tiny.tldr.formats.elf.relocation.count

1const std = @import("std");2const root = @import("../../../root.zig");3const elf = @import("../root.zig");4const relocation_model = @import("model.zig");56const Allocator = std.mem.Allocator;7const model = root.model;8const format = elf.format;9const output_section = elf.output_section;10const rela_size = format.rela_size;11const SectionHeader = format.SectionHeader;12const ObjectParseOptions = relocation_model.ObjectParseOptions;13const RelocationCounts = relocation_model.RelocationCounts;14const SectionMetadata = relocation_model.SectionMetadata;15const sectionBytes = format.sectionBytes;16const stringFromTable = format.stringFromTable;17const readU64 = format.readU64;18const writeU64 = format.writeU64;19const debugOutputIndexForName = output_section.debugOutputIndexForName;2021fn sectionNameFromTableOrEmpty(section_names: []const u8, section: SectionHeader) []const u8 {22    return stringFromTable(section_names, section.name_offset) catch "";23}2425pub fn scanSectionMetadata(sections: []const SectionHeader) SectionMetadata {26    var metadata = SectionMetadata{};27    for (sections, 0..) |section, index| {28        if (metadata.symtab_index == null and section.section_type == std.elf.SHT_SYMTAB) metadata.symtab_index = index;29        if (section.section_type == std.elf.SHT_GROUP) metadata.has_group_sections = true;30        if (section.section_type == std.elf.SHT_REL or section.section_type == std.elf.SHT_RELA) {31            metadata.has_relocation_sections = true;32        }33    }34    return metadata;35}3637pub fn countRelocationsBySection(38    allocator: Allocator,39    bytes: []const u8,40    sections: []const SectionHeader,41    section_names: []const u8,42    symtab_index: ?usize,43    parse_options: ObjectParseOptions,44) model.Error!RelocationCounts {45    if (symtab_index == null) return error.MissingSymbolTable;4647    const relocation_counts = try allocator.alloc(usize, sections.len);48    errdefer allocator.free(relocation_counts);49    @memset(relocation_counts, 0);5051    var duplicate_targets = false;52    for (sections) |section| {53        if (section.section_type == std.elf.SHT_REL or section.section_type == std.elf.SHT_RELA) {54            if (try relocationSectionSkipped(section, sections, section_names, parse_options)) continue;55        }56        if (section.section_type == std.elf.SHT_REL) return error.UnsupportedRelocation;57        if (section.section_type != std.elf.SHT_RELA) continue;58        if (section.entry_size != rela_size or section.size % rela_size != 0) return error.InvalidObject;59        if (section.info >= sections.len) return error.MissingSection;6061        const rela_bytes = try sectionBytes(bytes, section);62        const rela_count = rela_bytes.len / rela_size;63        const effective_count = if (relocationSectionAllNone(rela_bytes)) 0 else rela_count;64        if (relocation_counts[section.info] != 0 and effective_count != 0) duplicate_targets = true;65        if (effective_count > std.math.maxInt(usize) - relocation_counts[section.info]) return error.InvalidObject;66        relocation_counts[section.info] += effective_count;67    }6869    return .{70        .counts = relocation_counts,71        .duplicate_targets = duplicate_targets,72    };73}7475pub fn relocationSectionSkipped(76    section: SectionHeader,77    sections: []const SectionHeader,78    section_names: []const u8,79    parse_options: ObjectParseOptions,80) model.Error!bool {81    if (!parse_options.strip_debug) return false;82    if (section.info >= sections.len) return error.MissingSection;83    return debugOutputIndexForName(sectionNameFromTableOrEmpty(section_names, sections[section.info])) != null;84}8586pub fn relocationSectionAllNone(rela_bytes: []const u8) bool {87    var offset: usize = 0;88    while (offset < rela_bytes.len) : (offset += rela_size) {89        if (@as(u32, @truncate(readU64(rela_bytes, offset + 8))) != @backingInt(std.elf.R_X86_64.NONE)) return false;90    }91    return true;92}

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