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elf: create required linker-defined symbols

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This commit is contained in:
Jakub Konka
2023-09-10 08:41:13 +02:00
parent a6e9163284
commit a455b5692a
4 changed files with 99 additions and 18 deletions
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92
src/link/Elf.zig
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@@ -36,6 +36,7 @@ phdr_load_rw_index: ?u16 = null,
entry_addr: ?u64 = null,
page_size: u32,
default_sym_version: elf.Elf64_Versym,
/// .shstrtab buffer
shstrtab: StringTable(.strtab) = .{},
@@ -57,6 +58,23 @@ shstrtab_section_index: ?u16 = null,
strtab_section_index: ?u16 = null,
symtab_section_index: ?u16 = null,
// Linker-defined symbols
dynamic_index: ?Symbol.Index = null,
ehdr_start_index: ?Symbol.Index = null,
init_array_start_index: ?Symbol.Index = null,
init_array_end_index: ?Symbol.Index = null,
fini_array_start_index: ?Symbol.Index = null,
fini_array_end_index: ?Symbol.Index = null,
preinit_array_start_index: ?Symbol.Index = null,
preinit_array_end_index: ?Symbol.Index = null,
got_index: ?Symbol.Index = null,
plt_index: ?Symbol.Index = null,
end_index: ?Symbol.Index = null,
gnu_eh_frame_hdr_index: ?Symbol.Index = null,
dso_handle_index: ?Symbol.Index = null,
rela_iplt_start_index: ?Symbol.Index = null,
rela_iplt_end_index: ?Symbol.Index = null,
symbols: std.ArrayListUnmanaged(Symbol) = .{},
symbols_extra: std.ArrayListUnmanaged(u32) = .{},
resolver: std.AutoArrayHashMapUnmanaged(u32, Symbol.Index) = .{},
@@ -188,6 +206,10 @@ pub fn createEmpty(gpa: Allocator, options: link.Options) !*Elf {
.sparc64 => 0x2000,
else => 0x1000,
};
const default_sym_version: elf.Elf64_Versym = if (options.output_mode == .Lib and options.link_mode == .Dynamic)
elf.VER_NDX_GLOBAL
else
elf.VER_NDX_LOCAL;
var dwarf: ?Dwarf = if (!options.strip and options.module != null)
Dwarf.init(gpa, &self.base, options.target)
@@ -204,6 +226,7 @@ pub fn createEmpty(gpa: Allocator, options: link.Options) !*Elf {
.dwarf = dwarf,
.ptr_width = ptr_width,
.page_size = page_size,
.default_sym_version = default_sym_version,
};
const use_llvm = options.use_llvm;
if (use_llvm) {
@@ -987,11 +1010,12 @@ pub fn flushModule(self: *Elf, comp: *Compilation, prog_node: *std.Progress.Node
// corresponds to the Zig source code.
const module = self.base.options.module orelse return error.LinkingWithoutZigSourceUnimplemented;
self.linker_defined_index = blk: {
const index = @as(File.Index, @intCast(try self.files.addOne(gpa)));
self.files.set(index, .{ .linker_defined = .{ .index = index } });
break :blk index;
const compiler_rt_path: ?[]const u8 = blk: {
if (comp.compiler_rt_lib) |x| break :blk x.full_object_path;
if (comp.compiler_rt_obj) |x| break :blk x.full_object_path;
break :blk null;
};
_ = compiler_rt_path;
if (self.lazy_syms.getPtr(.none)) |metadata| {
// Most lazy symbols can be updated on first use, but
@@ -1023,6 +1047,16 @@ pub fn flushModule(self: *Elf, comp: *Compilation, prog_node: *std.Progress.Node
try dw.flushModule(module);
}
if (self.linker_defined_index == null) {
const index = @as(File.Index, @intCast(try self.files.addOne(gpa)));
self.files.set(index, .{ .linker_defined = .{ .index = index } });
self.linker_defined_index = index;
}
try self.addLinkerDefinedSymbols();
// Beyond this point, everything has been allocated a virtual address and we can resolve
// the relocations.
{
var it = self.relocs.iterator();
while (it.next()) |entry| {
@@ -2682,6 +2716,54 @@ pub fn deleteDeclExport(
sym_index.* = 0;
}
fn addLinkerDefinedSymbols(self: *Elf) !void {
const linker_defined_index = self.linker_defined_index orelse return;
const linker_defined = self.file(linker_defined_index).?.linker_defined;
self.dynamic_index = try linker_defined.addGlobal("_DYNAMIC", self);
self.ehdr_start_index = try linker_defined.addGlobal("__ehdr_start", self);
self.init_array_start_index = try linker_defined.addGlobal("__init_array_start", self);
self.init_array_end_index = try linker_defined.addGlobal("__init_array_end", self);
self.fini_array_start_index = try linker_defined.addGlobal("__fini_array_start", self);
self.fini_array_end_index = try linker_defined.addGlobal("__fini_array_end", self);
self.preinit_array_start_index = try linker_defined.addGlobal("__preinit_array_start", self);
self.preinit_array_end_index = try linker_defined.addGlobal("__preinit_array_end", self);
self.got_index = try linker_defined.addGlobal("_GLOBAL_OFFSET_TABLE_", self);
self.plt_index = try linker_defined.addGlobal("_PROCEDURE_LINKAGE_TABLE_", self);
self.end_index = try linker_defined.addGlobal("_end", self);
if (self.base.options.eh_frame_hdr) {
self.gnu_eh_frame_hdr_index = try linker_defined.addGlobal("__GNU_EH_FRAME_HDR", self);
}
if (self.globalByName("__dso_handle")) |index| {
if (self.symbol(index).file(self) == null)
self.dso_handle_index = try linker_defined.addGlobal("__dso_handle", self);
}
self.rela_iplt_start_index = try linker_defined.addGlobal("__rela_iplt_start", self);
self.rela_iplt_end_index = try linker_defined.addGlobal("__rela_iplt_end", self);
// for (self.objects.items) |index| {
// const object = self.getFile(index).?.object;
// for (object.atoms.items) |atom_index| {
// if (self.getStartStopBasename(atom_index)) |name| {
// const gpa = self.base.allocator;
// try self.start_stop_indexes.ensureUnusedCapacity(gpa, 2);
// const start = try std.fmt.allocPrintZ(gpa, "__start_{s}", .{name});
// defer gpa.free(start);
// const stop = try std.fmt.allocPrintZ(gpa, "__stop_{s}", .{name});
// defer gpa.free(stop);
// self.start_stop_indexes.appendAssumeCapacity(try internal.addSyntheticGlobal(start, self));
// self.start_stop_indexes.appendAssumeCapacity(try internal.addSyntheticGlobal(stop, self));
// }
// }
// }
linker_defined.resolveSymbols(self);
}
fn updateSymtabSize(self: *Elf) !void {
var sizes = SymtabSize{};
@@ -3193,7 +3275,7 @@ pub fn getOrPutGlobal(self: *Elf, name_off: u32) !GetOrPutGlobalResult {
};
}
pub fn getGlobalByName(self: *Elf, name: []const u8) ?Symbol.Index {
pub fn globalByName(self: *Elf, name: []const u8) ?Symbol.Index {
const name_off = self.strtab.getOffset(name) orelse return null;
return self.resolver.get(name_off);
}

16
src/link/Elf/LinkerDefined.zig
View File

@@ -22,7 +22,7 @@ pub fn addGlobal(self: *LinkerDefined, name: [:0]const u8, elf_file: *Elf) !u32
.st_value = 0,
.st_size = 0,
});
const off = try elf_file.internString("{s}", .{name});
const off = try elf_file.strtab.insert(gpa, name);
const gop = try elf_file.getOrPutGlobal(off);
self.symbols.addOneAssumeCapacity().* = gop.index;
return gop.index;
@@ -37,14 +37,12 @@ pub fn resolveSymbols(self: *LinkerDefined, elf_file: *Elf) void {
const global = elf_file.symbol(index);
if (self.asFile().symbolRank(this_sym, false) < global.symbolRank(elf_file)) {
global.* = .{
.value = 0,
.name = global.name,
.atom = 0,
.file = self.index,
.sym_idx = sym_idx,
.ver_idx = elf_file.default_sym_version,
};
global.value = 0;
global.name_offset = global.name_offset;
global.atom_index = 0;
global.file_index = self.index;
global.esym_index = sym_idx;
global.version_index = elf_file.default_sym_version;
}
}
}

2
src/link/Elf/Symbol.zig
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@@ -81,7 +81,7 @@ pub fn symbolRank(symbol: Symbol, elf_file: *Elf) u32 {
// .object => |x| !x.alive,
else => false,
};
return file_ptr.symbolRank(sym, in_archive);
return file_ptr.symbolRank(sym.*, in_archive);
}
pub fn address(symbol: Symbol, opts: struct {

7
src/link/Elf/file.zig
View File

@@ -25,8 +25,8 @@ pub const File = union(enum) {
switch (file) {
.zig_module => try writer.writeAll("(zig module)"),
.linker_defined => try writer.writeAll("(linker defined)"),
.object => |x| try writer.print("{}", .{x.fmtPath()}),
.shared_object => |x| try writer.writeAll(x.path),
// .object => |x| try writer.print("{}", .{x.fmtPath()}),
// .shared_object => |x| try writer.writeAll(x.path),
}
}
@@ -62,7 +62,8 @@ pub const File = union(enum) {
pub fn symbolRank(file: File, sym: elf.Elf64_Sym, in_archive: bool) u32 {
const base: u3 = blk: {
if (sym.st_shndx == elf.SHN_COMMON) break :blk if (in_archive) 6 else 5;
if (file == .shared or in_archive) break :blk switch (sym.st_bind()) {
// if (file == .shared or in_archive) break :blk switch (sym.st_bind()) {
if (in_archive) break :blk switch (sym.st_bind()) {
elf.STB_GLOBAL => 3,
else => 4,
};