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Implement writv syscall so that musl printf works (#26)

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Sam Clegg 2017-11-20 17:13:33 -08:00 committed by GitHub
parent 6a45034cab
commit b49da62f23
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1 changed files with 46 additions and 10 deletions
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56
arch/wasm32/wasm.js
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@ -24,14 +24,27 @@
var heap_size_bytes = 16 * 1024 * 1024;
var heap_size_pages = heap_size_bytes / (64 * 1024);
var memory = new WebAssembly.Memory({initial: heap_size_pages, maximum: heap_size_pages})
var heap = memory.buffer;
var heap_uint8 = new Uint8Array(heap);
var heap;
var heap_uint8;
var heap_uint32;
function setHeap(h) {
heap = h
heap_uint8 = new Uint8Array(heap);
heap_uint32 = new Uint32Array(heap);
heap_size_bytes = heap.byteLength;
}
setHeap(memory.buffer)
// Heap access helpers.
function charFromHeap(ptr) { return String.fromCharCode(heap_uint8[ptr]); }
function stringFromHeap(ptr) {
function stringFromHeap(ptr, len = -1) {
var str = '';
for (var i = ptr; i < heap_size_bytes && heap_uint8[i] != 0; ++i)
var end = heap_size_bytes;
if (len != -1)
end = ptr + len;
for (var i = ptr; i < end && heap_uint8[i] != 0; ++i)
str += charFromHeap(i);
return str;
}
@ -286,6 +299,9 @@ var stdio = (function() {
return {
// Internal.
__write_stdout: function(str) {
stdout_buf += str;
},
__flush_stdout: function() {
if (stdout_buf[-1] = '\n')
stdout_buf = stdout_buf.slice(0, -1);
@ -346,7 +362,7 @@ var stdio = (function() {
return character;
},
puts: function(str) {
stdout_buf += stringFromHeap(str) + '\n';
stdio.__write_stdout(stringFromHeap(str) + '\n');
stdio.__flush_stdout();
},
ungetc: NYI('ungetc'),
@ -1265,6 +1281,28 @@ syscall_numbers = (function() {
})();
function syscall_impl(n) {
// Special case for writev(stdout), essentially allowing printf to work
if (n == syscall_numbers["SYS_writev"]) {
if (arguments[1] == 1) {
var iov = arguments[2] / 4;
var iovcnt = arguments[3];
var rtn = 0;
for (var i = 0; i < iovcnt; i++) {
var ptr = heap_uint32[iov];
iov++;
var len = heap_uint32[iov];
iov++;
if (len > 0) {
stdio.__write_stdout(stringFromHeap(ptr, len));
rtn += len;
}
}
return rtn;
}
}
// For other syscalls we trace that args and then either return 0 (ignore
// the syscall) or -1, delare that we failed.
arg_count = arguments.length - 1;
var msg = 'syscall' + arg_count + '(' + syscall_names[n];
for (var arg_num = 0; arg_num < arg_count; arg_num++) {
@ -1272,6 +1310,7 @@ function syscall_impl(n) {
}
msg += ')';
print(msg);
var ignore_syscalls = [
syscall_numbers["SYS_set_thread_area"],
syscall_numbers["SYS_set_tid_address"]
@ -1327,11 +1366,8 @@ function load_wasm(file_path) {
// For the application exports its memory, we use that rather than
// the one we created. In this way this code works with modules that
// import or export their memory.
if (instance.exports.memory) {
heap = instance.exports.memory.buffer;
heap_uint8 = new Uint8Array(heap);
heap_size_bytes = heap.byteLength;
}
if (instance.exports.memory)
setHeap(instance.exports.memory.buffer);
return instance;
}