runtime, cmd/ld: make code more position-independent

Change the stack unwinding code to compensate for the dynamic
relocation of symbols.
Change the gc instruction GC_CALL to use a relative offset instead of
an absolute address.

R=golang-dev
CC=golang-dev
https://golang.org/cl/7248048

diff --git a/src/cmd/ld/data.c b/src/cmd/ld/data.c
index e557881e94bedd0bb0cb7093a3024debe7d90ee9..99385fdcc275fa9465eeff829c39b1152180039e 100644 (file)
--- a/src/cmd/ld/data.c
+++ b/src/cmd/ld/data.c
@@ -748,7 +748,6 @@ setuint64(Sym *s, vlong r, uint64 v)
        setuintxx(s, r, v, 8);
 }
 
-/*
 static vlong
 addaddrpcrelplus(Sym *s, Sym *t, int32 add)
 {
@@ -769,7 +768,6 @@ addaddrpcrelplus(Sym *s, Sym *t, int32 add)
        r->add = add;
        return i;
 }
-*/
 
 vlong
 addaddrplus(Sym *s, Sym *t, int32 add)
@@ -951,7 +949,7 @@ gcaddsym(Sym *gc, Sym *s, int32 off)
                //print("gcaddsym:    %s    %d    %s\n", s->name, s->size, gotype->name);
                adduintxx(gc, GC_CALL, PtrSize);
                adduintxx(gc, off, PtrSize);
-               addaddrplus(gc, decodetype_gc(gotype), 1*PtrSize);
+               addaddrpcrelplus(gc, decodetype_gc(gotype), 4*PtrSize);
        } else {
                //print("gcaddsym:    %s    %d    <unknown type>\n", s->name, s->size);
                for(a = -off&(PtrSize-1); a+PtrSize<=s->size; a+=PtrSize) {

diff --git a/src/pkg/runtime/mgc0.c b/src/pkg/runtime/mgc0.c
index dd6640717ad3705808316e73188c9ce3cd29c14b..a025121feff917ec9c9c57860224ad36cc6c8655 100644 (file)
--- a/src/pkg/runtime/mgc0.c
+++ b/src/pkg/runtime/mgc0.c
@@ -663,7 +663,7 @@ scanblock(Workbuf *wbuf, Obj *wp, uintptr nobj, bool keepworking)
                        // Stack push.
                        *stack_ptr-- = stack_top;
                        stack_top = (Frame){1, 0, stack_top.b + pc[1], pc+3 /*return address*/};
-                       pc = (uintptr*)pc[2];  // target of the CALL instruction
+                       pc = (uintptr*)((byte*)pc + (uintptr)pc[2]);  // target of the CALL instruction
                        continue;
 
                case GC_MAP_PTR:

diff --git a/src/pkg/runtime/mgc0.h b/src/pkg/runtime/mgc0.h
index a2798ef34e2c7ccfc41183fa15bec3c8cc17f079..87b604a36d9b166ef57b24157ecda387fb82fa89 100644 (file)
--- a/src/pkg/runtime/mgc0.h
+++ b/src/pkg/runtime/mgc0.h
@@ -12,6 +12,7 @@
 // Meaning of arguments:
 //   off      Offset (in bytes) from the start of the current object
 //   objgc    Pointer to GC info of an object
+//   objgcrel Offset to GC info of an object
 //   len      Length of an array
 //   elemsize Size (in bytes) of an element
 //   size     Size (in bytes)
@@ -21,7 +22,7 @@ enum {
        GC_APTR,        // Pointer to an arbitrary object. Args: (off)
        GC_ARRAY_START, // Start an array with a fixed length. Args: (off, len, elemsize)
        GC_ARRAY_NEXT,  // The next element of an array. Args: none
-       GC_CALL,        // Call a subroutine. Args: (off, objgc)
+       GC_CALL,        // Call a subroutine. Args: (off, objgcrel)
        GC_MAP_PTR,     // Go map. Args: (off, MapType*)
        GC_STRING,      // Go string. Args: (off)
        GC_EFACE,       // interface{}. Args: (off)

diff --git a/src/pkg/runtime/symtab.c b/src/pkg/runtime/symtab.c
index a8679b1069659d849390cff8604a99f70bb5c2c8..2cb7263ee775e36433317046b4c42701189064a6 100644 (file)
--- a/src/pkg/runtime/symtab.c
+++ b/src/pkg/runtime/symtab.c
@@ -93,6 +93,7 @@ walksymtab(void (*fn)(Sym*))
 
 static Func *func;
 static int32 nfunc;
+extern byte reloffset[];
 
 static byte **fname;
 static int32 nfname;
@@ -118,7 +119,7 @@ dofunc(Sym *sym)
                }
                f = &func[nfunc++];
                f->name = runtime·gostringnocopy(sym->name);
-               f->entry = sym->value;
+               f->entry = sym->value + (uint64)reloffset;
                if(sym->symtype == 'L' || sym->symtype == 'l')
                        f->frame = -sizeof(uintptr);
                break;