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w6a+w6l: DATAR directive for absolute-address relocs in .data

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Unblock literal initialisers for str/slice/struct globals by wiring
an R_X86_64_64 relocation kind through both assembler and static
linker.

w6a:
  - new A_DATAR directive, syntax `DATAR slot+off(SB),target(SB)`,
    records an R_X86_64_64 reloc at slot+off in .data pointing at
    target. The slot must be pre-defined by a prior DATAW;
  - parse_operand learned the `name+disp(SB)` shape so the slot's
    byte offset can be addressed explicitly;
  - Areloc carries a `section` flag (0=.text / 1=.data) and obj.c
    splits the reloc list into .rela.text and .rela.data, emitting
    the latter conditionally with sh_info pointing at .data.

w6l:
  - Lrel grows the same `section` flag; obj.c loads `.rela.data`
    sections into the global reloc list with offsets shifted by
    each input's data_off;
  - pass.c handles R_X86_64_64: target VA is data_va+sym.val for
    in_data symbols (else text_va+sym.val), addend is added, and
    the 8-byte slot is patched in l->data (or l->text).

Inputs without DATAR are unaffected — bootstrap, 991 (selfhost .o
diff) and 992 (selfhost exe diff) keep their byte-identical
output. 520_datar covers the new path: asm a DATAW+DATAR pair,
verify .rela.data has exactly one R_X86_64_64 entry, link, run,
confirm the relocated pointer feeds a 5-byte write that prints
"hello".

Selfhost mirror + w6c emission for str/slice/struct literal init
land in follow-ups.
This commit is contained in:
Hojun-Cho
2026-05-12 12:45:11 +09:00
parent 00d1120441
commit d998425391
11 changed files with 353 additions and 21 deletions
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6
cmd/w6a/a.h
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@@ -60,8 +60,9 @@ struct Asym {
};
struct Areloc {
u64 off; /* offset within .text where relocation lands */
int kind; /* R_X86_64_PLT32 (4), R_X86_64_PC32 (2) */
u64 off; /* offset within the relocation's section */
int section;/* 0 = .text (most relocs), 1 = .data (DATAR) */
int kind; /* R_X86_64_64 (1), R_X86_64_PC32 (2), R_X86_64_PLT32 (4) */
Asym *sym;
i64 addend;
Areloc *next;
@@ -111,5 +112,6 @@ void a_emit_byte(Asm*, u8);
void a_emit_u32(Asm*, u32);
void a_emit_data_byte(Asm*, u8);
void a_addreloc(Asm*, u64 off, int kind, Asym *s, i64 add);
void a_addreloc_data(Asm*, u64 off, int kind, Asym *s, i64 add);
#endif