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Code Issues 1 Releases Wiki Activity

Add JANET_MARSH_UNSAFE flag.

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This allows unmarshal to optional marshal raw
pointers and cfunctions and send them across threads.
This flag is only exposed in the C API as it is very easy
to misuse and cause segfaults.
This commit is contained in:
Calvin Rose 2020-04-19 10:55:00 -05:00
parent 122c77dbf6
commit 5054eb4276
3 changed files with 60 additions and 4 deletions
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58
src/core/marsh.c
View File

@ -61,7 +61,9 @@ enum {
LB_ABSTRACT, /* 217 */
LB_REFERENCE, /* 218 */
LB_FUNCENV_REF, /* 219 */
LB_FUNCDEF_REF /* 220 */
LB_FUNCDEF_REF, /* 220 */
LB_UNSAFE_CFUNCTION, /* 221 */
LB_UNSAFE_POINTER /* 222 */
} LeadBytes;
/* Helper to look inside an entry in an environment */
@ -563,9 +565,25 @@ static void marshal_one(MarshalState *st, Janet x, int flags) {
marshal_one_fiber(st, janet_unwrap_fiber(x), flags + 1);
return;
}
case JANET_CFUNCTION: {
if (!(flags & JANET_MARSHAL_UNSAFE)) goto no_registry;
MARK_SEEN();
pushbyte(st, LB_UNSAFE_CFUNCTION);
JanetCFunction cfn = janet_unwrap_cfunction(x);
pushbytes(st, (uint8_t *) &cfn, sizeof(JanetCFunction));
return;
}
case JANET_POINTER: {
if (!(flags & JANET_MARSHAL_UNSAFE)) goto no_registry;
MARK_SEEN();
pushbyte(st, LB_UNSAFE_POINTER);
void *ptr = janet_unwrap_pointer(x);
pushbytes(st, (uint8_t *) &ptr, sizeof(void *));
return;
}
no_registry:
default: {
janet_panicf("no registry value and cannot marshal %p", x);
return;
}
}
#undef MARK_SEEN
@ -1293,6 +1311,42 @@ static const uint8_t *unmarshal_one(
}
return data;
}
case LB_UNSAFE_POINTER: {
MARSH_EOS(st, data + sizeof(void *));
data++;
if (!(flags & JANET_MARSHAL_UNSAFE)) {
janet_panicf("unsafe flag not given, "
"will not unmarshal raw pointer at index %d",
(int)(data - st->start));
}
union {
void *ptr;
uint8_t bytes[sizeof(void *)];
} u;
memcpy(u.bytes, data, sizeof(void *));
data += sizeof(void *);
*out = janet_wrap_pointer(u.ptr);
janet_v_push(st->lookup, *out);
return data;
}
case LB_UNSAFE_CFUNCTION: {
MARSH_EOS(st, data + sizeof(JanetCFunction));
data++;
if (!(flags & JANET_MARSHAL_UNSAFE)) {
janet_panicf("unsafe flag not given, "
"will not unmarshal function pointer at index %d",
(int)(data - st->start));
}
union {
JanetCFunction ptr;
uint8_t bytes[sizeof(JanetCFunction)];
} u;
memcpy(u.bytes, data, sizeof(JanetCFunction));
data += sizeof(JanetCFunction);
*out = janet_wrap_cfunction(u.ptr);
janet_v_push(st->lookup, *out);
return data;
}
default: {
janet_panicf("unknown byte %x at index %d",
*data,

4
src/core/thread.c
View File

@ -329,7 +329,7 @@ int janet_thread_send(JanetThread *thread, Janet msg, double timeout) {
msgbuf->count = 0;
/* Start panic zone */
janet_marshal(msgbuf, msg, thread->encode, 0);
janet_marshal(msgbuf, msg, thread->encode, JANET_MARSHAL_UNSAFE);
/* End panic zone */
mailbox->messageNext = (mailbox->messageNext + 1) % mailbox->messageCapacity;
@ -379,7 +379,7 @@ int janet_thread_receive(Janet *msg_out, double timeout) {
const uint8_t *nextItem = NULL;
Janet item = janet_unmarshal(
msgbuf->data, msgbuf->count,
0, janet_thread_get_decode(), &nextItem);
JANET_MARSHAL_UNSAFE, janet_thread_get_decode(), &nextItem);
*msg_out = item;
/* Cleanup */

2
src/include/janet.h
View File

@ -1310,6 +1310,8 @@ typedef JanetBuildConfig(*JanetModconf)(void);
JANET_API JanetModule janet_native(const char *name, JanetString *error);
/* Marshaling */
#define JANET_MARSHAL_UNSAFE 0x20000
JANET_API void janet_marshal(
JanetBuffer *buf,
Janet x,