iPXE
Data Structures | Macros | Functions
comboot.c File Reference

SYSLINUX COMBOOT (16-bit) image format. More...

#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include <errno.h>
#include <assert.h>
#include <realmode.h>
#include <basemem.h>
#include <comboot.h>
#include <ipxe/uaccess.h>
#include <ipxe/image.h>
#include <ipxe/segment.h>
#include <ipxe/init.h>
#include <ipxe/features.h>
#include <ipxe/console.h>

Go to the source code of this file.

Data Structures

struct  comboot_psp
 COMBOOT PSP, copied to offset 0 of code segment. More...
 

Macros

#define COMBOOT_PSP_CMDLINE_OFFSET   0x81
 Offset in PSP of command line. More...
 
#define COMBOOT_MAX_CMDLINE_LEN   125
 Maximum length of command line in PSP (127 bytes minus space and CR) More...
 

Functions

 FILE_LICENCE (GPL2_OR_LATER)
 
 FEATURE (FEATURE_IMAGE, "COMBOOT", DHCP_EB_FEATURE_COMBOOT, 1)
 
static void comboot_copy_cmdline (struct image *image, userptr_t seg_userptr)
 Copy command line to PSP. More...
 
static void comboot_init_psp (struct image *image, userptr_t seg_userptr)
 Initialize PSP. More...
 
static int comboot_exec_loop (struct image *image)
 Execute COMBOOT image. More...
 
static int comboot_identify (struct image *image)
 Check image name extension. More...
 
static int comboot_prepare_segment (struct image *image)
 Load COMBOOT image into memory, preparing a segment and returning it. More...
 
static int comboot_probe (struct image *image)
 Probe COMBOOT image. More...
 
static int comboot_exec (struct image *image)
 Execute COMBOOT image. More...
 
struct image_type comboot_image_type __image_type (PROBE_NORMAL)
 SYSLINUX COMBOOT (16-bit) image type. More...
 

Detailed Description

SYSLINUX COMBOOT (16-bit) image format.

Definition in file comboot.c.

Macro Definition Documentation

◆ COMBOOT_PSP_CMDLINE_OFFSET

#define COMBOOT_PSP_CMDLINE_OFFSET   0x81

Offset in PSP of command line.

Definition at line 58 of file comboot.c.

◆ COMBOOT_MAX_CMDLINE_LEN

#define COMBOOT_MAX_CMDLINE_LEN   125

Maximum length of command line in PSP (127 bytes minus space and CR)

Definition at line 62 of file comboot.c.

Function Documentation

◆ FILE_LICENCE()

FILE_LICENCE ( GPL2_OR_LATER  )

◆ FEATURE()

FEATURE ( FEATURE_IMAGE  ,
"COMBOOT"  ,
DHCP_EB_FEATURE_COMBOOT  ,
 
)

◆ comboot_copy_cmdline()

static void comboot_copy_cmdline ( struct image image,
userptr_t  seg_userptr 
)
static

Copy command line to PSP.

Parameters
imageCOMBOOT image

Definition at line 70 of file comboot.c.

70  {
71  const char *cmdline = ( image->cmdline ? image->cmdline : "" );
72  int cmdline_len = strlen ( cmdline );
73  if( cmdline_len > COMBOOT_MAX_CMDLINE_LEN )
74  cmdline_len = COMBOOT_MAX_CMDLINE_LEN;
75  uint8_t len_byte = cmdline_len;
76  char spc = ' ', cr = '\r';
77 
78  /* Copy length to byte before command line */
79  copy_to_user ( seg_userptr, COMBOOT_PSP_CMDLINE_OFFSET - 1,
80  &len_byte, 1 );
81 
82  /* Command line starts with space */
83  copy_to_user ( seg_userptr,
85  &spc, 1 );
86 
87  /* Copy command line */
88  copy_to_user ( seg_userptr,
90  cmdline, cmdline_len );
91 
92  /* Command line ends with CR */
93  copy_to_user ( seg_userptr,
94  COMBOOT_PSP_CMDLINE_OFFSET + cmdline_len + 1,
95  &cr, 1 );
96 }
#define COMBOOT_PSP_CMDLINE_OFFSET
Offset in PSP of command line.
Definition: comboot.c:58
#define COMBOOT_MAX_CMDLINE_LEN
Maximum length of command line in PSP (127 bytes minus space and CR)
Definition: comboot.c:62
An executable image.
Definition: image.h:24
char * cmdline
Command line to pass to image.
Definition: image.h:39
static __always_inline void copy_to_user(userptr_t dest, off_t dest_off, const void *src, size_t len)
Copy data to user buffer.
Definition: uaccess.h:324
size_t strlen(const char *src)
Get length of string.
Definition: string.c:213
unsigned char uint8_t
Definition: stdint.h:10
Definition: sis900.h:22
uint32_t cmdline
Definition: multiboot.h:16

References cmdline, image::cmdline, COMBOOT_MAX_CMDLINE_LEN, COMBOOT_PSP_CMDLINE_OFFSET, copy_to_user(), cr, and strlen().

Referenced by comboot_init_psp().

◆ comboot_init_psp()

static void comboot_init_psp ( struct image image,
userptr_t  seg_userptr 
)
static

Initialize PSP.

Parameters
imageCOMBOOT image
seg_userptrsegment to initialize

Definition at line 104 of file comboot.c.

104  {
105  struct comboot_psp psp;
106 
107  /* Fill PSP */
108 
109  /* INT 20h instruction, byte order reversed */
110  psp.int20 = 0x20CD;
111 
112  /* get_fbms() returns BIOS free base memory counter, which is in
113  * kilobytes; x * 1024 / 16 == x * 64 == x << 6 */
114  psp.first_non_free_para = get_fbms() << 6;
115 
116  DBGC ( image, "COMBOOT %p: first non-free paragraph = 0x%x\n",
117  image, psp.first_non_free_para );
118 
119  /* Copy the PSP to offset 0 of segment.
120  * The rest of the PSP was already zeroed by
121  * comboot_prepare_segment. */
122  copy_to_user ( seg_userptr, 0, &psp, sizeof( psp ) );
123 
124  /* Copy the command line to the PSP */
125  comboot_copy_cmdline ( image, seg_userptr );
126 }
uint16_t int20
INT 20 instruction, executed if COMBOOT image returns with RET.
Definition: comboot.c:52
static unsigned int get_fbms(void)
Read the BIOS free base memory counter.
Definition: basemem.h:21
#define DBGC(...)
Definition: compiler.h:505
An executable image.
Definition: image.h:24
static void comboot_copy_cmdline(struct image *image, userptr_t seg_userptr)
Copy command line to PSP.
Definition: comboot.c:70
static __always_inline void copy_to_user(userptr_t dest, off_t dest_off, const void *src, size_t len)
Copy data to user buffer.
Definition: uaccess.h:324
COMBOOT PSP, copied to offset 0 of code segment.
Definition: comboot.c:50

References comboot_copy_cmdline(), copy_to_user(), DBGC, comboot_psp::first_non_free_para, get_fbms(), and comboot_psp::int20.

Referenced by comboot_exec_loop().

◆ comboot_exec_loop()

static int comboot_exec_loop ( struct image image)
static

Execute COMBOOT image.

Parameters
imageCOMBOOT image
Return values
rcReturn status code

Definition at line 134 of file comboot.c.

134  {
135  userptr_t seg_userptr = real_to_user ( COMBOOT_PSP_SEG, 0 );
136  int state;
137 
139 
140  switch ( state ) {
141  case 0: /* First time through; invoke COMBOOT program */
142 
143  /* Initialize PSP */
144  comboot_init_psp ( image, seg_userptr );
145 
146  /* Hook COMBOOT API interrupts */
148 
149  DBGC ( image, "executing 16-bit COMBOOT image at %4x:0100\n",
150  COMBOOT_PSP_SEG );
151 
152  /* Unregister image, so that a "boot" command doesn't
153  * throw us into an execution loop. We never
154  * reregister ourselves; COMBOOT images expect to be
155  * removed on exit.
156  */
158 
159  /* Store stack segment at 0x38 and stack pointer at 0x3A
160  * in the PSP and jump to the image */
162  REAL_CODE ( /* Save return address with segment on old stack */
163  "popw %%ax\n\t"
164  "pushw %%cs\n\t"
165  "pushw %%ax\n\t"
166  /* Set DS=ES=segment with image */
167  "movw %w0, %%ds\n\t"
168  "movw %w0, %%es\n\t"
169  /* Set SS:SP to new stack (end of image segment) */
170  "movw %w0, %%ss\n\t"
171  "xor %%sp, %%sp\n\t"
172  "pushw $0\n\t"
173  "pushw %w0\n\t"
174  "pushw $0x100\n\t"
175  /* Zero registers (some COM files assume GP regs are 0) */
176  "xorw %%ax, %%ax\n\t"
177  "xorw %%bx, %%bx\n\t"
178  "xorw %%cx, %%cx\n\t"
179  "xorw %%dx, %%dx\n\t"
180  "xorw %%si, %%si\n\t"
181  "xorw %%di, %%di\n\t"
182  "xorw %%bp, %%bp\n\t"
183  "lret\n\t" )
184  : : "r" ( COMBOOT_PSP_SEG ) : "eax" );
185  DBGC ( image, "COMBOOT %p: returned\n", image );
186  break;
187 
188  case COMBOOT_EXIT:
189  DBGC ( image, "COMBOOT %p: exited\n", image );
190  break;
191 
193  assert ( image->replacement );
194  DBGC ( image, "COMBOOT %p: exited to run kernel %s\n",
196  break;
197 
199  DBGC ( image, "COMBOOT %p: exited after executing command\n",
200  image );
201  break;
202 
203  default:
204  assert ( 0 );
205  break;
206  }
207 
210 
211  return 0;
212 }
uint8_t state
State.
Definition: eth_slow.h:47
#define COMBOOT_PSP_SEG
Segment used for COMBOOT PSP and image.
Definition: comboot.h:17
#define DBGC(...)
Definition: compiler.h:505
static void comboot_init_psp(struct image *image, userptr_t seg_userptr)
Initialize PSP.
Definition: comboot.c:104
An executable image.
Definition: image.h:24
#define COMBOOT_EXIT
Definition: comboot.h:119
assert((readw(&hdr->flags) &(GTF_reading|GTF_writing))==0)
rmjmp_buf comboot_return
Definition: comboot_call.c:82
void comboot_force_text_mode(void)
Set default text mode.
Definition: comboot_call.c:140
void unhook_comboot_interrupts()
Unhook BIOS interrupts related to COMBOOT API (INT 20h, 21h, 22h)
Definition: comboot_call.c:692
__asm__ __volatile__("\n1:\n\t" "movb -1(%2,%1), %%al\n\t" "stosb\n\t" "loop 1b\n\t" "xorl %%eax, %%eax\n\t" "mov %3, %1\n\t" "rep stosb\n\t" :"=&D"(discard_D), "=&c"(discard_c) :"r"(data), "g"(pad_len), "0"(value0), "1"(len) :"eax")
#define COMBOOT_EXIT_RUN_KERNEL
Definition: comboot.h:120
void unregister_image(struct image *image)
Unregister executable image.
Definition: image.c:252
__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")
void hook_comboot_interrupts()
Hook BIOS interrupts related to COMBOOT API (INT 20h, 21h, 22h)
Definition: comboot_call.c:659
#define COMBOOT_EXIT_COMMAND
Definition: comboot.h:121
#define rmsetjmp(_env)
Definition: rmsetjmp.h:17
struct image * replacement
Replacement image.
Definition: image.h:60
static __always_inline userptr_t real_to_user(unsigned int segment, unsigned int offset)
Convert segment:offset address to user buffer.
Definition: realmode.h:75
#define REAL_CODE(asm_code_str)
Definition: libkir.h:226
char * name
Name.
Definition: image.h:34
unsigned long userptr_t
A pointer to a user buffer.
Definition: uaccess.h:33

References __asm__(), __volatile__(), assert(), COMBOOT_EXIT, COMBOOT_EXIT_COMMAND, COMBOOT_EXIT_RUN_KERNEL, comboot_force_text_mode(), comboot_init_psp(), COMBOOT_PSP_SEG, comboot_return, DBGC, hook_comboot_interrupts(), image::name, REAL_CODE, real_to_user(), image::replacement, rmsetjmp, state, unhook_comboot_interrupts(), and unregister_image().

Referenced by comboot_exec().

◆ comboot_identify()

static int comboot_identify ( struct image image)
static

Check image name extension.

Parameters
imageCOMBOOT image
Return values
rcReturn status code

Definition at line 220 of file comboot.c.

220  {
221  const char *ext;
222 
223  ext = strrchr( image->name, '.' );
224 
225  if ( ! ext ) {
226  DBGC ( image, "COMBOOT %p: no extension\n",
227  image );
228  return -ENOEXEC;
229  }
230 
231  ++ext;
232 
233  if ( strcasecmp( ext, "cbt" ) ) {
234  DBGC ( image, "COMBOOT %p: unrecognized extension %s\n",
235  image, ext );
236  return -ENOEXEC;
237  }
238 
239  return 0;
240 }
char * strrchr(const char *src, int character)
Find rightmost character within a string.
Definition: string.c:259
#define ENOEXEC
Exec format error.
Definition: errno.h:519
#define DBGC(...)
Definition: compiler.h:505
int strcasecmp(const char *first, const char *second)
Compare case-insensitive strings.
Definition: string.c:192
An executable image.
Definition: image.h:24
uint16_t ext
Extended status.
Definition: ena.h:20
char * name
Name.
Definition: image.h:34

References DBGC, ENOEXEC, ext, image::name, strcasecmp(), and strrchr().

Referenced by comboot_probe().

◆ comboot_prepare_segment()

static int comboot_prepare_segment ( struct image image)
static

Load COMBOOT image into memory, preparing a segment and returning it.

Parameters
imageCOMBOOT image
Return values
rcReturn status code

Definition at line 247 of file comboot.c.

248 {
249  userptr_t seg_userptr;
250  size_t filesz, memsz;
251  int rc;
252 
253  /* Load image in segment */
254  seg_userptr = real_to_user ( COMBOOT_PSP_SEG, 0 );
255 
256  /* Allow etra 0x100 bytes before image for PSP */
257  filesz = image->len + 0x100;
258 
259  /* Ensure the entire 64k segment is free */
260  memsz = 0xFFFF;
261 
262  /* Prepare, verify, and load the real-mode segment */
263  if ( ( rc = prep_segment ( seg_userptr, filesz, memsz ) ) != 0 ) {
264  DBGC ( image, "COMBOOT %p: could not prepare segment: %s\n",
265  image, strerror ( rc ) );
266  return rc;
267  }
268 
269  /* Zero PSP */
270  memset_user ( seg_userptr, 0, 0, 0x100 );
271 
272  /* Copy image to segment:0100 */
273  memcpy_user ( seg_userptr, 0x100, image->data, 0, image->len );
274 
275  return 0;
276 }
struct arbelprm_rc_send_wqe rc
Definition: arbel.h:14
userptr_t data
Raw file image.
Definition: image.h:41
#define COMBOOT_PSP_SEG
Segment used for COMBOOT PSP and image.
Definition: comboot.h:17
#define DBGC(...)
Definition: compiler.h:505
An executable image.
Definition: image.h:24
void memset_user(userptr_t userptr, off_t offset, int c, size_t len)
Fill user buffer with a constant byte.
int prep_segment(userptr_t segment, size_t filesz, size_t memsz)
Prepare segment for loading.
Definition: segment.c:60
char * strerror(int errno)
Retrieve string representation of error number.
Definition: strerror.c:78
size_t len
Length of raw file image.
Definition: image.h:43
static __always_inline userptr_t real_to_user(unsigned int segment, unsigned int offset)
Convert segment:offset address to user buffer.
Definition: realmode.h:75
void memcpy_user(userptr_t dest, off_t dest_off, userptr_t src, off_t src_off, size_t len)
Copy data between user buffers.
unsigned long userptr_t
A pointer to a user buffer.
Definition: uaccess.h:33

References COMBOOT_PSP_SEG, image::data, DBGC, image::len, memcpy_user(), memset_user(), prep_segment(), rc, real_to_user(), and strerror().

Referenced by comboot_exec().

◆ comboot_probe()

static int comboot_probe ( struct image image)
static

Probe COMBOOT image.

Parameters
imageCOMBOOT image
Return values
rcReturn status code

Definition at line 284 of file comboot.c.

284  {
285  int rc;
286 
287  DBGC ( image, "COMBOOT %p: name '%s'\n",
288  image, image->name );
289 
290  /* Check if this is a COMBOOT image */
291  if ( ( rc = comboot_identify ( image ) ) != 0 ) {
292 
293  return rc;
294  }
295 
296  return 0;
297 }
static int comboot_identify(struct image *image)
Check image name extension.
Definition: comboot.c:220
struct arbelprm_rc_send_wqe rc
Definition: arbel.h:14
#define DBGC(...)
Definition: compiler.h:505
An executable image.
Definition: image.h:24
char * name
Name.
Definition: image.h:34

References comboot_identify(), DBGC, image::name, and rc.

◆ comboot_exec()

static int comboot_exec ( struct image image)
static

Execute COMBOOT image.

Parameters
imageCOMBOOT image
Return values
rcReturn status code

Definition at line 305 of file comboot.c.

305  {
306  int rc;
307 
308  /* Sanity check for filesize */
309  if( image->len >= 0xFF00 ) {
310  DBGC( image, "COMBOOT %p: image too large\n",
311  image );
312  return -ENOEXEC;
313  }
314 
315  /* Prepare segment and load image */
316  if ( ( rc = comboot_prepare_segment ( image ) ) != 0 ) {
317  return rc;
318  }
319 
320  /* Reset console */
321  console_reset();
322 
323  return comboot_exec_loop ( image );
324 }
struct arbelprm_rc_send_wqe rc
Definition: arbel.h:14
#define ENOEXEC
Exec format error.
Definition: errno.h:519
#define DBGC(...)
Definition: compiler.h:505
An executable image.
Definition: image.h:24
static int comboot_exec_loop(struct image *image)
Execute COMBOOT image.
Definition: comboot.c:134
size_t len
Length of raw file image.
Definition: image.h:43
static int comboot_prepare_segment(struct image *image)
Load COMBOOT image into memory, preparing a segment and returning it.
Definition: comboot.c:247
static void console_reset(void)
Reset console.
Definition: console.h:214

References comboot_exec_loop(), comboot_prepare_segment(), console_reset(), DBGC, ENOEXEC, image::len, and rc.

◆ __image_type()

struct image_type comboot_image_type __image_type ( PROBE_NORMAL  )

SYSLINUX COMBOOT (16-bit) image type.