tiny.tldr.formats.elf.got_table

1const std = @import("std");2const root = @import("../../root.zig");3const addressing = @import("address/root.zig");4const format = @import("format.zig");5const layout = @import("layout/root.zig");6const output_section = @import("section.zig");7const parser = @import("parser.zig");8const relocation = @import("relocation/root.zig");9const sections = @import("sections.zig");1011const Allocator = std.mem.Allocator;12const model = root.model;13const ObjectFile = parser.ObjectFile;14const GlobalSymbol = layout.GlobalSymbol;15const GotEntry = layout.GotEntry;16const GotLayout = layout.GotLayout;17const ObjectLayout = layout.ObjectLayout;18const OutputSection = layout.OutputSection;19const OutputSectionKind = output_section.OutputSectionKind;20const SymbolRef = layout.SymbolRef;21const output_section_count = output_section.output_section_count;22const foldedSection = sections.foldedSection;23const sectionDiscarded = sections.sectionDiscarded;24const sectionRelocationsAffectOutput = relocation.sectionRelocationsAffectOutput;25const symbolAddress = addressing.symbolAddress;26const symbolSectionDiscarded = sections.symbolSectionDiscarded;27const writeU64 = format.writeU64;2829pub fn collectEntries(30    allocator: Allocator,31    objects: []const ObjectFile,32    output_sections: *[output_section_count]OutputSection,33    globals: *const std.StringHashMapUnmanaged(GlobalSymbol),34) model.Error!GotLayout {35    var entries: std.ArrayListUnmanaged(GotEntry) = .empty;36    errdefer entries.deinit(allocator);3738    for (objects, 0..) |object, object_index| {39        if (object.relocations.len == 0) continue;40        for (object.sections, 0..) |_, section_index| {41            if (!sectionRelocationsAffectOutput(object, section_index)) continue;42            if (sectionDiscarded(object, section_index)) continue;43            if (foldedSection(object, section_index) != null) continue;44            for (object.relocationsForSection(section_index)) |relocation_record| {45                if (relocation_record.relocationType() != @backingInt(std.elf.R_X86_64.GOTPCREL)) continue;46                const ref = try canonicalSymbolRef(objects, globals, object_index, @intCast(relocation_record.symbolIndex()));47                if ((GotLayout{ .entries = entries.items }).entryOffset(ref) != null) continue;48                const offset = try checkedOffset(entries.items.len);49                try entries.append(allocator, .{ .ref = ref, .offset = offset });50            }51        }52    }5354    if (entries.items.len != 0) {55        const size = try checkedSize(entries.items.len);56        var output = &output_sections[@backingInt(OutputSectionKind.got)];57        output.file_size = size;58        output.memory_size = size;59        output.alignment = @max(output.alignment, 8);60    }6162    return .{ .entries = try entries.toOwnedSlice(allocator) };63}6465pub fn collectEntriesWithIfunc(66    allocator: Allocator,67    objects: []const ObjectFile,68    output_sections: *[output_section_count]OutputSection,69    globals: *const std.StringHashMapUnmanaged(GlobalSymbol),70    ifunc_collector: anytype,71) model.Error!GotLayout {72    var entries: std.ArrayListUnmanaged(GotEntry) = .empty;73    errdefer entries.deinit(allocator);7475    for (objects, 0..) |object, object_index| {76        if (object.relocations.len == 0) continue;77        for (object.sections, 0..) |_, section_index| {78            if (sectionDiscarded(object, section_index)) continue;79            if (foldedSection(object, section_index) != null) continue;80            const affects_output = sectionRelocationsAffectOutput(object, section_index);81            if (!affects_output) continue;82            for (object.relocationsForSection(section_index)) |relocation_record| {83                try ifunc_collector.observe(allocator, object_index, relocation_record);84                if (relocation_record.relocationType() != @backingInt(std.elf.R_X86_64.GOTPCREL)) continue;85                const ref = try canonicalSymbolRef(objects, globals, object_index, @intCast(relocation_record.symbolIndex()));86                if ((GotLayout{ .entries = entries.items }).entryOffset(ref) != null) continue;87                const offset = try checkedOffset(entries.items.len);88                try entries.append(allocator, .{ .ref = ref, .offset = offset });89            }90        }91    }9293    if (entries.items.len != 0) {94        const size = try checkedSize(entries.items.len);95        var output = &output_sections[@backingInt(OutputSectionKind.got)];96        output.file_size = size;97        output.memory_size = size;98        output.alignment = @max(output.alignment, 8);99    }100101    return .{ .entries = try entries.toOwnedSlice(allocator) };102}103104pub fn canonicalSymbolRef(105    objects: []const ObjectFile,106    globals: *const std.StringHashMapUnmanaged(GlobalSymbol),107    object_index: usize,108    symbol_index: usize,109) model.Error!SymbolRef {110    if (object_index >= objects.len) return error.UndefinedSymbol;111    const object = objects[object_index];112    if (symbol_index >= object.symbols.len) return error.UndefinedSymbol;113    const symbol = object.symbols[symbol_index];114    const current_ref = SymbolRef{ .object_index = object_index, .symbol_index = symbol_index };115    if (symbol.isUndefined()) {116        const global = globals.get(symbol.name) orelse return current_ref;117        return global.ref;118    }119    if ((symbolSectionDiscarded(object, symbol) or symbol.isCommon()) and symbol.name.len != 0) {120        const global = globals.get(symbol.name) orelse return current_ref;121        return global.ref;122    }123    return current_ref;124}125126pub fn writePayload(127    image: []u8,128    objects: []const ObjectFile,129    layouts: []const ObjectLayout,130    output_sections: []const OutputSection,131    globals: *const std.StringHashMapUnmanaged(GlobalSymbol),132    symbol_addresses: *addressing.Cache,133    got_layout: GotLayout,134) model.Error!void {135    if (got_layout.entries.len == 0) return;136    const got = output_sections[@backingInt(OutputSectionKind.got)];137    for (got_layout.entries) |entry| {138        const address = try symbolAddress(.serial, objects, layouts, output_sections, globals, symbol_addresses, entry.ref.object_index, entry.ref.symbol_index);139        writeU64(image, @intCast(got.file_offset + entry.offset), address);140    }141}142143fn checkedOffset(entry_count: usize) model.Error!u64 {144    if (entry_count > std.math.maxInt(u64) / 8) return error.InvalidRange;145    return @as(u64, @intCast(entry_count)) * 8;146}147148fn checkedSize(entry_count: usize) model.Error!u64 {149    return checkedOffset(entry_count);150}

1pub const got_table = @import("got.zig");