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Diffstat (limited to 'MdePkg/Library/BaseLib/X86Thunk.c')
| -rw-r--r-- | MdePkg/Library/BaseLib/X86Thunk.c | 268 |
1 files changed, 268 insertions, 0 deletions
diff --git a/MdePkg/Library/BaseLib/X86Thunk.c b/MdePkg/Library/BaseLib/X86Thunk.c new file mode 100644 index 000000000000..f0f801ed126b --- /dev/null +++ b/MdePkg/Library/BaseLib/X86Thunk.c @@ -0,0 +1,268 @@ +/** @file + Real Mode Thunk Functions for IA32 and x64. + + Copyright (c) 2006 - 2012, Intel Corporation. All rights reserved.<BR> + This program and the accompanying materials + are licensed and made available under the terms and conditions of the BSD License + which accompanies this distribution. The full text of the license may be found at + http://opensource.org/licenses/bsd-license.php. + + THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, + WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED. + +**/ + + +#include "BaseLibInternals.h" + +extern CONST UINT8 m16Start; +extern CONST UINT16 m16Size; +extern CONST UINT16 mThunk16Attr; +extern CONST UINT16 m16Gdt; +extern CONST UINT16 m16GdtrBase; +extern CONST UINT16 mTransition; + +/** + Invokes 16-bit code in big real mode and returns the updated register set. + + This function transfers control to the 16-bit code specified by CS:EIP using + the stack specified by SS:ESP in RegisterSet. The updated registers are saved + on the real mode stack and the starting address of the save area is returned. + + @param RegisterSet Values of registers before invocation of 16-bit code. + @param Transition The pointer to the transition code under 1MB. + + @return The pointer to a IA32_REGISTER_SET structure containing the updated + register values. + +**/ +IA32_REGISTER_SET * +EFIAPI +InternalAsmThunk16 ( + IN IA32_REGISTER_SET *RegisterSet, + IN OUT VOID *Transition + ); + +/** + Retrieves the properties for 16-bit thunk functions. + + Computes the size of the buffer and stack below 1MB required to use the + AsmPrepareThunk16(), AsmThunk16() and AsmPrepareAndThunk16() functions. This + buffer size is returned in RealModeBufferSize, and the stack size is returned + in ExtraStackSize. If parameters are passed to the 16-bit real mode code, + then the actual minimum stack size is ExtraStackSize plus the maximum number + of bytes that need to be passed to the 16-bit real mode code. + + If RealModeBufferSize is NULL, then ASSERT(). + If ExtraStackSize is NULL, then ASSERT(). + + @param RealModeBufferSize A pointer to the size of the buffer below 1MB + required to use the 16-bit thunk functions. + @param ExtraStackSize A pointer to the extra size of stack below 1MB + that the 16-bit thunk functions require for + temporary storage in the transition to and from + 16-bit real mode. + +**/ +VOID +EFIAPI +AsmGetThunk16Properties ( + OUT UINT32 *RealModeBufferSize, + OUT UINT32 *ExtraStackSize + ) +{ + ASSERT (RealModeBufferSize != NULL); + ASSERT (ExtraStackSize != NULL); + + *RealModeBufferSize = m16Size; + + // + // Extra 4 bytes for return address, and another 4 bytes for mode transition + // + *ExtraStackSize = sizeof (IA32_DWORD_REGS) + 8; +} + +/** + Prepares all structures a code required to use AsmThunk16(). + + Prepares all structures and code required to use AsmThunk16(). + + This interface is limited to be used in either physical mode or virtual modes with paging enabled where the + virtual to physical mappings for ThunkContext.RealModeBuffer is mapped 1:1. + + If ThunkContext is NULL, then ASSERT(). + + @param ThunkContext A pointer to the context structure that describes the + 16-bit real mode code to call. + +**/ +VOID +EFIAPI +AsmPrepareThunk16 ( + IN OUT THUNK_CONTEXT *ThunkContext + ) +{ + IA32_SEGMENT_DESCRIPTOR *RealModeGdt; + + ASSERT (ThunkContext != NULL); + ASSERT ((UINTN)ThunkContext->RealModeBuffer < 0x100000); + ASSERT (ThunkContext->RealModeBufferSize >= m16Size); + ASSERT ((UINTN)ThunkContext->RealModeBuffer + m16Size <= 0x100000); + + CopyMem (ThunkContext->RealModeBuffer, &m16Start, m16Size); + + // + // Point RealModeGdt to the GDT to be used in transition + // + // RealModeGdt[0]: Reserved as NULL descriptor + // RealModeGdt[1]: Code Segment + // RealModeGdt[2]: Data Segment + // RealModeGdt[3]: Call Gate + // + RealModeGdt = (IA32_SEGMENT_DESCRIPTOR*)( + (UINTN)ThunkContext->RealModeBuffer + m16Gdt); + + // + // Update Code & Data Segment Descriptor + // + RealModeGdt[1].Bits.BaseLow = + (UINT32)(UINTN)ThunkContext->RealModeBuffer & ~0xf; + RealModeGdt[1].Bits.BaseMid = + (UINT32)(UINTN)ThunkContext->RealModeBuffer >> 16; + + // + // Update transition code entry point offset + // + *(UINT32*)((UINTN)ThunkContext->RealModeBuffer + mTransition) += + (UINT32)(UINTN)ThunkContext->RealModeBuffer & 0xf; + + // + // Update Segment Limits for both Code and Data Segment Descriptors + // + if ((ThunkContext->ThunkAttributes & THUNK_ATTRIBUTE_BIG_REAL_MODE) == 0) { + // + // Set segment limits to 64KB + // + RealModeGdt[1].Bits.LimitHigh = 0; + RealModeGdt[1].Bits.G = 0; + RealModeGdt[2].Bits.LimitHigh = 0; + RealModeGdt[2].Bits.G = 0; + } + + // + // Update GDTBASE for this thunk context + // + *(VOID**)((UINTN)ThunkContext->RealModeBuffer + m16GdtrBase) = RealModeGdt; + + // + // Update Thunk Attributes + // + *(UINT32*)((UINTN)ThunkContext->RealModeBuffer + mThunk16Attr) = + ThunkContext->ThunkAttributes; +} + +/** + Transfers control to a 16-bit real mode entry point and returns the results. + + Transfers control to a 16-bit real mode entry point and returns the results. + AsmPrepareThunk16() must be called with ThunkContext before this function is used. + This function must be called with interrupts disabled. + + The register state from the RealModeState field of ThunkContext is restored just prior + to calling the 16-bit real mode entry point. This includes the EFLAGS field of RealModeState, + which is used to set the interrupt state when a 16-bit real mode entry point is called. + Control is transferred to the 16-bit real mode entry point specified by the CS and Eip fields of RealModeState. + The stack is initialized to the SS and ESP fields of RealModeState. Any parameters passed to + the 16-bit real mode code must be populated by the caller at SS:ESP prior to calling this function. + The 16-bit real mode entry point is invoked with a 16-bit CALL FAR instruction, + so when accessing stack contents, the 16-bit real mode code must account for the 16-bit segment + and 16-bit offset of the return address that were pushed onto the stack. The 16-bit real mode entry + point must exit with a RETF instruction. The register state is captured into RealModeState immediately + after the RETF instruction is executed. + + If EFLAGS specifies interrupts enabled, or any of the 16-bit real mode code enables interrupts, + or any of the 16-bit real mode code makes a SW interrupt, then the caller is responsible for making sure + the IDT at address 0 is initialized to handle any HW or SW interrupts that may occur while in 16-bit real mode. + + If EFLAGS specifies interrupts enabled, or any of the 16-bit real mode code enables interrupts, + then the caller is responsible for making sure the 8259 PIC is in a state compatible with 16-bit real mode. + This includes the base vectors, the interrupt masks, and the edge/level trigger mode. + + If THUNK_ATTRIBUTE_BIG_REAL_MODE is set in the ThunkAttributes field of ThunkContext, then the user code + is invoked in big real mode. Otherwise, the user code is invoked in 16-bit real mode with 64KB segment limits. + + If neither THUNK_ATTRIBUTE_DISABLE_A20_MASK_INT_15 nor THUNK_ATTRIBUTE_DISABLE_A20_MASK_KBD_CTRL are set in + ThunkAttributes, then it is assumed that the user code did not enable the A20 mask, and no attempt is made to + disable the A20 mask. + + If THUNK_ATTRIBUTE_DISABLE_A20_MASK_INT_15 is set and THUNK_ATTRIBUTE_DISABLE_A20_MASK_KBD_CTRL is clear in + ThunkAttributes, then attempt to use the INT 15 service to disable the A20 mask. If this INT 15 call fails, + then attempt to disable the A20 mask by directly accessing the 8042 keyboard controller I/O ports. + + If THUNK_ATTRIBUTE_DISABLE_A20_MASK_INT_15 is clear and THUNK_ATTRIBUTE_DISABLE_A20_MASK_KBD_CTRL is set in + ThunkAttributes, then attempt to disable the A20 mask by directly accessing the 8042 keyboard controller I/O ports. + + If ThunkContext is NULL, then ASSERT(). + If AsmPrepareThunk16() was not previously called with ThunkContext, then ASSERT(). + If both THUNK_ATTRIBUTE_DISABLE_A20_MASK_INT_15 and THUNK_ATTRIBUTE_DISABLE_A20_MASK_KBD_CTRL are set in + ThunkAttributes, then ASSERT(). + + This interface is limited to be used in either physical mode or virtual modes with paging enabled where the + virtual to physical mappings for ThunkContext.RealModeBuffer is mapped 1:1. + + @param ThunkContext A pointer to the context structure that describes the + 16-bit real mode code to call. + +**/ +VOID +EFIAPI +AsmThunk16 ( + IN OUT THUNK_CONTEXT *ThunkContext + ) +{ + IA32_REGISTER_SET *UpdatedRegs; + + ASSERT (ThunkContext != NULL); + ASSERT ((UINTN)ThunkContext->RealModeBuffer < 0x100000); + ASSERT (ThunkContext->RealModeBufferSize >= m16Size); + ASSERT ((UINTN)ThunkContext->RealModeBuffer + m16Size <= 0x100000); + ASSERT (((ThunkContext->ThunkAttributes & (THUNK_ATTRIBUTE_DISABLE_A20_MASK_INT_15 | THUNK_ATTRIBUTE_DISABLE_A20_MASK_KBD_CTRL)) != \ + (THUNK_ATTRIBUTE_DISABLE_A20_MASK_INT_15 | THUNK_ATTRIBUTE_DISABLE_A20_MASK_KBD_CTRL))); + + UpdatedRegs = InternalAsmThunk16 ( + ThunkContext->RealModeState, + ThunkContext->RealModeBuffer + ); + + CopyMem (ThunkContext->RealModeState, UpdatedRegs, sizeof (*UpdatedRegs)); +} + +/** + Prepares all structures and code for a 16-bit real mode thunk, transfers + control to a 16-bit real mode entry point, and returns the results. + + Prepares all structures and code for a 16-bit real mode thunk, transfers + control to a 16-bit real mode entry point, and returns the results. If the + caller only need to perform a single 16-bit real mode thunk, then this + service should be used. If the caller intends to make more than one 16-bit + real mode thunk, then it is more efficient if AsmPrepareThunk16() is called + once and AsmThunk16() can be called for each 16-bit real mode thunk. + + This interface is limited to be used in either physical mode or virtual modes with paging enabled where the + virtual to physical mappings for ThunkContext.RealModeBuffer is mapped 1:1. + + See AsmPrepareThunk16() and AsmThunk16() for the detailed description and ASSERT() conditions. + + @param ThunkContext A pointer to the context structure that describes the + 16-bit real mode code to call. + +**/ +VOID +EFIAPI +AsmPrepareAndThunk16 ( + IN OUT THUNK_CONTEXT *ThunkContext + ) +{ + AsmPrepareThunk16 (ThunkContext); + AsmThunk16 (ThunkContext); +} |