diff options
Diffstat (limited to 'MdeModulePkg/Universal/EbcDxe/AArch64/EbcLowLevel.S')
| -rw-r--r-- | MdeModulePkg/Universal/EbcDxe/AArch64/EbcLowLevel.S | 85 |
1 files changed, 65 insertions, 20 deletions
diff --git a/MdeModulePkg/Universal/EbcDxe/AArch64/EbcLowLevel.S b/MdeModulePkg/Universal/EbcDxe/AArch64/EbcLowLevel.S index b4b8531f1a..34794c06a6 100644 --- a/MdeModulePkg/Universal/EbcDxe/AArch64/EbcLowLevel.S +++ b/MdeModulePkg/Universal/EbcDxe/AArch64/EbcLowLevel.S @@ -35,30 +35,75 @@ ASM_GLOBAL ASM_PFX(mEbcInstructionBufferTemplate) //****************************************************************************
// UINTN EbcLLCALLEXNative(UINTN FuncAddr, UINTN NewStackPointer, VOID *FramePtr)
ASM_PFX(EbcLLCALLEXNative):
- stp x19, x20, [sp, #-16]!
- stp x29, x30, [sp, #-16]!
+ mov x8, x0 // Preserve x0
+ mov x9, x1 // Preserve x1
- mov x19, x0
- mov x20, sp
- sub x2, x2, x1 // Length = NewStackPointer-FramePtr
- sub sp, sp, x2
- sub sp, sp, #64 // Make sure there is room for at least 8 args in the new stack
- mov x0, sp
-
- bl CopyMem // Sp, NewStackPointer, Length
-
- ldp x0, x1, [sp], #16
- ldp x2, x3, [sp], #16
- ldp x4, x5, [sp], #16
- ldp x6, x7, [sp], #16
+ //
+ // If the EBC stack frame is smaller than or equal to 64 bytes, we know there
+ // are no stacked arguments #9 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 x3, x2, x1 // Length = NewStackPointer - FramePtr
+ cmp x3, #64
+ b.gt 1f
- blr x19
+ //
+ // While probably harmless in practice, we should not access the VM stack
+ // outside of the interval [NewStackPointer, FramePtr), which means we
+ // should not blindly fill all 8 argument registers with VM stack data.
+ // So instead, calculate how many argument registers we can fill based on
+ // the size of the VM stack frame, and skip the remaining ones.
+ //
+ adr x0, 0f // Take address of 'br' instruction below
+ bic x3, x3, #7 // Ensure correct alignment
+ sub x0, x0, x3, lsr #1 // Subtract 4 bytes for each arg to unstack
+ br x0 // Skip remaining argument registers
+
+ ldr x7, [x9, #56] // Call with 8 arguments
+ ldr x6, [x9, #48] // |
+ ldr x5, [x9, #40] // |
+ ldr x4, [x9, #32] // |
+ ldr x3, [x9, #24] // |
+ ldr x2, [x9, #16] // |
+ ldr x1, [x9, #8] // V
+ ldr x0, [x9] // Call with 1 argument
+
+0: br x8 // Call with no arguments
- mov sp, x20
- ldp x29, x30, [sp], #16
- ldp x19, x20, [sp], #16
+ //
+ // More than 64 bytes: we need to build the full native stack frame and copy
+ // the part of the VM stack exceeding 64 bytes (which may contain stacked
+ // arguments) to the native stack
+ //
+1: stp x29, x30, [sp, #-16]!
+ mov x29, sp
- ret
+ //
+ // Ensure that the stack pointer remains 16 byte aligned,
+ // even if the size of the VM stack frame is not a multiple of 16
+ //
+ add x1, x1, #64 // Skip over [potential] reg params
+ tbz x3, #3, 2f // Multiple of 16?
+ ldr x4, [x2, #-8]! // No? Then push one word
+ str x4, [sp, #-16]! // ... but use two slots
+ b 3f
+
+2: ldp x4, x5, [x2, #-16]!
+ stp x4, x5, [sp, #-16]!
+3: cmp x2, x1
+ b.gt 2b
+
+ ldp x0, x1, [x9]
+ ldp x2, x3, [x9, #16]
+ ldp x4, x5, [x9, #32]
+ ldp x6, x7, [x9, #48]
+
+ blr x8
+
+ mov sp, x29
+ ldp x29, x30, [sp], #16
+ ret
//****************************************************************************
// EbcLLEbcInterpret
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