Add support for Linux kernel 6.x to fetch attestation report

[takuro-sato]

Add support for Linux kernel 6.x to fetch attestation report.
Because I can't add tests which require SNP VM under amdsevsnp package, I tested the change in the following way.

Build test for fetching report

git apply --ignore-space-change <<EOF
diff --git a/pkg/amdsevsnp/report_test.go b/pkg/amdsevsnp/report_test.go
index e42af6de..65acbc91 100644
--- a/pkg/amdsevsnp/report_test.go
+++ b/pkg/amdsevsnp/report_test.go
@@ -4,6 +4,7 @@
 package amdsevsnp
 
 import (
+       "encoding/hex"
        "testing"
 )
 
@@ -51,3 +52,24 @@ func Test_Mirror_Nil_Slice(t *testing.T) {
                t.Fatalf("expected nil slice, got: %+v", result)
        }
 }
+
+func Test_Fetch_Report(t *testing.T) {
+       const REPORT_DATA_SIZE = 64
+       const REPORT_DATA_OFFSET = 80
+       // Report data for test
+       reportData := [REPORT_DATA_SIZE]byte{}
+       for i := 0; i < REPORT_DATA_SIZE; i++ {
+               reportData[i] = byte(i)
+       }
+       reportBytes, err := FetchRawSNPReport(reportData[:])
+       if err != nil {
+               t.Fatalf("fetching report failed: %v", err)
+       }
+       expectedByteString := hex.EncodeToString(reportData[:])
+
+       if expectedByteString != hex.EncodeToString(reportBytes[REPORT_DATA_OFFSET:REPORT_DATA_OFFSET+REPORT_DATA_SIZE]) {
+               t.Fatalf("report data doesn't match: expected: %s, actual: %s", expectedByteString, hex.EncodeToString(reportBytes[REPORT_DATA_OFFSET:REPORT_DATA_OFFSET+REPORT_DATA_SIZE]))
+       }
+
+       t.Logf("Report contents: %s\n", hex.EncodeToString(reportBytes))
+}
EOF

cd pkg/amdsevsnp/
CGO_ENABLED=0 go test -c

Run test

Copy amdsevsnp.test to a SNV VM first.

./amdsevsnp.test -test.v

It was tested in both 5.x and 6.x

[KenGordon]

We can't have this function as it may be construed as a derived work.

[KenGordon]

Hard wire the results. We will get rid of the 5.15 path very soon.

[takuro-sato]

Done. Tested it again in in both 5.x and 6.x.

[KenGordon]

Looks fine to me.

[helsaawy]

Can you add Test_Fetch_Report regardless and add a skip to the start of it:

func Test_Fetch_Report(t *testing.T) {
    if !isSNPVM6() {
        t.Skip("SNP is required")
    }
 
   // ...
}

that way we have the test if we ever set up SNP VMs, or want to test for regressions