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elf: make zig jump table indirection implicit via Symbol.address

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This commit is contained in:
Jakub Konka
2024-08-13 10:28:01 +02:00
parent d25c93a868
commit ce8886d57d
3 changed files with 35 additions and 38 deletions
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35
src/link/Elf/Atom.zig
View File

@@ -750,8 +750,6 @@ pub fn resolveRelocsAlloc(self: Atom, elf_file: *Elf, code: []u8) RelocError!voi
const S = target.address(.{}, elf_file);
// Address of the global offset table.
const GOT = elf_file.gotAddress();
// Address of the zig jump table entry if any.
const ZJT = target.zigJumpTableAddress(elf_file);
// Relative offset to the start of the global offset table.
const G = target.gotAddress(elf_file) - GOT;
// // Address of the thread pointer.
@@ -759,19 +757,18 @@ pub fn resolveRelocsAlloc(self: Atom, elf_file: *Elf, code: []u8) RelocError!voi
// Address of the dynamic thread pointer.
const DTP = elf_file.dtpAddress();
relocs_log.debug(" {s}: {x}: [{x} => {x}] GOT({x}) ZJT({x}) ({s})", .{
relocs_log.debug(" {s}: {x}: [{x} => {x}] GOT({x}) ({s})", .{
relocation.fmtRelocType(rel.r_type(), cpu_arch),
r_offset,
P,
S + A,
G + GOT + A,
ZJT + A,
target.name(elf_file),
});
try stream.seekTo(r_offset);
const args = ResolveArgs{ P, A, S, GOT, G, TP, DTP, ZJT };
const args = ResolveArgs{ P, A, S, GOT, G, TP, DTP };
switch (cpu_arch) {
.x86_64 => x86_64.resolveRelocAlloc(self, elf_file, rel, target, args, &it, code, &stream) catch |err| switch (err) {
@@ -956,7 +953,7 @@ pub fn resolveRelocsNonAlloc(self: Atom, elf_file: *Elf, code: []u8, undefs: any
// Address of the dynamic thread pointer.
const DTP = elf_file.dtpAddress();
const args = ResolveArgs{ P, A, S, GOT, 0, 0, DTP, 0 };
const args = ResolveArgs{ P, A, S, GOT, 0, 0, DTP };
relocs_log.debug(" {}: {x}: [{x} => {x}] ({s})", .{
relocation.fmtRelocType(rel.r_type(), cpu_arch),
@@ -1200,7 +1197,7 @@ const x86_64 = struct {
const cwriter = stream.writer();
const P, const A, const S, const GOT, const G, const TP, const DTP, const ZJT = args;
const P, const A, const S, const GOT, const G, const TP, const DTP = args;
switch (r_type) {
.NONE => unreachable,
@@ -1215,10 +1212,7 @@ const x86_64 = struct {
);
},
.PLT32 => {
const S_ = if (target.flags.zig_jump_table) ZJT else S;
try cwriter.writeInt(i32, @as(i32, @intCast(S_ + A - P)), .little);
},
.PLT32 => try cwriter.writeInt(i32, @as(i32, @intCast(S + A - P)), .little),
.PC32 => try cwriter.writeInt(i32, @as(i32, @intCast(S + A - P)), .little),
.GOTPCREL => try cwriter.writeInt(i32, @as(i32, @intCast(G + GOT + A - P)), .little),
@@ -1243,10 +1237,7 @@ const x86_64 = struct {
try cwriter.writeInt(i32, @as(i32, @intCast(G + GOT + A - P)), .little);
},
.@"32" => {
const S_ = if (target.flags.zig_jump_table) ZJT else S;
try cwriter.writeInt(u32, @as(u32, @truncate(@as(u64, @intCast(S_ + A)))), .little);
},
.@"32" => try cwriter.writeInt(u32, @as(u32, @truncate(@as(u64, @intCast(S + A)))), .little),
.@"32S" => try cwriter.writeInt(i32, @as(i32, @truncate(S + A)), .little),
.TPOFF32 => try cwriter.writeInt(i32, @as(i32, @truncate(S + A - TP)), .little),
@@ -1345,7 +1336,7 @@ const x86_64 = struct {
const r_type: elf.R_X86_64 = @enumFromInt(rel.r_type());
const cwriter = stream.writer();
_, const A, const S, const GOT, _, _, const DTP, _ = args;
_, const A, const S, const GOT, _, _, const DTP = args;
switch (r_type) {
.NONE => unreachable,
@@ -1728,9 +1719,8 @@ const aarch64 = struct {
const code = code_buffer[r_offset..][0..4];
const file_ptr = atom.file(elf_file).?;
const P, const A, const S, const GOT, const G, const TP, const DTP, const ZJT = args;
const P, const A, const S, const GOT, const G, const TP, const DTP = args;
_ = DTP;
_ = ZJT;
switch (r_type) {
.NONE => unreachable,
@@ -1932,7 +1922,7 @@ const aarch64 = struct {
const r_type: elf.R_AARCH64 = @enumFromInt(rel.r_type());
const cwriter = stream.writer();
_, const A, const S, _, _, _, _, _ = args;
_, const A, const S, _, _, _, _ = args;
switch (r_type) {
.NONE => unreachable,
@@ -2012,10 +2002,9 @@ const riscv = struct {
const r_offset = std.math.cast(usize, rel.r_offset) orelse return error.Overflow;
const cwriter = stream.writer();
const P, const A, const S, const GOT, const G, const TP, const DTP, const ZJT = args;
const P, const A, const S, const GOT, const G, const TP, const DTP = args;
_ = TP;
_ = DTP;
_ = ZJT;
switch (r_type) {
.NONE => unreachable,
@@ -2167,7 +2156,7 @@ const riscv = struct {
const r_offset = std.math.cast(usize, rel.r_offset) orelse return error.Overflow;
const cwriter = stream.writer();
_, const A, const S, const GOT, _, _, const DTP, _ = args;
_, const A, const S, const GOT, _, _, const DTP = args;
_ = GOT;
_ = DTP;
@@ -2203,7 +2192,7 @@ const riscv = struct {
const riscv_util = @import("../riscv.zig");
};
const ResolveArgs = struct { i64, i64, i64, i64, i64, i64, i64, i64 };
const ResolveArgs = struct { i64, i64, i64, i64, i64, i64, i64 };
const RelocError = error{
Overflow,

21
src/link/Elf/Symbol.zig
View File

@@ -101,7 +101,7 @@ pub fn symbolRank(symbol: Symbol, elf_file: *Elf) u32 {
return file_ptr.symbolRank(sym, in_archive);
}
pub fn address(symbol: Symbol, opts: struct { plt: bool = true }, elf_file: *Elf) i64 {
pub fn address(symbol: Symbol, opts: struct { plt: bool = true, zjt: bool = true }, elf_file: *Elf) i64 {
if (symbol.mergeSubsection(elf_file)) |msub| {
if (!msub.alive) return 0;
return msub.address(elf_file) + symbol.value;
@@ -109,6 +109,9 @@ pub fn address(symbol: Symbol, opts: struct { plt: bool = true }, elf_file: *Elf
if (symbol.flags.has_copy_rel) {
return symbol.copyRelAddress(elf_file);
}
if (symbol.flags.has_zjt and opts.zjt) {
return symbol.zjtAddress(elf_file);
}
if (symbol.flags.has_plt and opts.plt) {
if (!symbol.flags.is_canonical and symbol.flags.has_got) {
// We have a non-lazy bound function pointer, use that!
@@ -217,12 +220,12 @@ pub fn tlsDescAddress(symbol: Symbol, elf_file: *Elf) i64 {
return entry.address(elf_file);
}
pub fn zigJumpTableAddress(symbol: Symbol, elf_file: *Elf) i64 {
if (!symbol.flags.zig_jump_table) return 0;
pub fn zjtAddress(symbol: Symbol, elf_file: *Elf) i64 {
if (!symbol.flags.has_zjt) return 0;
const zo = elf_file.zigObjectPtr().?;
const jump_table = zo.jumpTablePtr().?;
const jt_index = symbol.extra(elf_file).zig_jump_table;
return jump_table.entryAddress(jt_index, zo, elf_file);
const index = symbol.extra(elf_file).zjt;
return jump_table.entryAddress(index, zo, elf_file);
}
pub fn dsoAlignment(symbol: Symbol, elf_file: *Elf) !u64 {
@@ -248,7 +251,7 @@ const AddExtraOpts = struct {
tlsgd: ?u32 = null,
gottp: ?u32 = null,
tlsdesc: ?u32 = null,
zig_jump_table: ?u32 = null,
zjt: ?u32 = null,
};
pub fn addExtra(symbol: *Symbol, opts: AddExtraOpts, elf_file: *Elf) void {
@@ -377,7 +380,7 @@ fn format2(
try writer.print("%{d} : {s} : @{x}", .{
symbol.esym_index,
symbol.fmtName(elf_file),
symbol.address(.{}, elf_file),
symbol.address(.{ .plt = false, .zjt = false }, elf_file),
});
if (symbol.file(elf_file)) |file_ptr| {
if (symbol.isAbs(elf_file)) {
@@ -454,7 +457,7 @@ pub const Flags = packed struct {
merge_subsection: bool = false,
/// Whether the symbol has __zig_jump_table indirection.
zig_jump_table: bool = false,
has_zjt: bool = false,
};
pub const Extra = struct {
@@ -468,7 +471,7 @@ pub const Extra = struct {
gottp: u32 = 0,
tlsdesc: u32 = 0,
merge_section: u32 = 0,
zig_jump_table: u32 = 0,
zjt: u32 = 0,
};
pub const Index = u32;

17
src/link/Elf/ZigObject.zig
View File

@@ -918,7 +918,7 @@ fn updateNavCode(
if (stt_bits == elf.STT_FUNC) {
const extra = sym.extra(elf_file);
const jump_table = self.jumpTablePtr().?;
jump_table.entries.items(.dirty)[extra.zig_jump_table] = true;
jump_table.entries.items(.dirty)[extra.zjt] = true;
}
}
} else if (code.len < old_size) {
@@ -1045,10 +1045,10 @@ pub fn updateFunc(
{
const sym = self.symbol(sym_index);
if (!sym.flags.zig_jump_table) {
if (!sym.flags.has_zjt) {
const index = try jump_table.addSymbol(gpa, sym_index);
sym.flags.zig_jump_table = true;
sym.addExtra(.{ .zig_jump_table = index }, elf_file);
sym.flags.has_zjt = true;
sym.addExtra(.{ .zjt = index }, elf_file);
try jump_table.updateSize(self, elf_file);
const old_vaddr = jump_table.address(self, elf_file);
try self.symbol(jump_table.sym_index).atom(elf_file).?.allocate(elf_file);
@@ -1108,7 +1108,7 @@ pub fn updateFunc(
}
} else {
const sym = self.symbol(sym_index);
const jt_index = sym.extra(elf_file).zig_jump_table;
const jt_index = sym.extra(elf_file).zjt;
var jt_entry = jump_table.entries.get(jt_index);
if (jt_entry.dirty) {
try jump_table.writeEntry(jt_index, self, elf_file);
@@ -1896,7 +1896,12 @@ pub const JumpTable = struct {
try writer.print(" @{x} : size({x})\n", .{ jt.address(zo, ef), jt.size(zo, ef) });
for (jt.entries.items(.sym_index), jt.entries.items(.dirty)) |sym_index, dirty| {
const sym = zo.symbol(sym_index);
try writer.print(" %{d} : {s} : @{x}", .{ sym_index, sym.name(ef), sym.address(.{}, ef) });
try writer.print(" {x} => {x} : %{d} : {s}", .{
sym.address(.{}, ef),
sym.address(.{ .zjt = false }, ef),
sym_index,
sym.name(ef),
});
if (dirty) try writer.writeAll(" : [!]");
try writer.writeByte('\n');
}