1 files changed, 42 insertions, 0 deletions
diff --git a/pkg/sentry/platform/ptrace/subprocess_amd64.go b/pkg/sentry/platform/ptrace/subprocess_amd64.go
index 4649a94a7..a55cff507 100644
--- a/pkg/sentry/platform/ptrace/subprocess_amd64.go
+++ b/pkg/sentry/platform/ptrace/subprocess_amd64.go
@@ -21,6 +21,8 @@ import (
 	"strings"
 	"syscall"
 
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/seccomp"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 )
 
@@ -143,3 +145,43 @@ func (t *thread) adjustInitRegsRip() {
 func initChildProcessPPID(initregs *syscall.PtraceRegs, ppid int32) {
 	initregs.R15 = uint64(ppid)
 }
+
+// patchSignalInfo patches the signal info to account for hitting the seccomp
+// filters from vsyscall emulation, specified below. We allow for SIGSYS as a
+// synchronous trap, but patch the structure to appear like a SIGSEGV with the
+// Rip as the faulting address.
+//
+// Note that this should only be called after verifying that the signalInfo has
+// been generated by the kernel.
+func patchSignalInfo(regs *syscall.PtraceRegs, signalInfo *arch.SignalInfo) {
+	if linux.Signal(signalInfo.Signo) == linux.SIGSYS {
+		signalInfo.Signo = int32(linux.SIGSEGV)
+
+		// Unwind the kernel emulation, if any has occurred. A SIGSYS is delivered
+		// with the si_call_addr field pointing to the current RIP. This field
+		// aligns with the si_addr field for a SIGSEGV, so we don't need to touch
+		// anything there. We do need to unwind emulation however, so we set the
+		// instruction pointer to the faulting value, and "unpop" the stack.
+		regs.Rip = signalInfo.Addr()
+		regs.Rsp -= 8
+	}
+}
+
+// enableCpuidFault enable cpuid-faulting; this may fail on older kernels or hardware,
+// so we just disregard the result. Host CPUID will be enabled.
+func enableCpuidFault() {
+	syscall.RawSyscall6(syscall.SYS_ARCH_PRCTL, linux.ARCH_SET_CPUID, 0, 0, 0, 0, 0)
+}
+
+// appendArchSeccompRules append architecture specific seccomp rules when creating BPF program.
+// Ref attachedThread() for more detail.
+func appendArchSeccompRules(rules []seccomp.RuleSet) []seccomp.RuleSet {
+	return append(rules, seccomp.RuleSet{
+		Rules: seccomp.SyscallRules{
+			syscall.SYS_ARCH_PRCTL: []seccomp.Rule{
+				{seccomp.AllowValue(linux.ARCH_SET_CPUID), seccomp.AllowValue(0)},
+			},
+		},
+		Action: linux.SECCOMP_RET_ALLOW,
+	})
+}