Subzero. WASM. Additional progress.

runtime/wasm-runtime.c

+//===- subzero/runtime/wasm-runtime.c - Subzero WASM runtime source -------===//
+//
+//                        The Subzero Code Generator
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the system calls required the the libc that is included

[Jim Stichnoth, 2016/04/14 20:03:43]

the the ==> in the
?

[Eric Holk, 2016/04/15 15:24:26]

I went with "by the..."

+// in WebAssembly programs.
+//
+//===----------------------------------------------------------------------===//
+
+#include <stdlib.h>
+#include <stdio.h>

[Jim Stichnoth, 2016/04/14 20:03:43]

sort?

[Eric Holk, 2016/04/15 15:24:26]

Done.

+#include <string.h>
+#include <unistd.h>
+
+extern char WASM_MEMORY;

[Jim Stichnoth, 2016/04/14 20:03:43]

I wonder if this could be extern char WASM_MEMORY[] ?

[Eric Holk, 2016/04/15 15:24:26]

Ah, much better. I tried `char *` initially and that crashed. I mistakenly
assumed `WASM_MEMORY[]` meant the same thing, but it turns out it works.

+
+void env$$abort() {
+  fprintf(stderr, "Aborting...\n");
+  abort();
+}
+
+void env$$_abort() { env$$abort(); }
+
+#define UNIMPLEMENTED(f)                                                       \
+  void env$$##f() {                                                            \
+    fprintf(stderr, "Unimplemented: " #f "\n");                                \
+    abort();                                                                   \
+  }
+
+UNIMPLEMENTED(sbrk)
+UNIMPLEMENTED(pthread_cleanup_push)
+UNIMPLEMENTED(pthread_cleanup_pop)
+UNIMPLEMENTED(pthread_self)
+UNIMPLEMENTED(__lock)
+UNIMPLEMENTED(__unlock)
+UNIMPLEMENTED(__syscall6)
+UNIMPLEMENTED(__syscall140)
+
+void *wasmPtr(int Index) {

[Jim Stichnoth, 2016/04/14 20:03:43]

Is Index allowed to be negative?  It seems like not because of the mask.  If it
can't be negative, consider declaring it as unsigned.

[Eric Holk, 2016/04/15 15:24:26]

It is, and it's actually quite common for it to be negative.

+  // TODO (eholk): get the mask from the WASM file.
+  const int MASK = 0x3fffff;

[Jim Stichnoth, 2016/04/14 20:03:43]

If I'm reading this right, there are only 22 bits = 4MB of memory available? 
Can you document what this is for?  because I must be missing something...

[Eric Holk, 2016/04/15 15:24:26]

The Wasm file says how many 64KB pages of memory it wants, which is used to
compute this mask. For development purposes, I just hardcoded the value that I'm
seeing in most tests, but the right thing to do here (and what I'm planning to
do soon) is to have the WasmTranslator emit a global variable with the requested
memory size.

+  Index &= MASK;
+
+  return &WASM_MEMORY + Index;
+}
+
+extern int __szwasm_main(int, char **);
+
+#define WASM_REF(Type, Index) ((Type *)wasmPtr(Index))
+#define WASM_DEREF(Type, Index) (*WASM_REF(Type, Index))
+
+int main(int argc, char **argv) { return __szwasm_main(argc, argv); }
+
+/// sys_write
+int env$$__syscall4(int Which, int VarArgs) {
+  int Fd = WASM_DEREF(int, VarArgs);
+  int Buffer = WASM_DEREF(int, VarArgs + 4);

[Jim Stichnoth, 2016/04/14 20:03:43]

Can you use sizeof() calculations instead of 4/8?

[Eric Holk, 2016/04/15 15:24:26]

Done.

+  int Length = WASM_DEREF(int, VarArgs + 8);
+
+  return write(Fd, WASM_REF(char *, Buffer), Length);
+}
+
+int env$$__syscall54(int A, int B) {

[Jim Stichnoth, 2016/04/14 20:03:44]

syscall4 was documented as sys_write.  What is this syscall54?

[Eric Holk, 2016/04/15 15:24:26]

sys_ioctl. I added a comment for it.

+  // fprintf(stderr, "Unimplemented: sys_ioctl(%d, %d)\n", a, b);

[Jim Stichnoth, 2016/04/14 20:03:44]

Remove the commented-out code?

[Eric Holk, 2016/04/15 15:24:26]

Done.

+  int Fd = WASM_DEREF(int, B);
+  int Op = WASM_DEREF(int, B + 4);
+  int ArgP = WASM_DEREF(int, B + 8);
+  // fprintf(stderr, "Fd=%d, Op=%d, ArgP=%d\n", Fd, Op, ArgP);
+  // abort();
+  return -25; /* ENOTTY */

[Jim Stichnoth, 2016/04/14 20:03:44]

Can you just return -ENOTTY ?

[Eric Holk, 2016/04/15 15:24:26]

Done.

+}
+
+int env$$__syscall146(int Which, int VarArgs) {
+  fprintf(stderr, "syscall146\n");
+
+  int Fd = WASM_DEREF(int, VarArgs);
+  int Iov = WASM_DEREF(int, VarArgs + 4);
+  int Iovcnt = WASM_DEREF(int, VarArgs + 8);
+
+  fprintf(stderr, "  Fd=%d, Iov=%d (%p), Iovcnt=%d\n", Fd, Iov, wasmPtr(Iov),
+          Iovcnt);
+
+  int Count = 0;
+
+  for (int I = 0; I < Iovcnt; ++I) {
+    void *Ptr = WASM_REF(void, WASM_DEREF(int, Iov + I * 8));
+    int Length = WASM_DEREF(int, Iov + I * 8 + 4);
+
+    fprintf(stderr, "  [%d] write(%d, %p, %d) = ", I, Fd, Ptr, Length);
+    int Curr = write(Fd, Ptr, Length);
+
+    fprintf(stderr, "%d\n", Curr);
+
+    if (Curr < 0) {
+      return -1;
+    }
+    Count += Curr;
+  }
+  fprintf(stderr, "  Count = %d\n", Count);
+  return Count;
+}