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elf: do not create atoms for section symbols that do not require it

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This commit is contained in:
Jakub Konka
2024-10-04 10:38:43 +02:00
committed by Andrew Kelley
parent ef7bac4aa5
commit c92c72d08c
3 changed files with 123 additions and 78 deletions
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7
src/link/Elf.zig
View File

@@ -3472,12 +3472,7 @@ fn resetShdrIndexes(self: *Elf, backlinks: []const u32) void {
}
}
if (self.zigObjectPtr()) |zo| {
for (zo.atoms_indexes.items) |atom_index| {
const atom_ptr = zo.atom(atom_index) orelse continue;
atom_ptr.output_section_index = backlinks[atom_ptr.output_section_index];
}
}
if (self.zigObjectPtr()) |zo| zo.resetShdrIndexes(backlinks);
for (self.comdat_group_sections.items) |*cg| {
cg.shndx = backlinks[cg.shndx];

3
src/link/Elf/Atom.zig
View File

@@ -935,9 +935,10 @@ fn format2(
_ = unused_fmt_string;
const atom = ctx.atom;
const elf_file = ctx.elf_file;
try writer.print("atom({d}) : {s} : @{x} : shdr({d}) : align({x}) : size({x})", .{
try writer.print("atom({d}) : {s} : @{x} : shdr({d}) : align({x}) : size({x}) : prev({}) : next({})", .{
atom.atom_index, atom.name(elf_file), atom.address(elf_file),
atom.output_section_index, atom.alignment.toByteUnits() orelse 0, atom.size,
atom.prev_atom_ref, atom.next_atom_ref,
});
if (atom.fdes(elf_file).len > 0) {
try writer.writeAll(" : fdes{ ");

191
src/link/Elf/ZigObject.zig
View File

@@ -101,6 +101,28 @@ pub fn init(self: *ZigObject, elf_file: *Elf, options: InitOptions) !void {
.dwarf => |v| {
var dwarf = Dwarf.init(&elf_file.base, v);
const addSectionSymbolWithAtom = struct {
fn addSectionSymbolWithAtom(
zo: *ZigObject,
allocator: Allocator,
name: [:0]const u8,
alignment: Atom.Alignment,
shndx: u32,
) !Symbol.Index {
const name_off = try zo.addString(allocator, name);
const sym_index = try zo.addSectionSymbol(allocator, name_off, shndx);
const sym = zo.symbol(sym_index);
const atom_index = try zo.newAtom(allocator, name_off);
const atom_ptr = zo.atom(atom_index).?;
atom_ptr.alignment = alignment;
atom_ptr.output_section_index = shndx;
sym.ref = .{ .index = atom_index, .file = zo.index };
zo.symtab.items(.shndx)[sym.esym_index] = atom_index;
zo.symtab.items(.elf_sym)[sym.esym_index].st_shndx = SHN_ATOM;
return sym_index;
}
}.addSectionSymbolWithAtom;
if (self.debug_str_index == null) {
const osec = try elf_file.addSection(.{
.name = try elf_file.insertShString(".debug_str"),
@@ -110,7 +132,7 @@ pub fn init(self: *ZigObject, elf_file: *Elf, options: InitOptions) !void {
.addralign = 1,
});
self.debug_str_section_dirty = true;
self.debug_str_index = try self.addSectionSymbol(gpa, ".debug_str", .@"1", osec);
self.debug_str_index = try addSectionSymbolWithAtom(self, gpa, ".debug_str", .@"1", osec);
elf_file.sections.items(.last_atom)[osec] = self.symbol(self.debug_str_index.?).ref;
}
@@ -121,7 +143,7 @@ pub fn init(self: *ZigObject, elf_file: *Elf, options: InitOptions) !void {
.addralign = 1,
});
self.debug_info_section_dirty = true;
self.debug_info_index = try self.addSectionSymbol(gpa, ".debug_info", .@"1", osec);
self.debug_info_index = try addSectionSymbolWithAtom(self, gpa, ".debug_info", .@"1", osec);
elf_file.sections.items(.last_atom)[osec] = self.symbol(self.debug_info_index.?).ref;
}
@@ -132,7 +154,7 @@ pub fn init(self: *ZigObject, elf_file: *Elf, options: InitOptions) !void {
.addralign = 1,
});
self.debug_abbrev_section_dirty = true;
self.debug_abbrev_index = try self.addSectionSymbol(gpa, ".debug_abbrev", .@"1", osec);
self.debug_abbrev_index = try addSectionSymbolWithAtom(self, gpa, ".debug_abbrev", .@"1", osec);
elf_file.sections.items(.last_atom)[osec] = self.symbol(self.debug_abbrev_index.?).ref;
}
@@ -143,7 +165,7 @@ pub fn init(self: *ZigObject, elf_file: *Elf, options: InitOptions) !void {
.addralign = 16,
});
self.debug_aranges_section_dirty = true;
self.debug_aranges_index = try self.addSectionSymbol(gpa, ".debug_aranges", .@"16", osec);
self.debug_aranges_index = try addSectionSymbolWithAtom(self, gpa, ".debug_aranges", .@"16", osec);
elf_file.sections.items(.last_atom)[osec] = self.symbol(self.debug_aranges_index.?).ref;
}
@@ -154,7 +176,7 @@ pub fn init(self: *ZigObject, elf_file: *Elf, options: InitOptions) !void {
.addralign = 1,
});
self.debug_line_section_dirty = true;
self.debug_line_index = try self.addSectionSymbol(gpa, ".debug_line", .@"1", osec);
self.debug_line_index = try addSectionSymbolWithAtom(self, gpa, ".debug_line", .@"1", osec);
elf_file.sections.items(.last_atom)[osec] = self.symbol(self.debug_line_index.?).ref;
}
@@ -167,7 +189,7 @@ pub fn init(self: *ZigObject, elf_file: *Elf, options: InitOptions) !void {
.addralign = 1,
});
self.debug_line_str_section_dirty = true;
self.debug_line_str_index = try self.addSectionSymbol(gpa, ".debug_line_str", .@"1", osec);
self.debug_line_str_index = try addSectionSymbolWithAtom(self, gpa, ".debug_line_str", .@"1", osec);
elf_file.sections.items(.last_atom)[osec] = self.symbol(self.debug_line_str_index.?).ref;
}
@@ -178,7 +200,7 @@ pub fn init(self: *ZigObject, elf_file: *Elf, options: InitOptions) !void {
.addralign = 1,
});
self.debug_loclists_section_dirty = true;
self.debug_loclists_index = try self.addSectionSymbol(gpa, ".debug_loclists", .@"1", osec);
self.debug_loclists_index = try addSectionSymbolWithAtom(self, gpa, ".debug_loclists", .@"1", osec);
elf_file.sections.items(.last_atom)[osec] = self.symbol(self.debug_loclists_index.?).ref;
}
@@ -189,7 +211,7 @@ pub fn init(self: *ZigObject, elf_file: *Elf, options: InitOptions) !void {
.addralign = 1,
});
self.debug_rnglists_section_dirty = true;
self.debug_rnglists_index = try self.addSectionSymbol(gpa, ".debug_rnglists", .@"1", osec);
self.debug_rnglists_index = try addSectionSymbolWithAtom(self, gpa, ".debug_rnglists", .@"1", osec);
elf_file.sections.items(.last_atom)[osec] = self.symbol(self.debug_rnglists_index.?).ref;
}
@@ -204,7 +226,7 @@ pub fn init(self: *ZigObject, elf_file: *Elf, options: InitOptions) !void {
.addralign = ptr_size,
});
self.eh_frame_section_dirty = true;
self.eh_frame_index = try self.addSectionSymbol(gpa, ".eh_frame", Atom.Alignment.fromNonzeroByteUnits(ptr_size), osec);
self.eh_frame_index = try addSectionSymbolWithAtom(self, gpa, ".eh_frame", Atom.Alignment.fromNonzeroByteUnits(ptr_size), osec);
elf_file.sections.items(.last_atom)[osec] = self.symbol(self.eh_frame_index.?).ref;
}
@@ -997,7 +1019,7 @@ pub fn lowerUav(
}
const osec = if (self.data_relro_index) |sym_index|
self.symbol(sym_index).atom(elf_file).?.output_section_index
self.symbol(sym_index).outputShndx(elf_file).?
else osec: {
const osec = try elf_file.addSection(.{
.name = try elf_file.insertShString(".data.rel.ro"),
@@ -1006,7 +1028,7 @@ pub fn lowerUav(
.flags = elf.SHF_ALLOC | elf.SHF_WRITE,
.offset = std.math.maxInt(u64),
});
self.data_relro_index = try self.addSectionSymbol(gpa, ".data.rel.ro", .@"1", osec);
self.data_relro_index = try self.addSectionSymbol(gpa, try self.addString(gpa, ".data.rel.ro"), osec);
break :osec osec;
};
@@ -1112,24 +1134,14 @@ pub fn getOrCreateMetadataForNav(
return gop.value_ptr.symbol_index;
}
// FIXME: we always create an atom to basically store size and alignment, however, this is only true for
// sections that have a single atom like the debug sections. It would be a better solution to decouple this
// concept from the atom, maybe.
fn addSectionSymbol(
self: *ZigObject,
allocator: Allocator,
name: [:0]const u8,
alignment: Atom.Alignment,
shndx: u32,
) !Symbol.Index {
const name_off = try self.addString(allocator, name);
const index = try self.newSymbolWithAtom(allocator, name_off);
fn addSectionSymbol(self: *ZigObject, allocator: Allocator, name_off: u32, shndx: u32) !Symbol.Index {
const index = try self.newLocalSymbol(allocator, name_off);
const sym = self.symbol(index);
const esym = &self.symtab.items(.elf_sym)[sym.esym_index];
esym.st_info |= elf.STT_SECTION;
const atom_ptr = self.atom(sym.ref.index).?;
atom_ptr.alignment = alignment;
atom_ptr.output_section_index = shndx;
// TODO create fake shdrs?
// esym.st_shndx = shndx;
sym.output_section_index = shndx;
return index;
}
@@ -1148,7 +1160,7 @@ fn getNavShdrIndex(
const nav_val = zcu.navValue(nav_index);
if (ip.isFunctionType(nav_val.typeOf(zcu).toIntern())) {
if (self.text_index) |symbol_index|
return self.symbol(symbol_index).atom(elf_file).?.output_section_index;
return self.symbol(symbol_index).outputShndx(elf_file).?;
const osec = try elf_file.addSection(.{
.type = elf.SHT_PROGBITS,
.flags = elf.SHF_ALLOC | elf.SHF_EXECINSTR,
@@ -1156,7 +1168,7 @@ fn getNavShdrIndex(
.addralign = 1,
.offset = std.math.maxInt(u64),
});
self.text_index = try self.addSectionSymbol(gpa, ".text", .@"1", osec);
self.text_index = try self.addSectionSymbol(gpa, try self.addString(gpa, ".text"), osec);
return osec;
}
const is_const, const is_threadlocal, const nav_init = switch (ip.indexToKey(nav_val.toIntern())) {
@@ -1171,18 +1183,18 @@ fn getNavShdrIndex(
} else true;
if (is_bss) {
if (self.tbss_index) |symbol_index|
return self.symbol(symbol_index).atom(elf_file).?.output_section_index;
return self.symbol(symbol_index).outputShndx(elf_file).?;
const osec = try elf_file.addSection(.{
.name = try elf_file.insertShString(".tbss"),
.flags = elf.SHF_ALLOC | elf.SHF_WRITE | elf.SHF_TLS,
.type = elf.SHT_NOBITS,
.addralign = 1,
});
self.tbss_index = try self.addSectionSymbol(gpa, ".tbss", .@"1", osec);
self.tbss_index = try self.addSectionSymbol(gpa, try self.addString(gpa, ".tbss"), osec);
return osec;
}
if (self.tdata_index) |symbol_index|
return self.symbol(symbol_index).atom(elf_file).?.output_section_index;
return self.symbol(symbol_index).outputShndx(elf_file).?;
const osec = try elf_file.addSection(.{
.type = elf.SHT_PROGBITS,
.flags = elf.SHF_ALLOC | elf.SHF_WRITE | elf.SHF_TLS,
@@ -1190,12 +1202,12 @@ fn getNavShdrIndex(
.addralign = 1,
.offset = std.math.maxInt(u64),
});
self.tdata_index = try self.addSectionSymbol(gpa, ".tdata", .@"1", osec);
self.tdata_index = try self.addSectionSymbol(gpa, try self.addString(gpa, ".tdata"), osec);
return osec;
}
if (is_const) {
if (self.data_relro_index) |symbol_index|
return self.symbol(symbol_index).atom(elf_file).?.output_section_index;
return self.symbol(symbol_index).outputShndx(elf_file).?;
const osec = try elf_file.addSection(.{
.name = try elf_file.insertShString(".data.rel.ro"),
.type = elf.SHT_PROGBITS,
@@ -1203,14 +1215,14 @@ fn getNavShdrIndex(
.flags = elf.SHF_ALLOC | elf.SHF_WRITE,
.offset = std.math.maxInt(u64),
});
self.data_relro_index = try self.addSectionSymbol(gpa, ".data.rel.ro", .@"1", osec);
self.data_relro_index = try self.addSectionSymbol(gpa, try self.addString(gpa, ".data.rel.ro"), osec);
return osec;
}
if (nav_init != .none and Value.fromInterned(nav_init).isUndefDeep(zcu))
return switch (zcu.navFileScope(nav_index).mod.optimize_mode) {
.Debug, .ReleaseSafe => {
if (self.data_index) |symbol_index|
return self.symbol(symbol_index).atom(elf_file).?.output_section_index;
return self.symbol(symbol_index).outputShndx(elf_file).?;
const osec = try elf_file.addSection(.{
.name = try elf_file.insertShString(".data"),
.type = elf.SHT_PROGBITS,
@@ -1218,24 +1230,19 @@ fn getNavShdrIndex(
.flags = elf.SHF_ALLOC | elf.SHF_WRITE,
.offset = std.math.maxInt(u64),
});
self.data_index = try self.addSectionSymbol(
gpa,
".data",
Atom.Alignment.fromNonzeroByteUnits(ptr_size),
osec,
);
self.data_index = try self.addSectionSymbol(gpa, try self.addString(gpa, ".data"), osec);
return osec;
},
.ReleaseFast, .ReleaseSmall => {
if (self.bss_index) |symbol_index|
return self.symbol(symbol_index).atom(elf_file).?.output_section_index;
return self.symbol(symbol_index).outputShndx(elf_file).?;
const osec = try elf_file.addSection(.{
.type = elf.SHT_NOBITS,
.flags = elf.SHF_ALLOC | elf.SHF_WRITE,
.name = try elf_file.insertShString(".bss"),
.addralign = 1,
});
self.bss_index = try self.addSectionSymbol(gpa, ".bss", .@"1", osec);
self.bss_index = try self.addSectionSymbol(gpa, try self.addString(gpa, ".bss"), osec);
return osec;
},
};
@@ -1244,18 +1251,18 @@ fn getNavShdrIndex(
} else true;
if (is_bss) {
if (self.bss_index) |symbol_index|
return self.symbol(symbol_index).atom(elf_file).?.output_section_index;
return self.symbol(symbol_index).outputShndx(elf_file).?;
const osec = try elf_file.addSection(.{
.type = elf.SHT_NOBITS,
.flags = elf.SHF_ALLOC | elf.SHF_WRITE,
.name = try elf_file.insertShString(".bss"),
.addralign = 1,
});
self.bss_index = try self.addSectionSymbol(gpa, ".bss", .@"1", osec);
self.bss_index = try self.addSectionSymbol(gpa, try self.addString(gpa, ".bss"), osec);
return osec;
}
if (self.data_index) |symbol_index|
return self.symbol(symbol_index).atom(elf_file).?.output_section_index;
return self.symbol(symbol_index).outputShndx(elf_file).?;
const osec = try elf_file.addSection(.{
.name = try elf_file.insertShString(".data"),
.type = elf.SHT_PROGBITS,
@@ -1263,12 +1270,7 @@ fn getNavShdrIndex(
.flags = elf.SHF_ALLOC | elf.SHF_WRITE,
.offset = std.math.maxInt(u64),
});
self.data_index = try self.addSectionSymbol(
gpa,
".data",
Atom.Alignment.fromNonzeroByteUnits(ptr_size),
osec,
);
self.data_index = try self.addSectionSymbol(gpa, try self.addString(gpa, ".data"), osec);
return osec;
}
@@ -1521,7 +1523,7 @@ pub fn updateFunc(
.addralign = 1,
.offset = std.math.maxInt(u64),
});
self.text_index = try self.addSectionSymbol(gpa, ".text", .@"1", osec);
self.text_index = try self.addSectionSymbol(gpa, try self.addString(gpa, ".text"), osec);
break :osec osec;
};
const name_off = try self.addString(gpa, name);
@@ -1688,7 +1690,7 @@ fn updateLazySymbol(
const output_section_index = switch (sym.kind) {
.code => if (self.text_index) |sym_index|
self.symbol(sym_index).atom(elf_file).?.output_section_index
self.symbol(sym_index).outputShndx(elf_file).?
else osec: {
const osec = try elf_file.addSection(.{
.name = try elf_file.insertShString(".text"),
@@ -1697,11 +1699,11 @@ fn updateLazySymbol(
.flags = elf.SHF_ALLOC | elf.SHF_EXECINSTR,
.offset = std.math.maxInt(u64),
});
self.text_index = try self.addSectionSymbol(gpa, ".text", .@"1", osec);
self.text_index = try self.addSectionSymbol(gpa, try self.addString(gpa, ".text"), osec);
break :osec osec;
},
.const_data => if (self.rodata_index) |sym_index|
self.symbol(sym_index).atom(elf_file).?.output_section_index
self.symbol(sym_index).outputShndx(elf_file).?
else osec: {
const osec = try elf_file.addSection(.{
.name = try elf_file.insertShString(".rodata"),
@@ -1710,7 +1712,7 @@ fn updateLazySymbol(
.flags = elf.SHF_ALLOC,
.offset = std.math.maxInt(u64),
});
self.rodata_index = try self.addSectionSymbol(gpa, ".rodata", .@"1", osec);
self.rodata_index = try self.addSectionSymbol(gpa, try self.addString(gpa, ".rodata"), osec);
break :osec osec;
},
};
@@ -2011,20 +2013,10 @@ fn allocateAtom(self: *ZigObject, atom_ptr: *Atom, elf_file: *Elf) !void {
}
shdr.sh_addralign = @max(shdr.sh_addralign, atom_ptr.alignment.toByteUnits().?);
const sect_atom_ptr = for ([_]?Symbol.Index{
self.text_index,
self.rodata_index,
self.data_relro_index,
self.data_index,
self.tdata_index,
}) |maybe_sym_index| {
const sect_sym_index = maybe_sym_index orelse continue;
const sect_atom_ptr = self.symbol(sect_sym_index).atom(elf_file).?;
if (sect_atom_ptr.output_section_index == atom_ptr.output_section_index) break sect_atom_ptr;
} else null;
if (sect_atom_ptr) |sap| {
sap.size = shdr.sh_size;
sap.alignment = Atom.Alignment.fromNonzeroByteUnits(shdr.sh_addralign);
if (self.sectionSymbol(atom_ptr.output_section_index, elf_file)) |sym| {
assert(sym.atom(elf_file) == null and sym.mergeSubsection(elf_file) == null);
const esym = &self.symtab.items(.elf_sym)[sym.esym_index];
esym.st_size += atom_ptr.size + Elf.padToIdeal(atom_ptr.size);
}
// This function can also reallocate an atom.
@@ -2053,10 +2045,67 @@ fn growAtom(self: *ZigObject, atom_ptr: *Atom, elf_file: *Elf) !void {
}
}
pub fn resetShdrIndexes(self: *ZigObject, backlinks: anytype) void {
for (self.atoms_indexes.items) |atom_index| {
const atom_ptr = self.atom(atom_index) orelse continue;
atom_ptr.output_section_index = backlinks[atom_ptr.output_section_index];
}
inline for ([_]?Symbol.Index{
self.text_index,
self.rodata_index,
self.data_relro_index,
self.data_index,
self.bss_index,
self.tdata_index,
self.tbss_index,
self.eh_frame_index,
self.debug_info_index,
self.debug_abbrev_index,
self.debug_aranges_index,
self.debug_str_index,
self.debug_line_index,
self.debug_line_str_index,
self.debug_loclists_index,
self.debug_rnglists_index,
}) |maybe_sym_index| {
if (maybe_sym_index) |sym_index| {
const sym = self.symbol(sym_index);
sym.output_section_index = backlinks[sym.output_section_index];
}
}
}
pub fn asFile(self: *ZigObject) File {
return .{ .zig_object = self };
}
pub fn sectionSymbol(self: *ZigObject, shndx: u32, elf_file: *Elf) ?*Symbol {
inline for ([_]?Symbol.Index{
self.text_index,
self.rodata_index,
self.data_relro_index,
self.data_index,
self.bss_index,
self.tdata_index,
self.tbss_index,
self.eh_frame_index,
self.debug_info_index,
self.debug_abbrev_index,
self.debug_aranges_index,
self.debug_str_index,
self.debug_line_index,
self.debug_line_str_index,
self.debug_loclists_index,
self.debug_rnglists_index,
}) |maybe_sym_index| {
if (maybe_sym_index) |sym_index| {
const sym = self.symbol(sym_index);
if (sym.outputShndx(elf_file) == shndx) return sym;
}
}
return null;
}
pub fn addString(self: *ZigObject, allocator: Allocator, string: []const u8) !u32 {
return self.strtab.insert(allocator, string);
}