linux-user: Move syscall error detection into safe_syscall_base

The current api from safe_syscall_base() is to return -errno, which is
the interface provided by *some* linux kernel abis.  The wrapper macro,
safe_syscall(), detects error, stores into errno, and returns -1, to
match the api of the system syscall().

For those kernel abis that do not return -errno natively, this leads
to double syscall error detection.  E.g. Linux ppc64, which sets the
SO flag for error.

Simplify the usage from C by moving the error detection into assembly,
and usage from assembly by providing a C helper with which to set errno.

Reviewed-by: Warner Losh <imp@bsdimp.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

1 files changed, 5 insertions, 11 deletions

diff --git a/linux-user/safe-syscall.h b/linux-user/safe-syscall.h
index aaa9ffc0e2..97837faddb 100644
--- a/linux-user/safe-syscall.h
+++ b/linux-user/safe-syscall.h
@@ -127,21 +127,15 @@
 #ifdef HAVE_SAFE_SYSCALL
 /* The core part of this function is implemented in assembly */
 extern long safe_syscall_base(int *pending, long number, ...);
+extern long safe_syscall_set_errno_tail(int value);
+
 /* These are defined by the safe-syscall.inc.S file */
 extern char safe_syscall_start[];
 extern char safe_syscall_end[];
 
-#define safe_syscall(...)                                               \
-    ({                                                                  \
-        long ret_;                                                      \
-        int *psp_ = &((TaskState *)thread_cpu->opaque)->signal_pending; \
-        ret_ = safe_syscall_base(psp_, __VA_ARGS__);                    \
-        if (is_error(ret_)) {                                           \
-            errno = -ret_;                                              \
-            ret_ = -1;                                                  \
-        }                                                               \
-        ret_;                                                           \
-    })
+#define safe_syscall(...)                                                 \
+    safe_syscall_base(&((TaskState *)thread_cpu->opaque)->signal_pending, \
+                      __VA_ARGS__)
 
 #else