Clean up base-library structure

This patch moves the base library from src/base to src/lib/base,
flattens the library-internal directory structure, and moves the common
parts of the library-description files to base/lib/mk/base.inc and
base/lib/mk/base-common.inc.

Furthermore, the patch fixes a few cosmetic issues (whitespace and
comments only) that I encountered while browsing the result.

Fixes #1952

repos/base-linux/src/lib/base/thread_env.cc

@@ -0,0 +1,111 @@
+/*
+ * \brief  Thread-environment support common to all programs
+ * \author Martin Stein
+ * \date   2013-12-13
+ */
+
+/*
+ * Copyright (C) 2013 Genode Labs GmbH
+ *
+ * This file is part of the Genode OS framework, which is distributed
+ * under the terms of the GNU General Public License version 2.
+ */
+
+/* Genode includes */
+#include <base/stdint.h>
+#include <base/env.h>
+
+#include <linux_syscalls.h>
+
+using namespace Genode;
+
+extern addr_t * __initial_sp;
+
+/*
+ * Define 'lx_environ' pointer.
+ */
+char **lx_environ;
+
+/**
+ * Natively aligned memory location used in the lock implementation
+ */
+int main_thread_futex_counter __attribute__((aligned(sizeof(addr_t))));
+
+/**
+ * Genode console hook
+ */
+extern "C" int stdout_write(char const *);
+
+/*
+ * Core lacks the hook, so provide a base-linux specific weak implementation
+ */
+extern "C" __attribute__((weak)) int stdout_write(char const *s)
+{
+	return raw_write_str(s);
+}
+
+/**
+ * Signal handler for exceptions like segmentation faults
+ */
+void exception_signal_handler(int signum)
+{
+	char const *reason = nullptr;
+
+	switch (signum) {
+	case LX_SIGILL:  reason = "Illegal instruction";      break;
+	case LX_SIGBUS:  reason = "Bad memory access";        break;
+	case LX_SIGFPE:  reason = "Floating point exception"; break;
+	case LX_SIGSEGV: reason = "Segmentation fault";       break;
+
+	default: /* unexpected signal */ return;
+	}
+
+	/*
+	 * We can't use Genode::printf() as the exception may have occurred in the
+	 * Genode console library itself, which uses a mutex. Therefore, we use
+	 * Genode::snprintf() and call the console hook directly to minimize
+	 * overlaps with other code paths.
+	 */
+	static char msg[128];
+	snprintf(msg, sizeof(msg),
+	         ESC_ERR "%s (signum=%d), see Linux kernel log for details" ESC_END "\n",
+	         reason, signum);
+	stdout_write(msg);
+
+	/*
+	 * We reset the signal handler to SIG_DFL and trigger exception again,
+	 * i.e., terminate the process.
+	 */
+	lx_sigaction(signum, nullptr);
+	return;
+}
+
+
+void lx_exception_signal_handlers()
+{
+	lx_sigaction(LX_SIGILL,  exception_signal_handler);
+	lx_sigaction(LX_SIGBUS,  exception_signal_handler);
+	lx_sigaction(LX_SIGFPE,  exception_signal_handler);
+	lx_sigaction(LX_SIGSEGV, exception_signal_handler);
+}
+
+
+/*****************************
+ ** Startup library support **
+ *****************************/
+
+void prepare_init_main_thread()
+{
+	/*
+	 * Initialize the 'lx_environ' pointer
+	 *
+	 * environ = &argv[argc + 1]
+	 * __initial_sp[0] = argc (always 1 in Genode)
+	 * __initial_sp[1] = argv[0]
+	 * __initial_sp[2] = NULL
+	 * __initial_sp[3] = environ
+	 */
+	lx_environ = (char**)&__initial_sp[3];
+
+	lx_exception_signal_handlers();
+}