cmd/link: use correct length for pcln.cutab

The pcln.cutab slice holds uint32 elements, as can be seen in the
runtime.moduledata type. The slice was being created with the len
(and cap) set to the size of the slice, which means that the count
was four times too large. This patch sets the correct len/cap.

This doesn't matter for the runtime because nothing looks at
the len of cutab. Since the incorrect len is larger, all valid
indexes remain valid. Using the correct length means that more
invalid indexes will be caught at run time, but such cases are unlikely.
Still, using the correct len is less confusing.

While we're here use the simpler sliceSym for pcln.pclntab.

Change-Id: I09f680b3287467120d994b171c86c784085e3d27
Reviewed-on: https://go-review.googlesource.com/c/go/+/707595
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Cherry Mui <[email protected]>
Reviewed-by: Carlos Amedee <[email protected]>
Auto-Submit: Ian Lance Taylor <[email protected]>

Author: ianlancetaylor

src/cmd/link/internal/ld/symtab.go

@@ -645,7 +645,7 @@ func (ctxt *Link) symtab(pcln *pclntab) []sym.SymKind {
 	sliceSym(pcln.funcnametab)
 
 	// The cutab slice
-	sliceSym(pcln.cutab)
+	slice(pcln.cutab, uint64(ldr.SymSize(pcln.cutab))/4)
 
 	// The filetab slice
 	sliceSym(pcln.filetab)
@@ -654,7 +654,7 @@ func (ctxt *Link) symtab(pcln *pclntab) []sym.SymKind {
 	sliceSym(pcln.pctab)
 
 	// The pclntab slice
-	slice(pcln.pclntab, uint64(ldr.SymSize(pcln.pclntab)))
+	sliceSym(pcln.pclntab)
 
 	// The ftab slice
 	slice(pcln.pclntab, uint64(pcln.nfunc+1))