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authorbenjaminion <ben@edginet.org>2017-07-12 04:22:38 +0800
committerbenjaminion <ben@edginet.org>2017-07-12 04:22:38 +0800
commit3bc935d932da3d7e8ff21bb3057276338c4ad497 (patch)
tree36bd8668c7908189707690942a3e1806a3c0c113
parent0b17ff1bdde6a56d3c9b48e8c40da7ad4e9a43f5 (diff)
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LLL: rewrite alloc to avoid issues with edge cases.
-rw-r--r--liblll/CodeFragment.cpp28
-rw-r--r--liblll/CompilerState.cpp2
-rw-r--r--test/liblll/EndToEndTest.cpp55
3 files changed, 79 insertions, 6 deletions
diff --git a/liblll/CodeFragment.cpp b/liblll/CodeFragment.cpp
index 56c1e26a..f637dfb1 100644
--- a/liblll/CodeFragment.cpp
+++ b/liblll/CodeFragment.cpp
@@ -523,14 +523,30 @@ void CodeFragment::constructOperation(sp::utree const& _t, CompilerState& _s)
requireSize(1);
requireDeposit(0, 1);
- m_asm.append(Instruction::MSIZE);
- m_asm.append(u256(0));
+ // (alloc N):
+ // - Evaluates to (msize) before the allocation - the start of the allocated memory
+ // - Does not allocate memory when N is zero
+ // - Size of memory allocated is N bytes rounded up to a multiple of 32
+ // - Uses MLOAD to expand MSIZE to avoid modifying memory.
+
+ auto end = m_asm.newTag();
+ m_asm.append(Instruction::MSIZE); // Result will be original top of memory
+ m_asm.append(code[0].m_asm, 1); // The alloc argument N
+ m_asm.append(Instruction::DUP1);
+ m_asm.append(Instruction::ISZERO);// (alloc 0) does not change MSIZE
+ m_asm.appendJumpI(end);
m_asm.append(u256(1));
- m_asm.append(code[0].m_asm, 1);
- m_asm.append(Instruction::MSIZE);
+ m_asm.append(Instruction::DUP2); // Copy N
+ m_asm.append(Instruction::SUB); // N-1
+ m_asm.append(u256(0x1f)); // Bit mask
+ m_asm.append(Instruction::NOT); // Invert
+ m_asm.append(Instruction::AND); // Align N-1 on 32 byte boundary
+ m_asm.append(Instruction::MSIZE); // MSIZE is cheap
m_asm.append(Instruction::ADD);
- m_asm.append(Instruction::SUB);
- m_asm.append(Instruction::MSTORE8);
+ m_asm.append(Instruction::MLOAD); // Updates MSIZE
+ m_asm.append(Instruction::POP); // Discard the result of the MLOAD
+ m_asm.append(end);
+ m_asm.append(Instruction::POP); // Discard duplicate N
_s.usedAlloc = true;
}
diff --git a/liblll/CompilerState.cpp b/liblll/CompilerState.cpp
index 5d38bb8c..9701e16b 100644
--- a/liblll/CompilerState.cpp
+++ b/liblll/CompilerState.cpp
@@ -46,6 +46,8 @@ void CompilerState::populateStandard()
{
static const string s = "{"
"(def 'panic () (asm INVALID))"
+ // Alternative macro version of alloc, which is currently implemented in the parser
+ // "(def 'alloc (n) (raw (msize) (when n (pop (mload (+ (msize) (& (- n 1) (~ 0x1f))))))))"
"(def 'allgas (- (gas) 21))"
"(def 'send (to value) (call allgas to value 0 0 0 0))"
"(def 'send (gaslimit to value) (call gaslimit to value 0 0 0 0))"
diff --git a/test/liblll/EndToEndTest.cpp b/test/liblll/EndToEndTest.cpp
index 7f4dd91a..4e896fd0 100644
--- a/test/liblll/EndToEndTest.cpp
+++ b/test/liblll/EndToEndTest.cpp
@@ -467,6 +467,61 @@ BOOST_AUTO_TEST_CASE(send_three_args)
BOOST_CHECK(balanceAt(Address(0xdead)) == 42);
}
+// Regression test for edge case that previously failed
+BOOST_AUTO_TEST_CASE(alloc_zero)
+{
+ char const* sourceCode = R"(
+ (returnlll
+ (seq
+ (mstore 0x00 (~ 0))
+ (alloc 0)
+ (return 0x00 0x20)))
+ )";
+ compileAndRun(sourceCode);
+ BOOST_CHECK(callFallback() == encodeArgs(u256(-1)));
+}
+
+BOOST_AUTO_TEST_CASE(alloc_size)
+{
+ char const* sourceCode = R"(
+ (returnlll
+ (seq
+ (mstore 0x00 0) ; reserve space for the result of the alloc
+ (mstore 0x00 (alloc (calldataload 0x04)))
+ (return (- (msize) (mload 0x00)))))
+ )";
+ compileAndRun(sourceCode);
+ BOOST_CHECK(callContractFunction("test()", 0) == encodeArgs(u256(0)));
+ BOOST_CHECK(callContractFunction("test()", 1) == encodeArgs(u256(32)));
+ BOOST_CHECK(callContractFunction("test()", 32) == encodeArgs(u256(32)));
+ BOOST_CHECK(callContractFunction("test()", 33) == encodeArgs(u256(64)));
+}
+
+BOOST_AUTO_TEST_CASE(alloc_start)
+{
+ char const* sourceCode = R"(
+ (returnlll
+ (seq
+ (mstore 0x40 0) ; Set initial MSIZE to 0x60
+ (return (alloc 1))))
+ )";
+ compileAndRun(sourceCode);
+ BOOST_CHECK(callFallback() == encodeArgs(96));
+}
+
+BOOST_AUTO_TEST_CASE(alloc_with_variable)
+{
+ char const* sourceCode = R"(
+ (returnlll
+ (seq
+ (set 'x (alloc 1))
+ (mstore8 @x 42) ; ASCII '*'
+ (return @x 0x20)))
+ )";
+ compileAndRun(sourceCode);
+ BOOST_CHECK(callFallback() == encodeArgs("*"));
+}
+
BOOST_AUTO_TEST_CASE(msg_six_args)
{
char const* sourceCode = R"(