lib/proxy: relay stdout, stderr through built-in proxies

proxy_outfd, proxy_errfd are the file descriptors of these built-in
proxies, for issuing formatted printouts without incurring switches to
the inband stage.

evl_printf() is a shorthand call formatting its argument list before
sending the resulting string through proxy_outfd.

include/evl/proxy.h

@@ -10,6 +10,7 @@
 #include <stdarg.h>
 #include <sys/types.h>
 #include <linux/types.h>
+#include <stdio.h>
 
 #ifdef __cplusplus
 extern "C" {
@@ -28,6 +29,11 @@ int evl_vprint_proxy(int proxyfd,
 int evl_print_proxy(int proxyfd,
 		const char *fmt, ...);
 
+int evl_printf(const char *fmt, ...);
+
+extern int proxy_outfd,
+	proxy_errfd;
+
 #ifdef __cplusplus
 }
 #endif

lib/init.c

@@ -58,8 +58,8 @@ static inline int generic_init(void)
 
 	/*
 	 * Failing to open the control device with ENOENT is a clear
-	 * sign that we have no EVL core in there. Return with
-	 * -ENOSYS to give a clear hint about this.
+	 * sign that we have no EVL core in there. Return with -ENOSYS
+	 * to give a clear hint about this.
 	 */
 	ctlfd = open(EVL_CONTROL_DEV, O_RDWR);
 	if (ctlfd < 0)
@@ -102,6 +102,7 @@ static inline int generic_init(void)
 		goto fail;
 	}
 
+	pthread_atfork(NULL, NULL, atfork_unmap_shmem);
 	evl_ctlfd = ctlfd;
 	evl_shared_memory = shmem;
 
@@ -220,8 +221,7 @@ static inline int do_init(void)
 	if (ret)
 		return ret;
 
-	pthread_atfork(NULL, NULL, atfork_unmap_shmem);
-
+	init_proxy_streams();
 	install_signal_handlers();
 
 	return 0;

lib/internal.h

@@ -35,6 +35,8 @@ int arch_evl_init(void);
 
 int attach_evl_clocks(void);
 
+void init_proxy_streams(void);
+
 int create_evl_element(const char *type,
 		       const char *name,
 		       void *attrs,

lib/proxy.c

@@ -15,9 +15,25 @@
 #include <uapi/evl/proxy.h>
 #include "internal.h"
 
+#define STDSTREAM_BUFSZ  16384
+
 static __thread __attribute__ ((tls_model (EVL_TLS_MODEL)))
 char fmt_buf[1024];
 
+int proxy_outfd = -EBADF, proxy_errfd = -EBADF;
+
+void init_proxy_streams(void)
+{
+	/*
+	 * This might fail if stdout/stderr are closed, just ignore if
+	 * so.
+	 */
+	proxy_outfd = evl_new_proxy(fileno(stdout), STDSTREAM_BUFSZ, 0,
+		"stdout:%d", getpid());
+	proxy_errfd = evl_new_proxy(fileno(stderr), STDSTREAM_BUFSZ, 0,
+		"stderr:%d", getpid());
+}
+
 int evl_new_proxy(int fd, size_t bufsz, size_t granularity,
 		const char *fmt, ...)
 {
@@ -67,3 +83,24 @@ int evl_print_proxy(int proxyfd, const char *fmt, ...)
 
 	return ret;
 }
+
+int evl_printf(const char *fmt, ...)
+{
+	va_list ap;
+	int ret;
+
+	va_start(ap, fmt);
+
+	/*
+	 * If evl_init() has not run yet, we can resort to vprintf()
+	 * since latency is not an issue.
+	 */
+	if (evl_ctlfd < 0)
+		ret = vprintf(fmt, ap);
+	else
+		ret = evl_vprint_proxy(proxy_outfd, fmt, ap);
+
+	va_end(ap);
+
+	return ret;
+}