authorgravatar for kubkon@jakubkonka.comJakub Konka <kubkon@jakubkonka.com> 2022-04-18 23:53:41+02:00
committergravatar for noreply@github.comGitHub <noreply@github.com> 2022-04-18 23:53:41+02:00
logb03345f32a5ba2849ddbeeae0e31e0e77ca01b01
tree4100326d0b400a38525d980739214feaf48508b8
parent5195b87639a1dc56b90751d0aecc4fcf4f2a1bb0
parent3a63fa6b7f56a2f384ebd460e80c00e6bbd2efee
signature Signed by PGP key 4AEE18F83AFDEB23

Merge pull request #11024 from topolarity/wasi-stage2

stage2: Add limited WASI support for selfExePath and globalCacheDir

4 files changed, 80 insertions(+), 8 deletions(-)

lib/std/fs.zig+47
......@@ -2547,6 +2547,15 @@ pub const SelfExePathError = os.ReadLinkError || os.SysCtlError || os.RealPathEr
25472547/// `selfExePath` except allocates the result on the heap.
25482548/// Caller owns returned memory.
25492549pub fn selfExePathAlloc(allocator: Allocator) ![]u8 {
2550 if (builtin.os.tag == .wasi) {
2551 var args = try std.process.argsWithAllocator(allocator);
2552 defer args.deinit();
2553 // On WASI, argv[0] is always just the basename of the current executable
2554 const exe_name = args.next() orelse return error.FileNotFound;
2555
2556 var buf: [MAX_PATH_BYTES]u8 = undefined;
2557 return allocator.dupe(u8, try selfExePathWasi(&buf, exe_name));
2558 }
25502559 // Use of MAX_PATH_BYTES here is justified as, at least on one tested Linux
25512560 // system, readlink will completely fail to return a result larger than
25522561 // PATH_MAX even if given a sufficiently large buffer. This makes it
......@@ -2643,10 +2652,48 @@ pub fn selfExePath(out_buffer: []u8) SelfExePathError![]u8 {
26432652 const end_index = std.unicode.utf16leToUtf8(out_buffer, utf16le_slice) catch unreachable;
26442653 return out_buffer[0..end_index];
26452654 },
2655 .wasi => @compileError("std.fs.selfExePath not supported for WASI. Use std.fs.selfExePathAlloc instead."),
26462656 else => @compileError("std.fs.selfExePath not supported for this target"),
26472657 }
26482658}
26492659
2660/// WASI-specific implementation of selfExePath
2661///
2662/// On WASI argv0 is always just the executable basename, so this function relies
2663/// using a fixed executable directory path: "/zig"
2664///
2665/// This path can be configured in wasmtime using `--mapdir=/zig::/path/to/zig/dir/`
2666fn selfExePathWasi(out_buffer: []u8, argv0: []const u8) SelfExePathError![]const u8 {
2667 var allocator = std.heap.FixedBufferAllocator.init(out_buffer);
2668 var alloc = allocator.allocator();
2669
2670 // Check these paths:
2671 // 1. "/zig/{exe_name}"
2672 // 2. "/zig/bin/{exe_name}"
2673 const base_paths_to_check = &[_][]const u8{ "/zig", "/zig/bin" };
2674 const exe_names_to_check = &[_][]const u8{ path.basename(argv0), "zig.wasm" };
2675
2676 for (base_paths_to_check) |base_path| {
2677 for (exe_names_to_check) |exe_name| {
2678 const test_path = path.join(alloc, &.{ base_path, exe_name }) catch continue;
2679
2680 // Make sure it's a file we're pointing to
2681 const file = os.fstatat(os.wasi.AT.FDCWD, test_path, 0) catch continue;
2682 if (file.filetype != .REGULAR_FILE) continue;
2683
2684 // Path seems to be valid, let's try to turn it into an absolute path
2685 var real_path_buf: [MAX_PATH_BYTES]u8 = undefined;
2686 if (os.realpath(test_path, &real_path_buf)) |real_path| {
2687 if (real_path.len > out_buffer.len)
2688 return error.NameTooLong;
2689 mem.copy(u8, out_buffer, real_path);
2690 return out_buffer[0..real_path.len];
2691 } else |_| continue;
2692 }
2693 }
2694 return error.FileNotFound;
2695}
2696
26502697/// The result is UTF16LE-encoded.
26512698pub fn selfExePathW() [:0]const u16 {
26522699 const image_path_name = &os.windows.peb().ProcessParameters.ImagePathName;
src/Cache.zig+11-7
......@@ -762,18 +762,22 @@ pub const Manifest = struct {
762762
763763 fn downgradeToSharedLock(self: *Manifest) !void {
764764 if (!self.have_exclusive_lock) return;
765 const manifest_file = self.manifest_file.?;
766 try manifest_file.downgradeLock();
765 if (std.process.can_spawn or !builtin.single_threaded) { // Some targets (WASI) do not support flock
766 const manifest_file = self.manifest_file.?;
767 try manifest_file.downgradeLock();
768 }
767769 self.have_exclusive_lock = false;
768770 }
769771
770772 fn upgradeToExclusiveLock(self: *Manifest) !void {
771773 if (self.have_exclusive_lock) return;
772 const manifest_file = self.manifest_file.?;
773 // Here we intentionally have a period where the lock is released, in case there are
774 // other processes holding a shared lock.
775 manifest_file.unlock();
776 try manifest_file.lock(.Exclusive);
774 if (std.process.can_spawn or !builtin.single_threaded) { // Some targets (WASI) do not support flock
775 const manifest_file = self.manifest_file.?;
776 // Here we intentionally have a period where the lock is released, in case there are
777 // other processes holding a shared lock.
778 manifest_file.unlock();
779 try manifest_file.lock(.Exclusive);
780 }
777781 self.have_exclusive_lock = true;
778782 }
779783
src/introspect.zig+12-1
......@@ -1,6 +1,7 @@
11const std = @import("std");
22const builtin = @import("builtin");
33const mem = std.mem;
4const os = std.os;
45const fs = std.fs;
56const Compilation = @import("Compilation.zig");
67
......@@ -80,5 +81,15 @@ pub fn resolveGlobalCacheDir(allocator: mem.Allocator) ![]u8 {
8081 }
8182 }
8283
83 return fs.getAppDataDir(allocator, appname);
84 if (builtin.os.tag == .wasi) {
85 // On WASI, we have no way to get an App data dir, so we try to use a fixed
86 // Preopen path "/cache" as a last resort
87 const path = "/cache";
88
89 const file = os.fstatat(os.wasi.AT.FDCWD, path, 0) catch return error.CacheDirUnavailable;
90 if (file.filetype != .DIRECTORY) return error.CacheDirUnavailable;
91 return allocator.dupe(u8, path);
92 } else {
93 return fs.getAppDataDir(allocator, appname);
94 }
8495}
src/main.zig+10
......@@ -162,6 +162,16 @@ pub fn main() anyerror!void {
162162 return mainArgs(gpa_tracy.allocator(), arena, args);
163163 }
164164
165 // WASI: `--dir` instructs the WASM runtime to "preopen" a directory, making
166 // it available to the us, the guest program. This is the only way for us to
167 // access files/dirs on the host filesystem
168 if (builtin.os.tag == .wasi) {
169 // This sets our CWD to "/preopens/cwd"
170 // Dot-prefixed preopens like `--dir=.` are "mounted" at "/preopens/cwd"
171 // Other preopens like `--dir=lib` are "mounted" at "/"
172 try std.os.initPreopensWasi(std.heap.page_allocator, "/preopens/cwd");
173 }
174
165175 return mainArgs(gpa, arena, args);
166176}
167177