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Bare metal: fix handling of int 0x15 eax = 0xe820 memory map

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This commit is contained in:
tkchia 2022-09-11 09:02:33 +00:00
parent 3de35e196c
commit 816a71bfa0
2 changed files with 28 additions and 17 deletions
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29
ape/ape.S
View file

@ -329,7 +329,7 @@ dsknfo: push %bx
movpp %es,%ds
xor %si,%si
mov %si,%es
mov $0x1510,%si # mman::pc_drive_base_table
mov $0x1d10,%si # mman::pc_drive_base_table
xchg %si,%di
movsw #→ headunloadtime, headloadtime
movsw #→ shutofftime, bytespersector
@ -382,11 +382,11 @@ pcread: push %ax
add $512>>4,%si
mov %si,%es
inc %al # ++sector
cmp 0x151c,%al # mman::pc_drive_last_sector
cmp 0x1d1c,%al # mman::pc_drive_last_sector
jbe 2f
mov $1,%al
inc %dh # ++head
cmp 0x1520,%dh # mman::pc_drive_last_head
cmp 0x1d20,%dh # mman::pc_drive_last_head
jbe 2f
xor %dh,%dh
inc %cx # ++cylinder
@ -1291,27 +1291,38 @@ lcheck: pushf # check for i8086 / i8088 / i80186
// Gets memory map from BIOS.
e820: mov $0x0510>>4,%di # mman::e820
mov %di,%es
xor %edi,%edi # es:di is destination buffer
xor %di,%di # es:di is destination buffer
xor %ebx,%ebx # ebx is an api state tracker
1: mov $0xE820,%eax # magic
mov $8+8+4+4,%ecx # sizeof(struct SmapEntry)
mov $0x534d4150,%edx # magic number
movl $1,8+8+4/*SmapEntry::acpi3*/(%di) # prefill ACPI attributes;
# apparently some buggy BIOSes say
# that they return this field, yet
# do not fill it correctly
int $0x15 # ax,bx,cx,dx,di → ax,bx,cx
jc 9f # cf = unsupported or abuse
cmp %edx,%eax # more magic means success
jne 9f
test %cx,%cx # discard empty results
jz 5f
mov 8/*LODWORD(SmapEntry::size)*/(%di),%eax
or 8+4/*HIDWORD(SmapEntry::size)*/(%di),%eax
jz 5f
cmp $8+8+4+1,%cx # discard if ignore flag
jb 4f
testb $1/*ignore*/,8+8+4/*SmapEntry::__acpi3*/(%di)
jnz 5f
testb $1/*don't ignore*/,8+8+4/*SmapEntry::acpi3*/(%di)
jz 5f
4: add $8+8+4+4,%di # keep entry
5: test %ebx,%ebx # last entry?
jz 8f
cmp $0x1000,%di
cmp $(256-1)*(8+8+4+4),%di
jb 1b
8: ret
8: xor %ax,%ax # add a blank sentinel entry
mov $(8+8)/2,%cx
cld
rep stosw
ret
9: mov $REAL(str.e820),%di
call rldie
.endfn e820
@ -1407,7 +1418,7 @@ pinit: push %ds
//
// @see Intel Manual V3A §4.1.2
golong: cli
lidt 0x1522 # mman::bad_idt
lidt 0x1d22 # mman::bad_idt
mov %cr4,%eax
or $CR4_PAE|CR4_PGE|CR4_OSFXSR,%eax
mov %eax,%cr4

16
libc/runtime/mman.internal.h
View file

@ -9,14 +9,14 @@ struct mman {
int32_t pdpi; /* 0x0508 */
int32_t e820n; /* 0x050a */
struct SmapEntry e820[256]; /* 0x0510 */
char pc_drive_base_table[11]; /* 0x1510 */
unsigned char pc_drive_type; /* 0x151b */
unsigned char pc_drive_last_sector; /* 0x151c */
unsigned short pc_drive_last_cylinder; /* 0x151d */
unsigned char pc_drives_attached; /* 0x151f */
unsigned char pc_drive_last_head; /* 0x1520 */
unsigned char pc_drive; /* 0x1521 */
char bad_idt[6]; /* 0x1522 */
char pc_drive_base_table[11]; /* 0x1d10 */
unsigned char pc_drive_type; /* 0x1d1b */
unsigned char pc_drive_last_sector; /* 0x1d1c */
unsigned short pc_drive_last_cylinder; /* 0x1d1d */
unsigned char pc_drives_attached; /* 0x1d1f */
unsigned char pc_drive_last_head; /* 0x1d20 */
unsigned char pc_drive; /* 0x1d21 */
char bad_idt[6]; /* 0x1d22 */
};
COSMOPOLITAN_C_END_