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Merge pull request #18918 from ziglang/elf-better-addr-mgmt
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elf: store relative offsets in atom and symbol
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@kubkon
kubkon authored Feb 14, 2024
2 parents 5f92558 + 216a559 commit 3f55932
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Showing 8 changed files with 139 additions and 156 deletions.
130 changes: 60 additions & 70 deletions src/link/Elf.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -138,40 +138,40 @@ comdat_group_sections: std.ArrayListUnmanaged(ComdatGroupSection) = .{},

/// Tracked section headers with incremental updates to Zig object.
/// .rela.* sections are only used when emitting a relocatable object file.
zig_text_section_index: ?u16 = null,
zig_data_rel_ro_section_index: ?u16 = null,
zig_data_section_index: ?u16 = null,
zig_bss_section_index: ?u16 = null,
zig_got_section_index: ?u16 = null,

debug_info_section_index: ?u16 = null,
debug_abbrev_section_index: ?u16 = null,
debug_str_section_index: ?u16 = null,
debug_aranges_section_index: ?u16 = null,
debug_line_section_index: ?u16 = null,

copy_rel_section_index: ?u16 = null,
dynamic_section_index: ?u16 = null,
dynstrtab_section_index: ?u16 = null,
dynsymtab_section_index: ?u16 = null,
eh_frame_section_index: ?u16 = null,
eh_frame_rela_section_index: ?u16 = null,
eh_frame_hdr_section_index: ?u16 = null,
hash_section_index: ?u16 = null,
gnu_hash_section_index: ?u16 = null,
got_section_index: ?u16 = null,
got_plt_section_index: ?u16 = null,
interp_section_index: ?u16 = null,
plt_section_index: ?u16 = null,
plt_got_section_index: ?u16 = null,
rela_dyn_section_index: ?u16 = null,
rela_plt_section_index: ?u16 = null,
versym_section_index: ?u16 = null,
verneed_section_index: ?u16 = null,

shstrtab_section_index: ?u16 = null,
strtab_section_index: ?u16 = null,
symtab_section_index: ?u16 = null,
zig_text_section_index: ?u32 = null,
zig_data_rel_ro_section_index: ?u32 = null,
zig_data_section_index: ?u32 = null,
zig_bss_section_index: ?u32 = null,
zig_got_section_index: ?u32 = null,

debug_info_section_index: ?u32 = null,
debug_abbrev_section_index: ?u32 = null,
debug_str_section_index: ?u32 = null,
debug_aranges_section_index: ?u32 = null,
debug_line_section_index: ?u32 = null,

copy_rel_section_index: ?u32 = null,
dynamic_section_index: ?u32 = null,
dynstrtab_section_index: ?u32 = null,
dynsymtab_section_index: ?u32 = null,
eh_frame_section_index: ?u32 = null,
eh_frame_rela_section_index: ?u32 = null,
eh_frame_hdr_section_index: ?u32 = null,
hash_section_index: ?u32 = null,
gnu_hash_section_index: ?u32 = null,
got_section_index: ?u32 = null,
got_plt_section_index: ?u32 = null,
interp_section_index: ?u32 = null,
plt_section_index: ?u32 = null,
plt_got_section_index: ?u32 = null,
rela_dyn_section_index: ?u32 = null,
rela_plt_section_index: ?u32 = null,
versym_section_index: ?u32 = null,
verneed_section_index: ?u32 = null,

shstrtab_section_index: ?u32 = null,
strtab_section_index: ?u32 = null,
symtab_section_index: ?u32 = null,

// Linker-defined symbols
dynamic_index: ?Symbol.Index = null,
Expand Down Expand Up @@ -931,7 +931,7 @@ pub fn initMetadata(self: *Elf, options: InitMetadataOptions) !void {
try self.base.file.?.pwriteAll(&[1]u8{0}, end_pos);
}

pub fn growAllocSection(self: *Elf, shdr_index: u16, needed_size: u64) !void {
pub fn growAllocSection(self: *Elf, shdr_index: u32, needed_size: u64) !void {
const shdr = &self.shdrs.items[shdr_index];
const maybe_phdr = if (self.phdr_to_shdr_table.get(shdr_index)) |phndx| &self.phdrs.items[phndx] else null;
const is_zerofill = shdr.sh_type == elf.SHT_NOBITS;
Expand Down Expand Up @@ -981,7 +981,7 @@ pub fn growAllocSection(self: *Elf, shdr_index: u16, needed_size: u64) !void {

pub fn growNonAllocSection(
self: *Elf,
shdr_index: u16,
shdr_index: u32,
needed_size: u64,
min_alignment: u32,
requires_file_copy: bool,
Expand Down Expand Up @@ -1018,7 +1018,7 @@ pub fn growNonAllocSection(
self.markDirty(shdr_index);
}

pub fn markDirty(self: *Elf, shdr_index: u16) void {
pub fn markDirty(self: *Elf, shdr_index: u32) void {
const zig_object = self.zigObjectPtr().?;
if (zig_object.dwarf) |_| {
if (self.debug_info_section_index.? == shdr_index) {
Expand Down Expand Up @@ -1332,7 +1332,6 @@ pub fn flushModule(self: *Elf, arena: Allocator, prog_node: *std.Progress.Node)
try self.sortPhdrs();
try self.allocateNonAllocSections();
self.allocateSpecialPhdrs();
self.allocateAtoms();
self.allocateLinkerDefinedSymbols();

// Dump the state for easy debugging.
Expand All @@ -1352,7 +1351,7 @@ pub fn flushModule(self: *Elf, arena: Allocator, prog_node: *std.Progress.Node)
if (shdr.sh_type == elf.SHT_NOBITS) continue;
const code = try zig_object.codeAlloc(self, atom_index);
defer gpa.free(code);
const file_offset = shdr.sh_offset + atom_ptr.value - shdr.sh_addr;
const file_offset = shdr.sh_offset + atom_ptr.value;
atom_ptr.resolveRelocsAlloc(self, code) catch |err| switch (err) {
// TODO
error.RelaxFail, error.InvalidInstruction, error.CannotEncode => {
Expand Down Expand Up @@ -2907,7 +2906,7 @@ pub fn writeElfHeader(self: *Elf) !void {
mem.writeInt(u32, hdr_buf[index..][0..4], 1, endian);
index += 4;

const e_entry = if (self.entry_index) |entry_index| self.symbol(entry_index).value else 0;
const e_entry = if (self.entry_index) |entry_index| self.symbol(entry_index).address(.{}, self) else 0;
const phdr_table_offset = if (self.phdr_table_index) |phndx| self.phdrs.items[phndx].p_offset else 0;
switch (self.ptr_width) {
.p32 => {
Expand Down Expand Up @@ -2970,7 +2969,7 @@ pub fn writeElfHeader(self: *Elf) !void {
mem.writeInt(u16, hdr_buf[index..][0..2], e_shnum, endian);
index += 2;

mem.writeInt(u16, hdr_buf[index..][0..2], self.shstrtab_section_index.?, endian);
mem.writeInt(u16, hdr_buf[index..][0..2], @intCast(self.shstrtab_section_index.?), endian);
index += 2;

assert(index == e_ehsize);
Expand Down Expand Up @@ -3710,7 +3709,7 @@ fn sortPhdrs(self: *Elf) error{OutOfMemory}!void {
}
}

fn shdrRank(self: *Elf, shndx: u16) u8 {
fn shdrRank(self: *Elf, shndx: u32) u8 {
const shdr = self.shdrs.items[shndx];
const name = self.getShString(shdr.sh_name);
const flags = shdr.sh_flags;
Expand Down Expand Up @@ -3760,7 +3759,7 @@ fn shdrRank(self: *Elf, shndx: u16) u8 {

pub fn sortShdrs(self: *Elf) !void {
const Entry = struct {
shndx: u16,
shndx: u32,

pub fn lessThan(elf_file: *Elf, lhs: @This(), rhs: @This()) bool {
return elf_file.shdrRank(lhs.shndx) < elf_file.shdrRank(rhs.shndx);
Expand All @@ -3771,15 +3770,15 @@ pub fn sortShdrs(self: *Elf) !void {
var entries = try std.ArrayList(Entry).initCapacity(gpa, self.shdrs.items.len);
defer entries.deinit();
for (0..self.shdrs.items.len) |shndx| {
entries.appendAssumeCapacity(.{ .shndx = @as(u16, @intCast(shndx)) });
entries.appendAssumeCapacity(.{ .shndx = @intCast(shndx) });
}

mem.sort(Entry, entries.items, self, Entry.lessThan);

const backlinks = try gpa.alloc(u16, entries.items.len);
const backlinks = try gpa.alloc(u32, entries.items.len);
defer gpa.free(backlinks);
for (entries.items, 0..) |entry, i| {
backlinks[entry.shndx] = @as(u16, @intCast(i));
backlinks[entry.shndx] = @intCast(i);
}

const slice = try self.shdrs.toOwnedSlice(gpa);
Expand All @@ -3793,10 +3792,10 @@ pub fn sortShdrs(self: *Elf) !void {
try self.resetShdrIndexes(backlinks);
}

fn resetShdrIndexes(self: *Elf, backlinks: []const u16) !void {
fn resetShdrIndexes(self: *Elf, backlinks: []const u32) !void {
const gpa = self.base.comp.gpa;

for (&[_]*?u16{
for (&[_]*?u32{
&self.eh_frame_section_index,
&self.eh_frame_rela_section_index,
&self.eh_frame_hdr_section_index,
Expand Down Expand Up @@ -4192,7 +4191,7 @@ pub fn allocateAllocSections(self: *Elf) error{OutOfMemory}!void {
// virtual and file offsets. However, the simple one will do for one
// as we are more interested in quick turnaround and compatibility
// with `findFreeSpace` mechanics than anything else.
const Cover = std.ArrayList(u16);
const Cover = std.ArrayList(u32);
const gpa = self.base.comp.gpa;
var covers: [max_number_of_object_segments]Cover = undefined;
for (&covers) |*cover| {
Expand Down Expand Up @@ -4348,7 +4347,7 @@ pub fn allocateNonAllocSections(self: *Elf) !void {
}

fn allocateSpecialPhdrs(self: *Elf) void {
for (&[_]struct { ?u16, ?u16 }{
for (&[_]struct { ?u16, ?u32 }{
.{ self.phdr_interp_index, self.interp_section_index },
.{ self.phdr_dynamic_index, self.dynamic_section_index },
.{ self.phdr_gnu_eh_frame_index, self.eh_frame_hdr_section_index },
Expand All @@ -4371,7 +4370,7 @@ fn allocateSpecialPhdrs(self: *Elf) void {
if (self.phdr_tls_index) |index| {
const slice = self.shdrs.items;
const phdr = &self.phdrs.items[index];
var shndx: u16 = 0;
var shndx: u32 = 0;
while (shndx < slice.len) {
const shdr = slice[shndx];
if (shdr.sh_flags & elf.SHF_TLS == 0) {
Expand Down Expand Up @@ -4402,15 +4401,6 @@ fn allocateSpecialPhdrs(self: *Elf) void {
}
}

pub fn allocateAtoms(self: *Elf) void {
if (self.zigObjectPtr()) |zig_object| {
zig_object.allocateTlvAtoms(self);
}
for (self.objects.items) |index| {
self.file(index).?.object.allocateAtoms(self);
}
}

fn writeAtoms(self: *Elf) !void {
const gpa = self.base.comp.gpa;

Expand Down Expand Up @@ -4464,7 +4454,7 @@ fn writeAtoms(self: *Elf) !void {
const atom_ptr = self.atom(atom_index).?;
assert(atom_ptr.flags.alive);

const offset = math.cast(usize, atom_ptr.value - shdr.sh_addr - base_offset) orelse
const offset = math.cast(usize, atom_ptr.value - base_offset) orelse
return error.Overflow;
const size = math.cast(usize, atom_ptr.size) orelse return error.Overflow;

Expand Down Expand Up @@ -5148,8 +5138,8 @@ const CsuObjects = struct {
}
};

pub fn isZigSection(self: Elf, shndx: u16) bool {
inline for (&[_]?u16{
pub fn isZigSection(self: Elf, shndx: u32) bool {
inline for (&[_]?u32{
self.zig_text_section_index,
self.zig_data_rel_ro_section_index,
self.zig_data_section_index,
Expand All @@ -5163,8 +5153,8 @@ pub fn isZigSection(self: Elf, shndx: u16) bool {
return false;
}

pub fn isDebugSection(self: Elf, shndx: u16) bool {
inline for (&[_]?u16{
pub fn isDebugSection(self: Elf, shndx: u32) bool {
inline for (&[_]?u32{
self.debug_info_section_index,
self.debug_abbrev_section_index,
self.debug_str_section_index,
Expand Down Expand Up @@ -5202,7 +5192,7 @@ fn addPhdr(self: *Elf, opts: struct {
return index;
}

pub fn addRelaShdr(self: *Elf, name: [:0]const u8, shndx: u16) !u16 {
pub fn addRelaShdr(self: *Elf, name: [:0]const u8, shndx: u32) !u32 {
const entsize: u64 = switch (self.ptr_width) {
.p32 => @sizeOf(elf.Elf32_Rela),
.p64 => @sizeOf(elf.Elf64_Rela),
Expand Down Expand Up @@ -5233,9 +5223,9 @@ pub const AddSectionOpts = struct {
offset: u64 = 0,
};

pub fn addSection(self: *Elf, opts: AddSectionOpts) !u16 {
pub fn addSection(self: *Elf, opts: AddSectionOpts) !u32 {
const gpa = self.base.comp.gpa;
const index = @as(u16, @intCast(self.shdrs.items.len));
const index = @as(u32, @intCast(self.shdrs.items.len));
const shdr = try self.shdrs.addOne(gpa);
shdr.* = .{
.sh_name = try self.insertShString(opts.name),
Expand All @@ -5252,10 +5242,10 @@ pub fn addSection(self: *Elf, opts: AddSectionOpts) !u16 {
return index;
}

pub fn sectionByName(self: *Elf, name: [:0]const u8) ?u16 {
pub fn sectionByName(self: *Elf, name: [:0]const u8) ?u32 {
for (self.shdrs.items, 0..) |*shdr, i| {
const this_name = self.getShString(shdr.sh_name);
if (mem.eql(u8, this_name, name)) return @as(u16, @intCast(i));
if (mem.eql(u8, this_name, name)) return @intCast(i);
} else return null;
}

Expand Down
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