ed/raddebugger
1
0
Fork 0
mirror of https://github.com/Ed94/raddebugger.git synced 2026-08-08 14:58:08 +00:00
Code Issues Packages Projects Releases Wiki Activity

refine COMDAT symlink handling

Browse Source 
Stop treating COMDAT section-definition symbols as symlink anchors.
Keep zero-sized COMDAT sections only when they have an owned symlink,
so referenced empty COMDAT symbols still resolve while marker sections
like .gsspr/.gssep are skipped.

Update COMDAT/ICF tests to cover zero-sized COMDAT relocation behavior
and the adjusted removed-COMDAT handling.
This commit is contained in:
Nikita Smith
2026-07-27 14:47:18 -07:00
committed by Ryan Fleury
parent 8ec931d724
commit d1b0bc0af7
3 changed files with 62 additions and 62 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/linker/lnk.c
+14 -10
View File
@@ -3414,8 +3414,10 @@ lnk_section_definition_is_before(void *raw_a, void *raw_b)
}
internal B32
lnk_should_gather_section(COFF_SectionHeader *sect_header, COFF_SectionFlags sect_flags)
lnk_should_gather_section(LNK_Obj *obj, U64 sect_idx, COFF_SectionHeader *sect_header)
{
COFF_SectionFlags sect_flags = obj->section_flags[sect_idx];
// removed sections were eliminated before image layout
if (sect_flags & COFF_SectionFlag_LnkRemove) {
return 0;
@@ -3426,13 +3428,19 @@ lnk_should_gather_section(COFF_SectionHeader *sect_header, COFF_SectionFlags sec
return 0;
}
// non-COMDAT empty sections do not need image contributions
// empty COMDATs with symlinks can still anchor symbols at offset zero
if (sect_header->fsize == 0) {
if (~sect_flags & COFF_SectionFlag_LnkCOMDAT) {
return 0;
}
// keep zero-size COMDATs so symbols at offset zero still get mapped
LNK_ObjSymbolRef symlink_ref = {0};
if (!lnk_obj_get_comdat_symlink(obj, sect_idx + 1, &symlink_ref)) {
return 0;
}
// gather only COMDAT leaders
AssertAlways(symlink_ref.obj == obj);
}
return 1;
@@ -3457,7 +3465,7 @@ THREAD_POOL_TASK_FUNC(lnk_gather_sections_task)
for EachIndex(sect_idx, obj->header.section_count_no_null) {
COFF_SectionHeader *sect_header = &section_table[sect_idx];
if ( ! lnk_should_gather_section(sect_header, obj->section_flags[sect_idx])) { continue; }
if ( ! lnk_should_gather_section(obj, sect_idx, sect_header)) { continue; }
Temp temp = temp_begin(scratch.arena);
@@ -3591,7 +3599,7 @@ THREAD_POOL_TASK_FUNC(lnk_gather_sections_task)
COFF_SectionFlags sect_flags = obj->section_flags[sect_idx];
task->sect_map[obj_idx][sect_idx] = sc;
if ( ! lnk_should_gather_section(sect_header, sect_flags)) { continue; }
if ( ! lnk_should_gather_section(obj, sect_idx, sect_header)) { continue; }
LNK_SectionContribChunk *sc_chunk = 0;
{
@@ -3849,14 +3857,10 @@ THREAD_POOL_TASK_FUNC(lnk_patch_regular_symbols_task)
for (U64 symbol_idx = 0; symbol_idx < obj->header.symbol_count; symbol_idx += (1 + symbol.aux_symbol_count)) {
symbol = lnk_parsed_symbol_from_coff_symbol_idx(obj, symbol_idx);
if (task->u.patch_symtabs.was_symbol_patched[obj_idx][symbol_idx]) {
continue;
}
if (task->u.patch_symtabs.was_symbol_patched[obj_idx][symbol_idx]) { continue; }
COFF_SymbolValueInterpType interp = coff_interp_symbol(symbol.section_number, symbol.value, symbol.storage_class);
if (interp == COFF_SymbolValueInterp_Regular) {
COFF_SectionHeader *sect_header = lnk_coff_section_header_from_section_number(obj, symbol.section_number);
LNK_SectionContrib *sc = task->sect_map[obj_idx][symbol.section_number-1];
U32 section_number;
U32 value;
src/linker/lnk_obj.c
+16 -18
View File
@@ -486,19 +486,15 @@ lnk_symlinks_from_obj(Arena *arena, LNK_SymbolTable *symtab, LNK_Obj *obj)
if (symbol.storage_class == COFF_SymStorageClass_External && symbol.aux_symbol_count == 0) {
B32 can_set_symlink = (symlink->obj == 0 || symbol.value == 0);
if (!can_set_symlink && symlink->obj == obj) {
// NOTE: The section definition is a fallback symlink. Public symbols inside a
// discarded COMDAT need to target the selected public symbol's offset,
// not the selected section base plus the discarded symbol's offset.
// MSVC vftables are also preferred over other public symbols in the
// same section so ICF can keep vftable COMDATs in their own color space.
COFF_ParsedSymbol symlink_symbol = lnk_parsed_symbol_from_coff_symbol_idx(symlink->obj, symlink->symbol_idx);
B32 symlink_is_section_defn = (symlink_symbol.section_number == symbol.section_number &&
symlink_symbol.storage_class == COFF_SymStorageClass_Static &&
symlink_symbol.aux_symbol_count > 0);
B32 symlink_is_non_vftable = (symlink_symbol.section_number == symbol.section_number &&
!str8_starts_with(symlink_symbol.name, str8_lit(MSCRT_VFTABLE_SYMBOL_PREFIX)));
B32 symbol_is_vftable = str8_starts_with(symbol.name, str8_lit(MSCRT_VFTABLE_SYMBOL_PREFIX));
can_set_symlink = (symlink_is_section_defn || (symbol_is_vftable && symlink_is_non_vftable));
COFF_ParsedSymbol leader = lnk_parsed_symbol_from_coff_symbol_idx(symlink->obj, symlink->symbol_idx);
B32 leader_is_same_section = leader.section_number == symbol.section_number;
B32 leader_is_static_anchor = (leader_is_same_section && leader.storage_class == COFF_SymStorageClass_Static && leader.aux_symbol_count == 0);
B32 leader_is_vftable = str8_starts_with(leader.name, str8_lit(MSCRT_VFTABLE_SYMBOL_PREFIX));
B32 current_is_vftable = str8_starts_with(symbol.name, str8_lit(MSCRT_VFTABLE_SYMBOL_PREFIX));
// prefer public symbols to local static anchors; prefer vftable public
// symbols to other public symbols so ICF keeps vftables in their own color space
can_set_symlink = (leader_is_static_anchor || (leader_is_same_section && current_is_vftable && !leader_is_vftable));
}
if (can_set_symlink) {
@@ -507,15 +503,17 @@ lnk_symlinks_from_obj(Arena *arena, LNK_SymbolTable *symtab, LNK_Obj *obj)
*symlink = lnk_ref_from_symbol(link_symbol->symbol);
}
}
continue;
}
// section definitions
if (symlink->obj == 0 && symbol.storage_class == COFF_SymStorageClass_Static && symbol.aux_symbol_count > 0) {
// static symbols
else if (symbol.storage_class == COFF_SymStorageClass_Static) {
if (symbol.aux_symbol_count == 0) {
if (symlink->obj == 0) {
*symlink = (LNK_ObjSymbolRef){ obj, symbol_idx };
}
}
}
}
return symlinks;
}
src/linker/tests/linker_tests.c
+26 -28
View File
@@ -3510,30 +3510,18 @@ TEST(icf_vftable_external_symbol_at_nonzero_offset)
T_Ok(actual_lea_target == b_vftable_ptr - pe.image_base);
}
// A referenced zero-sized COMDAT symbol is meaningful enough for
// relocations, even though the COMDAT contributes no bytes to the image.
TEST(zero_length_comdat_referenced_by_reloc)
{
if (t_id_linker() != Linker_radlink) { return; }
U8 data[8] = {0};
T_Ok(t_write_entry_obj());
T_Ok(t_write_def_obj("leader.obj", (T_COFF_DefObj){
.machine = T_COFF_DefSetMachine(X64),
.sections = (T_COFF_DefSection[]){
{ "empty", ".rdata", str8_zero(), .flags = "r:data@1", .raw_flags = COFF_SectionFlag_LnkCOMDAT },
{0}
},
.symbols = (T_COFF_DefSymbol[]){
T_COFF_DefSymbol_Secdef("empty", COFF_ComdatSelect_Any),
T_COFF_DefSymbol_Extern("EMPTY", "empty", 0),
{0}
}
}));
T_Ok(t_write_def_obj("ref.obj", (T_COFF_DefObj){
.machine = T_COFF_DefSetMachine(X64),
.sections = (T_COFF_DefSection[]){
{ "empty", ".rdata", str8_zero(), .flags = "r:data@1", .raw_flags = COFF_SectionFlag_LnkCOMDAT },
{ "pad", ".rdata$a", str8_lit("xy"), .flags = "r:data@1" },
{ "empty", ".rdata$b", str8_zero(), .flags = "r:data@1", .raw_flags = COFF_SectionFlag_LnkCOMDAT },
{ "data", ".data", str8_array_fixed(data), .flags = "rw:data", .relocs = (T_COFF_DefReloc[]){
T_COFF_DefReloc(X64_Addr64, 0, "EMPTY"),
{0}
@@ -3547,8 +3535,26 @@ TEST(zero_length_comdat_referenced_by_reloc)
}
}));
t_invoke_linkerf("/subsystem:console /entry:entry /out:a.exe /opt:ref entry.obj leader.obj ref.obj");
t_invoke_linkerf("/subsystem:console /entry:entry /out:a.exe /opt:ref entry.obj ref.obj");
T_Ok(g_last_exit_code == 0);
String8 exe = t_read_file(arena, str8_lit("a.exe"));
PE_BinInfo pe = pe_bin_info_from_data(arena, exe);
COFF_SectionHeader *section_table = (COFF_SectionHeader *)str8_substr(exe, pe.section_table_range).str;
COFF_SectionHeader *rdata_section = coff_section_header_from_name(str8_zero(), section_table, pe.section_count, str8_lit(".rdata"));
COFF_SectionHeader *data_section = coff_section_header_from_name(str8_zero(), section_table, pe.section_count, str8_lit(".data"));
T_Ok(rdata_section != 0);
T_Ok(data_section != 0);
U64 empty_va = 0;
str8_deserial_read_struct(exe, data_section->foff, &empty_va);
B32 empty_after_pad = empty_va >= pe.image_base + rdata_section->voff + 2;
T_Ok(empty_after_pad);
U64 empty_off_in_rdata = empty_va - pe.image_base - rdata_section->voff;
T_Ok(rdata_section->foff + empty_off_in_rdata <= exe.size);
T_Ok(exe.str[rdata_section->foff + empty_off_in_rdata - 2] == 'x');
T_Ok(exe.str[rdata_section->foff + empty_off_in_rdata - 1] == 'y');
}
TEST(zero_length_static_comdat_referenced_by_reloc)
@@ -4270,7 +4276,7 @@ TEST(reloc_against_removed_comdat)
}));
t_invoke_linkerf("/subsystem:console /entry:entry /out:a.exe a.obj b.obj entry.obj");
T_Ok(g_last_exit_code == LNK_Error_RelocationAgainstRemovedSection);
T_Ok(g_last_exit_code == 0);
}
TEST(sect_align)
@@ -8874,25 +8880,17 @@ TEST(icf_llvm_addrsig)
t_invoke(t_clang_path(), str8f(arena, "%S -o %S -c -ffunction-sections -target x86_64-pc-windows-msvc", main_path, main_obj_path), max_U64);
T_Ok(g_last_exit_code == 0);
String8 a_path = t_make_file_path(arena, str8_lit("a.exe"));
t_invoke_linkerf("%S /opt:icf /out:a.exe libcmt.lib", main_obj_path);
T_Ok(g_last_exit_code == 0);
String8 a_path = t_make_file_path(arena, str8_lit("a.exe"));
t_invoke(a_path, str8_zero(), max_U64);
if (t_id_linker() == Linker_radlink) {
T_Ok(g_last_exit_code == 1);
} else {
T_Ok(g_last_exit_code == 0);
}
if (t_id_linker() == Linker_radlink) {
t_invoke_linkerf("%S /opt:icf /out:a.exe libcmt.lib /llvm_addrsig:no", main_obj_path);
T_Ok(g_last_exit_code == 0);
t_invoke(a_path, str8_zero(), max_U64);
T_Ok(g_last_exit_code == 0);
}
}
// .llvm_addrsig can name an undefined external whose definition is in another