The setup_arch() function in arch/i386/kernel/setup.c is cast to the __init type where it runs only once at system initialization time. The setup_arch() function takes in a pointer to any Linux command-line data entered at boot time and initializes many of the architecture-specific subsystems, such as memory, I/O, processors, and consoles:
/*
* Determine if we were loaded by an EFI loader. If so, then we have also been
* passed the efi memmap, systab, etc., so we should use these data structures
* for initialization. Note, the efi init code path is determined by the
* global efi_enabled. This allows the same kernel image to be used on existing
* systems (with a traditional BIOS) as well as on EFI systems.
*/
/*
* setup_arch - architecture-specific boot-time initializations
*
* Note: On x86_64, fixmaps are ready for use even before this is called.
*/
void __init setup_arch(char **cmdline_p)
{
int acpi = 0;
int k8 = 0;
#ifdef CONFIG_X86_32
//see below comment 1
memcpy(&boot_cpu_data, &new_cpu_data, sizeof(new_cpu_data));
visws_early_detect();
#else
//see below comment 2
printk(KERN_INFO "Command line: %s\n", boot_command_line);
#endif
/* VMI may relocate the fixmap; do this before touching ioremap area */
vmi_init();
early_trap_init();
early_cpu_init();//Identify the specific processor
early_ioremap_init();
//see below comment 3, ROOT_DEV is a global variable
ROOT_DEV = old_decode_dev(boot_params.hdr.root_dev);
screen_info = boot_params.screen_info;
edid_info = boot_params.edid_info;
#ifdef CONFIG_X86_32
apm_info.bios = boot_params.apm_bios_info;
ist_info = boot_params.ist_info;
if (boot_params.sys_desc_table.length != 0) {
set_mca_bus(boot_params.sys_desc_table.table[3] & 0x2);
machine_id = boot_params.sys_desc_table.table[0];
machine_submodel_id = boot_params.sys_desc_table.table[1];
BIOS_revision = boot_params.sys_desc_table.table[2];
}
#endif
saved_video_mode = boot_params.hdr.vid_mode;
bootloader_type = boot_params.hdr.type_of_loader;
if ((bootloader_type >> 4) == 0xe) {
bootloader_type &= 0xf;
bootloader_type |= (boot_params.hdr.ext_loader_type+0x10) << 4;
}
bootloader_version = bootloader_type & 0xf;
bootloader_version |= boot_params.hdr.ext_loader_ver << 4;
#ifdef CONFIG_BLK_DEV_RAM
rd_image_start = boot_params.hdr.ram_size & RAMDISK_IMAGE_START_MASK;
rd_prompt = ((boot_params.hdr.ram_size & RAMDISK_PROMPT_FLAG) != 0);
rd_doload = ((boot_params.hdr.ram_size & RAMDISK_LOAD_FLAG) != 0);
#endif
#ifdef CONFIG_EFI
if (!strncmp((char *)&boot_params.efi_info.efi_loader_signature,
#ifdef CONFIG_X86_32
"EL32",
#else
"EL64",
#endif
4)) {
efi_enabled = 1;
efi_reserve_early();
}
#endif
x86_init.oem.arch_setup();
//see below comment 4
setup_memory_map();
//parse boot_params
parse_setup_data();
/* update the e820_saved too */
e820_reserve_setup_data();
/**
* copy_edd() - Copy the BIOS EDD information
* from boot_params into a safe place.
*/
copy_edd();
if (!boot_params.hdr.root_flags)
root_mountflags &= ~MS_RDONLY;
//see below comment 5,Initialize memory-management structs from the BIOS-provided memory map.
init_mm.start_code = (unsigned long) _text;
init_mm.end_code = (unsigned long) _etext;
init_mm.end_data = (unsigned long) _edata;
init_mm.brk = _brk_end;
code_resource.start = virt_to_phys(_text);
code_resource.end = virt_to_phys(_etext)-1;
data_resource.start = virt_to_phys(_etext);
data_resource.end = virt_to_phys(_edata)-1;
bss_resource.start = virt_to_phys(&__bss_start);
bss_resource.end = virt_to_phys(&__bss_stop)-1;
#ifdef CONFIG_CMDLINE_BOOL
#ifdef CONFIG_CMDLINE_OVERRIDE
strlcpy(boot_command_line, builtin_cmdline, COMMAND_LINE_SIZE);
#else
if (builtin_cmdline[0]) {
/* append boot loader cmdline to builtin */
strlcat(builtin_cmdline, " ", COMMAND_LINE_SIZE);
strlcat(builtin_cmdline, boot_command_line, COMMAND_LINE_SIZE);
strlcpy(boot_command_line, builtin_cmdline, COMMAND_LINE_SIZE);
}
#endif
#endif
strlcpy(command_line, boot_command_line, COMMAND_LINE_SIZE);
*cmdline_p = command_line;
/*
* x86_configure_nx() is called before parse_early_param() to detect
* whether hardware doesn't support NX (so that the early EHCI debug
* console setup can safely call set_fixmap()). It may then be called
* again from within noexec_setup() during parsing early parameters
* to honor the respective command line option.
*/
x86_configure_nx();
//see below comment 6
parse_early_param();
x86_report_nx();
/* Must be before kernel pagetables are setup */
vmi_activate();
/* after early param, so could get panic from serial */
reserve_early_setup_data();
if (acpi_mps_check()) {
#ifdef CONFIG_X86_LOCAL_APIC
disable_apic = 1;
#endif
setup_clear_cpu_cap(X86_FEATURE_APIC);
}
#ifdef CONFIG_PCI
if (pci_early_dump_regs)
early_dump_pci_devices();
#endif
finish_e820_parsing();
if (efi_enabled)
efi_init();
dmi_scan_machine();
dmi_check_system(bad_bios_dmi_table);
/*
* VMware detection requires dmi to be available, so this
* needs to be done after dmi_scan_machine, for the BP.
*/
init_hypervisor_platform();
x86_init.resources.probe_roms();
/* after parse_early_param, so could debug it */
insert_resource(&iomem_resource, &code_resource);
insert_resource(&iomem_resource, &data_resource);
insert_resource(&iomem_resource, &bss_resource);
trim_bios_range();
#ifdef CONFIG_X86_32
if (ppro_with_ram_bug()) {
e820_update_range(0x70000000ULL, 0x40000ULL, E820_RAM,
E820_RESERVED);
sanitize_e820_map(e820.map, ARRAY_SIZE(e820.map), &e820.nr_map);
printk(KERN_INFO "fixed physical RAM map:\n");
e820_print_map("bad_ppro");
}
#else
early_gart_iommu_check();
#endif
/*
* partially used pages are not usable - thus
* we are rounding upwards:
*/
max_pfn = e820_end_of_ram_pfn();
/* preallocate 4k for mptable mpc */
early_reserve_e820_mpc_new();
/* update e820 for memory not covered by WB MTRRs */
mtrr_bp_init();
if (mtrr_trim_uncached_memory(max_pfn))
max_pfn = e820_end_of_ram_pfn();
#ifdef CONFIG_X86_32
/* max_low_pfn get updated here */
find_low_pfn_range();
#else
num_physpages = max_pfn;
check_x2apic();
/* How many end-of-memory variables you have, grandma! */
/* need this before calling reserve_initrd */
if (max_pfn > (1UL<<(32 - PAGE_SHIFT)))
max_low_pfn = e820_end_of_low_ram_pfn();
else
max_low_pfn = max_pfn;
high_memory = (void *)__va(max_pfn * PAGE_SIZE - 1) + 1;
max_pfn_mapped = KERNEL_IMAGE_SIZE >> PAGE_SHIFT;
#endif
#ifdef CONFIG_X86_CHECK_BIOS_CORRUPTION
setup_bios_corruption_check();
#endif
printk(KERN_DEBUG "initial memory mapped : 0 - %08lx\n",
max_pfn_mapped<
reserve_brk();
/*
* Find and reserve possible boot-time SMP configuration:
*/
find_smp_config();
reserve_ibft_region();
reserve_trampoline_memory();
#ifdef CONFIG_ACPI_SLEEP
/*
* Reserve low memory region for sleep support.
* even before init_memory_mapping
*/
acpi_reserve_wakeup_memory();
#endif
init_gbpages();
/* max_pfn_mapped is updated here */
max_low_pfn_mapped = init_memory_mapping(0, max_low_pfn<
max_pfn_mapped = max_low_pfn_mapped;
#ifdef CONFIG_X86_64
if (max_pfn > max_low_pfn) {
max_pfn_mapped = init_memory_mapping(1UL<<32,
max_pfn<
/* can we preseve max_low_pfn ?*/
max_low_pfn = max_pfn;
}
#endif
/*
* NOTE: On x86-32, only from this point on, fixmaps are ready for use.
*/
#ifdef CONFIG_PROVIDE_OHCI1394_DMA_INIT
if (init_ohci1394_dma_early)
init_ohci1394_dma_on_all_controllers();
#endif
reserve_initrd();
reserve_crashkernel();
vsmp_init();
io_delay_init();
/*
* Parse the ACPI tables for possible boot-time SMP configuration.
*/
acpi_boot_table_init();
early_acpi_boot_init();
#ifdef CONFIG_ACPI_NUMA
/*
* Parse SRAT to discover nodes.
*/
acpi = acpi_numa_init();
#endif
#ifdef CONFIG_K8_NUMA
if (!acpi)
k8 = !k8_numa_init(0, max_pfn);
#endif
initmem_init(0, max_pfn, acpi, k8);
#ifndef CONFIG_NO_BOOTMEM
early_res_to_bootmem(0, max_low_pfn<
#endif
dma32_reserve_bootmem();
#ifdef CONFIG_KVM_CLOCK
kvmclock_init();
#endif
x86_init.paging.pagetable_setup_start(swapper_pg_dir);
paging_init();
x86_init.paging.pagetable_setup_done(swapper_pg_dir);
tboot_probe();
#ifdef CONFIG_X86_64
map_vsyscall();
#endif
generic_apic_probe();
early_quirks();
/*
* Read APIC and some other early information from ACPI tables.
*/
acpi_boot_init();
sfi_init();
/*
* get boot-time SMP configuration:
*/
if (smp_found_config)
get_smp_config();
prefill_possible_map();
#ifdef CONFIG_X86_64
init_cpu_to_node();
#endif
init_apic_mappings();
ioapic_init_mappings();
/* need to wait for io_apic is mapped */
probe_nr_irqs_gsi();
kvm_guest_init();
e820_reserve_resources();
e820_mark_nosave_regions(max_low_pfn);
x86_init.resources.reserve_resources();
e820_setup_gap();
#ifdef CONFIG_VT
#if defined(CONFIG_VGA_CONSOLE)
if (!efi_enabled || (efi_mem_type(0xa0000) != EFI_CONVENTIONAL_MEMORY))
conswitchp = &vga_con;
#elif defined(CONFIG_DUMMY_CONSOLE)
conswitchp = &dummy_con;
#endif
#endif
x86_init.oem.banner();
mcheck_init();
}
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Comment 1:new_cpu_data, boot_cpu_data are defined in arch/x86/kernel/setup.c, boot_cpu_data is filled at boot time.
#ifdef CONFIG_X86_32
/* cpu data as detected by the assembly code in head.S */
struct cpuinfo_x86 new_cpu_data __cpuinitdata = {0, 0, 0, 0, -1, 1, 0, 0, -1};
/* common cpu data for all cpus */
struct cpuinfo_x86 boot_cpu_data __read_mostly = {0, 0, 0, 0, -1, 1, 0, 0, -1};
EXPORT_SYMBOL(boot_cpu_data);
|
processor.h
/*
* CPU type and hardware bug flags. Kept separately for each CPU.
* Members of this structure are referenced in head.S, so think twice
* before touching them. [mj]
*/
struct cpuinfo_x86 {
__u8 x86; /* CPU family */
__u8 x86_vendor; /* CPU vendor */
__u8 x86_model;
__u8 x86_mask;
#ifdef CONFIG_X86_32
char wp_works_ok; /* It doesn't on 386's */
/* Problems on some 486Dx4's and old 386's: */
char hlt_works_ok;
char hard_math;
char rfu;
char fdiv_bug;
char f00f_bug;
char coma_bug;
char pad0;
#else
/* Number of 4K pages in DTLB/ITLB combined(in pages): */
int x86_tlbsize;
#endif
__u8 x86_virt_bits;
__u8 x86_phys_bits;
/* CPUID returned core id bits: */
__u8 x86_coreid_bits;
/* Max extended CPUID function supported: */
__u32 extended_cpuid_level;
/* Maximum supported CPUID level, -1=no CPUID: */
int cpuid_level;
__u32 x86_capability[NCAPINTS];
char x86_vendor_id[16];
char x86_model_id[64];
/* in KB - valid for CPUS which support this call: */
int x86_cache_size;
int x86_cache_alignment; /* In bytes */
int x86_power;
unsigned long loops_per_jiffy;
#ifdef CONFIG_SMP
/* cpus sharing the last level cache: */
cpumask_var_t llc_shared_map;
#endif
/* cpuid returned max cores value: */
u16 x86_max_cores;
u16 apicid;
u16 initial_apicid;
u16 x86_clflush_size;
#ifdef CONFIG_SMP
/* number of cores as seen by the OS: */
u16 booted_cores;
/* Physical processor id: */
u16 phys_proc_id;
/* Core id: */
u16 cpu_core_id;
/* Index into per_cpu list: */
u16 cpu_index;
#endif
} __attribute__((__aligned__(SMP_CACHE_BYTES)));
|
Comment 2:boot_command_line is defined in init/main.c
/* Untouched command line saved by arch-specific code. */
char __initdata boot_command_line[COMMAND_LINE_SIZE];
|
Comment 3:Global variable boot_params defined in arch/x86/kernel/setup.c
struct boot_params __initdata boot_params;
|
/* The so-called "zeropage" */
struct boot_params {
struct screen_info screen_info; /* 0x000 */
struct apm_bios_info apm_bios_info; /* 0x040 */
__u8 _pad2[4]; /* 0x054 */
__u64 tboot_addr; /* 0x058 */
struct ist_info ist_info; /* 0x060 */
__u8 _pad3[16]; /* 0x070 */
__u8 hd0_info[16]; /* obsolete! */ /* 0x080 */
__u8 hd1_info[16]; /* obsolete! */ /* 0x090 */
struct sys_desc_table sys_desc_table; /* 0x0a0 */
__u8 _pad4[144]; /* 0x0b0 */
struct edid_info edid_info; /* 0x140 */
struct efi_info efi_info; /* 0x1c0 */
__u32 alt_mem_k; /* 0x1e0 */
__u32 scratch; /* Scratch field! */ /* 0x1e4 */
__u8 e820_entries; /* 0x1e8 */
__u8 eddbuf_entries; /* 0x1e9 */
__u8 edd_mbr_sig_buf_entries; /* 0x1ea */
__u8 _pad6[6]; /* 0x1eb */
struct setup_header hdr; /* setup header */ /* 0x1f1 */
__u8 _pad7[0x290-0x1f1-sizeof(struct setup_header)];
__u32 edd_mbr_sig_buffer[EDD_MBR_SIG_MAX]; /* 0x290 */
struct e820entry e820_map[E820MAX]; /* 0x2d0 */
__u8 _pad8[48]; /* 0xcd0 */
struct edd_info eddbuf[EDDMAXNR]; /* 0xd00 */
__u8 _pad9[276]; /* 0xeec */
} __attribute__((packed));
|
Comment 4:dmesg | grep BIOS, print following message:
lee@LEE:~$ dmesg |grep BIOS
[ 0.000000] BIOS-provided physical RAM map:
[ 0.000000] BIOS-e820: 0000000000000000 - 000000000009e400 (usable)
[ 0.000000] BIOS-e820: 000000000009e400 - 00000000000a0000 (reserved)
[ 0.000000] BIOS-e820: 00000000000dc000 - 0000000000100000 (reserved)
[ 0.000000] BIOS-e820: 0000000000100000 - 000000007d6a1000 (usable)
[ 0.000000] BIOS-e820: 000000007d6a1000 - 000000007d6a7000 (reserved)
[ 0.000000] BIOS-e820: 000000007d6a7000 - 000000007d7bd000 (usable)
[ 0.000000] BIOS-e820: 000000007d7bd000 - 000000007d80f000 (reserved)
[ 0.000000] BIOS-e820: 000000007d80f000 - 000000007d908000 (usable)
[ 0.000000] BIOS-e820: 000000007d908000 - 000000007db0f000 (reserved)
[ 0.000000] BIOS-e820: 000000007db0f000 - 000000007db19000 (usable)
[ 0.000000] BIOS-e820: 000000007db19000 - 000000007db1f000 (reserved)
[ 0.000000] BIOS-e820: 000000007db1f000 - 000000007db64000 (usable)
[ 0.000000] BIOS-e820: 000000007db64000 - 000000007db9f000 (ACPI NVS)
[ 0.000000] BIOS-e820: 000000007db9f000 - 000000007dc00000 (ACPI data)
[ 0.000000] BIOS-e820: 000000007dc00000 - 000000007de00000 (reserved)
[ 0.000000] BIOS-e820: 000000007e000000 - 0000000080000000 (reserved)
[ 0.000000] BIOS-e820: 00000000e0000000 - 00000000f0000000 (reserved)
[ 0.000000] BIOS-e820: 00000000fec00000 - 00000000fec10000 (reserved)
[ 0.000000] BIOS-e820: 00000000fed00000 - 00000000fed00400 (reserved)
[ 0.000000] BIOS-e820: 00000000fed10000 - 00000000fed14000 (reserved)
[ 0.000000] BIOS-e820: 00000000fed18000 - 00000000fed1a000 (reserved)
[ 0.000000] BIOS-e820: 00000000fed1c000 - 00000000fed90000 (reserved)
[ 0.000000] BIOS-e820: 00000000fee00000 - 00000000fee01000 (reserved)
[ 0.000000] BIOS-e820: 00000000ff800000 - 0000000100000000 (reserved)
Those message is printed in function setup_memory_map():
void __init setup_memory_map(void)
{
char *who;
who = x86_init.resources.memory_setup();
memcpy(&e820_saved, &e820, sizeof(struct e820map));
printk(KERN_INFO "BIOS-provided physical RAM map:\n");
e820_print_map(who);
}
|
x86_init is a global variable defined in arch/x86/kernel/x86_init.c
/*
* The platform setup functions are preset with the default functions
* for standard PC hardware.
*/
struct x86_init_ops x86_init __initdata = {
.resources = {
.probe_roms = x86_init_noop,
.reserve_resources = reserve_standard_io_resources,
.memory_setup = default_machine_specific_memory_setup,
},
.mpparse = {
.mpc_record = x86_init_uint_noop,
.setup_ioapic_ids = x86_init_noop,
.mpc_apic_id = default_mpc_apic_id,
.smp_read_mpc_oem = default_smp_read_mpc_oem,
.mpc_oem_bus_info = default_mpc_oem_bus_info,
.find_smp_config = default_find_smp_config,
.get_smp_config = default_get_smp_config,
},
.irqs = {
.pre_vector_init = init_ISA_irqs,
.intr_init = native_init_IRQ,
.trap_init = x86_init_noop,
},
.oem = {
.arch_setup = x86_init_noop,
.banner = default_banner,
},
.paging = {
.pagetable_setup_start = native_pagetable_setup_start,
.pagetable_setup_done = native_pagetable_setup_done,
},
.timers = {
.setup_percpu_clockev = setup_boot_APIC_clock,
.tsc_pre_init = x86_init_noop,
.timer_init = hpet_time_init,
},
.iommu = {
.iommu_init = iommu_init_noop,
},
.pci = {
.init = x86_default_pci_init,
.init_irq = x86_default_pci_init_irq,
.fixup_irqs = x86_default_pci_fixup_irqs,
},
};
|
default_machine_specific_memory_setup() is defined in arch/x86/kernel/e820.c
char *__init default_machine_specific_memory_setup(void)
{
char *who = "BIOS-e820";
u32 new_nr;
/*
* Try to copy the BIOS-supplied E820-map.
*
* Otherwise fake a memory map; one section from 0k->640k,
* the next section from 1mb->appropriate_mem_k
*/
new_nr = boot_params.e820_entries;
sanitize_e820_map(boot_params.e820_map,
ARRAY_SIZE(boot_params.e820_map),
&new_nr);
boot_params.e820_entries = new_nr;
if (append_e820_map(boot_params.e820_map, boot_params.e820_entries)
< 0) {
u64 mem_size;
/* compare results from other methods and take the greater */
if (boot_params.alt_mem_k
< boot_params.screen_info.ext_mem_k) {
mem_size = boot_params.screen_info.ext_mem_k;
who = "BIOS-88";
} else {
mem_size = boot_params.alt_mem_k;
who = "BIOS-e801";
}
e820.nr_map = 0;
e820_add_region(0, LOWMEMSIZE(), E820_RAM);
e820_add_region(HIGH_MEMORY, mem_size << 10, E820_RAM);
}
/* In case someone cares... */
return who;
}
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Comment 5:First, init_mm is a struct_mm type, define in init-mm.c, which belongs to process 0.
struct mm_struct init_mm = {
.mm_rb = RB_ROOT,
.pgd = swapper_pg_dir,
.mm_users = ATOMIC_INIT(2),
.mm_count = ATOMIC_INIT(1),
.mmap_sem = __RWSEM_INITIALIZER(init_mm.mmap_sem),
.page_table_lock = __SPIN_LOCK_UNLOCKED(init_mm.page_table_lock),
.mmlist = LIST_HEAD_INIT(init_mm.mmlist),
.cpu_vm_mask = CPU_MASK_ALL,
};
|
Second, _text, _textd, _datad represent kernel code segment and data segment.
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