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WasmPageAllocator: fix bug not aligning allocations

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This commit is contained in:
Jonathan Marler 2020-06-27 22:19:15 -06:00 committed by Andrew Kelley
parent 581d16154b
commit 374e3e42e0
1 changed files with 18 additions and 10 deletions
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28
lib/std/heap.zig
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@ -285,7 +285,7 @@ const WasmPageAllocator = struct {
// Revisit if this is settled: https://github.com/ziglang/zig/issues/3806
const not_found = std.math.maxInt(usize);
fn useRecycled(self: FreeBlock, num_pages: usize) usize {
fn useRecycled(self: FreeBlock, num_pages: usize, alignment: u29) usize {
@setCold(true);
for (self.data) |segment, i| {
const spills_into_next = @bitCast(i128, segment) < 0;
@ -298,7 +298,8 @@ const WasmPageAllocator = struct {
var count: usize = 0;
while (j + count < self.totalPages() and self.getBit(j + count) == .free) {
count += 1;
if (count >= num_pages) {
const addr = j * mem.page_size;
if (count >= num_pages and mem.isAligned(addr, alignment)) {
self.setBits(j, num_pages, .used);
return j;
}
@ -329,29 +330,36 @@ const WasmPageAllocator = struct {
fn alloc(allocator: *Allocator, len: usize, alignment: u29, len_align: u29) error{OutOfMemory}![]u8 {
const page_count = nPages(len);
const page_idx = try allocPages(page_count);
const page_idx = try allocPages(page_count, alignment);
return @intToPtr([*]u8, page_idx * mem.page_size)
[0..alignPageAllocLen(page_count * mem.page_size, len, len_align)];
}
fn allocPages(page_count: usize) !usize {
fn allocPages(page_count: usize, alignment: u29) !usize {
{
const idx = conventional.useRecycled(page_count);
const idx = conventional.useRecycled(page_count, alignment);
if (idx != FreeBlock.not_found) {
return idx;
}
}
const idx = extended.useRecycled(page_count);
const idx = extended.useRecycled(page_count, alignment);
if (idx != FreeBlock.not_found) {
return idx + extendedOffset();
}
const prev_page_count = @wasmMemoryGrow(0, @intCast(u32, page_count));
if (prev_page_count <= 0) {
const next_page_idx = @wasmMemorySize(0);
const next_page_addr = next_page_idx * mem.page_size;
const aligned_addr = mem.alignForward(next_page_addr, alignment);
const drop_page_count = @divExact(aligned_addr - next_page_addr, mem.page_size);
const result = @wasmMemoryGrow(0, @intCast(u32, drop_page_count + page_count));
if (result <= 0)
return error.OutOfMemory;
assert(result == next_page_idx);
const aligned_page_idx = next_page_idx + drop_page_count;
if (drop_page_count > 0) {
freePages(next_page_idx, aligned_page_idx);
}
return @intCast(usize, prev_page_count);
return @intCast(usize, aligned_page_idx);
}
fn freePages(start: usize, end: usize) void {