[nolibc] Change internal syscall API to remove reliance on libc's errno.

This change moves to a model where the error value of a system call is
potentially contained in the return value itself rather than being
implicit in errno.  The helper function internal_iserror can be used
to extract the error value from a return value.  On platforms other
than Linux/x86_64 this still uses errno, but other platforms are free
to port their error handling to this new model.

Differential Revision: http://llvm-reviews.chandlerc.com/D756

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@181436 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 24 insertions, 0 deletions

diff --git a/lib/sanitizer_common/sanitizer_syscall_generic.inc b/lib/sanitizer_common/sanitizer_syscall_generic.inc
new file mode 100644
index 000000000..aac20a5f2
--- /dev/null
+++ b/lib/sanitizer_common/sanitizer_syscall_generic.inc
@@ -0,0 +1,24 @@
+//===-- sanitizer_syscall_generic.inc ---------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Generic implementations of internal_syscall and internal_iserror.
+//
+//===----------------------------------------------------------------------===//
+
+#define internal_syscall syscall
+
+bool internal_iserror(uptr retval, int *rverrno) {
+  if (retval == (uptr)-1) {
+    if (rverrno)
+      *rverrno = errno;
+    return true;
+  } else {
+    return false;
+  }
+}