c: avoid generating relocations in .rodata (putting such objects in .data instead for now)

3 files changed, 30 insertions, 13 deletions

diff --git a/amd64/emit.c b/amd64/emit.c
index 2f4ad13..7ee1f93 100644
--- a/amd64/emit.c
+++ b/amd64/emit.c
@@ -337,7 +337,9 @@ encode(uchar **pcode, const struct desc *tab, int ntab, enum irclass k, struct o
          if (mem.cindex == NOINDEX) {
             /* %rip(var) */
             static uchar offs[NOPERENC] = { [EN_MI8] = 1, [EN_MI16] = 2, [EN_MI32] = 4 };
-            enum relockind r = (!conht[mem.con].deref && ccopt.pic) ? (rex ? REL_GOTPCRELX : REL_GOTPCRELX_REX) : REL_PCREL32;
+            enum relockind r =
+               (!conht[mem.con].deref && ccopt.pic) ? (rex ? REL_GOTPCRELX : REL_GOTPCRELX_REX)
+                                                    : REL_PCREL32;
             int off = -4 - offs[en->operenc];
             B(/*mod 0*/ (reg & 7) << 3 | RBP);
             objreloc(xcon2sym(mem.con), r, Stext, *pcode - objout.textbegin, mem.disp + off);
diff --git a/c/c.c b/c/c.c
index 377ccc8..094931f 100644
--- a/c/c.c
+++ b/c/c.c
@@ -1136,7 +1136,10 @@ struct initparser {
    struct arena **arena;
    uint arrlen;
    enum evalmode ev;
-   bool dyn; /* size is not known until parsing done (implicit array size) */
+   bool dyn; /* when set, data is written to a temporary buffer first, because either:
+                  - size is not known until parsing done (implicit array size)
+                  - data section is not known until parsing done (to avoid relocs in .rodata)
+                otherwise write to the corresponding object data section buffer directly */
    union {
       struct init *init; /* for initializer with automatic storage */
       struct {  /* for static storage (dyn = 0) */
@@ -1225,10 +1228,15 @@ expr2reloc(union ref *psym, vlong *paddend, const struct expr *ex)
    } else Fail: assert(0 && "non static reloc");
 }
 
+static bool
+rodatarelocok(void)
+{
+   return !(ccopt.pie | ccopt.pic);
+}
+
 static void
 iniwrite(struct comp *cm, struct initparser *ip, uint off, uint bitsiz, uint bitoff, union type ty, struct expr *ex)
 {
-   uchar *p;
    if (ex->ty.t == TYSTRUCT) {
       assert(ty.bits == ex->ty.bits);
       for (uint i = 0, n = nmemb(ex->ty); i < n; ++i) {
@@ -1237,6 +1245,7 @@ iniwrite(struct comp *cm, struct initparser *ip, uint off, uint bitsiz, uint bit
          iniwrite(cm, ip, off + suboff, bitsiz, bitoff, sub, exprdup(cm, &mkexpr(EGETF, ex->span, sub, .sub = ex)));
       }
    } else if (ip->ev == EVSTATICINI) {
+      uchar *p;
       uint siz = typesize(ty);
       if (ip->dyn) {
          if (ip->ddat.n < off + siz) {
@@ -1287,6 +1296,7 @@ iniwrite(struct comp *cm, struct initparser *ip, uint off, uint bitsiz, uint bit
          expr2reloc(&sym, &addend, ex);
          assert(sym.t == RXCON);
          if (!ip->dyn) {
+            assert(ip->sec != Srodata || rodatarelocok());
             objreloc(xcon2sym(sym.i), targ_64bit ? REL_ABS64 : REL_ABS32,
                      ip->sec, ip->off + off, addend);
          } else {
@@ -1556,8 +1566,12 @@ initializer(struct comp *cm, union type *ty, enum evalmode ev, bool globl,
    ip->arena = &cm->exarena;
    ip->ev = ev;
    if (ev == EVSTATICINI) {
-      if (ty->t == TYARRAY && !typearrlen(*ty)) {
+      if (ty->t == TYARRAY && isincomplete(*ty)) {
          ip->dyn = 1;
+      } else if (qual & QCONST && !rodatarelocok()) {
+         ip->dyn = 1;
+         vresize(&ip->ddat, typesize(*ty));
+         memset(ip->ddat.p, 0, typesize(*ty));
       } else {
          ip->sec = qual & QCONST ? Srodata : Sdata;
          ip->off = objnewdat(name, ip->sec, globl, typesize(*ty), typealign(*ty));
@@ -1572,17 +1586,16 @@ initializer(struct comp *cm, union type *ty, enum evalmode ev, bool globl,
       if (ex.t == ESTRLIT && chrarrayof(*ty, typechild(ex.ty))) {
          inistrlit(cm, &ex, ty);
          iniwrite(cm, ip, 0, 0, 0, *ty, &ex);
-         if (ip->dyn)
-            goto Dynfix;
-      }
-      if (!initcheck(*ty, &ex))
+      } else if (!initcheck(*ty, &ex)) {
          error(&ex.span, "cannot initialize '%ty' with expression of type '%ty'", *ty, ex.ty);
-      else {
+      } else {
          if (ev && !eval(&ex, ev) && ev != EVFOLD)
             error(&ex.span, "cannot evaluate expression statically");
          else
             iniwrite(cm, ip, 0, 0, 0, *ty, &ex);
       }
+      if (ip->dyn)
+         goto Dynfix;
       return ex;
    }
 
@@ -1634,14 +1647,14 @@ initializer(struct comp *cm, union type *ty, enum evalmode ev, bool globl,
          error(&span, "array cannot have zero length");
       *ty = mkarrtype(typechild(*ty), ty->flag & TFCHLDQUAL, len);
    Dynfix:
-      sec = qual & QCONST ? Srodata : Sdata;
+      if (qual & QCONST && (ip->drel == NULL || rodatarelocok()))
+         sec = Srodata;
+      else
+         sec = Sdata;
       off = objnewdat(name, sec, globl, siz = typesize(*ty), align = typealign(*ty));
       p = sec == Srodata ? objout.rodata.p : objout.data.p;
       memcpy(p + off, ip->ddat.p, ip->ddat.n);
       memset(p + off + ip->ddat.n, 0, typesize(*ty) - ip->ddat.n);
-      vpush(&dattab, ((struct irdat) {
-         align, globl, sec, siz, off, name
-      }));
       vfree(&ip->ddat);
       for (struct dreloc *rel = ip->drel; rel; rel = rel->link) {
          objreloc(rel->sym, targ_64bit ? REL_ABS64 : REL_ABS32, sec, off + rel->off, rel->addend);
diff --git a/test/reloc.c b/test/reloc.c
index 0695770..ccc03ec 100644
--- a/test/reloc.c
+++ b/test/reloc.c
@@ -1,5 +1,7 @@
 
 
+const void *const relro = &relro;
+
 float get_value(unsigned x)
 {
    static const float values [] = {1.1f, 1.2f, 1.3f, 1.4f};