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java: properly implement code_copy_fn #545

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axic merged 2 commits into from
Oct 14, 2020
Merged

java: properly implement code_copy_fn #545

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de80e27
java: ensure direct buffer is returned via HostContext
axic Oct 14, 2020
6659e42
java: properly implement code_copy_fn
axic Sep 30, 2020
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28 changes: 18 additions & 10 deletions bindings/java/c/host.c
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Original file line number Diff line number Diff line change
Expand Up @@ -229,15 +229,19 @@ static evmc_bytes32 get_code_hash_fn(struct evmc_host_context* context, const ev
return result;
}

static inline size_t min(size_t a, size_t b)
{
return (a > b) ? b : a;
}

static size_t copy_code_fn(struct evmc_host_context* context,
const evmc_address* address,
size_t code_offset,
uint8_t* buffer_data,
size_t buffer_size)
{
(void)buffer_size; // FIXME: buffer_size suspiciously unused.
const char java_method_name[] = "copy_code";
const char java_method_signature[] = "(I[BI)Ljava/nio/ByteBuffer;";
const char java_method_signature[] = "(I[B)Ljava/nio/ByteBuffer;";

assert(context != NULL);
JNIEnv* jenv = attach();
Expand All @@ -253,23 +257,27 @@ static size_t copy_code_fn(struct evmc_host_context* context,

// set java method params
jbyteArray jaddress = CopyDataToJava(jenv, address, sizeof(struct evmc_address));
jint jcode_offset = (jint)code_offset;

// call java method
jobject jresult = (*jenv)->CallStaticObjectMethod(jenv, host_class, method, context->index,
jaddress, jcode_offset);
jobject jresult =
(*jenv)->CallStaticObjectMethod(jenv, host_class, method, context->index, jaddress);
assert(jresult != NULL);

// copy jresult back to buffer_data
buffer_data = (uint8_t*)(*jenv)->GetDirectBufferAddress(jenv, jresult);
(void)buffer_data;
assert(buffer_data != NULL);
size_t code_size;
uint8_t* code = GetDirectBuffer(jenv, jresult, &code_size);

size_t result = get_code_size_fn(context, address) - code_offset;
size_t length = 0;
if (code_offset < code_size)
{
length = min(buffer_size, code_size - code_offset);
if (length > 0)
memcpy(buffer_data, code + code_offset, length);
}

(*jenv)->ReleaseByteArrayElements(jenv, jaddress, (jbyte*)address, 0);

return result;
return length;
}

static void selfdestruct_fn(struct evmc_host_context* context,
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30 changes: 15 additions & 15 deletions bindings/java/java/src/main/java/org/ethereum/evmc/Host.java
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,13 @@
* <p>The set of all callback functions expected by VM instances.
*/
final class Host {
static private ByteBuffer ensureDirectBuffer(ByteBuffer input) {
// Reallocate if needed.
if (!input.isDirect())
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@chfast chfast Oct 14, 2020

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No idea what it does. Is this even tested?

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@axic axic Oct 14, 2020 •
edited
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Not all of them are, but get/set_storage is. This helper enforces that the ByteBuffer is in a format ("direct buffer") which can be queried from JNI (e.g. the GetDirectBuffer helper in C won't assert). The tests always use "direct buffer" though so we never seen an assert.

return ByteBuffer.allocateDirect(input.remaining()).put(input);
return input;
}

/** Check account existence callback function. */
static boolean account_exists(int context_index, byte[] address) {
HostContext context =
Expand All @@ -31,7 +38,7 @@ static ByteBuffer get_storage(int context_index, byte[] address, byte[] key) {
requireNonNull(
getContext(context_index),
"HostContext does not exist for context_index: " + context_index);
return context.getStorage(address, key);
return ensureDirectBuffer(context.getStorage(address, key));
}

/** Set storage callback function. */
Expand All @@ -48,7 +55,7 @@ static ByteBuffer get_balance(int context_index, byte[] address) {
requireNonNull(
getContext(context_index),
"HostContext does not exist for context_index: " + context_index);
return context.getBalance(address);
return ensureDirectBuffer(context.getBalance(address));
}

/** Get code size callback function. */
Expand All @@ -66,23 +73,16 @@ static ByteBuffer get_code_hash(int context_index, byte[] address) {
requireNonNull(
getContext(context_index),
"HostContext does not exist for context_index: " + context_index);
return context.getCodeHash(address);
return ensureDirectBuffer(context.getCodeHash(address));
}

/** Copy code callback function. */
static ByteBuffer copy_code(int context_index, byte[] address, int code_offset) {
static ByteBuffer copy_code(int context_index, byte[] address) {
HostContext context =
requireNonNull(
getContext(context_index),
"HostContext does not exist for context_index: " + context_index);
byte[] code = context.getCode(address).array();

if (code != null && code_offset > 0 && code_offset < code.length) {
int length = code.length - code_offset;
return ByteBuffer.allocateDirect(length).put(code, code_offset, length);
}

return ByteBuffer.allocateDirect(0);
return ensureDirectBuffer(context.getCode(address));
}

/** Selfdestruct callback function. */
Expand All @@ -100,7 +100,7 @@ static ByteBuffer call(int context_index, ByteBuffer msg) {
requireNonNull(
getContext(context_index),
"HostContext does not exist for context_index: " + context_index);
return context.call(msg);
return ensureDirectBuffer(context.call(msg));
}

/** Get transaction context callback function. */
Expand All @@ -109,7 +109,7 @@ static ByteBuffer get_tx_context(int context_index) {
requireNonNull(
getContext(context_index),
"HostContext does not exist for context_index: " + context_index);
return context.getTxContext();
return ensureDirectBuffer(context.getTxContext());
}

/** Get block hash callback function. */
Expand All @@ -118,7 +118,7 @@ static ByteBuffer get_block_hash_fn(int context_index, long number) {
requireNonNull(
getContext(context_index),
"HostContext does not exist for context_index: " + context_index);
return context.getBlockHash(number);
return ensureDirectBuffer(context.getBlockHash(number));
}

/** Emit log callback function. */
Expand Down