Commit 0b92404ddf71c72664d2d4dd252e211a9678492d | zig

author	Jakub Konka <kubkon@jakubkonka.com> 2024-08-29 07:30:36+02:00
committer	Jakub Konka <kubkon@jakubkonka.com> 2024-09-04 13:34:25+02:00
log	0b92404ddf71c72664d2d4dd252e211a9678492d
tree	72f12db832f936b041f873b93227646b2ae41b95
parent	37a1f0e7f2586b1fd3c88c3483f0c9f731f41a30

elf: allocate .data in ZigObject similarly to .eh_frame

2 files changed, 72 insertions(+), 61 deletions(-)

src
- link
  - Elf.zig
  - Elf
    ZigObject.zig

src/link/Elf.zig+32-20

 @@ -59,8 +59,6 @@ phdrs: std.ArrayListUnmanaged(elf.Elf64_Phdr) = .{},
 phdr_zig_load_re_index: ?u16 = null,
 /// The index into the program headers of a PT_LOAD program header with Read flag
 phdr_zig_load_ro_index: ?u16 = null,
-/// The index into the program headers of a PT_LOAD program header with Write flag
-phdr_zig_load_rw_index: ?u16 = null,
 /// Special program headers
 /// PT_PHDR
 @@ -126,7 +124,6 @@ comdat_group_sections: std.ArrayListUnmanaged(ComdatGroupSection) = .{},
 /// .rela.* sections are only used when emitting a relocatable object file.
 zig_text_section_index: ?u32 = null,
 zig_data_rel_ro_section_index: ?u32 = null,
-zig_data_section_index: ?u32 = null,
 debug_info_section_index: ?u32 = null,
 debug_abbrev_section_index: ?u32 = null,
 @@ -3491,7 +3488,6 @@ fn resetShdrIndexes(self: *Elf, backlinks: []const u32) void {
         &self.verneed_section_index,
         &self.zig_text_section_index,
         &self.zig_data_rel_ro_section_index,
-        &self.zig_data_section_index,
         &self.debug_info_section_index,
         &self.debug_abbrev_section_index,
         &self.debug_str_section_index,
 @@ -3589,12 +3585,16 @@ fn updateSectionSizes(self: *Elf) !void {
     for (slice.items(.shdr), slice.items(.atom_list), 0..) |*shdr, atom_list, shndx| {
         if (atom_list.items.len == 0) continue;
         if (self.requiresThunks() and shdr.sh_flags & elf.SHF_EXECINSTR != 0) continue;
-        if (self.zigObjectPtr()) |zo| {
+        if (self.zigObjectPtr()) |zo| blk: {
-            if (zo.bss_index) |sym_index| {
+            const sym_index = for ([_]?Symbol.Index{
-                const atom_ptr = zo.symbol(sym_index).atom(self).?;
+                zo.data_index,
-                if (shndx == atom_ptr.output_section_index) {
+                zo.bss_index,
-                    shdr.sh_size = atom_ptr.size;
+            }) |maybe_idx| {
-                }
+                if (maybe_idx) |idx| break idx;
+            } else break :blk;
+            const atom_ptr = zo.symbol(sym_index).atom(self).?;
+            if (shndx == atom_ptr.output_section_index) {
+                shdr.sh_size = atom_ptr.size;
             }
         }
         for (atom_list.items) |ref| {
 @@ -3929,10 +3929,16 @@ pub fn allocateAllocSections(self: *Elf) !void {
             }
             new_offset = alignment.@"align"(shndx, shdr.sh_addralign, new_offset);
-            if (shndx == self.eh_frame_section_index) eh_frame: {
+            if (self.zigObjectPtr()) |zo| blk: {
-                const zo = self.zigObjectPtr() orelse break :eh_frame;
+                const existing_size = for ([_]?Symbol.Index{
-                const sym = zo.symbol(zo.eh_frame_index orelse break :eh_frame);
+                    zo.data_index,
-                const existing_size = sym.atom(self).?.size;
+                    zo.eh_frame_index,
+                }) |maybe_sym_index| {
+                    const sect_sym_index = maybe_sym_index orelse continue;
+                    const sect_atom_ptr = zo.symbol(sect_sym_index).atom(self).?;
+                    if (sect_atom_ptr.output_section_index != shndx) continue;
+                    break sect_atom_ptr.size;
+                } else break :blk;
                 log.debug("moving {s} from 0x{x} to 0x{x}", .{
                     self.getShString(shdr.sh_name),
                     shdr.sh_offset,
 @@ -4096,10 +4102,17 @@ fn writeAtoms(self: *Elf) !void {
                 if (atom_ptr.output_section_index == shndx) break :base_offset atom_ptr.size;
             }
             break :base_offset 0;
-        } else if (@as(u32, @intCast(shndx)) == self.eh_frame_section_index) base_offset: {
+        } else if (self.zigObjectPtr()) |zo| base_offset: {
-            const zo = self.zigObjectPtr() orelse break :base_offset 0;
+            const sym_index = for ([_]?Symbol.Index{
-            const sym = zo.symbol(zo.eh_frame_index orelse break :base_offset 0);
+                zo.data_index,
-            break :base_offset sym.atom(self).?.size;
+                zo.eh_frame_index,
+            }) |maybe_idx| {
+                if (maybe_idx) |idx| break idx;
+            } else break :base_offset 0;
+            const sym = zo.symbol(sym_index);
+            const atom_ptr = sym.atom(self).?;
+            if (atom_ptr.output_section_index == @as(u32, @intCast(shndx))) break :base_offset atom_ptr.size;
+            break :base_offset 0;
         } else 0;
         const sh_offset = shdr.sh_offset + base_offset;
         const sh_size = math.cast(usize, shdr.sh_size - base_offset) orelse return error.Overflow;
 @@ -4806,7 +4819,6 @@ 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,
     }) |index| {
         if (index == shndx) return true;
     }
 @@ -5507,7 +5519,7 @@ fn requiresThunks(self: Elf) bool {
 /// so that we reserve enough space for the program header table up-front.
 /// Bump these numbers when adding or deleting a Zig specific pre-allocated segment, or adding
 /// more special-purpose program headers.
-pub const number_of_zig_segments = 4;
+pub const number_of_zig_segments = 2;
 const max_number_of_object_segments = 9;
 const max_number_of_special_phdrs = 5;

src/link/Elf/ZigObject.zig+40-41

 @@ -61,6 +61,7 @@ debug_loclists_index: ?Symbol.Index = null,
 debug_rnglists_index: ?Symbol.Index = null,
 eh_frame_index: ?Symbol.Index = null,
 bss_index: ?Symbol.Index = null,
+data_index: ?Symbol.Index = null,
 pub const global_symbol_bit: u32 = 0x80000000;
 pub const symbol_mask: u32 = 0x7fffffff;
 @@ -104,7 +105,7 @@ pub fn init(self: *ZigObject, elf_file: *Elf, options: InitOptions) !void {
         }
     }.fillSection;
-    comptime assert(Elf.number_of_zig_segments == 4);
+    comptime assert(Elf.number_of_zig_segments == 2);
     if (!elf_file.base.isRelocatable()) {
         if (elf_file.phdr_zig_load_re_index == null) {
 @@ -135,21 +136,6 @@ pub fn init(self: *ZigObject, elf_file: *Elf, options: InitOptions) !void {
                 .flags = elf.PF_R | elf.PF_W,
             });
         }
-        if (elf_file.phdr_zig_load_rw_index == null) {
-            const alignment = elf_file.page_size;
-            const filesz: u64 = 1024;
-            const off = try elf_file.findFreeSpace(filesz, alignment);
-            elf_file.phdr_zig_load_rw_index = try elf_file.addPhdr(.{
-                .type = elf.PT_LOAD,
-                .offset = off,
-                .filesz = filesz,
-                .addr = if (ptr_size >= 4) 0x10000000 else 0xc000,
-                .memsz = filesz,
-                .@"align" = alignment,
-                .flags = elf.PF_R | elf.PF_W,
-            });
-        }
     }
     if (elf_file.zig_text_section_index == null) {
 @@ -194,27 +180,6 @@ pub fn init(self: *ZigObject, elf_file: *Elf, options: InitOptions) !void {
         }
     }
-    if (elf_file.zig_data_section_index == null) {
-        elf_file.zig_data_section_index = try elf_file.addSection(.{
-            .name = try elf_file.insertShString(".data.zig"),
-            .type = elf.SHT_PROGBITS,
-            .addralign = ptr_size,
-            .flags = elf.SHF_ALLOC | elf.SHF_WRITE,
-            .offset = std.math.maxInt(u64),
-        });
-        const shdr = &elf_file.sections.items(.shdr)[elf_file.zig_data_section_index.?];
-        const phndx = &elf_file.sections.items(.phndx)[elf_file.zig_data_section_index.?];
-        try fillSection(elf_file, shdr, 1024, elf_file.phdr_zig_load_rw_index);
-        if (elf_file.base.isRelocatable()) {
-            _ = try elf_file.addRelaShdr(
-                try elf_file.insertShString(".rela.data.zig"),
-                elf_file.zig_data_section_index.?,
-            );
-        } else {
-            phndx.* = elf_file.phdr_zig_load_rw_index.?;
-        }
-    }
     switch (comp.config.debug_format) {
         .strip => {},
         .dwarf => |v| {
 @@ -1246,6 +1211,8 @@ fn getNavShdrIndex(
     sym_index: Symbol.Index,
     code: []const u8,
 ) error{OutOfMemory}!u32 {
+    const gpa = elf_file.base.comp.gpa;
+    const ptr_size = elf_file.ptrWidthBytes();
     const ip = &zcu.intern_pool;
     const any_non_single_threaded = elf_file.base.comp.config.any_non_single_threaded;
     const nav_val = zcu.navValue(nav_index);
 @@ -1276,7 +1243,19 @@ fn getNavShdrIndex(
     if (is_const) return elf_file.zig_data_rel_ro_section_index.?;
     if (nav_init != .none and Value.fromInterned(nav_init).isUndefDeep(zcu))
         return switch (zcu.navFileScope(nav_index).mod.optimize_mode) {
-            .Debug, .ReleaseSafe => elf_file.zig_data_section_index.?,
+            .Debug, .ReleaseSafe => {
+                if (self.data_index) |symbol_index|
+                    return self.symbol(symbol_index).atom(elf_file).?.output_section_index;
+                const osec = try elf_file.addSection(.{
+                    .name = try elf_file.insertShString(".data"),
+                    .type = elf.SHT_PROGBITS,
+                    .addralign = ptr_size,
+                    .flags = elf.SHF_ALLOC | elf.SHF_WRITE,
+                    .offset = std.math.maxInt(u64),
+                });
+                self.data_index = try self.addSectionSymbol(gpa, ".data", .@"1", osec);
+                return osec;
+            },
             .ReleaseFast, .ReleaseSmall => {
                 if (self.bss_index) |symbol_index|
                     return self.symbol(symbol_index).atom(elf_file).?.output_section_index;
 @@ -1286,7 +1265,7 @@ fn getNavShdrIndex(
                     .name = try elf_file.insertShString(".bss"),
                     .addralign = 1,
                 });
-                self.bss_index = try self.addSectionSymbol(elf_file.base.comp.gpa, ".bss", .@"1", osec);
+                self.bss_index = try self.addSectionSymbol(gpa, ".bss", .@"1", osec);
                 return osec;
             },
         };
 @@ -1302,10 +1281,20 @@ fn getNavShdrIndex(
             .name = try elf_file.insertShString(".bss"),
             .addralign = 1,
         });
-        self.bss_index = try self.addSectionSymbol(elf_file.base.comp.gpa, ".bss", .@"1", osec);
+        self.bss_index = try self.addSectionSymbol(gpa, ".bss", .@"1", osec);
         return osec;
     }
-    return elf_file.zig_data_section_index.?;
+    if (self.data_index) |symbol_index|
+        return self.symbol(symbol_index).atom(elf_file).?.output_section_index;
+    const osec = try elf_file.addSection(.{
+        .name = try elf_file.insertShString(".data"),
+        .type = elf.SHT_PROGBITS,
+        .addralign = ptr_size,
+        .flags = elf.SHF_ALLOC | elf.SHF_WRITE,
+        .offset = std.math.maxInt(u64),
+    });
+    self.data_index = try self.addSectionSymbol(gpa, ".data", .@"1", osec);
+    return osec;
 }
 fn updateNavCode(
 @@ -2014,6 +2003,16 @@ fn allocateAtom(self: *ZigObject, atom_ptr: *Atom, elf_file: *Elf) !void {
     }
     shdr.sh_addralign = @max(shdr.sh_addralign, atom_ptr.alignment.toByteUnits().?);
+    const sect_atom_ptr = for ([_]?Symbol.Index{self.data_index}) |maybe_sym_index| {
+        const sect_sym_index = maybe_sym_index orelse continue;
+        const sect_atom_ptr = self.symbol(sect_sym_index).atom(elf_file).?;
+        if (sect_atom_ptr.output_section_index == atom_ptr.output_section_index) break sect_atom_ptr;
+    } else null;
+    if (sect_atom_ptr) |sap| {
+        sap.size = shdr.sh_size;
+        sap.alignment = Atom.Alignment.fromNonzeroByteUnits(shdr.sh_addralign);
+    }
     // This function can also reallocate an atom.
     // In this case we need to "unplug" it from its previous location before
     // plugging it in to its new location.