Commit 46c932a2c9650f14ae8035d7382d825bfabdc0a5 | zig

author	Luuk de Gram <luuk@degram.dev> 2022-09-01 22:02:24+02:00
committer	Luuk de Gram <luuk@degram.dev> 2022-09-07 18:53:16+02:00
log	46c932a2c9650f14ae8035d7382d825bfabdc0a5
tree	e819d6b20acb736af12a5b7f35ce4c34e17f3600
parent	c347751338a4a1e2874207674fb47908fd601484
signature	Commit is signed but in an unrecognized format.

wasm-linker: perform debug relocations

This correctly performs a relocation for debug sections.
The result is that the wasm-linker can now correctly create
a binary from object files while preserving all debug information.

3 files changed, 16 insertions(+), 6 deletions(-)

src
- link
  - Wasm.zig
  - Wasm
    Atom.zig
    Object.zig

src/link/Wasm.zig+12

...	@@ -221,6 +221,18 @@ pub const SymbolLoc = struct {	...	@@ -221,6 +221,18 @@ pub const SymbolLoc = struct {
221	}	221	}
222	return wasm_bin.string_table.get(wasm_bin.symbols.items[self.index].name);	222	return wasm_bin.string_table.get(wasm_bin.symbols.items[self.index].name);
223	}	223	}
		224
		225	/// From a given symbol location, returns the final location.
		226	/// e.g. when a symbol was resolved and replaced by the symbol
		227	/// in a different file, this will return said location.
		228	/// If the symbol wasn't replaced by another, this will return
		229	/// the given location itself.
		230	pub fn finalLoc(self: SymbolLoc, wasm_bin: *const Wasm) SymbolLoc {
		231	if (wasm_bin.discarded.get(self)) \|new_loc\| {
		232	return new_loc.finalLoc(wasm_bin);
		233	}
		234	return self;
		235	}
224	};	236	};
225		237
226	/// Generic string table that duplicates strings	238	/// Generic string table that duplicates strings

src/link/Wasm/Atom.zig+3-4

src/link/Wasm/Object.zig+1-2

 @@ -387,11 +387,10 @@ fn Parser(comptime ReaderType: type) type {
                                 .data = debug_content.ptr,
                                 .size = debug_size,
                                 .index = try self.object.string_table.put(gpa, name),
-                                .offset = len - debug_size,
+                                .offset = 0, // debug sections only contain 1 entry, so no need to calculate offset
                                 .section_index = section_index,
                             });
                         } else {
-                            log.info("found unknown custom section '{s}' - skipping parsing", .{name});
                             try reader.skipBytes(reader.context.bytes_left, .{});
                         }
                     },

...	@@ -145,7 +145,7 @@ pub fn resolveRelocs(self: Atom, wasm_bin: const Wasm) void {	...	@@ -145,7 +145,7 @@ pub fn resolveRelocs(self: Atom, wasm_bin: const Wasm) void {
145	/// All values will be represented as a `u64` as all values can fit within it.	145	/// All values will be represented as a `u64` as all values can fit within it.
146	/// The final value must be casted to the correct size.	146	/// The final value must be casted to the correct size.
147	fn relocationValue(self: Atom, relocation: types.Relocation, wasm_bin: *const Wasm) u64 {	147	fn relocationValue(self: Atom, relocation: types.Relocation, wasm_bin: *const Wasm) u64 {
148	const target_loc: Wasm.SymbolLoc = .{ .file = self.file, .index = relocation.index };	148	const target_loc = (Wasm.SymbolLoc{ .file = self.file, .index = relocation.index }).finalLoc(wasm_bin);
149	const symbol = target_loc.getSymbol(wasm_bin).*;	149	const symbol = target_loc.getSymbol(wasm_bin).*;
150	switch (relocation.relocation_type) {	150	switch (relocation.relocation_type) {
151	.R_WASM_FUNCTION_INDEX_LEB => return symbol.index,	151	.R_WASM_FUNCTION_INDEX_LEB => return symbol.index,
...	@@ -174,8 +174,7 @@ fn relocationValue(self: Atom, relocation: types.Relocation, wasm_bin: *const Wa	...	@@ -174,8 +174,7 @@ fn relocationValue(self: Atom, relocation: types.Relocation, wasm_bin: *const Wa
174	=> {	174	=> {
175	std.debug.assert(symbol.tag == .data and !symbol.isUndefined());	175	std.debug.assert(symbol.tag == .data and !symbol.isUndefined());
176	const merge_segment = wasm_bin.base.options.output_mode != .Obj;	176	const merge_segment = wasm_bin.base.options.output_mode != .Obj;
177	const target_atom_loc = wasm_bin.discarded.get(target_loc) orelse target_loc;	177	const target_atom = wasm_bin.symbol_atom.get(target_loc).?;
178	const target_atom = wasm_bin.symbol_atom.get(target_atom_loc).?;
179	const segment_info = if (target_atom.file) \|object_index\| blk: {	178	const segment_info = if (target_atom.file) \|object_index\| blk: {
180	break :blk wasm_bin.objects.items[object_index].segment_info;	179	break :blk wasm_bin.objects.items[object_index].segment_info;
181	} else wasm_bin.segment_info.items;	180	} else wasm_bin.segment_info.items;
...	@@ -187,6 +186,6 @@ fn relocationValue(self: Atom, relocation: types.Relocation, wasm_bin: *const Wa	...	@@ -187,6 +186,6 @@ fn relocationValue(self: Atom, relocation: types.Relocation, wasm_bin: *const Wa
187	.R_WASM_EVENT_INDEX_LEB => return symbol.index,	186	.R_WASM_EVENT_INDEX_LEB => return symbol.index,
188	.R_WASM_SECTION_OFFSET_I32,	187	.R_WASM_SECTION_OFFSET_I32,
189	.R_WASM_FUNCTION_OFFSET_I32,	188	.R_WASM_FUNCTION_OFFSET_I32,
190	=> return relocation.offset,	189	=> return relocation.addend orelse 0,
191	}	190	}
192	}	191	}