1280 MB（0x50000000）のメモリにアクセスすると、osイメージの動作が異なる理由

Question

https://github.com/Incarnation-p-lee/excaliburに小さなOSを1つ開発しています。最近、ページを有効にすると、1280 MBのメモリにアクセスすると1つの差分出力が見つかりました。次のコードを仮定してください：

static inline void 
test_paging(void) 
{ 
    uint32 *ptr; 

    // ptr = (void *)0x800000; 
    // *ptr = 0xdeadbeaf; 
    // ptr = (void *)0x4ffffffc; 
    ptr = (void *)0x50000000; 
    *ptr = 0xdeadbeaf; 
} 
[0x00000000] Boot loader magic -> 0x2badb002. 
[0x00000000] In Protect Mode. 
[0x00000000] Paging disabled. 
[0x00000000] OS image start -> 0x00100000 
[0x00000000] OS image end -> 0x00109000 
[0x00000000] Stack base 0x00100fb4. 
[0x00000000] Physical memory lower -> 0000000636 KB. 
[0x00000000] Physical memory upper -> 0000261056 KB. 
[0x00000000] GDT table initialized. 
[0x00000000] IDT table initialized. 
[0x00000000] IRQ timer initialized. 
[0x00000003] Page enabled from 0x00000000 -> 0x0011c004. 
[0x0000000b] Page initialized. 
[0x0000000b] In Protect Mode. 
[0x0000000b] Paging enabled. 
[0x0000000b] Divide by zero at eip -> 0x00101071. 
[0x0000000b] Breakpoint at eip -> 0x00101072. 
[0x0000000b] Divide by zero at eip -> 0x00101074. 
[0x0000000b] Unsupported isq 0000000013. 
Assertion: Unsupported ISR 
fail. 
    at function isr_handler_main 
    in file src/interrupt/isr/isr_handler.c:0000000014 
Enter KERNEL PANIC T.T ... 
? 

しかし、私は0x4ffffffcにアクセスしたいとき、ページフォールトを引き起こしましたか？私のオプションでは、0x4ffffffcと0x50000000の両方がページフォールトを引き起こすはずです。

static inline void 
test_paging(void) 
{ 
    uint32 *ptr; 

    // ptr = (void *)0x800000; 
    // *ptr = 0xdeadbeaf; 
    ptr = (void *)0x4ffffffc; 
    // ptr = (void *)0x50000000; 
    *ptr = 0xdeadbeaf; 
} 
[0x00000000] In Protect Mode. 
[0x00000000] Paging disabled. 
[0x00000000] OS image start -> 0x00100000 
[0x00000000] OS image end -> 0x00109000 
[0x00000000] Stack base 0x00100fb4. 
[0x00000000] Physical memory lower -> 0000000636 KB. 
[0x00000000] Physical memory upper -> 0000261056 KB. 
[0x00000000] GDT table initialized. 
[0x00000000] IDT table initialized. 
[0x00000000] IRQ timer initialized. 
[0x00000003] Page enabled from 0x00000000 -> 0x0011c004. 
[0x00000006] Page initialized. 
[0x00000006] In Protect Mode. 
[0x00000006] Paging enabled. 
[0x00000006] Divide by zero at eip -> 0x00101071. 
[0x00000006] Breakpoint at eip -> 0x00101072. 
[0x00000006] Divide by zero at eip -> 0x00101074. 
Page is not present. 
Page is Read-Only. 
Page Fault at address 0x4ffffffc. 
Assertion: Page Fault fail. 
    at function isr_14_paging_fault_handler 
    in file src/interrupt/isr/isr_handler.c:0000000076 
Enter KERNEL PANIC T.T ... 
? 

関連コードと構造体定義

void 
descriptor_table_gdt_initialize(void) 
{ 
    gdt_reg.limit = sizeof(gdt) - 1; 
    gdt_reg.base = (uint32)&gdt; 

    gdt_entry_set(0, 0, 0, 0, 0); 
    gdt_entry_set(1, CODE_SEG_BASE, CODE_SEG_LMT, CODE_SEG_ACC, CODE_SEG_FLAG); 
    gdt_entry_set(2, DATA_SEG_BASE, DATA_SEG_LMT, DATA_SEG_ACC, DATA_SEG_FLAG); 
    gdt_entry_set(3, 0, USR_CODE_SEG_LMT, USR_CODE_SEG_ACC, USR_CODE_SEG_FLAG); 
    gdt_entry_set(4, 0, USR_DATA_SEG_LMT, USR_DATA_SEG_ACC, USR_DATA_SEG_FLAG); 

    gdt_table_flush((uint32)&gdt_reg); 

    printf_vga_tk("GDT table initialized.\n"); 
} 

static inline void 
gdt_entry_set(uint32 i, uint32 base, uint32 limit, uint16 acc, uint8 flags) 
{ 
    kassert(i < GDT_ENTRY_CNT); 

    gdt[i].base_l = U32_BITS(base, 0, 24); 
    gdt[i].base_h = (uint8)U32_BITS(base, 24, 8); 

    gdt[i].lmt_l = (uint16)U32_BITS(limit, 0, 16); 
    gdt[i].flags.lmt_h = (uint8)U32_BITS(limit, 16, 4); 

    gdt[i].access.acc = (uint8)U32_BIT(acc, ACC_AC_IDX); 
    gdt[i].access.rw = (uint8)U32_BIT(acc, ACC_RW_IDX); 
    gdt[i].access.dc = (uint8)U32_BIT(acc, ACC_DC_IDX); 
    gdt[i].access.ex = (uint8)U32_BIT(acc, ACC_EX_IDX); 
    gdt[i].access.dt = (uint8)U32_BIT(acc, ACC_DT_IDX); 
    gdt[i].access.dpl = (uint8)U32_BITS(acc, ACC_DPL_IDX, ACC_DPL_LEN); 
    gdt[i].access.p = (uint8)U32_BIT(acc, ACC_P_IDX); 

    gdt[i].flags.avl = (uint8)U32_BIT(flags, FLAG_A_IDX); 
    gdt[i].flags.pack = 0; 
    gdt[i].flags.db = (uint8)U32_BIT(flags, FLAG_DB_IDX); 
    gdt[i].flags.g = (uint8)U32_BIT(flags, FLAG_G_IDX); 
} 

#define U32_BIT(x, idx)   ((uint32)(x) >> (idx) & 0x1) 
#define U32_BITS(x, s, l)   (((uint32)(x) >> (s)) & ((0x1 << (l)) - 1)) 

#define CODE_SEG_BASE    0x0 
#define CODE_SEG_LMT    0xffffffff 

#define DATA_SEG_BASE    0x0 
#define DATA_SEG_LMT    0xffffffff 

#define STACK_SEG_BASE   0x300000 
#define STACK_SEG_LMT    0xfffff 

#define USR_CODE_SEG_LMT   0xffffffff 
#define USR_DATA_SEG_LMT   0xffffffff 

static s_gdt_entry_t gdt[GDT_ENTRY_CNT]; 
static s_gdt_register_t gdt_reg; 

extern void gdt_table_flush(uint32); 

[GLOBAL gdt_table_flush] 
gdt_table_flush: 
    mov  eax, [esp + 4] 
    lgdt  [eax] 

    mov  ax, 0x10  ; data segment selector 
    mov  ds, ax 
    mov  es, ax 
    mov  fs, ax 
    mov  gs, ax 
    mov  ss, ax 

    jmp  0x8: .flush ; will change cs register implicitly 
.flush: 
    ret 

/* 
* Global Descriptor Table Register 
* 47       16 15     0 
* +----------------------------+-------------------+ 
* | 32-bit Linear Base Address | 16-bit Table Limit| 
* +----------------------------+-------------------+ 
*/ 
struct gdt_register { 
    uint16 limit; 
    uint32 base; 
} __attribute__((packed)); 

/* 
* Descriptor Attribute 
* 15 14 13 12 11    8 7 6 5 4 3 2 1 0 
* +---+-----+---+-----+----------------+---+-----+----+----+----+----+----+ 
* | G | D/B | 0 | AVL | Seg limit high | P | DPL | DT | EX | DC | RW | AC | 
* +---+-----+---+-----+----------------+---+-----+----+----+----+----+----+ 
*/ 
struct gdt_attribute_access { 
    uint8 acc:1; // Segment has been accessed or not 
    uint8 rw:1; // Read-only or Read/Write 
    uint8 dc:1; // Direction for data segment, 0 grow up, 1 grow down or 
       // Execution for code segment, 0 indicate DPL and more DPL 
       //        1 indicate only the DPL specify 
    uint8 ex:1; // Segment can be executed or not. 
    uint8 dt:1; // Descriptor Type, always 1 for GDT 
    uint8 dpl:2; // Descriptor privilege level, ring 0-3 
    uint8 p:1; // Segment is present or not 
} __attribute__((packed)); 

struct gdt_attribute_flags { 
    uint8 avl:1; 
    uint8 pack:1; 
    uint8 db:1; // Operand size, 0 16-bit 1 32-bit 
    uint8 g:1;  // Granularity which defines the limit unit in byte or 4KB 
    uint8 lmt_h:4; // High 4 bit of limit, bit <16, 19> of limit 
} __attribute__((packed)); 

/* 
* Global Descriptor Table Entry (Global Descriptor) 
* Each represent a segment in GDT. 
* 63   55  51   47  39   15   0 
* +-----------+-------+------------+--------+----------+-----------+ 
* | base high | flags | limit high | access | base low | limit low | 
* +-----------+-------+------------+--------+----------+-----------+ 
* base contains 32-bit 
* limit contains 20-bit 
*/ 
struct gdt_entry { 
    uint16      lmt_l; 
    uint32      base_l:24; 
    struct gdt_attribute_access access; 
    struct gdt_attribute_flags flags; 
    uint8      base_h; 
} __attribute__((packed)); 

Bochsの設定

# configuration file generated by Bochs 
plugin_ctrl: unmapped=1, biosdev=1, speaker=1, extfpuirq=1, parallel=1, serial=1, gameport=1 
config_interface: win32config 
display_library: win32 
memory: host=256, guest=256 
romimage: file="C:\Program Files (x86)\Bochs-2.6.8/BIOS-bochs-latest" 
vgaromimage: file="C:\Program Files (x86)\Bochs-2.6.8/VGABIOS-lgpl-latest" 
boot: floppy 
floppy_bootsig_check: disabled=0 
floppya: type=1_44, 1_44="C:\Users\pli\Desktop\workspace\bochs\floppy.img", status=inserted, write_protected=0 
# no floppyb 
ata0: enabled=1, ioaddr1=0x1f0, ioaddr2=0x3f0, irq=14 
ata0-master: type=none 
ata0-slave: type=none 
ata1: enabled=1, ioaddr1=0x170, ioaddr2=0x370, irq=15 
ata1-master: type=none 
ata1-slave: type=none 
ata2: enabled=0 
ata3: enabled=0 
pci: enabled=1, chipset=i440fx 
vga: extension=vbe, update_freq=5, realtime=1 
cpu: count=1, ips=1000000, model=bx_generic, reset_on_triple_fault=0, cpuid_limit_winnt=0, ignore_bad_msrs=1, mwait_is_nop=0 
cpuid: level=6, stepping=3, model=3, family=6, vendor_string="GenuineIntel", brand_string="    Intel(R) Pentium(R) 4 CPU  " 
cpuid: mmx=1, apic=xapic, simd=sse2, sse4a=0, misaligned_sse=0, sep=1, movbe=0, adx=0 
cpuid: aes=0, sha=0, xsave=0, xsaveopt=0, x86_64=1, 1g_pages=0, pcid=0, fsgsbase=0 
cpuid: smep=0, smap=0, mwait=1, vmx=1 
print_timestamps: enabled=0 
port_e9_hack: enabled=0 
private_colormap: enabled=0 
clock: sync=realtime, time0=local, rtc_sync=0 
# no cmosimage 
# no loader 
log: bochsout.txt 
logprefix: %t%e%d 
debug: action=ignore 
info: action=report 
error: action=report 
panic: action=ask 
keyboard: type=mf, serial_delay=250, paste_delay=100000, user_shortcut=none 
mouse: type=ps2, enabled=0, toggle=ctrl+mbutton 
sound: waveoutdrv=win, waveout=none, waveindrv=win, wavein=none, midioutdrv=win, midiout=none 
speaker: enabled=1, mode=sound 
parport1: enabled=1, file=none 
parport2: enabled=0 
com1: enabled=1, mode=null 
com2: enabled=0 
com3: enabled=0 
com4: enabled=0 

Answer 1

編集：私は非常に申し訳ないアドレスを変換するとき、私はセグメンテーションとページングの秩序を混乱さ..

Answer 2

最後に、この問題の根本原因を発見しました。 zwolに同意すると、gdtテーブルを設定するときのバグです。制限とベースは4KBの設定で設定する必要があります。バイト単位ではありません。そのため、メモリが0x50000000より大きいとGPFがトリガされますが、ページフォルトはトリガされませんでした。