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wasm linker: fix TLS data segments

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fix calculation of alignment and size

include __tls_align and __tls_size globals along with __tls_base

include them only if the TLS segment is emitted

add missing reloc logic for memory_addr_tls_sleb

fix name of data segments to include only the prefix
This commit is contained in:
Andrew Kelley 2025-01-15 18:17:37 -08:00
parent 10db1b9eda
commit 9dd6efb7e4
2 changed files with 39 additions and 25 deletions
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63
src/link/Wasm/Flush.zig
View file

@ -330,16 +330,6 @@ pub fn finish(f: *Flush, wasm: *Wasm) !void {
try wasm.addFunction(.__wasm_init_memory, &.{}, &.{});
}
// When we have TLS GOT entries and shared memory is enabled,
// we must perform runtime relocations or else we don't create the function.
if (shared_memory) {
// This logic that checks `any_tls_relocs` is missing the part where it
// also notices threadlocal globals from Zcu code.
if (wasm.any_tls_relocs) try wasm.addFunction(.__wasm_apply_global_tls_relocs, &.{}, &.{});
try wasm.addFunction(.__wasm_init_tls, &.{.i32}, &.{});
try wasm.globals.put(gpa, .__tls_base, {});
}
try wasm.tables.ensureUnusedCapacity(gpa, 1);
if (f.indirect_function_table.entries.len > 0) {
@ -446,17 +436,25 @@ pub fn finish(f: *Flush, wasm: *Wasm) !void {
const want_new_segment = b: {
if (is_obj) break :b false;
switch (seen_tls) {
.before => if (category == .tls) {
virtual_addrs.tls_base = if (shared_memory) 0 else @intCast(start_addr);
virtual_addrs.tls_align = alignment;
seen_tls = .during;
break :b f.data_segment_groups.items.len > 0;
.before => switch (category) {
.tls => {
virtual_addrs.tls_base = if (shared_memory) 0 else @intCast(start_addr);
virtual_addrs.tls_align = alignment;
seen_tls = .during;
break :b f.data_segment_groups.items.len > 0;
},
else => {},
},
.during => if (category != .tls) {
virtual_addrs.tls_size = @intCast(start_addr - virtual_addrs.tls_base.?);
virtual_addrs.tls_align = virtual_addrs.tls_align.maxStrict(alignment);
seen_tls = .after;
break :b true;
.during => switch (category) {
.tls => {
virtual_addrs.tls_align = virtual_addrs.tls_align.maxStrict(alignment);
virtual_addrs.tls_size = @intCast(memory_ptr - virtual_addrs.tls_base.?);
break :b false;
},
else => {
seen_tls = .after;
break :b true;
},
},
.after => {},
}
@ -480,6 +478,9 @@ pub fn finish(f: *Flush, wasm: *Wasm) !void {
.first_segment = first_segment,
.end_addr = @intCast(memory_ptr),
});
if (category == .tls and seen_tls == .during) {
virtual_addrs.tls_size = @intCast(memory_ptr - virtual_addrs.tls_base.?);
}
}
if (shared_memory and wasm.any_passive_inits) {
@ -537,6 +538,19 @@ pub fn finish(f: *Flush, wasm: *Wasm) !void {
}
f.memory_layout_finished = true;
// When we have TLS GOT entries and shared memory is enabled, we must
// perform runtime relocations or else we don't create the function.
if (shared_memory and virtual_addrs.tls_base != null) {
// This logic that checks `any_tls_relocs` is missing the part where it
// also notices threadlocal globals from Zcu code.
if (wasm.any_tls_relocs) try wasm.addFunction(.__wasm_apply_global_tls_relocs, &.{}, &.{});
try wasm.addFunction(.__wasm_init_tls, &.{.i32}, &.{});
try wasm.globals.ensureUnusedCapacity(gpa, 3);
wasm.globals.putAssumeCapacity(.__tls_base, {});
wasm.globals.putAssumeCapacity(.__tls_size, {});
wasm.globals.putAssumeCapacity(.__tls_align, {});
}
var section_index: u32 = 0;
// Index of the code section. Used to tell relocation table where the section lives.
var code_section_index: ?u32 = null;
@ -986,9 +1000,8 @@ pub fn finish(f: *Flush, wasm: *Wasm) !void {
}
segment_offset += @intCast(binary_bytes.items.len - code_start);
}
assert(group_index == f.data_segment_groups.items.len);
replaceVecSectionHeader(binary_bytes, header_offset, .data, group_index);
replaceVecSectionHeader(binary_bytes, header_offset, .data, @intCast(f.data_segment_groups.items.len));
data_section_index = section_index;
section_index += 1;
}
@ -1128,7 +1141,7 @@ fn emitNameSection(
try leb.writeUleb128(binary_bytes.writer(gpa), total_data_segments);
for (data_segment_groups, 0..) |group, i| {
const name = group.first_segment.name(wasm);
const name, _ = splitSegmentName(group.first_segment.name(wasm));
try leb.writeUleb128(binary_bytes.writer(gpa), @as(u32, @intCast(i)));
try leb.writeUleb128(binary_bytes.writer(gpa), @as(u32, @intCast(name.len)));
try binary_bytes.appendSlice(gpa, name);
@ -1680,8 +1693,8 @@ fn applyRelocs(code: []u8, code_offset: u32, relocs: Wasm.ObjectRelocation.Itera
.memory_addr_rel_sleb64 => @panic("TODO implement relocation memory_addr_rel_sleb64"),
.memory_addr_sleb => reloc_sleb_addr(sliced_code, .fromObjectData(wasm, pointee.data, addend.*)),
.memory_addr_sleb64 => reloc_sleb64_addr(sliced_code, .fromObjectData(wasm, pointee.data, addend.*)),
.memory_addr_tls_sleb => @panic("TODO implement relocation memory_addr_tls_sleb"),
.memory_addr_tls_sleb64 => @panic("TODO implement relocation memory_addr_tls_sleb64"),
.memory_addr_tls_sleb => reloc_sleb_addr(sliced_code, .fromObjectData(wasm, pointee.data, addend.*)),
.memory_addr_tls_sleb64 => reloc_sleb64_addr(sliced_code, .fromObjectData(wasm, pointee.data, addend.*)),
.memory_addr_import_i32 => reloc_u32_addr(sliced_code, .fromSymbolName(wasm, pointee.symbol_name, addend.*)),
.memory_addr_import_i64 => reloc_u64_addr(sliced_code, .fromSymbolName(wasm, pointee.symbol_name, addend.*)),

1
test/link/wasm/shared-memory/build.zig
View file

@ -43,6 +43,7 @@ fn add(b: *std.Build, test_step: *std.Build.Step, optimize_mode: std.builtin.Opt
check_exe.checkInHeaders();
check_exe.checkExact("Section export");
check_exe.checkExact("entries 2");
check_exe.checkExact("name foo");
check_exe.checkExact("name memory"); // ensure we also export memory again
// This section *must* be emit as the start function is set to the index