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wasm: Place the stack at the start of memory

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Luuk de Gram 2022-01-11 20:21:22 +01:00
parent 48731ccea9
commit f767f8e3dc
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1 changed files with 20 additions and 8 deletions
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28
src/link/Wasm.zig
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@ -494,9 +494,21 @@ fn setupMemory(self: *Wasm) !void {
log.debug("Setting up memory layout", .{});
const page_size = 64 * 1024;
const stack_size = self.base.options.stack_size_override orelse page_size * 1;
const stack_alignment = 16;
var memory_ptr: u64 = self.base.options.global_base orelse 1024;
memory_ptr = std.mem.alignForwardGeneric(u64, memory_ptr, stack_alignment);
const stack_alignment = 16; // wasm's stack alignment as specified by tool-convention
// Always place the stack at the start by default
// unless the user specified the global-base flag
var place_stack_first = true;
var memory_ptr: u64 = if (self.base.options.global_base) |base| blk: {
place_stack_first = false;
break :blk base;
} else 0;
if (place_stack_first) {
memory_ptr = std.mem.alignForwardGeneric(u64, memory_ptr, stack_alignment);
memory_ptr += stack_size;
// We always put the stack pointer global at index 0
self.globals.items[0].init.i32_const = @bitCast(i32, @intCast(u32, memory_ptr));
}
var offset: u32 = @intCast(u32, memory_ptr);
for (self.segments.items) |*segment, i| {
@ -510,8 +522,11 @@ fn setupMemory(self: *Wasm) !void {
offset += segment.size;
}
memory_ptr = std.mem.alignForwardGeneric(u64, memory_ptr, stack_alignment);
memory_ptr += stack_size;
if (!place_stack_first) {
memory_ptr = std.mem.alignForwardGeneric(u64, memory_ptr, stack_alignment);
memory_ptr += stack_size;
self.globals.items[0].init.i32_const = @bitCast(i32, @intCast(u32, memory_ptr));
}
// Setup the max amount of pages
// For now we only support wasm32 by setting the maximum allowed memory size 2^32-1
@ -554,9 +569,6 @@ fn setupMemory(self: *Wasm) !void {
self.memories.limits.max = @intCast(u32, max_memory / page_size);
log.debug("Maximum memory pages: {d}", .{self.memories.limits.max});
}
// We always put the stack pointer global at index 0
self.globals.items[0].init.i32_const = @bitCast(i32, @intCast(u32, memory_ptr));
}
fn resetState(self: *Wasm) void {