From: George Dunlap <george.dunlap@citrix.com>
Date: Thu, 26 Dec 2019 17:43:17 +0000 (+0000)
Subject: go/xenlight: Fix CpuidPoliclyList conversion
X-Git-Tag: archive/raspbian/4.14.0+80-gd101b417b7-1+rpi1^2~63^2~862
X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=084974fe715399ba9b4f60be3420f15c68cbfe59;p=xen.git

go/xenlight: Fix CpuidPoliclyList conversion

Empty Go strings should be converted to `nil` libxl_cpuid_policy_list;
otherwise libxl_cpuid_parse_config gets confused.

Also, libxl_cpuid_policy_list returns a weird error, not a "normal"
libxl error; if it returns one of these non-standard errors, convert
it to ErrorInval.

Finally, make the fromC() method take a pointer, and set the value of
CpuidPolicyList such that it will generate a valid CpuidPolicyList in
response.

Signed-off-by: George Dunlap <george.dunlap@citrix.com>
Reviewed-by: Nick Rosbrook <rosbrookn@ainfosec.com>
---

diff --git a/tools/golang/xenlight/xenlight.go b/tools/golang/xenlight/xenlight.go
index b1587b964f..1299981713 100644
--- a/tools/golang/xenlight/xenlight.go
+++ b/tools/golang/xenlight/xenlight.go
@@ -306,9 +306,14 @@ func (el *EvLink) toC(cel *C.libxl_ev_link) (err error) { return }
 // empty when it is returned from libxl.
 type CpuidPolicyList string
 
-func (cpl CpuidPolicyList) fromC(ccpl *C.libxl_cpuid_policy_list) error { return nil }
+func (cpl *CpuidPolicyList) fromC(ccpl *C.libxl_cpuid_policy_list) error { *cpl = ""; return nil }
 
 func (cpl CpuidPolicyList) toC(ccpl *C.libxl_cpuid_policy_list) error {
+	if cpl == "" {
+		*ccpl = nil
+		return nil
+	}
+
 	s := C.CString(string(cpl))
 	defer C.free(unsafe.Pointer(s))
 
@@ -316,7 +321,8 @@ func (cpl CpuidPolicyList) toC(ccpl *C.libxl_cpuid_policy_list) error {
 	if ret != 0 {
 		C.libxl_cpuid_dispose(ccpl)
 
-		return Error(-ret)
+		// libxl_cpuid_parse_config doesn't return a normal libxl error.
+		return ErrorInval
 	}
 
 	return nil