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https://github.com/jart/cosmopolitan.git
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[WIP] Get bare metal working outside of an emulator (#609)
You can now run bare metal on bare metal!
* Fix handling of int 0x15 eax = 0xe820 memory map
* Fix some issues in initial page table creation
* hello4.com now works outside emulators
* Ensure area for identity page tables are zeroed first
* Simplify logic for creating page table entries, this partly
reverts 577c0f6226
* Add degenerate MBR partition entry, to ease testing
Co-authored-by: tkchia <tkchia-cosmo@gmx.com>
This commit is contained in:
tkchia
Justine Tunney
parent
c03359c637
commit
116bda997e
3 changed files with 55 additions and 35 deletions
67
ape/ape.S
67
ape/ape.S
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@ -329,7 +329,7 @@ dsknfo: push %bx
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movpp %es,%ds
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xor %si,%si
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mov %si,%es
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mov $0x1510,%si # mman::pc_drive_base_table
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mov $0x1d10,%si # mman::pc_drive_base_table
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xchg %si,%di
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movsw #→ headunloadtime, headloadtime
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movsw #→ shutofftime, bytespersector
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@ -382,11 +382,11 @@ pcread: push %ax
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add $512>>4,%si
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mov %si,%es
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inc %al # ++sector
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cmp 0x151c,%al # mman::pc_drive_last_sector
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cmp 0x1d1c,%al # mman::pc_drive_last_sector
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jbe 2f
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mov $1,%al
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inc %dh # ++head
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cmp 0x1520,%dh # mman::pc_drive_last_head
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cmp 0x1d20,%dh # mman::pc_drive_last_head
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jbe 2f
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xor %dh,%dh
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inc %cx # ++cylinder
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@ -485,19 +485,19 @@ ape.mbrpad:
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ape_disk:
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.stub ape.diskid,quad
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.org 0x1be,0x00
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.macro .partn x
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.stub ape.part\x\().status,byte # 0=absent / 0x80=present
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.stub ape.part\x\().first.head,byte # in low 6 bits
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.stub ape.part\x\().first.cylinder,byte
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.stub ape.part\x\().first.sector,byte
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.stub ape.part\x\().filesystem,byte
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.stub ape.part\x\().last.head,byte
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.stub ape.part\x\().last.cylinder,byte
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.stub ape.part\x\().last.sector,byte
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.stub ape.part\x\().lba,long # c₀*Cₙ + h₀*Hₙ + s₀*Sₙ
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.stub ape.part\x\().sector.count,long # sectors are 512 bytes
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.macro .partn x:req sta h0 s0 c0 fs h9 s9 c9 lba0 nsec
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.stub ape.part\x\().status,byte,\sta # 0=non-boot / 0x80=active
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.stub ape.part\x\().first.head,byte,\h0
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.stub ape.part\x\().first.sector,byte,\s0 # in low 6 bits
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.stub ape.part\x\().first.cylinder,byte,\c0
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.stub ape.part\x\().filesystem,byte,\fs
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.stub ape.part\x\().last.head,byte,\h9
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.stub ape.part\x\().last.sector,byte,\s9
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.stub ape.part\x\().last.cylinder,byte,\c9
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.stub ape.part\x\().lba,long,\lba0 # c₀*Cₙ + h₀*Hₙ + s₀*Sₙ
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.stub ape.part\x\().sector.count,long,\nsec # sectors are 512 bytes
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.endm
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.partn 1
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.partn 1,0x80,0,1,0,0x7f,0xff,0xff,0xff,0,0xffffffff
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.partn 2
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.partn 3
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.partn 4
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@ -1291,27 +1291,38 @@ lcheck: pushf # check for i8086 / i8088 / i80186
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// Gets memory map from BIOS.
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e820: mov $0x0510>>4,%di # mman::e820
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mov %di,%es
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xor %edi,%edi # es:di is destination buffer
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xor %di,%di # es:di is destination buffer
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xor %ebx,%ebx # ebx is an api state tracker
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1: mov $0xE820,%eax # magic
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mov $8+8+4+4,%ecx # sizeof(struct SmapEntry)
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mov $0x534d4150,%edx # magic number
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movl $1,8+8+4/*SmapEntry::acpi3*/(%di) # prefill ACPI attributes;
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# apparently some buggy BIOSes say
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# that they return this field, yet
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# do not fill it correctly
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int $0x15 # ax,bx,cx,dx,di → ax,bx,cx
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jc 9f # cf = unsupported or abuse
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cmp %edx,%eax # more magic means success
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jne 9f
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test %cx,%cx # discard empty results
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jz 5f
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mov 8/*LODWORD(SmapEntry::size)*/(%di),%eax
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or 8+4/*HIDWORD(SmapEntry::size)*/(%di),%eax
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jz 5f
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cmp $8+8+4+1,%cx # discard if ignore flag
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jb 4f
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testb $1/*ignore*/,8+8+4/*SmapEntry::__acpi3*/(%di)
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jnz 5f
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testb $1/*don't ignore*/,8+8+4/*SmapEntry::acpi3*/(%di)
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jz 5f
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4: add $8+8+4+4,%di # keep entry
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5: test %ebx,%ebx # last entry?
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jz 8f
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cmp $0x1000,%di
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cmp $(256-1)*(8+8+4+4),%di
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jb 1b
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8: ret
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8: xor %ax,%ax # add a blank sentinel entry
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mov $(8+8)/2,%cx
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cld
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rep stosw
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ret
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9: mov $REAL(str.e820),%di
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call rldie
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.endfn e820
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@ -1381,9 +1392,16 @@ a20: cli
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// Initializes long mode paging.
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pinit: push %ds
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push %es
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#define SEG 0x79000
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mov $SEG>>4,%ax
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mov %ax,%ds
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mov %ax,%es
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xor %di,%di
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xor %ax,%ax
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mov $(0x7f000-SEG)/2,%cx
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cld
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rep stosw
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movl $0x7d000+PAGE_V+PAGE_RW,0x7e000-SEG # PDPT←PML4T (+)
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movl $0x7c000+PAGE_V+PAGE_RW,0x7e800-SEG # PDPT←PML4T (-)
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movl $0x7b000+PAGE_V+PAGE_RW,0x7d000-SEG # PDT←PDPT (+)
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@ -1392,13 +1410,14 @@ pinit: push %ds
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movl $0x79000+PAGE_V+PAGE_RW,0x7a000-SEG # PD←PDT (-)
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mov $512,%cx # PD±2MB
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mov $PAGE_V+PAGE_RW,%eax
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xor %si,%si
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0: mov %eax,(%si)
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xor %di,%di
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0: stosl
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add $0x1000,%eax
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add $8,%si
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scasl # di += 4
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loop 0b
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mov $0x7e000,%eax # PML4T←CR3
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mov %eax,%cr3
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pop %es
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pop %ds
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ret
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.endfn pinit
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@ -1407,7 +1426,7 @@ pinit: push %ds
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//
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// @see Intel Manual V3A §4.1.2
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golong: cli
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lidt 0x1522 # mman::bad_idt
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lidt 0x1d22 # mman::bad_idt
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mov %cr4,%eax
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or $CR4_PAE|CR4_PGE|CR4_OSFXSR,%eax
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mov %eax,%cr4
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@ -74,6 +74,7 @@ noasan textreal uint64_t *__get_virtual(struct mman *mm, uint64_t *t,
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if (!(*e & PAGE_V)) {
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if (!maketables) return NULL;
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if (!(p = __new_page(mm))) return NULL;
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__clear_page(BANE + p);
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*e = p | PAGE_V | PAGE_RW;
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}
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t = (uint64_t *)(BANE + (*e & PAGE_TA));
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@ -117,7 +118,7 @@ static noasan textreal void __invert_memory(struct mman *mm, uint64_t *pml4t) {
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uint64_t i, j, *m, p, pe;
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for (i = 0; i < mm->e820n; ++i) {
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for (p = mm->e820[i].addr, pe = mm->e820[i].addr + mm->e820[i].size;
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p + 0x200000 < pe; p += 4096) {
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p != pe + 0x200000; p += 4096) {
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m = __get_virtual(mm, pml4t, BANE + p, true);
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if (m && !(*m & PAGE_V)) {
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*m = p | PAGE_V | PAGE_RW;
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@ -150,7 +151,7 @@ noasan textreal void __map_phdrs(struct mman *mm, uint64_t *pml4t, uint64_t b) {
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v = b + p->p_offset + i;
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m = MAX(m, v);
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} else {
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v = __clear_page(__new_page(mm));
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v = __clear_page(BANE + __new_page(mm));
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}
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*__get_virtual(mm, pml4t, p->p_vaddr + i, true) = (v & PAGE_TA) | f;
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}
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@ -7,16 +7,16 @@ COSMOPOLITAN_C_START_
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struct mman {
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int64_t pdp; /* 0x0500 */
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int32_t pdpi; /* 0x0508 */
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int32_t e820n; /* 0x050a */
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int32_t e820n; /* 0x050c */
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struct SmapEntry e820[256]; /* 0x0510 */
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char pc_drive_base_table[11]; /* 0x1510 */
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unsigned char pc_drive_type; /* 0x151b */
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unsigned char pc_drive_last_sector; /* 0x151c */
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unsigned short pc_drive_last_cylinder; /* 0x151d */
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unsigned char pc_drives_attached; /* 0x151f */
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unsigned char pc_drive_last_head; /* 0x1520 */
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unsigned char pc_drive; /* 0x1521 */
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char bad_idt[6]; /* 0x1522 */
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char pc_drive_base_table[11]; /* 0x1d10 */
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unsigned char pc_drive_type; /* 0x1d1b */
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unsigned char pc_drive_last_sector; /* 0x1d1c */
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unsigned short pc_drive_last_cylinder; /* 0x1d1d */
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unsigned char pc_drives_attached; /* 0x1d1f */
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unsigned char pc_drive_last_head; /* 0x1d20 */
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unsigned char pc_drive; /* 0x1d21 */
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char bad_idt[6]; /* 0x1d22 */
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};
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COSMOPOLITAN_C_END_
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