Commit 10bf58b2db0e340137228f706ee2e8a67b46a892 | zig

author	Luuk de Gram <luuk@degram.dev> 2023-06-21 21:43:11+02:00
committer	Luuk de Gram <luuk@degram.dev> 2023-06-26 20:00:57+02:00
log	10bf58b2db0e340137228f706ee2e8a67b46a892
tree	4bee037f76f15189cf25a819cddf08b5da27274b
parent	a97dbdfa0b1246913ba90cd5c05ff633e9003cb9
signature	Commit is signed but in an unrecognized format.

store allocator & remove global assembly

We now store the original allocator that was used to allocate the
memory required for the thread. This allocator can then be used
in any cleanup functionality to ensure the memory is freed correctly.

Secondly, we now use a function to set the stack pointer instead of
generating a function using global assembly. This is a lot cleaner
and more readable.

1 files changed, 26 insertions(+), 22 deletions(-)

lib
- std
  - Thread.zig

lib/std/Thread.zig+26-22

...	...	@@ -739,32 +739,24 @@ const PosixThreadImpl = struct {
739	739	};
740	740
741	741	const WasiThreadImpl = struct {
742		comptime {
743		// Sets the stack pointer, which is needed after creating a new thread
744		// to ensure the stack of the main thread isn't being poluted.
745		asm (
746		\\ .text
747		\\ .export_name __set_stack_pointer, __set_stack_pointer
748		\\ .globaltype __stack_pointer, i32
749		\\ .hidden wasi_thread_start
750		\\ .globl wasi_thread_start
751		\\ .type __set_stack_pointer, @function
752		\\
753		\\ __set_stack_pointer:
754		\\ .functype __set_stack_pointer (i32) -> ()
755		\\ local.get 0 # The raw pointer which replaces the stack pointer
756		\\ global.set __stack_pointer
757		\\ end_function
758		);
759		}
760	742	thread: *WasiThread,
761	743
762	744	pub const ThreadHandle = i32;
763	745	threadlocal var tls_thread_id: Id = 0;
764	746
765	747	const WasiThread = struct {
	748	/// Thread ID
766	749	tid: Atomic(i32) = Atomic(i32).init(0),
	750	/// Contains all memory which was allocated to bootstrap this thread, including:
	751	/// - Guard page
	752	/// - Stack
	753	/// - TLS segment
	754	/// - `Instance`
	755	/// All memory is freed upon call to `join`
767	756	memory: []u8,
	757	/// The allocator used to allocate the thread's memory,
	758	/// which is also used during `join` to ensure clean-up.
	759	allocator: std.mem.Allocator,
768	760	};
769	761
770	762	/// A meta-data structure used to bootstrap a thread
...	...	@@ -790,7 +782,7 @@ const WasiThreadImpl = struct {
790	782	}
791	783
792	784	fn getHandle(self: Impl) ThreadHandle {
793		return self.thread.tid;
	785	return self.thread.tid.load(.SeqCst);
794	786	}
795	787
796	788	fn detach(self: Impl) void {
...	...	@@ -813,7 +805,6 @@ const WasiThreadImpl = struct {
813	805	}
814	806	};
815	807
816		var guard_offset: usize = undefined;
817	808	var stack_offset: usize = undefined;
818	809	var tls_offset: usize = undefined;
819	810	var wrapper_offset: usize = undefined;
...	...	@@ -824,8 +815,11 @@ const WasiThreadImpl = struct {
824	815	// - The TLS segment
825	816	// - `Instance` - containing information about how to call the user's function.
826	817	const map_bytes = blk: {
	818	// start with atleast a single page, which is used as a guard to prevent
	819	// other threads clobbering our new thread.
	820	// Unfortunately, WebAssembly has no notion of read-only segments, so this
	821	// is only a temporary measure until the entire page is "run over".
827	822	var bytes: usize = std.wasm.page_size;
828		guard_offset = bytes;
829	823
830	824	bytes = std.mem.alignForward(usize, bytes, 16); // align stack to 16 bytes
831	825	stack_offset = bytes;
...	...	@@ -855,7 +849,7 @@ const WasiThreadImpl = struct {
855	849
856	850	const instance = @ptrCast(*Instance, @alignCast(@alignOf(Instance), &allocated_memory[instance_offset]));
857	851	instance.* = .{
858		.thread = .{ .memory = allocated_memory },
	852	.thread = .{ .memory = allocated_memory, .allocator = config.allocator.? },
859	853	.base = @ptrToInt(allocated_memory.ptr),
860	854	.tls_base = tls_offset,
861	855	.stack_pointer = stack_offset,
...	...	@@ -923,6 +917,16 @@ const WasiThreadImpl = struct {
923	917	: [ret] "=r" (-> u32),
924	918	);
925	919	}
	920
	921	/// Allows for setting the stack pointer in the WebAssembly module.
	922	inline fn __set_stack_pointer(addr: [*]u8) void {
	923	asm volatile (
	924	\\ local.get %[ptr]
	925	\\ global.set __stack_pointer
	926	:
	927	: [ptr] "r" (addr),
	928	);
	929	}
926	930	};
927	931
928	932	const LinuxThreadImpl = struct {