[PATCH] MdeModulePkg/EbcDxe: add ARM support

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

This is a port of the recently proposed AARCH64 implementation of
the EBC runtime to ARM. It is a proof of concept: it runs
HelloWorld.efi, but it is likely that there are issues with
function argument marshalling that are difficult to solve.
In particular, UINT64 register arguments are passed in even/odd
pairs, which would require padding on the VM stack.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 MdeModulePkg/Universal/EbcDxe/Arm/EbcLowLevel.S | 155 +++++++
 MdeModulePkg/Universal/EbcDxe/Arm/EbcSupport.c  | 467 ++++++++++++++++++++
 2 files changed, 622 insertions(+)

diff --git a/MdeModulePkg/Universal/EbcDxe/Arm/EbcLowLevel.S b/MdeModulePkg/Universal/EbcDxe/Arm/EbcLowLevel.S
new file mode 100644
index 000000000000..cc71fcf355df
--- /dev/null
+++ b/MdeModulePkg/Universal/EbcDxe/Arm/EbcLowLevel.S
@@ -0,0 +1,155 @@
+///** @file
+//
+//  This code provides low level routines that support the Virtual Machine
+//  for option ROMs.
+//
+//  Copyright (c) 2016, Linaro, Ltd. All rights reserved.<BR>
+//  Copyright (c) 2015, The Linux Foundation. All rights reserved.<BR>
+//  Copyright (c) 2007 - 2014, 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.
+//
+//**/
+
+ASM_GLOBAL ASM_PFX(EbcLLCALLEXNative);
+ASM_GLOBAL ASM_PFX(EbcLLEbcInterpret);
+ASM_GLOBAL ASM_PFX(EbcLLExecuteEbcImageEntryPoint);
+
+ASM_GLOBAL ASM_PFX(mEbcInstructionBufferTemplate);
+
+//****************************************************************************
+// EbcLLCALLEX
+//
+// This function is called to execute an EBC CALLEX instruction.
+// This instruction requires that we thunk out to external native
+// code. For ARM, we copy the VM stack into the main stack and then pop
+// the first 4 arguments off according to the ARM Procedure Call Standard
+// On return, we restore the stack pointer to its original location.
+//
+//****************************************************************************
+// UINTN EbcLLCALLEXNative(UINTN FuncAddr, UINTN NewStackPointer, VOID *FramePtr)
+    .type   EbcLLCALLEXNative, %function
+ASM_PFX(EbcLLCALLEXNative):
+    mov     ip, r1                  // Preserve r1
+
+    //
+    // If the EBC stack frame is smaller than or equal to 32 bytes, we know there
+    // are no stacked arguments #5 and beyond that we need to copy to the native
+    // stack. In this case, we can perform a tail call which is much more
+    // efficient, since there is no need to touch the native stack at all.
+    //
+    sub     r3, r2, r1              // Length = NewStackPointer - FramePtr
+    cmp     r3, #32
+    bgt     1f
+
+    adr     r1, 0f
+    sub     r1, r1, r3, lsr #1
+    bx      r1
+
+    ldr     r3, [ip, #12]
+    ldr     r2, [ip, #8]
+    ldr     r1, [ip, #4]
+    ldr     ip, [ip]
+
+0:  eor     r0, r0, ip              // Swap r0 and ip
+    eor     ip, r0, ip
+    eor     r0, r0, ip
+
+    bx      ip
+
+    //
+    // More than 32 bytes: we need to build the full native stack frame and copy
+    // the part of the VM stack exceeding 32 bytes (which may contain stacked
+    // arguments) to the native stack
+    //
+1:  stmdb   sp!, {r4-r6, lr}
+    mov     r4, sp
+    mov     r5, r0
+
+    //
+    // Ensure that the stack pointer remains 8 byte aligned,
+    // even if the size of the VM stack frame is not a multiple of 8
+    //
+    add     r1, r1, #32             // Skip over [potential] reg params
+    tst     r1, #7                  // Multiple of 8?
+    beq     2f
+    ldr     r3, [r2, #-4]!          // No? Then push one word
+    str     r3, [sp, #-8]!          // ... but use two slots
+    b       3f
+
+2:  ldrd    r0, r1, [r2, #-8]!
+    strd    r0, r1, [sp, #-8]!
+3:  cmp     r2, ip
+    bgt     2b
+
+    ldrd    r0, r1, [ip]
+    ldrd    r2, r3, [ip, #8]
+
+    blx     r5
+
+    mov     sp, r4
+    ldmia   sp!, {r4-r6, pc}
+
+//****************************************************************************
+// EbcLLEbcInterpret
+//
+// This function is called by the thunk code to handle an Native to EBC call
+// This can handle up to 16 arguments (1-4 on in r0-r3, 5-16 are on the stack)
+// ip contains the Entry point that will be the first argument when
+// EBCInterpret is called.
+//
+//****************************************************************************
+    .type   EbcLLEbcInterpret, %function
+ASM_PFX(EbcLLEbcInterpret):
+    stmdb   sp!, {r4, lr}
+
+    // push the entry point and the address of args #5 - #16 onto the stack
+    add     r4, sp, #8
+    str     ip, [sp, #-8]!
+    str     r4, [sp, #4]
+
+    // call C-code
+    bl      ASM_PFX(EbcInterpret)
+
+    add     sp, sp, #8
+    ldmia   sp!, {r4, pc}
+
+//****************************************************************************
+// EbcLLExecuteEbcImageEntryPoint
+//
+// This function is called by the thunk code to handle the image entry point
+// x16 contains the Entry point that will be the third argument when
+// ExecuteEbcImageEntryPoint is called.
+//
+//****************************************************************************
+    .thumb
+    .type   EbcLLExecuteEbcImageEntryPoint, %function
+ASM_PFX(EbcLLExecuteEbcImageEntryPoint):
+    mov     r2, ip
+
+    // tail call to C code
+    b       ASM_PFX(ExecuteEbcImageEntryPoint)
+
+//****************************************************************************
+// mEbcInstructionBufferTemplate
+//****************************************************************************
+    .section    ".rodata", "a"
+    .align      2
+    .arm
+ASM_PFX(mEbcInstructionBufferTemplate):
+    ldr     ip, 0f
+    ldr     pc, 1f
+
+    //
+    // Add a magic code here to help the VM recognize the thunk.
+    //
+    .long   0xCA112EBC
+
+0:  .long   0   // EBC_ENTRYPOINT_SIGNATURE
+1:  .long   0   // EBC_LL_EBC_ENTRYPOINT_SIGNATURE
diff --git a/MdeModulePkg/Universal/EbcDxe/Arm/EbcSupport.c b/MdeModulePkg/Universal/EbcDxe/Arm/EbcSupport.c
new file mode 100644
index 000000000000..7ec26f3330e1
--- /dev/null
+++ b/MdeModulePkg/Universal/EbcDxe/Arm/EbcSupport.c
@@ -0,0 +1,467 @@
+/** @file
+  This module contains EBC support routines that are customized based on
+  the target AArch64 processor.
+
+Copyright (c) 2016, Linaro, Ltd. All rights reserved.<BR>
+Copyright (c) 2015, The Linux Foundation. All rights reserved.<BR>
+Copyright (c) 2006 - 2014, 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 "EbcInt.h"
+#include "EbcExecute.h"
+
+//
+// Amount of space that is not used in the stack
+//
+#define STACK_REMAIN_SIZE (1024 * 4)
+
+#pragma pack(1)
+typedef struct {
+  UINT32    Instr[2];
+  UINT32    Magic;
+  UINT32    EbcEntryPoint;
+  UINT32    EbcLlEntryPoint;
+} EBC_INSTRUCTION_BUFFER;
+#pragma pack()
+
+extern CONST EBC_INSTRUCTION_BUFFER       mEbcInstructionBufferTemplate;
+
+/**
+  Begin executing an EBC image.
+  This is used for Ebc Thunk call.
+
+  @return The value returned by the EBC application we're going to run.
+
+**/
+UINT64
+EFIAPI
+EbcLLEbcInterpret (
+  VOID
+  );
+
+/**
+  Begin executing an EBC image.
+  This is used for Ebc image entrypoint.
+
+  @return The value returned by the EBC application we're going to run.
+
+**/
+UINT64
+EFIAPI
+EbcLLExecuteEbcImageEntryPoint (
+  VOID
+  );
+
+/**
+  Pushes a 32 bit unsigned value to the VM stack.
+
+  @param VmPtr  The pointer to current VM context.
+  @param Arg    The value to be pushed.
+
+**/
+VOID
+PushU32 (
+  IN VM_CONTEXT *VmPtr,
+  IN UINT32     Arg
+  )
+{
+  //
+  // Advance the VM stack down, and then copy the argument to the stack.
+  // Hope it's aligned.
+  //
+  VmPtr->Gpr[0] -= sizeof (UINT32);
+  *(UINT32 *)(UINTN)VmPtr->Gpr[0] = Arg;
+}
+
+
+/**
+  Begin executing an EBC image.
+
+  This is a thunk function.
+
+  @param  Arg1                  The 1st argument.
+  @param  Arg2                  The 2nd argument.
+  @param  Arg3                  The 3rd argument.
+  @param  Arg4                  The 4th argument.
+  @param  Arg8                  The 8th argument.
+  @param  EntryPoint            The entrypoint of EBC code.
+  @param  Args5_16[]            Array containing arguments #5 to #16.
+
+  @return The value returned by the EBC application we're going to run.
+
+**/
+UINT64
+EFIAPI
+EbcInterpret (
+  IN UINTN      Arg1,
+  IN UINTN      Arg2,
+  IN UINTN      Arg3,
+  IN UINTN      Arg4,
+  IN UINTN      EntryPoint,
+  IN UINTN      Args5_16[]
+  )
+{
+  //
+  // Create a new VM context on the stack
+  //
+  VM_CONTEXT  VmContext;
+  UINTN       Addr;
+  EFI_STATUS  Status;
+  UINTN       StackIndex;
+
+  //
+  // Get the EBC entry point
+  //
+  Addr = EntryPoint;
+
+  //
+  // Now clear out our context
+  //
+  ZeroMem ((VOID *) &VmContext, sizeof (VM_CONTEXT));
+
+  //
+  // Set the VM instruction pointer to the correct location in memory.
+  //
+  VmContext.Ip = (VMIP) Addr;
+
+  //
+  // Initialize the stack pointer for the EBC. Get the current system stack
+  // pointer and adjust it down by the max needed for the interpreter.
+  //
+
+  //
+  // Adjust the VM's stack pointer down.
+  //
+
+  Status = GetEBCStack((EFI_HANDLE)(UINTN)-1, &VmContext.StackPool, &StackIndex);
+  if (EFI_ERROR(Status)) {
+    return Status;
+  }
+  VmContext.StackTop = (UINT8*)VmContext.StackPool + (STACK_REMAIN_SIZE);
+  VmContext.Gpr[0] = (UINT32) ((UINT8*)VmContext.StackPool + STACK_POOL_SIZE);
+  VmContext.HighStackBottom = (UINTN) VmContext.Gpr[0];
+  VmContext.Gpr[0] -= sizeof (UINTN);
+
+  //
+  // Align the stack on a natural boundary.
+  //
+  VmContext.Gpr[0] &= ~(VM_REGISTER)(sizeof (UINTN) - 1);
+
+  //
+  // Put a magic value in the stack gap, then adjust down again.
+  //
+  *(UINTN *) (UINTN) (VmContext.Gpr[0]) = (UINTN) VM_STACK_KEY_VALUE;
+  VmContext.StackMagicPtr             = (UINTN *) (UINTN) VmContext.Gpr[0];
+
+  //
+  // The stack upper to LowStackTop is belong to the VM.
+  //
+  VmContext.LowStackTop   = (UINTN) VmContext.Gpr[0];
+
+  //
+  // For the worst case, assume there are 4 arguments passed in registers, store
+  // them to VM's stack.
+  //
+  PushU32 (&VmContext, (UINT32) Args5_16[11]);
+  PushU32 (&VmContext, (UINT32) Args5_16[10]);
+  PushU32 (&VmContext, (UINT32) Args5_16[9]);
+  PushU32 (&VmContext, (UINT32) Args5_16[8]);
+  PushU32 (&VmContext, (UINT32) Args5_16[7]);
+  PushU32 (&VmContext, (UINT32) Args5_16[6]);
+  PushU32 (&VmContext, (UINT32) Args5_16[5]);
+  PushU32 (&VmContext, (UINT32) Args5_16[4]);
+  PushU32 (&VmContext, (UINT32) Args5_16[3]);
+  PushU32 (&VmContext, (UINT32) Args5_16[2]);
+  PushU32 (&VmContext, (UINT32) Args5_16[1]);
+  PushU32 (&VmContext, (UINT32) Args5_16[0]);
+  PushU32 (&VmContext, (UINT32) Arg4);
+  PushU32 (&VmContext, (UINT32) Arg3);
+  PushU32 (&VmContext, (UINT32) Arg2);
+  PushU32 (&VmContext, (UINT32) Arg1);
+
+  //
+  // Interpreter assumes 64-bit return address is pushed on the stack.
+  // AArch64 does not do this so pad the stack accordingly.
+  //
+  PushU32 (&VmContext, 0x0UL);
+  PushU32 (&VmContext, 0x0UL);
+  PushU32 (&VmContext, 0x12345678UL);
+  PushU32 (&VmContext, 0x87654321UL);
+
+  //
+  // For AArch64, this is where we say our return address is
+  //
+  VmContext.StackRetAddr  = (UINT64) VmContext.Gpr[0];
+
+  //
+  // We need to keep track of where the EBC stack starts. This way, if the EBC
+  // accesses any stack variables above its initial stack setting, then we know
+  // it's accessing variables passed into it, which means the data is on the
+  // VM's stack.
+  // When we're called, on the stack (high to low) we have the parameters, the
+  // return address, then the saved ebp. Save the pointer to the return address.
+  // EBC code knows that's there, so should look above it for function parameters.
+  // The offset is the size of locals (VMContext + Addr + saved ebp).
+  // Note that the interpreter assumes there is a 16 bytes of return address on
+  // the stack too, so adjust accordingly.
+  //  VmContext.HighStackBottom = (UINTN)(Addr + sizeof (VmContext) + sizeof (Addr));
+  //
+
+  //
+  // Begin executing the EBC code
+  //
+  EbcExecute (&VmContext);
+
+  //
+  // Return the value in R[7] unless there was an error
+  //
+  ReturnEBCStack(StackIndex);
+  return (UINT64) VmContext.Gpr[7];
+}
+
+
+/**
+  Begin executing an EBC image.
+
+  @param  ImageHandle      image handle for the EBC application we're executing
+  @param  SystemTable      standard system table passed into an driver's entry
+                           point
+  @param  EntryPoint       The entrypoint of EBC code.
+
+  @return The value returned by the EBC application we're going to run.
+
+**/
+UINT64
+EFIAPI
+ExecuteEbcImageEntryPoint (
+  IN EFI_HANDLE           ImageHandle,
+  IN EFI_SYSTEM_TABLE     *SystemTable,
+  IN UINTN                EntryPoint
+  )
+{
+  //
+  // Create a new VM context on the stack
+  //
+  VM_CONTEXT  VmContext;
+  UINTN       Addr;
+  EFI_STATUS  Status;
+  UINTN       StackIndex;
+
+  //
+  // Get the EBC entry point
+  //
+  Addr = EntryPoint;
+
+  //
+  // Now clear out our context
+  //
+  ZeroMem ((VOID *) &VmContext, sizeof (VM_CONTEXT));
+
+  //
+  // Save the image handle so we can track the thunks created for this image
+  //
+  VmContext.ImageHandle = ImageHandle;
+  VmContext.SystemTable = SystemTable;
+
+  //
+  // Set the VM instruction pointer to the correct location in memory.
+  //
+  VmContext.Ip = (VMIP) Addr;
+
+  //
+  // Initialize the stack pointer for the EBC. Get the current system stack
+  // pointer and adjust it down by the max needed for the interpreter.
+  //
+
+  //
+  // Allocate stack pool
+  //
+  Status = GetEBCStack(ImageHandle, &VmContext.StackPool, &StackIndex);
+  if (EFI_ERROR(Status)) {
+    return Status;
+  }
+  VmContext.StackTop = (UINT8*)VmContext.StackPool + (STACK_REMAIN_SIZE);
+  VmContext.Gpr[0] = (UINT64)(UINTN) ((UINT8*)VmContext.StackPool + STACK_POOL_SIZE);
+  VmContext.HighStackBottom = (UINTN)VmContext.Gpr[0];
+  VmContext.Gpr[0] -= sizeof (UINTN);
+
+  //
+  // Put a magic value in the stack gap, then adjust down again
+  //
+  *(UINTN *) (UINTN) (VmContext.Gpr[0]) = (UINTN) VM_STACK_KEY_VALUE;
+  VmContext.StackMagicPtr             = (UINTN *) (UINTN) VmContext.Gpr[0];
+
+  //
+  // Align the stack on a natural boundary
+  //  VmContext.Gpr[0] &= ~(sizeof(UINTN) - 1);
+  //
+  VmContext.LowStackTop   = (UINTN) VmContext.Gpr[0];
+  VmContext.Gpr[0] -= sizeof (UINTN);
+  *(UINTN *) (UINTN) (VmContext.Gpr[0]) = (UINTN) SystemTable;
+  VmContext.Gpr[0] -= sizeof (UINTN);
+  *(UINTN *) (UINTN) (VmContext.Gpr[0]) = (UINTN) ImageHandle;
+
+  VmContext.Gpr[0] -= 16;
+  VmContext.StackRetAddr  = (UINT64) VmContext.Gpr[0];
+  //
+  // VM pushes 16-bytes for return address. Simulate that here.
+  //
+
+  //
+  // Begin executing the EBC code
+  //
+  EbcExecute (&VmContext);
+
+  //
+  // Return the value in R[7] unless there was an error
+  //
+  ReturnEBCStack(StackIndex);
+  return (UINT64) VmContext.Gpr[7];
+}
+
+
+/**
+  Create thunks for an EBC image entry point, or an EBC protocol service.
+
+  @param  ImageHandle           Image handle for the EBC image. If not null, then
+                                we're creating a thunk for an image entry point.
+  @param  EbcEntryPoint         Address of the EBC code that the thunk is to call
+  @param  Thunk                 Returned thunk we create here
+  @param  Flags                 Flags indicating options for creating the thunk
+
+  @retval EFI_SUCCESS           The thunk was created successfully.
+  @retval EFI_INVALID_PARAMETER The parameter of EbcEntryPoint is not 16-bit
+                                aligned.
+  @retval EFI_OUT_OF_RESOURCES  There is not enough memory to created the EBC
+                                Thunk.
+  @retval EFI_BUFFER_TOO_SMALL  EBC_THUNK_SIZE is not larger enough.
+
+**/
+EFI_STATUS
+EbcCreateThunks (
+  IN EFI_HANDLE           ImageHandle,
+  IN VOID                 *EbcEntryPoint,
+  OUT VOID                **Thunk,
+  IN  UINT32              Flags
+  )
+{
+  EBC_INSTRUCTION_BUFFER       *InstructionBuffer;
+
+  //
+  // Check alignment of pointer to EBC code
+  //
+  if ((UINT32) (UINTN) EbcEntryPoint & 0x01) {
+    return EFI_INVALID_PARAMETER;
+  }
+
+  InstructionBuffer = AllocatePool (sizeof (EBC_INSTRUCTION_BUFFER));
+  if (InstructionBuffer == NULL) {
+    return EFI_OUT_OF_RESOURCES;
+  }
+
+  //
+  // Give them the address of our buffer we're going to fix up
+  //
+  *Thunk = InstructionBuffer;
+
+  //
+  // Copy whole thunk instruction buffer template
+  //
+  CopyMem (InstructionBuffer, &mEbcInstructionBufferTemplate,
+    sizeof (EBC_INSTRUCTION_BUFFER));
+
+  //
+  // Patch EbcEntryPoint and EbcLLEbcInterpret
+  //
+  InstructionBuffer->EbcEntryPoint = (UINT32)EbcEntryPoint;
+  if ((Flags & FLAG_THUNK_ENTRY_POINT) != 0) {
+    InstructionBuffer->EbcLlEntryPoint = (UINT32)EbcLLExecuteEbcImageEntryPoint;
+  } else {
+    InstructionBuffer->EbcLlEntryPoint = (UINT32)EbcLLEbcInterpret;
+  }
+
+  //
+  // Add the thunk to the list for this image. Do this last since the add
+  // function flushes the cache for us.
+  //
+  EbcAddImageThunk (ImageHandle, InstructionBuffer,
+    sizeof (EBC_INSTRUCTION_BUFFER));
+
+  return EFI_SUCCESS;
+}
+
+
+/**
+  This function is called to execute an EBC CALLEX instruction.
+  The function check the callee's content to see whether it is common native
+  code or a thunk to another piece of EBC code.
+  If the callee is common native code, use EbcLLCAllEXASM to manipulate,
+  otherwise, set the VM->IP to target EBC code directly to avoid another VM
+  be startup which cost time and stack space.
+
+  @param  VmPtr            Pointer to a VM context.
+  @param  FuncAddr         Callee's address
+  @param  NewStackPointer  New stack pointer after the call
+  @param  FramePtr         New frame pointer after the call
+  @param  Size             The size of call instruction
+
+**/
+VOID
+EbcLLCALLEX (
+  IN VM_CONTEXT   *VmPtr,
+  IN UINTN        FuncAddr,
+  IN UINTN        NewStackPointer,
+  IN VOID         *FramePtr,
+  IN UINT8        Size
+  )
+{
+  CONST EBC_INSTRUCTION_BUFFER *InstructionBuffer;
+
+  //
+  // Processor specific code to check whether the callee is a thunk to EBC.
+  //
+  InstructionBuffer = (EBC_INSTRUCTION_BUFFER *)FuncAddr;
+
+  if (CompareMem (InstructionBuffer, &mEbcInstructionBufferTemplate,
+        sizeof(EBC_INSTRUCTION_BUFFER) - 2 * sizeof (UINT32)) == 0) {
+    //
+    // The callee is a thunk to EBC, adjust the stack pointer down 16 bytes and
+    // put our return address and frame pointer on the VM stack.
+    // Then set the VM's IP to new EBC code.
+    //
+    VmPtr->Gpr[0] -= 8;
+    VmWriteMemN (VmPtr, (UINTN) VmPtr->Gpr[0], (UINTN) FramePtr);
+    VmPtr->FramePtr = (VOID *) (UINTN) VmPtr->Gpr[0];
+    VmPtr->Gpr[0] -= 8;
+    VmWriteMem64 (VmPtr, (UINTN) VmPtr->Gpr[0], (UINT64) (UINTN) (VmPtr->Ip + Size));
+
+    VmPtr->Ip = (VMIP) InstructionBuffer->EbcEntryPoint;
+  } else {
+    //
+    // The callee is not a thunk to EBC, call native code,
+    // and get return value.
+    //
+    // Note that we will not be able to distinguish which part of the interval
+    // [NewStackPointer, FramePtr) consists of stacked function arguments for
+    // this call, and which part simply consists of locals in the caller's
+    // stack frame. All we know is that there is an 8 byte gap at the top that
+    // we can ignore.
+    //
+    VmPtr->Gpr[7] = EbcLLCALLEXNative (FuncAddr, NewStackPointer, FramePtr - 8);
+
+    //
+    // Advance the IP.
+    //
+    VmPtr->Ip += Size;
+  }
+}
+
-- 
2.7.4