On Wed, Aug 17, 2016 at 04:59:04PM +0200, Ard Biesheuvel wrote: > Instead of pessimistically copying at least 64 bytes from the VM stack > to the native stack, and popping off the register arguments again > before doing the native call, try to avoid touching the stack completely > if the VM stack frame is < 64 bytes. Also, if the stack frame does exceed
Should this say "does not"? > 64 bytes, there is no need to copy the first 64 bytes, since we are passing > those in registers anyway. > > Contributed-under: TianoCore Contribution Agreement 1.0 > Signed-off-by: Ard Biesheuvel <ard.biesheu...@linaro.org> > --- > MdeModulePkg/Universal/EbcDxe/AArch64/EbcLowLevel.S | 73 +++++++++++++++----- > 1 file changed, 55 insertions(+), 18 deletions(-) > > diff --git a/MdeModulePkg/Universal/EbcDxe/AArch64/EbcLowLevel.S > b/MdeModulePkg/Universal/EbcDxe/AArch64/EbcLowLevel.S > index cb7a70b5a4f8..d95713e82b0f 100644 > --- a/MdeModulePkg/Universal/EbcDxe/AArch64/EbcLowLevel.S > +++ b/MdeModulePkg/Universal/EbcDxe/AArch64/EbcLowLevel.S > @@ -35,30 +35,67 @@ 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 > + // > + // 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 > > - bl CopyMem // Sp, NewStackPointer, Length > + adr x0, 0f > + sub x0, x0, x3, lsr #1 > + br x0 > > - ldp x0, x1, [sp], #16 > - ldp x2, x3, [sp], #16 > - ldp x4, x5, [sp], #16 > - ldp x6, x7, [sp], #16 > + ldr x7, [x9, #56] > + ldr x6, [x9, #48] > + ldr x5, [x9, #40] > + ldr x4, [x9, #32] > + ldr x3, [x9, #24] > + ldr x2, [x9, #16] > + ldr x1, [x9, #8] > + ldr x0, [x9] Why not keep using ldp, but with x9? > > - blr x19 > +0: br x8 > > - 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 > -- > 2.7.4 > _______________________________________________ edk2-devel mailing list edk2-devel@lists.01.org https://lists.01.org/mailman/listinfo/edk2-devel
