Go 1.17 support for the KVM platform

Go 1.17 adds a new register-based calling convention. While transparent for
most applications, the KVM platform needs special work in a few cases.

First of all, we need the actual address of some assembly functions, rather
than the address of a wrapper. See http://gvisor.dev/pr/5832 for complete
discussion of this.

More relevant to this CL is that ABI0-to-ABIInternal wrappers (i.e., calls from
assembly to Go) access the G via FS_BASE. The KVM quite fast-and-loose about
the Go environment, often calling into (nosplit) Go functions with
uninitialized FS_BASE.

That will no longer work in Go 1.17, so this CL changes the platform to
consistently restore FS_BASE before calling into Go code.

This CL does not affect arm64 code. Go 1.17 does not support the register-based
calling convention for arm64 (it will come in 1.18), but arm64 also does not
use a non-standard register like FS_BASE for TLS, so it may not require any
changes.

PiperOrigin-RevId: 384234305

1 files changed, 2 insertions, 2 deletions

diff --git a/pkg/ring0/offsets_amd64.go b/pkg/ring0/offsets_amd64.go
index ca4075b09..dd48118af 100644
--- a/pkg/ring0/offsets_amd64.go
+++ b/pkg/ring0/offsets_amd64.go
@@ -95,6 +95,6 @@ func Emit(w io.Writer) {
 	fmt.Fprintf(w, "#define PTRACE_FLAGS    0x%02x\n", reflect.ValueOf(&p.Eflags).Pointer()-reflect.ValueOf(p).Pointer())
 	fmt.Fprintf(w, "#define PTRACE_RSP      0x%02x\n", reflect.ValueOf(&p.Rsp).Pointer()-reflect.ValueOf(p).Pointer())
 	fmt.Fprintf(w, "#define PTRACE_SS       0x%02x\n", reflect.ValueOf(&p.Ss).Pointer()-reflect.ValueOf(p).Pointer())
-	fmt.Fprintf(w, "#define PTRACE_FS       0x%02x\n", reflect.ValueOf(&p.Fs_base).Pointer()-reflect.ValueOf(p).Pointer())
-	fmt.Fprintf(w, "#define PTRACE_GS       0x%02x\n", reflect.ValueOf(&p.Gs_base).Pointer()-reflect.ValueOf(p).Pointer())
+	fmt.Fprintf(w, "#define PTRACE_FS_BASE  0x%02x\n", reflect.ValueOf(&p.Fs_base).Pointer()-reflect.ValueOf(p).Pointer())
+	fmt.Fprintf(w, "#define PTRACE_GS_BASE  0x%02x\n", reflect.ValueOf(&p.Gs_base).Pointer()-reflect.ValueOf(p).Pointer())
 }