Cheri-research/cheri-cap-lib
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Use Dapeng's algorithm (adapted from his verified verilog) for

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SetAddress.
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jon
2021-02-01 18:42:01 +00:00
parent 6f8e3fa503
commit 6e8df02532
1 changed files with 8 additions and 27 deletions
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35
CHERICC_Fat.bsv
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@@ -2,6 +2,7 @@
* Copyright (c) 2015-2019 Jonathan Woodruff
* Copyright (c) 2017-2021 Alexandre Joannou
* Copyright (c) 2019 Peter Rugg
* Copyright (c) 2021 Dapeng Gao
* All rights reserved.
*
* This software was developed by SRI International and the University of
@@ -648,34 +649,14 @@ endfunction
function VnD#(CapFat) setAddress(CapFat cap, CapAddr address, TempFields tf);
CapFat ret = setCapPointer(cap, address);
Exp e = cap.bounds.exp;
// Calculate what the upper bits of the new address must be if it is to be in
// representable bounds.
// Calculate what the difference in the upper bits of the new and original addresses must be if
// the new address is within representable bounds.
Bool newAddrHi = truncateLSB(ret.addrBits) < tf.repBoundTopBits;
// Shift amount needed to look at only the bits above the mantissa.
Exp toUpperBits = e + fromInteger(valueOf(MW));
CapAddrPlus1 mask = -1 << toUpperBits;
CapAddrPlus1 newAddrDiff =
(signExtend(cap.address)&mask) - (signExtend(address)&mask);
// Assert that the bits above the mantissa are all equal.
Bool inRepBounds = True;
// If the difference between the upper bits of the new address and the
// current address does not match the expected difference, call it outside of
// representable bounds. We construct the "actual" diff assuming that the
// inRepBounds check above succeeded.
Int#(2) diff = ?;
if (newAddrDiff == 0) diff = 0;
else if (newAddrDiff == mask) diff = -1;
else if (newAddrDiff == (mask^(mask<<1))) diff = 1;
else inRepBounds = False;
let t2 = tuple2;
Int#(2) expectedDiff = case (t2(tf.addrHi,newAddrHi))
t2(True, True): return 0;
t2(True, False): return 1;
t2(False, True): return -1;
t2(False, False): return 0;
endcase;
if (diff != expectedDiff) inRepBounds = False;
if (e >= resetExp - 2) inRepBounds = True;
Bit#(TSub#(CapAddrW,MW)) deltaAddrHi = signExtend({1'b0,pack(newAddrHi)} - {1'b0,pack(tf.addrHi)}) << e;
// Calculate the actual difference between the upper bits of the new address and the original address.
Bit#(TSub#(CapAddrW,MW)) mask = -1 << e;
Bit#(TSub#(CapAddrW,MW)) deltaAddrUpper = (truncateLSB(cap.address)&mask) - (truncateLSB(address)&mask);
Bool inRepBounds = deltaAddrHi == deltaAddrUpper;
if (!inRepBounds) ret.isCapability = False;
return VnD {v: inRepBounds, d: ret};
endfunction