sys: check that target consts are defined

Currently when we get target consts with target.ConstMap["name"]
during target initialization, we just get 0 for missing consts.
This is error-prone as we can mis-type a const, or a const may
be undefined only on some archs (as we have common unix code
shared between several OSes).
Check that all the consts are actually defined.
The check detects several violations, to fix them:
1. move mremap to linux as it's only defined on linux
2. move S_IFMT to openbsd, as it's only defined and used on openbsd
3. define missing MAP_ANONYMOUS for freebsd and netbsd
4. fix extract for netbsd

1 files changed, 11 insertions, 0 deletions

diff --git a/prog/target.go b/prog/target.go
index bff59ea4f..db8b1835e 100644
--- a/prog/target.go
+++ b/prog/target.go
@@ -169,6 +169,17 @@ func (target *Target) initTarget() {
 	initAnyTypes(target)
 }
 
+func (target *Target) GetConst(name string) uint64 {
+	if target.ConstMap == nil {
+		panic("GetConst can only be used during target initialization")
+	}
+	v, ok := target.ConstMap[name]
+	if !ok {
+		panic(fmt.Sprintf("const %v is not defined for %v/%v", name, target.OS, target.Arch))
+	}
+	return v
+}
+
 type Gen struct {
 	r *randGen
 	s *state