16_t w[2];
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uint8_t b[4];
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} com32_reg32_t;
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typedef struct {
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uint16_t gs; /* Offset 0 */
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uint16_t fs; /* Offset 2 */
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uint16_t es; /* Offset 4 */
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uint16_t ds; /* Offset 6 */
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com32_reg32_t edi; /* Offset 8 */
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com32_reg32_t esi; /* Offset 12 */
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com32_reg32_t ebp; /* Offset 16 */
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com32_reg32_t _unused_esp; /* Offset 20 */
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com32_reg32_t ebx; /* Offset 24 */
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com32_reg32_t edx; /* Offset 28 */
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com32_reg32_t ecx; /* Offset 32 */
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com32_reg32_t eax; /* Offset 36 */
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com32_reg32_t eflags; /* Offset 40 */
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} com32sys_t;
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typedef struct {
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uint32_t eax; /* Offset 0 */
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uint32_t ecx; /* Offset 4 */
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uint32_t edx; /* Offset 8 */
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uint32_t ebx; /* Offset 12 */
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uint32_t esp; /* Offset 16 */
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uint32_t ebp; /* Offset 20 */
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uint32_t esi; /* Offset 24 */
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uint32_t edi; /* Offset 28 */
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uint32_t eip; /* Offset 32 */
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} syslinux_pm_regs;
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typedef struct {
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uint16_t es; /* Offset 0 */
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uint16_t _unused_cs; /* Offset 2 */
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uint16_t ds; /* Offset 4 */
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uint16_t ss; /* Offset 6 */
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uint16_t fs; /* Offset 8 */
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uint16_t gs; /* Offset 10 */
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uint32_t eax; /* Offset 12 */
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uint32_t ecx; /* Offset 16 */
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uint32_t edx; /* Offset 20 */
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uint32_t ebx; /* Offset 24 */
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uint32_t esp; /* Offset 28 */
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uint32_t ebp; /* Offset 32 */
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uint32_t esi; /* Offset 36 */
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uint32_t edi; /* Offset 40 */
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uint16_t ip; /* Offset 44 */
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uint16_t cs; /* Offset 46 */
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} syslinux_rm_regs;
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typedef struct {
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uint32_t dest;
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uint32_t src;
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uint32_t len;
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} comboot_shuffle_descriptor;
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extern void hook_comboot_interrupts ( );
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extern void unhook_comboot_interrupts ( );
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/* These are not the correct prototypes, but it doens't matter,
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* as we only ever get the address of these functions;
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* they are only called from COM32 code running in PHYS_CODE
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*/
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extern void com32_intcall_wrapper ( );
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extern void com32_farcall_wrapper ( );
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extern void com32_cfarcall_wrapper ( );
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extern void com32_irq_wrapper ( );
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/* Resolve a hostname to an (IPv4) address */
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extern int comboot_resolv ( const char *name, struct in_addr *address );
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/* setjmp/longjmp context buffer used to return after loading an image */
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extern rmjmp_buf comboot_return;
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/* Replacement image when exiting with COMBOOT_EXIT_RUN_KERNEL */
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extern struct image *comboot_replacement_image;
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extern void *com32_external_esp;
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#define COMBOOT_EXIT 1
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#define COMBOOT_EXIT_RUN_KERNEL 2
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#define COMBOOT_EXIT_COMMAND 3
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extern void comboot_force_text_mode ( void );
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#define COMBOOT_VIDEO_GRAPHICS 0x01
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#define COMBOOT_VIDEO_NONSTANDARD 0x02
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#define COMBOOT_VIDEO_VESA 0x04
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#define COMBOOT_VIDEO_NOTEXT 0x08
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#endif
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