iPXE
Functions | Variables
bootsector.c File Reference

x86 bootsector image format More...

#include <errno.h>
#include <realmode.h>
#include <biosint.h>
#include <bootsector.h>
#include <ipxe/console.h>

Go to the source code of this file.

Functions

 FILE_LICENCE (GPL2_OR_LATER_OR_UBDL)
void bootsector_exec_fail (void)
 Restart point for INT 18 or 19.
int call_bootsector (unsigned int segment, unsigned int offset, unsigned int drive)
 Jump to preloaded bootsector.

Variables

static struct segoff int18_vector
 Vector for storing original INT 18 handler.
static struct segoff int19_vector
 Vector for storing original INT 19 handler.

Detailed Description

x86 bootsector image format

Definition in file bootsector.c.

Function Documentation

◆ FILE_LICENCE()

FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL )

◆ bootsector_exec_fail()

void bootsector_exec_fail ( void )
extern

Restart point for INT 18 or 19.

Referenced by call_bootsector().

◆ call_bootsector()

int call_bootsector ( unsigned int segment,
unsigned int offset,
unsigned int drive )

Jump to preloaded bootsector.

Parameters
segmentReal-mode segment
offsetReal-mode offset
driveDrive number to pass to boot sector
Return values
rcReturn status code

Definition at line 64 of file bootsector.c.

65 {
66 int discard_b, discard_D, discard_d;
67
68 /* Reset console, since boot sector will probably use it */
69 console_reset();
70
71 DBG ( "Booting from boot sector at %04x:%04x\n", segment, offset );
72
73 /* Hook INTs 18 and 19 to capture failure paths */
74 hook_bios_interrupt ( 0x18, ( intptr_t ) bootsector_exec_fail,
75 &int18_vector );
76 hook_bios_interrupt ( 0x19, ( intptr_t ) bootsector_exec_fail,
77 &int19_vector );
78
79 /* Boot the loaded sector
80 *
81 * We assume that the boot sector may completely destroy our
82 * real-mode stack, so we preserve everything we need in
83 * static storage.
84 */
85 __asm__ __volatile__ ( REAL_CODE ( /* Save return address off-stack */
86 "popw %%cs:saved_retaddr\n\t"
87 /* Save stack pointer */
88 "movw %%ss, %%ax\n\t"
89 "movw %%ax, %%cs:saved_ss\n\t"
90 "movw %%sp, %%cs:saved_sp\n\t"
91 /* Save frame pointer (gcc bug) */
92 "movl %%ebp, %%cs:saved_ebp\n\t"
93 /* Prepare jump to boot sector */
94 "pushw %%bx\n\t"
95 "pushw %%di\n\t"
96 /* Clear all registers */
97 "xorl %%eax, %%eax\n\t"
98 "xorl %%ebx, %%ebx\n\t"
99 "xorl %%ecx, %%ecx\n\t"
100 /* %edx contains drive number */
101 "xorl %%esi, %%esi\n\t"
102 "xorl %%edi, %%edi\n\t"
103 "xorl %%ebp, %%ebp\n\t"
104 "movw %%ax, %%ds\n\t"
105 "movw %%ax, %%es\n\t"
106 "movw %%ax, %%fs\n\t"
107 "movw %%ax, %%gs\n\t"
108 /* Jump to boot sector */
109 "sti\n\t"
110 "lret\n\t"
111 /* Preserved variables */
112 "\nsaved_ebp: .long 0\n\t"
113 "\nsaved_ss: .word 0\n\t"
114 "\nsaved_sp: .word 0\n\t"
115 "\nsaved_retaddr: .word 0\n\t"
116 /* Boot failure return point */
117 "\nbootsector_exec_fail:\n\t"
118 /* Restore frame pointer (gcc bug) */
119 "movl %%cs:saved_ebp, %%ebp\n\t"
120 /* Restore stack pointer */
121 "movw %%cs:saved_ss, %%ax\n\t"
122 "movw %%ax, %%ss\n\t"
123 "movw %%cs:saved_sp, %%sp\n\t"
124 /* Return via saved address */
125 "jmp *%%cs:saved_retaddr\n\t" )
126 : "=b" ( discard_b ), "=D" ( discard_D ),
127 "=d" ( discard_d )
128 : "b" ( segment ), "D" ( offset ),
129 "d" ( drive )
130 : "eax", "ecx", "esi" );
131
132 DBG ( "Booted disk returned via INT 18 or 19\n" );
133
134 /* Unhook INTs 18 and 19 */
135 unhook_bios_interrupt ( 0x18, ( intptr_t ) bootsector_exec_fail,
136 &int18_vector );
137 unhook_bios_interrupt ( 0x19, ( intptr_t ) bootsector_exec_fail,
138 &int19_vector );
139
140 return -ECANCELED;
141}
__volatile__
__asm__ __volatile__("call *%9" :"=a"(result), "=c"(discard_ecx), "=d"(discard_edx) :"d"(0), "a"(code), "b"(0), "c"(in_phys), "D"(0), "S"(out_phys), "m"(hypercall))
intptr_t
unsigned long intptr_t
Definition stdint.h:21
discard_D
void * discard_D
Definition bigint.h:32
hook_bios_interrupt
void hook_bios_interrupt(unsigned int interrupt, unsigned int handler, struct segoff *chain_vector)
Hook INT vector.
Definition biosint.c:25
unhook_bios_interrupt
int unhook_bios_interrupt(unsigned int interrupt, unsigned int handler, struct segoff *chain_vector)
Unhook INT vector.
Definition biosint.c:70
int19_vector
static struct segoff int19_vector
Vector for storing original INT 19 handler.
Definition bootsector.c:51
int18_vector
static struct segoff int18_vector
Vector for storing original INT 18 handler.
Definition bootsector.c:44
bootsector_exec_fail
void bootsector_exec_fail(void)
Restart point for INT 18 or 19.
offset
uint16_t offset
Offset to command line.
Definition bzimage.h:3
DBG
#define DBG(...)
Print a debugging message.
Definition compiler.h:498
drive
uint8_t drive
Drive number.
Definition int13.h:5
ECANCELED
#define ECANCELED
Operation canceled.
Definition errno.h:344
console_reset
static void console_reset(void)
Reset console.
Definition console.h:215
REAL_CODE
#define REAL_CODE(asm_code_str)
Definition libkir.h:226
segment
uint16_t segment
Code segment.
Definition librm.h:3
__asm__
__asm__(".section \".rodata\", \"a\", " PROGBITS "\n\t" "\nprivate_key_data:\n\t" ".size private_key_data, ( . - private_key_data )\n\t" ".equ private_key_len, ( . - private_key_data )\n\t" ".previous\n\t")

References __asm__(), __volatile__(), bootsector_exec_fail(), console_reset(), DBG, discard_D, drive, ECANCELED, hook_bios_interrupt(), int18_vector, int19_vector, offset, REAL_CODE, segment, and unhook_bios_interrupt().

Referenced by int13_boot().

Variable Documentation

◆ int18_vector

struct segoff int18_vector
static

Vector for storing original INT 18 handler.

We do not chain to this vector, so there is no need to place it in .text16.

Definition at line 44 of file bootsector.c.

Referenced by call_bootsector().

◆ int19_vector

struct segoff int19_vector
static

Vector for storing original INT 19 handler.

We do not chain to this vector, so there is no need to place it in .text16.

Definition at line 51 of file bootsector.c.

Referenced by call_bootsector().

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