srctree

Jakub Konka parent c22bb380 e401930f
elf: store relative offsets in atom and symbol

inline split

src/link/Elf.zig added: 69, removed: 86, total 0

@@ -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.

@@ -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 => {

@@ -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 => {

@@ -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;

@@ -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;

src/link/Elf/Atom.zig added: 69, removed: 86, total 0

@@ -54,6 +54,12 @@ pub fn name(self: Atom, elf_file: *Elf) []const u8 {

};

}

pub fn address(self: Atom, elf_file: *Elf) u64 {

const shndx = self.outputShndx() orelse return self.value;

const shdr = elf_file.shdrs.items[shndx];

return shdr.sh_addr + self.value;

}

pub fn file(self: Atom, elf_file: *Elf) ?File {

return elf_file.file(self.file_index);

}

@@ -85,14 +91,17 @@ pub fn priority(self: Atom, elf_file: *Elf) u64 {

/// File offset relocation happens transparently, so it is not included in

/// this calculation.

pub fn capacity(self: Atom, elf_file: *Elf) u64 {

const next_value = if (elf_file.atom(self.next_index)) |next| next.value else std.math.maxInt(u32);

return next_value - self.value;

const next_addr = if (elf_file.atom(self.next_index)) |next|

next.address(elf_file)

else

std.math.maxInt(u32);

return next_addr - self.address(elf_file);

}

pub fn freeListEligible(self: Atom, elf_file: *Elf) bool {

// No need to keep a free list node for the last block.

const next = elf_file.atom(self.next_index) orelse return false;

const cap = next.value - self.value;

const cap = next.address(elf_file) - self.address(elf_file);

const ideal_cap = Elf.padToIdeal(self.size);

if (cap <= ideal_cap) return false;

const surplus = cap - ideal_cap;

@@ -160,15 +169,15 @@ pub fn allocate(self: *Atom, elf_file: *Elf) !void {

atom_placement = last.atom_index;

break :blk new_start_vaddr;

} else {

break :blk shdr.sh_addr;

break :blk 0;

}

};

log.debug("allocated atom({d}) : '{s}' at 0x{x} to 0x{x}", .{

self.atom_index,

self.name(elf_file),

self.value,

self.value + self.size,

self.address(elf_file),

self.address(elf_file) + self.size,

});

const expand_section = if (atom_placement) |placement_index|

@@ -176,7 +185,7 @@ pub fn allocate(self: *Atom, elf_file: *Elf) !void {

else

true;

if (expand_section) {

const needed_size = (self.value + self.size) - shdr.sh_addr;

const needed_size = self.value + self.size;

try elf_file.growAllocSection(self.outputShndx().?, needed_size);

last_atom_index.* = self.atom_index;

@@ -301,7 +310,7 @@ pub fn relocs(self: Atom, elf_file: *Elf) []align(1) const elf.Elf64_Rela {

}

pub fn writeRelocs(self: Atom, elf_file: *Elf, out_relocs: *std.ArrayList(elf.Elf64_Rela)) !void {

relocs_log.debug("0x{x}: {s}", .{ self.value, self.name(elf_file) });

relocs_log.debug("0x{x}: {s}", .{ self.address(elf_file), self.name(elf_file) });

const file_ptr = self.file(elf_file).?;

for (self.relocs(elf_file)) |rel| {

@@ -322,7 +331,7 @@ pub fn writeRelocs(self: Atom, elf_file: *Elf, out_relocs: *std.ArrayList(elf.El

var r_sym: u32 = 0;

switch (target.type(elf_file)) {

elf.STT_SECTION => {

r_addend += @intCast(target.value);

r_addend += @intCast(target.address(.{}, elf_file));

r_sym = elf_file.sectionSymbolOutputSymtabIndex(target.outputShndx().?);

else => {

@@ -778,7 +787,7 @@ fn reportUndefined(

}

pub fn resolveRelocsAlloc(self: Atom, elf_file: *Elf, code: []u8) !void {

relocs_log.debug("0x{x}: {s}", .{ self.value, self.name(elf_file) });

relocs_log.debug("0x{x}: {s}", .{ self.address(elf_file), self.name(elf_file) });

const file_ptr = self.file(elf_file).?;

var stream = std.io.fixedBufferStream(code);

@@ -802,7 +811,7 @@ pub fn resolveRelocsAlloc(self: Atom, elf_file: *Elf, code: []u8) !void {

// https://intezer.com/blog/malware-analysis/executable-and-linkable-format-101-part-3-relocations/

// Address of the source atom.

const P = @as(i64, @intCast(self.value + rel.r_offset));

const P = @as(i64, @intCast(self.address(elf_file) + rel.r_offset));

// Addend from the relocation.

const A = rel.r_addend;

// Address of the target symbol - can be address of the symbol within an atom or address of PLT stub.

@@ -969,7 +978,7 @@ fn resolveDynAbsReloc(

) !void {

const comp = elf_file.base.comp;

const gpa = comp.gpa;

const P = self.value + rel.r_offset;

const P = self.address(elf_file) + rel.r_offset;

const A = rel.r_addend;

const S = @as(i64, @intCast(target.address(.{}, elf_file)));

const is_writeable = self.inputShdr(elf_file).sh_flags & elf.SHF_WRITE != 0;

@@ -1058,7 +1067,7 @@ fn applyDynamicReloc(value: i64, elf_file: *Elf, writer: anytype) !void {

}

pub fn resolveRelocsNonAlloc(self: Atom, elf_file: *Elf, code: []u8, undefs: anytype) !void {

relocs_log.debug("0x{x}: {s}", .{ self.value, self.name(elf_file) });

relocs_log.debug("0x{x}: {s}", .{ self.address(elf_file), self.name(elf_file) });

const file_ptr = self.file(elf_file).?;

var stream = std.io.fixedBufferStream(code);

@@ -1097,7 +1106,7 @@ pub fn resolveRelocsNonAlloc(self: Atom, elf_file: *Elf, code: []u8, undefs: any

// We will use equation format to resolve relocations:

// https://intezer.com/blog/malware-analysis/executable-and-linkable-format-101-part-3-relocations/

const P = @as(i64, @intCast(self.value + rel.r_offset));

const P = @as(i64, @intCast(self.address(elf_file) + rel.r_offset));

// Addend from the relocation.

const A = rel.r_addend;

// Address of the target symbol - can be address of the symbol within an atom or address of PLT stub.

@@ -1248,7 +1257,7 @@ fn format2(

const atom = ctx.atom;

const elf_file = ctx.elf_file;

try writer.print("atom({d}) : {s} : @{x} : shdr({d}) : align({x}) : size({x})", .{

atom.atom_index, atom.name(elf_file), atom.value,

atom.atom_index, atom.name(elf_file), atom.address(elf_file),

atom.output_section_index, atom.alignment, atom.size,

});

if (atom.fde_start != atom.fde_end) {

src/link/Elf/Object.zig added: 69, removed: 86, total 0

@@ -718,21 +718,11 @@ pub fn addAtomsToOutputSections(self: *Object, elf_file: *Elf) !void {

if (!gop.found_existing) gop.value_ptr.* = .{};

try gop.value_ptr.append(gpa, atom_index);

}

pub fn allocateAtoms(self: Object, elf_file: *Elf) void {

for (self.atoms.items) |atom_index| {

const atom = elf_file.atom(atom_index) orelse continue;

if (!atom.flags.alive) continue;

const shdr = elf_file.shdrs.items[atom.output_section_index];

atom.value += shdr.sh_addr;

}

for (self.locals()) |local_index| {

const local = elf_file.symbol(local_index);

const atom = local.atom(elf_file) orelse continue;

if (!atom.flags.alive) continue;

local.value += atom.value;

local.output_section_index = atom.output_section_index;

}

@@ -741,7 +731,6 @@ pub fn allocateAtoms(self: Object, elf_file: *Elf) void {

const atom = global.atom(elf_file) orelse continue;

if (!atom.flags.alive) continue;

if (global.file(elf_file).?.index() != self.index) continue;

global.value += atom.value;

global.output_section_index = atom.output_section_index;

}

src/link/Elf/Symbol.zig added: 69, removed: 86, total 0

@@ -104,6 +104,9 @@ pub fn address(symbol: Symbol, opts: struct { plt: bool = true }, elf_file: *Elf

// Lazy-bound function it is!

return symbol.pltAddress(elf_file);

}

if (symbol.atom(elf_file)) |atom_ptr| {

return atom_ptr.address(elf_file) + symbol.value;

}

return symbol.value;

}

@@ -247,11 +250,11 @@ pub fn setOutputSym(symbol: Symbol, elf_file: *Elf, out: *elf.Elf64_Sym) void {

if (symbol.flags.is_canonical) break :blk symbol.address(.{}, elf_file);

break :blk 0;

}

if (st_shndx == elf.SHN_ABS or st_shndx == elf.SHN_COMMON) break :blk symbol.value;

if (st_shndx == elf.SHN_ABS or st_shndx == elf.SHN_COMMON) break :blk symbol.address(.{ .plt = false }, elf_file);

const shdr = &elf_file.shdrs.items[st_shndx];

if (shdr.sh_flags & elf.SHF_TLS != 0 and file_ptr != .linker_defined)

break :blk symbol.value - elf_file.tlsAddress();

break :blk symbol.value;

break :blk symbol.address(.{ .plt = false }, elf_file) - elf_file.tlsAddress();

break :blk symbol.address(.{ .plt = false }, elf_file);

};

out.st_info = (st_bind << 4) | st_type;

out.st_other = esym.st_other;

@@ -323,7 +326,11 @@ fn format2(

_ = options;

_ = unused_fmt_string;

const symbol = ctx.symbol;

try writer.print("%{d} : {s} : @{x}", .{ symbol.esym_index, symbol.fmtName(ctx.elf_file), symbol.value });

try writer.print("%{d} : {s} : @{x}", .{

symbol.esym_index,

symbol.fmtName(ctx.elf_file),

symbol.address(.{}, ctx.elf_file),

});

if (symbol.file(ctx.elf_file)) |file_ptr| {

if (symbol.isAbs(ctx.elf_file)) {

if (symbol.elfSym(ctx.elf_file).st_shndx == elf.SHN_UNDEF) {

src/link/Elf/ZigObject.zig added: 69, removed: 86, total 0

@@ -401,19 +401,6 @@ pub fn claimUnresolvedObject(self: ZigObject, elf_file: *Elf) void {

}

pub fn allocateTlvAtoms(self: ZigObject, elf_file: *Elf) void {

for (self.tls_variables.keys(), self.tls_variables.values()) |atom_index, tlv| {

const atom = elf_file.atom(atom_index) orelse continue;

if (!atom.flags.alive) continue;

const local = elf_file.symbol(tlv.symbol_index);

const shdr = elf_file.shdrs.items[atom.output_section_index];

atom.value += shdr.sh_addr;

local.value = atom.value;

// TODO exported TLS vars

}

pub fn scanRelocs(self: *ZigObject, elf_file: *Elf, undefs: anytype) !void {

const gpa = elf_file.base.comp.gpa;

for (self.atoms.items) |atom_index| {

@@ -644,7 +631,7 @@ pub fn codeAlloc(self: ZigObject, elf_file: *Elf, atom_index: Atom.Index) ![]u8

return code;

}

const file_offset = shdr.sh_offset + atom.value - shdr.sh_addr;

const file_offset = shdr.sh_offset + atom.value;

const size = std.math.cast(usize, atom.size) orelse return error.Overflow;

const code = try gpa.alloc(u8, size);

errdefer gpa.free(code);

@@ -664,7 +651,7 @@ pub fn getDeclVAddr(

) !u64 {

const this_sym_index = try self.getOrCreateMetadataForDecl(elf_file, decl_index);

const this_sym = elf_file.symbol(this_sym_index);

const vaddr = this_sym.value;

const vaddr = this_sym.address(.{}, elf_file);

const parent_atom = elf_file.symbol(reloc_info.parent_atom_index).atom(elf_file).?;

try parent_atom.addReloc(elf_file, .{

.r_offset = reloc_info.offset,

@@ -682,7 +669,7 @@ pub fn getAnonDeclVAddr(

) !u64 {

const sym_index = self.anon_decls.get(decl_val).?.symbol_index;

const sym = elf_file.symbol(sym_index);

const vaddr = sym.value;

const vaddr = sym.address(.{}, elf_file);

const parent_atom = elf_file.symbol(reloc_info.parent_atom_index).atom(elf_file).?;

try parent_atom.addReloc(elf_file, .{

.r_offset = reloc_info.offset,

@@ -941,13 +928,13 @@ fn updateDeclCode(

if (old_size > 0 and elf_file.base.child_pid == null) {

const capacity = atom_ptr.capacity(elf_file);

const need_realloc = code.len > capacity or !required_alignment.check(sym.value);

const need_realloc = code.len > capacity or !required_alignment.check(atom_ptr.value);

if (need_realloc) {

try atom_ptr.grow(elf_file);

log.debug("growing {s} from 0x{x} to 0x{x}", .{ decl_name, old_vaddr, atom_ptr.value });

if (old_vaddr != atom_ptr.value) {

sym.value = atom_ptr.value;

esym.st_value = atom_ptr.value;

sym.value = 0;

esym.st_value = 0;

if (!elf_file.base.isRelocatable()) {

log.debug(" (writing new offset table entry)", .{});

@@ -963,9 +950,9 @@ fn updateDeclCode(

try atom_ptr.allocate(elf_file);

errdefer self.freeDeclMetadata(elf_file, sym_index);

sym.value = atom_ptr.value;

sym.value = 0;

sym.flags.needs_zig_got = true;

esym.st_value = atom_ptr.value;

esym.st_value = 0;

if (!elf_file.base.isRelocatable()) {

const gop = try sym.getOrCreateZigGotEntry(sym_index, elf_file);

@@ -981,7 +968,7 @@ fn updateDeclCode(

.iov_len = code.len,

}};

var remote_vec: [1]std.os.iovec_const = .{.{

.iov_base = @as([*]u8, @ptrFromInt(@as(usize, @intCast(sym.value)))),

.iov_base = @as([*]u8, @ptrFromInt(@as(usize, @intCast(sym.address(.{}, elf_file))))),

.iov_len = code.len,

}};

const rc = std.os.linux.process_vm_writev(pid, &code_vec, &remote_vec, 0);

@@ -996,7 +983,7 @@ fn updateDeclCode(

const shdr = elf_file.shdrs.items[shdr_index];

if (shdr.sh_type != elf.SHT_NOBITS) {

const file_offset = shdr.sh_offset + sym.value - shdr.sh_addr;

const file_offset = shdr.sh_offset + atom_ptr.value;

try elf_file.base.file.?.pwriteAll(code, file_offset);

}

@@ -1022,12 +1009,14 @@ fn updateTlv(

const esym = &self.local_esyms.items(.elf_sym)[sym.esym_index];

const atom_ptr = sym.atom(elf_file).?;

sym.value = 0;

sym.output_section_index = shndx;

atom_ptr.output_section_index = shndx;

sym.name_offset = try self.strtab.insert(gpa, decl_name);

atom_ptr.flags.alive = true;

atom_ptr.name_offset = sym.name_offset;

esym.st_value = 0;

esym.st_name = sym.name_offset;

esym.st_info = elf.STT_TLS;

esym.st_size = code.len;

@@ -1117,7 +1106,7 @@ pub fn updateFunc(

try self.dwarf.?.commitDeclState(

mod,

decl_index,

sym.value,

sym.address(.{}, elf_file),

sym.atom(elf_file).?.size,

ds,

);

@@ -1202,7 +1191,7 @@ pub fn updateDecl(

try self.dwarf.?.commitDeclState(

mod,

decl_index,

sym.value,

sym.address(.{}, elf_file),

sym.atom(elf_file).?.size,

ds,

);

@@ -1281,9 +1270,9 @@ fn updateLazySymbol(

try atom_ptr.allocate(elf_file);

errdefer self.freeDeclMetadata(elf_file, symbol_index);

local_sym.value = atom_ptr.value;

local_sym.value = 0;

local_sym.flags.needs_zig_got = true;

local_esym.st_value = atom_ptr.value;

local_esym.st_value = 0;

if (!elf_file.base.isRelocatable()) {

const gop = try local_sym.getOrCreateZigGotEntry(symbol_index, elf_file);

@@ -1291,7 +1280,7 @@ fn updateLazySymbol(

}

const shdr = elf_file.shdrs.items[output_section_index];

const file_offset = shdr.sh_offset + atom_ptr.value - shdr.sh_addr;

const file_offset = shdr.sh_offset + atom_ptr.value;

try elf_file.base.file.?.pwriteAll(code, file_offset);

}

@@ -1384,11 +1373,11 @@ fn lowerConst(

// TODO rename and re-audit this method

errdefer self.freeDeclMetadata(elf_file, sym_index);

local_sym.value = atom_ptr.value;

local_esym.st_value = atom_ptr.value;

local_sym.value = 0;

local_esym.st_value = 0;

const shdr = elf_file.shdrs.items[output_section_index];

const file_offset = shdr.sh_offset + atom_ptr.value - shdr.sh_addr;

const file_offset = shdr.sh_offset + atom_ptr.value;

try elf_file.base.file.?.pwriteAll(code, file_offset);

return .{ .ok = sym_index };

src/link/Elf/eh_frame.zig added: 69, removed: 86, total 0

@@ -409,7 +409,7 @@ fn emitReloc(elf_file: *Elf, rec: anytype, sym: *const Symbol, rel: elf.Elf64_Re

var r_sym: u32 = 0;

switch (sym.type(elf_file)) {

elf.STT_SECTION => {

r_addend += @intCast(sym.value);

r_addend += @intCast(sym.address(.{}, elf_file));

r_sym = elf_file.sectionSymbolOutputSymtabIndex(sym.outputShndx().?);

else => {

src/link/Elf/relocatable.zig added: 69, removed: 86, total 0

@@ -195,7 +195,6 @@ pub fn flushObject(elf_file: *Elf, comp: *Compilation, module_obj_path: ?[]const

try allocateAllocSections(elf_file);

try elf_file.allocateNonAllocSections();

elf_file.allocateAtoms();

if (build_options.enable_logging) {

state_log.debug("{}", .{elf_file.dumpState()});

src/link/Elf/synthetic_sections.zig added: 69, removed: 86, total 0

@@ -297,7 +297,7 @@ pub const ZigGotSection = struct {

const off = zig_got.entryOffset(index, elf_file);

const vaddr = zig_got.entryAddress(index, elf_file);

const entry = zig_got.entries.items[index];

const value = elf_file.symbol(entry).value;

const value = elf_file.symbol(entry).address(.{}, elf_file);

switch (entry_size) {

2 => {

var buf: [2]u8 = undefined;

@@ -1004,7 +1004,7 @@ pub const GotPltSection = struct {

{

// [0]: _DYNAMIC

const symbol = elf_file.symbol(elf_file.dynamic_index.?);

try writer.writeInt(u64, symbol.value, .little);

try writer.writeInt(u64, symbol.address(.{}, elf_file), .little);

}

// [1]: 0x0

// [2]: 0x0