From 119057ea74b0770eb3c61480b449705da4432edd Mon Sep 17 00:00:00 2001
From: Harald Hoyer <harald@redhat.com>
Date: Tue, 26 Jan 2021 09:48:26 +0100
Subject: [PATCH] feat(shim): add logging

Signed-off-by: Harald Hoyer <harald@redhat.com>
---
 internal/shim-sev/src/syscall.rs | 31 ++++++++++++++++++++++++++++++-
 internal/syscall/src/base.rs     |  4 ++++
 2 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/internal/shim-sev/src/syscall.rs b/internal/shim-sev/src/syscall.rs
index 5efa026c..3a8bad86 100644
--- a/internal/shim-sev/src/syscall.rs
+++ b/internal/shim-sev/src/syscall.rs
@@ -7,10 +7,11 @@ use crate::allocator::ALLOCATOR;
 use crate::asm::_enarx_asm_triple_fault;
 use crate::attestation::SEV_SECRET;
 use crate::eprintln;
-use crate::hostcall::{HostCall, HOST_CALL_ALLOC};
+use crate::hostcall::{shim_write_all, HostCall, HostFd, HOST_CALL_ALLOC};
 use crate::paging::SHIM_PAGETABLE;
 use crate::payload::{NEXT_BRK_RWLOCK, NEXT_MMAP_RWLOCK};
 use core::convert::TryFrom;
+use core::fmt::{self, Write};
 use core::mem::size_of;
 use core::ops::{Deref, DerefMut};
 use primordial::{Address, Register};
@@ -133,6 +134,19 @@ extern "sysv64" fn syscall_rust(
 
     let ret = h.syscall(a, b, c, d, e, f, nr);
 
+    if nr != libc::SYS_write as _ && usize::from(a) != libc::STDERR_FILENO as _ {
+        match ret {
+            Err(e) => match e {
+                libc::EINVAL => eprintln!("= EINVAL"),
+                libc::EAGAIN => eprintln!("= EAGAIN"),
+                libc::EFAULT => eprintln!("= EFAULT"),
+                libc::ENOSYS => eprintln!("= ENOSYS"),
+                e => eprintln!("= Err({})", e),
+            },
+            Ok([rax, _]) => eprintln!("= {}", usize::from(rax)),
+        }
+    }
+
     match ret {
         Err(e) => X8664DoubleReturn {
             rax: e.checked_neg().unwrap() as _,
@@ -152,6 +166,17 @@ struct Handler {
     argv: [usize; 6],
 }
 
+impl fmt::Write for Handler {
+    fn write_str(&mut self, s: &str) -> fmt::Result {
+        shim_write_all(
+            unsafe { HostFd::from_raw_fd(libc::STDOUT_FILENO) },
+            s.as_bytes(),
+        )
+        .map_err(|_| fmt::Error)?;
+        Ok(())
+    }
+}
+
 impl AddressValidator for Handler {
     #[inline(always)]
     fn validate_const_mem_fn(&self, _ptr: *const (), _size: usize) -> bool {
@@ -215,6 +240,10 @@ impl BaseSyscallHandler for Handler {
 
         eprintln!(")");
     }
+
+    fn log(&mut self, args: fmt::Arguments) {
+        let _ = self.write_fmt(args);
+    }
 }
 
 impl EnarxSyscallHandler for Handler {
diff --git a/internal/syscall/src/base.rs b/internal/syscall/src/base.rs
index 9f3c5f32..afc9db83 100644
--- a/internal/syscall/src/base.rs
+++ b/internal/syscall/src/base.rs
@@ -2,6 +2,7 @@
 
 //! basic syscall handler functions
 
+use core::fmt;
 use primordial::Register;
 use sallyport::{Cursor, Request, Result};
 
@@ -38,4 +39,7 @@ pub trait BaseSyscallHandler {
 
     /// Output tracing information about the syscall
     fn trace(&mut self, name: &str, argc: usize);
+
+    /// Log debug output
+    fn log(&mut self, _args: fmt::Arguments) {}
 }