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int elf_x86_load(int argc, char **argv, const char *buf, off_t
len,
struct kexec_info *info)//******************
{
struct mem_ehdr ehdr;
const char *command_line;
char *modified_cmdline;
int command_line_len;
int modified_cmdline_len;
const char *ramdisk;
unsigned long entry, max_addr;
int arg_style;
#define ARG_STYLE_ELF 0
#define ARG_STYLE_LINUX 1
#define ARG_STYLE_NONE 2
int opt;
#define OPT_APPEND (OPT_ARCH_MAX+0)
#define OPT_REUSE_CMDLINE (OPT_ARCH_MAX+1)
#define OPT_RAMDISK (OPT_ARCH_MAX+2)
#define OPT_ARGS_ELF (OPT_ARCH_MAX+3)
#define OPT_ARGS_LINUX (OPT_ARCH_MAX+4)
#define OPT_ARGS_NONE (OPT_ARCH_MAX+5)
static const struct option
options[] = {//參見http://xuwenzhang.org/blog/tag/getopt_long/
noted by peter.guo
KEXEC_ARCH_OPTIONS
{ "command-line", 1, NULL, OPT_APPEND },
{ "append", 1, NULL, OPT_APPEND },
{ "reuse-cmdline", 1, NULL, OPT_REUSE_CMDLINE },
{ "initrd", 1, NULL, OPT_RAMDISK },
{ "ramdisk", 1, NULL, OPT_RAMDISK },
{ "args-elf", 0, NULL, OPT_ARGS_ELF },
{ "args-linux", 0, NULL, OPT_ARGS_LINUX },
{ "args-none", 0, NULL, OPT_ARGS_NONE },
{ 0, 0, NULL, 0 },
};
static const char short_options[] = KEXEC_OPT_STR "";
/*
* Parse the command line arguments
*/
arg_style = ARG_STYLE_ELF;
command_line = 0;
modified_cmdline = 0;
modified_cmdline_len = 0;
ramdisk = 0;
while((opt = getopt_long(argc, argv, short_options, options, 0)) != -1){//屬於gnu體系
switch(opt) {
default:
/* Ignore core options */
if (opt < OPT_ARCH_MAX) {
break;
}
case '?':
usage();
return -1;
case OPT_APPEND://進入此!
command_line = optarg;
break;
case OPT_REUSE_CMDLINE:
command_line = get_command_line();
break;
case OPT_RAMDISK: //進入此!
ramdisk = optarg;
break;
case OPT_ARGS_ELF:
arg_style = ARG_STYLE_ELF;
break;
case OPT_ARGS_LINUX://進入此!
arg_style = ARG_STYLE_LINUX;
break;
case OPT_ARGS_NONE:
#ifdef __i386__
arg_style = ARG_STYLE_NONE;
#else
die("--args-none only works on arch i386\n");
#endif
break;
}
}
command_line_len = 0;
if (command_line) {
command_line_len = strlen(command_line) +1;
}
/* Need to append some command line parameters internally in case of
* taking crash dumps.
*/
if (info->kexec_flags & (KEXEC_ON_CRASH|KEXEC_PRESERVE_CONTEXT)) {
modified_cmdline = xmalloc(COMMAND_LINE_SIZE);//分配一個新的空間來盛命令行!
memset((void *)modified_cmdline, 0, COMMAND_LINE_SIZE);
if (command_line) {
strncpy(modified_cmdline, command_line,
COMMAND_LINE_SIZE);
modified_cmdline[COMMAND_LINE_SIZE - 1] = '\0';
}
modified_cmdline_len = strlen(modified_cmdline);
}
/* Load the ELF executable */
elf_exec_build_load(info, &ehdr, buf, len, 0);//========================>
entry = ehdr.e_entry;
max_addr = elf_max_addr(&ehdr);
/* Do we want arguments? */
if (arg_style != ARG_STYLE_NONE) {//=====>
/* Load the setup code *///===========>pay more attention to purgatory!!!!!!
elf_rel_build_load(info, &info->rhdr, (char *) purgatory,purgatory_size,
0, ULONG_MAX, 1, 0);
}
if (arg_style == ARG_STYLE_NONE) {
info->entry = (void *)entry;
}
else if (arg_style == ARG_STYLE_ELF) {
unsigned long note_base;
struct entry32_regs regs;
uint32_t arg1, arg2;
/* Setup the ELF boot notes */
note_base = elf_boot_notes(info, max_addr,
(unsigned char *) command_line, command_line_len);
/* Initialize the stack arguments */
arg2 = 0; /* No return
address */
arg1 = note_base;
elf_rel_set_symbol(&info->rhdr, "stack_arg32_1", &arg1, sizeof(arg1));
elf_rel_set_symbol(&info->rhdr, "stack_arg32_2", &arg2, sizeof(arg2));
/* Initialize the registers */
elf_rel_get_symbol(&info->rhdr, "entry32_regs", ®s, sizeof(regs));
regs.eip = entry; /*
The entry point */
regs.esp = elf_rel_get_addr(&info->rhdr, "stack_arg32_2");
elf_rel_set_symbol(&info->rhdr, "entry32_regs", ®s, sizeof(regs));
if (ramdisk) {
die("Ramdisks not supported with generic elf arguments");
}
}
else if (arg_style == ARG_STYLE_LINUX) {//=====>got
it !!!!!!
struct x86_linux_faked_param_header *hdr;
unsigned long param_base;
const unsigned char *ramdisk_buf;
off_t ramdisk_length;
struct entry32_regs regs;
int rc = 0;
/* Get the linux parameter header */
hdr = xmalloc(sizeof(*hdr));
/* Hack: With some ld versions, vmlinux program headers show
* a gap of two pages between bss segment and data segment
* but effectively kernel considers it as bss segment and
* overwrites the any data placed there. Hence bloat the
* memsz of parameter segment to 16K to avoid being placed
* in such gaps.
* This is a makeshift solution until it is fixed in kernel
*/
param_base = add_buffer(info, hdr, sizeof(*hdr), 16*1024,
16, 0, max_addr, 1);
/* Initialize the parameter header */
memset(hdr, 0, sizeof(*hdr));
init_linux_parameters(&hdr->hdr);
/* Add a ramdisk to the current image */
ramdisk_buf = NULL;
ramdisk_length = 0;
if (ramdisk) {
ramdisk_buf = (unsigned char *) slurp_file(ramdisk,&ramdisk_length);
}
/* If panic kernel is being loaded, additional segments need
* to be created. */
if (info->kexec_flags & (KEXEC_ON_CRASH|KEXEC_PRESERVE_CONTEXT)) {
/*
Command line: ro root=LABEL=/ rhgb quiet irqpoll maxcpus=1 reset_devicesmemmap=exactmap memmap=640K@0K
memmap=5264K@16384K
memmap=125152K@22288K elfcorehdr=147440K (0x8ffc000)
memmap=56K#1834688K memmap=136K#1834744K memmap=128K#1834880K memmap=1024K$4193280K //紅色部分'#'代表specific memory forACPI data. '$'代表specific memory as reserved. 沒在代碼中查找到？
/此處得到相關的memmap和elfcorehdr參數並存入新的命令行參數中
*/
rc = load_crashdump_segments(info, modified_cmdline,
max_addr, 0);
if (rc < 0)
return -1;
/* Use new command line. */
command_line = modified_cmdline;
command_line_len = strlen(modified_cmdline) + 1;
}
/* Tell the kernel what is going on */
setup_linux_bootloader_parameters(info, &hdr->hdr, param_base,
offsetof(struct x86_linux_faked_param_header, command_line),
command_line, command_line_len,
ramdisk_buf, ramdisk_length);//======>got
it !!!!!!
/* Fill in the information bios calls would usually provide */
setup_linux_system_parameters(&hdr->hdr, info->kexec_flags);
/* Initialize the registers */
elf_rel_get_symbol(&info->rhdr, "entry32_regs", ®s, sizeof(regs));
regs.ebx = 0; /*
Bootstrap processor */
regs.esi = param_base; /*
Pointer to the parameters */
regs.eip = entry; /*
The entry point */
regs.esp = elf_rel_get_addr(&info->rhdr, "stack_end"); /*
Stack, unused */
elf_rel_set_symbol(&info->rhdr, "entry32_regs", ®s, sizeof(regs));
}
else {
die("Unknown argument style\n");
}
return 0;
}
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