Commit d9069cbe2cf88634eb556b3063ede5af4a5cced4 | zig

author	Jakub Konka <kubkon@jakubkonka.com> 2024-03-08 14:30:06+01:00
committer	Jakub Konka <kubkon@jakubkonka.com> 2024-03-08 22:46:17+01:00
log	d9069cbe2cf88634eb556b3063ede5af4a5cced4
tree	9f31a51a05820db7ec5b680c562227f24c4c296d
parent	310cef09724067f4df38b42c928cb120fdc09df8

elf+aarch64: relax TLSDESC for executables

1 files changed, 62 insertions(+), 28 deletions(-)

src
- link
  - Elf
    Atom.zig

src/link/Elf/Atom.zig+62-28

 @@ -1633,7 +1633,7 @@ const aarch64 = struct {
             .TLSDESC_ADD_LO12,
             => {
                 const should_relax = elf_file.base.isStatic() or (!is_dyn_lib and !symbol.flags.import);
-                if (!should_relax and true) { // TODO
+                if (!should_relax) {
                     symbol.flags.needs_tlsdesc = true;
                 }
             },
 @@ -1659,7 +1659,7 @@ const aarch64 = struct {
         target: *const Symbol,
         args: ResolveArgs,
         it: *RelocsIterator,
-        code: []u8,
+        code_buffer: []u8,
         stream: anytype,
     ) (error{ UnexpectedRemainder, DivisionByZero } || RelocError)!void {
         _ = it;
 @@ -1667,6 +1667,7 @@ const aarch64 = struct {
         const r_type: elf.R_AARCH64 = @enumFromInt(rel.r_type());
         const r_offset = std.math.cast(usize, rel.r_offset) orelse return error.Overflow;
         const cwriter = stream.writer();
+        const code = code_buffer[rel.r_offset..][0..4];
         const P, const A, const S, const GOT, const G, const TP, const DTP, const ZIG_GOT = args;
         _ = DTP;
 @@ -1700,7 +1701,7 @@ const aarch64 = struct {
                     });
                     return;
                 };
-                aarch64_util.writeBranchImm(disp, code[r_offset..][0..4]);
+                aarch64_util.writeBranchImm(disp, code);
             },
             .ADR_PREL_PG_HI21 => {
 @@ -1708,14 +1709,14 @@ const aarch64 = struct {
                 const saddr = @as(u64, @intCast(P));
                 const taddr = @as(u64, @intCast(S + A));
                 const pages = @as(u21, @bitCast(try aarch64_util.calcNumberOfPages(saddr, taddr)));
-                aarch64_util.writeAdrpInst(pages, code[r_offset..][0..4]);
+                aarch64_util.writeAdrpInst(pages, code);
             },
             .ADR_GOT_PAGE => if (target.flags.has_got) {
                 const saddr = @as(u64, @intCast(P));
                 const taddr = @as(u64, @intCast(G + GOT + A));
                 const pages = @as(u21, @bitCast(try aarch64_util.calcNumberOfPages(saddr, taddr)));
-                aarch64_util.writeAdrpInst(pages, code[r_offset..][0..4]);
+                aarch64_util.writeAdrpInst(pages, code);
             } else {
                 // TODO: relax
                 var err = try elf_file.addErrorWithNotes(1);
 @@ -1730,12 +1731,12 @@ const aarch64 = struct {
             .LD64_GOT_LO12_NC => {
                 assert(target.flags.has_got);
                 const taddr = @as(u64, @intCast(G + GOT + A));
-                aarch64_util.writeLoadStoreRegInst(@divExact(@as(u12, @truncate(taddr)), 8), code[rel.r_offset..][0..4]);
+                aarch64_util.writeLoadStoreRegInst(@divExact(@as(u12, @truncate(taddr)), 8), code);
             },
             .ADD_ABS_LO12_NC => {
                 const taddr = @as(u64, @intCast(S + A));
-                aarch64_util.writeAddImmInst(@truncate(taddr), code[rel.r_offset..][0..4]);
+                aarch64_util.writeAddImmInst(@truncate(taddr), code);
             },
             .LDST8_ABS_LO12_NC,
 @@ -1754,48 +1755,79 @@ const aarch64 = struct {
                     .LDST128_ABS_LO12_NC => @divExact(@as(u12, @truncate(taddr)), 16),
                     else => unreachable,
                 };
-                aarch64_util.writeLoadStoreRegInst(offset, code[rel.r_offset..][0..4]);
+                aarch64_util.writeLoadStoreRegInst(offset, code);
             },
             .TLSLE_ADD_TPREL_HI12 => {
                 const value = math.cast(i12, (S + A - TP) >> 12) orelse
                     return error.Overflow;
-                aarch64_util.writeAddImmInst(@bitCast(value), code[rel.r_offset..][0..4]);
+                aarch64_util.writeAddImmInst(@bitCast(value), code);
             },
             .TLSLE_ADD_TPREL_LO12_NC => {
                 const value: i12 = @truncate(S + A - TP);
-                aarch64_util.writeAddImmInst(@bitCast(value), code[rel.r_offset..][0..4]);
+                aarch64_util.writeAddImmInst(@bitCast(value), code);
             },
             .TLSDESC_ADR_PAGE21 => {
-                assert(target.flags.has_tlsdesc); // TODO relax
+                if (target.flags.has_tlsdesc) {
-                const S_: i64 = @intCast(target.tlsDescAddress(elf_file));
+                    const S_: i64 = @intCast(target.tlsDescAddress(elf_file));
-                const saddr: u64 = @intCast(P);
+                    const saddr: u64 = @intCast(P);
-                const taddr: u64 = @intCast(S_ + A);
+                    const taddr: u64 = @intCast(S_ + A);
-                relocs_log.debug("      [{x} => {x}]", .{ P, taddr });
+                    relocs_log.debug("      [{x} => {x}]", .{ P, taddr });
-                const pages: u21 = @bitCast(try aarch64_util.calcNumberOfPages(saddr, taddr));
+                    const pages: u21 = @bitCast(try aarch64_util.calcNumberOfPages(saddr, taddr));
-                aarch64_util.writeAdrpInst(pages, code[rel.r_offset..][0..4]);
+                    aarch64_util.writeAdrpInst(pages, code);
+                } else {
+                    relocs_log.debug("      relaxing adrp => nop", .{});
+                    mem.writeInt(u32, code, Instruction.nop().toU32(), .little);
+                }
             },
             .TLSDESC_LD64_LO12 => {
-                const S_: i64 = @intCast(target.tlsDescAddress(elf_file));
+                if (target.flags.has_tlsdesc) {
-                const taddr: u64 = @intCast(S_ + A);
+                    const S_: i64 = @intCast(target.tlsDescAddress(elf_file));
-                relocs_log.debug("      [{x} => {x}]", .{ P, taddr });
+                    const taddr: u64 = @intCast(S_ + A);
-                const offset: u12 = try math.divExact(u12, @truncate(taddr), 8);
+                    relocs_log.debug("      [{x} => {x}]", .{ P, taddr });
-                aarch64_util.writeLoadStoreRegInst(offset, code[rel.r_offset..][0..4]);
+                    const offset: u12 = try math.divExact(u12, @truncate(taddr), 8);
+                    aarch64_util.writeLoadStoreRegInst(offset, code);
+                } else {
+                    relocs_log.debug("      relaxing ldr => nop", .{});
+                    mem.writeInt(u32, code, Instruction.nop().toU32(), .little);
+                }
             },
             .TLSDESC_ADD_LO12 => {
-                const S_: i64 = @intCast(target.tlsDescAddress(elf_file));
+                if (target.flags.has_tlsdesc) {
-                const taddr: u64 = @intCast(S_ + A);
+                    const S_: i64 = @intCast(target.tlsDescAddress(elf_file));
-                relocs_log.debug("      [{x} => {x}]", .{ P, taddr });
+                    const taddr: u64 = @intCast(S_ + A);
-                const offset: u12 = @truncate(taddr);
+                    relocs_log.debug("      [{x} => {x}]", .{ P, taddr });
-                aarch64_util.writeAddImmInst(offset, code[rel.r_offset..][0..4]);
+                    const offset: u12 = @truncate(taddr);
+                    aarch64_util.writeAddImmInst(offset, code);
+                } else {
+                    const old_inst = Instruction{
+                        .add_subtract_immediate = mem.bytesToValue(std.meta.TagPayload(
+                            Instruction,
+                            Instruction.add_subtract_immediate,
+                        ), code),
+                    };
+                    const rd: Register = @enumFromInt(old_inst.add_subtract_immediate.rd);
+                    relocs_log.debug("      relaxing add({s}) => movz(x0, {x})", .{ @tagName(rd), S + A - TP });
+                    const value: u16 = @bitCast(math.cast(i16, (S + A - TP) >> 16) orelse return error.Overflow);
+                    mem.writeInt(u32, code, Instruction.movz(.x0, value, 16).toU32(), .little);
+                }
             },
             .TLSDESC_CALL => if (!target.flags.has_tlsdesc) {
-                mem.writeInt(u32, code[rel.r_offset..][0..4], aarch64_util.Instruction.nop().toU32(), .little);
+                const old_inst = Instruction{
+                    .unconditional_branch_register = mem.bytesToValue(std.meta.TagPayload(
+                        Instruction,
+                        Instruction.unconditional_branch_register,
+                    ), code),
+                };
+                const rn: Register = @enumFromInt(old_inst.unconditional_branch_register.rn);
+                relocs_log.debug("      relaxing br({s}) => movk(x0, {x})", .{ @tagName(rn), S + A - TP });
+                const value: u16 = @bitCast(@as(i16, @truncate(S + A - TP)));
+                mem.writeInt(u32, code, Instruction.movk(.x0, value, 0).toU32(), .little);
             },
             else => try atom.reportUnhandledRelocError(rel, elf_file),
 @@ -1830,6 +1862,8 @@ const aarch64 = struct {
     }
     const aarch64_util = @import("../aarch64.zig");
+    const Instruction = aarch64_util.Instruction;
+    const Register = aarch64_util.Register;
 };
 const riscv = struct {