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wasm: Emit debug sections

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This commit adds the ability to emit the following debug sections:
.debug_info
.debug_abbrev
.debug_line
.debug_str

Line information and files are now being loaded correctly by browser debuggers.
This commit is contained in:
Luuk de Gram 2022-05-04 21:25:33 +02:00
parent 9b6b7034c2
commit 2ae2ac33d9
3 changed files with 99 additions and 27 deletions
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56
src/link/Dwarf.zig
View File

@ -963,21 +963,18 @@ pub fn commitDeclState(
const wasm_file = file.cast(File.Wasm).?;
const segment_index = try wasm_file.getDebugLineIndex();
const segment = &wasm_file.segments.items[segment_index];
const debug_atom = wasm_file.atoms.get(segment_index).?;
const debug_line = &wasm_file.debug_line;
if (needed_size != segment.size) {
log.debug(" needed size does not equal allocated size: {d}", .{needed_size});
if (needed_size > segment.size) {
log.debug(" allocating {d} bytes for debug line information", .{needed_size - segment.size});
try debug_atom.code.resize(self.allocator, needed_size);
std.mem.set(u8, debug_atom.code.items[segment.size..], 0);
log.debug(" allocating {d} bytes for 'debug line' information", .{needed_size - segment.size});
try debug_line.resize(self.allocator, needed_size);
mem.set(u8, debug_line.items[segment.size..], 0);
}
debug_atom.size = needed_size;
segment.size = needed_size;
}
// since we can tighly pack the debug lines, wasm does not require
// us to pad with Nops.
const offset = segment.offset + src_fn.off;
std.mem.copy(u8, debug_atom.code.items[offset..], dbg_line_buffer.items);
mem.copy(u8, debug_line.items[offset..], dbg_line_buffer.items);
},
else => unreachable,
}
@ -1116,7 +1113,9 @@ fn updateDeclDebugInfoAllocation(self: *Dwarf, file: *File, atom: *Atom, len: u3
const file_pos = debug_info_sect.offset + atom.off;
try pwriteDbgInfoNops(d_sym.file, file_pos, 0, &[0]u8{}, atom.len, false);
},
.wasm => {},
.wasm => {
log.debug(" todo: updateDeclDebugInfoAllocation for Wasm: {d}", .{atom.len});
},
else => unreachable,
}
// TODO Look at the free list before appending at the end.
@ -1241,6 +1240,23 @@ fn writeDeclDebugInfo(self: *Dwarf, file: *File, atom: *Atom, dbg_info_buf: []co
trailing_zero,
);
},
.wasm => {
const wasm_file = file.cast(File.Wasm).?;
const segment_index = try wasm_file.getDebugInfoIndex();
const segment = &wasm_file.segments.items[segment_index];
const debug_info = &wasm_file.debug_info;
if (needed_size != segment.size) {
log.debug(" needed size does not equal allocated size: {d}", .{needed_size});
if (needed_size > segment.size) {
log.debug(" allocating {d} bytes for 'debug info' information", .{needed_size - segment.size});
try debug_info.resize(self.allocator, needed_size);
mem.set(u8, debug_info.items[segment.size..], 0);
}
segment.size = needed_size;
}
const offset = segment.offset + atom.off;
mem.copy(u8, debug_info.items[offset..], dbg_info_buf);
},
else => unreachable,
}
}
@ -1279,8 +1295,7 @@ pub fn updateDeclLineNumber(self: *Dwarf, file: *File, decl: *const Module.Decl)
const segment_index = wasm_file.getDebugLineIndex() catch unreachable;
const segment = wasm_file.segments.items[segment_index];
const offset = segment.offset + decl.fn_link.wasm.src_fn.off + self.getRelocDbgLineOff();
const debug_atom = wasm_file.atoms.get(segment_index).?;
std.mem.copy(u8, debug_atom.code.items[offset..], &data);
mem.copy(u8, wasm_file.debug_line.items[offset..], &data);
},
else => unreachable,
}
@ -1514,6 +1529,11 @@ pub fn writeDbgAbbrev(self: *Dwarf, file: *File) !void {
const file_pos = debug_abbrev_sect.offset + abbrev_offset;
try d_sym.file.pwriteAll(&abbrev_buf, file_pos);
},
.wasm => {
const wasm_file = file.cast(File.Wasm).?;
try wasm_file.debug_abbrev.resize(wasm_file.base.allocator, needed_size);
mem.copy(u8, wasm_file.debug_abbrev.items, &abbrev_buf);
},
else => unreachable,
}
}
@ -1621,6 +1641,10 @@ pub fn writeDbgInfoHeader(self: *Dwarf, file: *File, module: *Module, low_pc: u6
const file_pos = debug_info_sect.offset;
try pwriteDbgInfoNops(d_sym.file, file_pos, 0, di_buf.items, jmp_amt, false);
},
.wasm => {
const wasm_file = file.cast(File.Wasm).?;
mem.copy(u8, wasm_file.debug_info.items, di_buf.items);
},
else => unreachable,
}
}
@ -2004,6 +2028,10 @@ pub fn writeDbgLineHeader(self: *Dwarf, file: *File, module: *Module) !void {
const file_pos = debug_line_sect.offset;
try pwriteDbgLineNops(d_sym.file, file_pos, 0, di_buf.items, jmp_amt);
},
.wasm => {
const wasm_file = file.cast(File.Wasm).?;
mem.copy(u8, wasm_file.debug_line.items, di_buf.items);
},
else => unreachable,
}
}
@ -2127,6 +2155,8 @@ pub fn flushModule(self: *Dwarf, file: *File, module: *Module) !void {
const debug_info_sect = &dwarf_segment.sections.items[d_sym.debug_info_section_index.?];
break :blk debug_info_sect.offset;
},
// for wasm, the offset is always 0 as we write to memory first
.wasm => break :blk @as(u32, 0),
else => unreachable,
}
};
@ -2145,6 +2175,10 @@ pub fn flushModule(self: *Dwarf, file: *File, module: *Module) !void {
const d_sym = &macho_file.d_sym.?;
try d_sym.file.pwriteAll(&buf, file_pos + reloc.atom.off + reloc.offset);
},
.wasm => {
const wasm_file = file.cast(File.Wasm).?;
mem.copy(u8, wasm_file.debug_info.items[reloc.atom.off + reloc.offset ..], &buf);
},
else => unreachable,
}
}

61
src/link/Wasm.zig
View File

@ -90,6 +90,14 @@ string_table: StringTable = .{},
/// Debug information for wasm
dwarf: ?Dwarf = null,
// *debug information* //
/// Contains all bytes for the '.debug_info' section
debug_info: std.ArrayListUnmanaged(u8) = .{},
/// Contains all bytes for the '.debug_line' section
debug_line: std.ArrayListUnmanaged(u8) = .{},
/// Contains all bytes for the '.debug_abbrev' section
debug_abbrev: std.ArrayListUnmanaged(u8) = .{},
// Output sections
/// Output type section
func_types: std.ArrayListUnmanaged(wasm.Type) = .{},
@ -501,6 +509,10 @@ pub fn deinit(self: *Wasm) void {
if (self.dwarf) |*dwarf| {
dwarf.deinit();
}
self.debug_info.deinit(gpa);
self.debug_line.deinit(gpa);
self.debug_abbrev.deinit(gpa);
}
pub fn allocateDeclIndexes(self: *Wasm, decl_index: Module.Decl.Index) !void {
@ -576,7 +588,9 @@ pub fn updateFunc(self: *Wasm, mod: *Module, func: *Module.Fn, air: Air, livenes
&self.base,
mod,
decl,
// Actual value will be written after relocation
// Actual value will be written after relocation.
// For Wasm, this is the offset relative to the code section
// which isn't known until flush().
0,
code.len,
&decl_state.?,
@ -1016,10 +1030,12 @@ fn parseAtom(self: *Wasm, atom: *Atom, kind: Kind) !void {
// segment indexes can be off by 1 due to also containing a segment
// for the code section, so we must check if the existing segment
// is larger than that of the code section, and substract the index by 1 in such case.
const info_add = if (self.code_section_index) |idx| blk: {
var info_add = if (self.code_section_index) |idx| blk: {
if (idx < index) break :blk @as(u32, 1);
break :blk 0;
} else @as(u32, 0);
if (self.debug_info_index != null) info_add += 1;
if (self.debug_line_index != null) info_add += 1;
symbol.index = index - info_add;
// segment info already exists, so free its memory
self.base.allocator.free(segment_name);
@ -1320,11 +1336,8 @@ fn setupMemory(self: *Wasm) !void {
}
var offset: u32 = @intCast(u32, memory_ptr);
for (self.segments.items) |*segment, i| {
// skip 'code' segments
if (self.code_section_index) |index| {
if (index == i) continue;
}
for (self.data_segments.values()) |segment_index| {
const segment = &self.segments.items[segment_index];
memory_ptr = std.mem.alignForwardGeneric(u64, memory_ptr, segment.alignment);
memory_ptr += segment.size;
segment.offset = offset;
@ -1588,6 +1601,7 @@ fn resetState(self: *Wasm) void {
self.symbol_atom.clearRetainingCapacity();
self.code_section_index = null;
self.debug_info_index = null;
self.debug_line_index = null;
}
pub fn flush(self: *Wasm, comp: *Compilation, prog_node: *std.Progress.Node) !void {
@ -2016,10 +2030,43 @@ pub fn flushModule(self: *Wasm, comp: *Compilation, prog_node: *std.Progress.Nod
try self.emitDataRelocations(file, arena, data_index, symbol_table);
}
} else if (!self.base.options.strip) {
if (self.dwarf) |*dwarf| {
if (self.debug_info_index != null) {
_ = dwarf;
try dwarf.writeDbgAbbrev(&self.base);
try dwarf.writeDbgInfoHeader(&self.base, mod, 0, 0);
try dwarf.writeDbgLineHeader(&self.base, mod);
try emitDebugSection(file, self.debug_info.items, ".debug_info");
try emitDebugSection(file, self.debug_abbrev.items, ".debug_abbrev"); // TODO
try emitDebugSection(file, self.debug_line.items, ".debug_line");
try emitDebugSection(file, dwarf.strtab.items, ".debug_str");
}
}
try self.emitNameSection(file, arena);
}
}
fn emitDebugSection(file: fs.File, data: []const u8, name: []const u8) !void {
const header_offset = try reserveCustomSectionHeader(file);
const writer = file.writer();
try leb.writeULEB128(writer, @intCast(u32, name.len));
try writer.writeAll(name);
try file.writevAll(&[_]std.os.iovec_const{.{
.iov_base = data.ptr,
.iov_len = data.len,
}});
const start = header_offset + 6 + name.len + getULEB128Size(@intCast(u32, name.len));
log.debug("Emit debug section: '{s}' start=0x{x:0>8} end=0x{x:0>8}", .{ name, start, start + data.len });
try writeCustomSectionHeader(
file,
header_offset,
@intCast(u32, (try file.getPos()) - header_offset - 6),
);
}
fn emitNameSection(self: *Wasm, file: fs.File, arena: Allocator) !void {
const Name = struct {
index: u32,

9
src/link/Wasm/Atom.zig
View File

@ -90,15 +90,6 @@ pub fn getFirst(self: *Atom) *Atom {
return tmp;
}
/// Returns the atom for the given `symbol_index`.
/// This can be either the `Atom` itself, or one of its locals.
pub fn symbolAtom(self: *Atom, symbol_index: u32) *Atom {
if (self.sym_index == symbol_index) return self;
return for (self.locals.items) |*local_atom| {
if (local_atom.sym_index == symbol_index) break local_atom;
} else unreachable; // Used a symbol index not present in this atom or its children.
}
/// Returns the location of the symbol that represents this `Atom`
pub fn symbolLoc(self: Atom) Wasm.SymbolLoc {
return .{ .file = self.file, .index = self.sym_index };