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[FAST486]

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Fix segment initialization. The cached descriptors must have valid values
during the switch to protected mode.
For some odd reason, GCC makes the FAST486_GDT_ENTRY structure 12 bytes
instead of 8 if there is a bit field with more than 16 bits, so split
the Base field into Base and BaseMid.
Add size checks below important structure declarations.


svn path=/branches/ntvdm/; revision=60825
This commit is contained in:
Aleksandar Andrejevic 2013-11-02 00:47:43 +00:00
parent dcbdbb7d9f
commit d80b788ff4
3 changed files with 24 additions and 3 deletions
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16
include/reactos/libs/fast486/fast486.h
View file

@ -251,10 +251,13 @@ typedef struct _FAST486_SEG_REG
ULONG Base;
} FAST486_SEG_REG, *PFAST486_SEG_REG;
#pragma pack(push, 1)
typedef struct
{
ULONG Limit : 16;
ULONG Base : 24;
ULONG Base : 16;
ULONG BaseMid : 8;
ULONG Accessed : 1;
ULONG ReadWrite : 1;
ULONG DirConf : 1;
@ -270,6 +273,9 @@ typedef struct
ULONG BaseHigh : 8;
} FAST486_GDT_ENTRY, *PFAST486_GDT_ENTRY;
/* Verify the structure size */
C_ASSERT(sizeof(FAST486_GDT_ENTRY) == sizeof(ULONGLONG));
typedef struct
{
ULONG Offset : 16;
@ -283,6 +289,9 @@ typedef struct
ULONG OffsetHigh : 16;
} FAST486_CALL_GATE, *PFAST486_CALL_GATE;
/* Verify the structure size */
C_ASSERT(sizeof(FAST486_CALL_GATE) == sizeof(ULONGLONG));
typedef struct
{
ULONG Offset : 16;
@ -295,6 +304,11 @@ typedef struct
ULONG OffsetHigh : 16;
} FAST486_IDT_ENTRY, *PFAST486_IDT_ENTRY;
/* Verify the structure size */
C_ASSERT(sizeof(FAST486_IDT_ENTRY) == sizeof(ULONGLONG));
#pragma pack(pop)
typedef struct _FAST486_TABLE_REG
{
USHORT Size;

2
lib/fast486/common.inl
View file

@ -260,7 +260,7 @@ Fast486LoadSegment(PFAST486_STATE State,
/* Update the cache entry */
CachedDescriptor->Selector = Selector;
CachedDescriptor->Base = GdtEntry.Base | (GdtEntry.BaseHigh << 24);
CachedDescriptor->Base = GdtEntry.Base | (GdtEntry.BaseMid << 16) | (GdtEntry.BaseHigh << 24);
CachedDescriptor->Limit = GdtEntry.Limit | (GdtEntry.LimitHigh << 16);
CachedDescriptor->Accessed = GdtEntry.Accessed;
CachedDescriptor->ReadWrite = GdtEntry.ReadWrite;

9
lib/fast486/fast486.c
View file

@ -239,13 +239,20 @@ Fast486Reset(PFAST486_STATE State)
/* Initialize segments */
for (i = 0; i < FAST486_NUM_SEG_REGS; i++)
{
/* Set the selector, base and limit, other values don't apply in real mode */
State->SegmentRegs[i].Selector = 0;
State->SegmentRegs[i].Base = 0;
State->SegmentRegs[i].Limit = 0xFFFF;
State->SegmentRegs[i].Present = TRUE;
State->SegmentRegs[i].ReadWrite = TRUE;
State->SegmentRegs[i].Executable = FALSE;
State->SegmentRegs[i].DirConf = FALSE;
State->SegmentRegs[i].SystemType = 1; // Segment descriptor
State->SegmentRegs[i].Dpl = 0;
State->SegmentRegs[i].Size = FALSE; // 16-bit
}
/* Initialize the code segment */
State->SegmentRegs[FAST486_REG_CS].Executable = TRUE;
State->SegmentRegs[FAST486_REG_CS].Selector = 0xF000;
State->SegmentRegs[FAST486_REG_CS].Base = 0xFFFF0000;