$NetBSD$

--- plugins/DebuggerCore/unix/netbsd/FeatureDetect.cpp.orig	2017-02-19 02:09:05.342456556 +0000
+++ plugins/DebuggerCore/unix/netbsd/FeatureDetect.cpp
@@ -0,0 +1,174 @@
+/*
+Copyright (C) 2016 - 2016 Evan Teran
+                          evan.teran@gmail.com
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "FeatureDetect.h"
+#include "version.h"
+
+#include <iostream>
+#include <iomanip>
+#include <string>
+#include <sys/wait.h>
+#include <sys/ptrace.h>
+#include <sys/types.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+namespace DebuggerCorePlugin {
+namespace feature {
+namespace {
+
+// Custom class to work with files, since various wrappers
+// appear to be unreliable to check whether writes succeeded
+class File {
+	int fd;
+	bool success;
+
+public:
+	File(const std::string &filename) {
+		fd = ::open(filename.c_str(), O_RDWR);
+		success = fd != -1;
+	}
+
+	ssize_t write(const void *buf, size_t count) {
+		const auto result = ::write(fd, buf, count);
+		success = result != -1;
+		return result;
+	}
+
+	ssize_t read(void *buf, size_t count) {
+		const auto result = ::read(fd, buf, count);
+		success = result != -1;
+		return result;
+	}
+
+	size_t seekp(size_t offset) {
+		const auto result = ::lseek(fd, offset, SEEK_SET);
+		success = result != -1;
+		return result;
+	}
+
+	~File() {
+		close(fd);
+	}
+
+	explicit operator bool() {
+		return success;
+	}
+};
+
+void kill_child(int pid) {
+	if (kill(pid, SIGKILL) == -1) {
+		perror("failed to kill child");
+	}
+}
+
+}
+
+//------------------------------------------------------------------------------
+// Name: detect_proc_access
+// Desc: detects whether or not reads/writes through /proc/<pid>/mem work
+//       correctly
+//------------------------------------------------------------------------------
+bool detect_proc_access(bool *read_broken, bool *write_broken) {
+
+	switch (pid_t pid = fork()) {
+	case 0:
+		if (ptrace(PTRACE_TRACEME, 0, 0, 0) < 0) {
+			perror("child: PTRACE_TRACEME failed");
+			abort();
+		}
+
+		// force a signal
+		raise(SIGCONT);
+
+		for (;;) {
+			sleep(10);
+		}
+		abort();
+
+	case -1:
+		perror("fork");
+		return false;
+
+	default: {
+		int status;
+		if (waitpid(pid, &status, __WALL) == -1) {
+			perror("parent: waitpid failed");
+			kill_child(pid);
+			return false;
+		}
+
+		if (!WIFSTOPPED(status) || WSTOPSIG(status) != SIGCONT) {
+			std::cerr << "unexpected status returned by waitpid: 0x" << std::hex << status << "\n";
+			kill_child(pid);
+			return false;
+		}
+
+		File file("/proc/" + std::to_string(pid) + "/mem");
+		if (!file) {
+			perror("failed to open memory file");
+			kill_child(pid);
+			return false;
+		}
+
+		const auto pageAlignMask = ~(sysconf(_SC_PAGESIZE) - 1);
+		const auto addr = reinterpret_cast<uintptr_t>(&edb::version) & pageAlignMask;
+		file.seekp(addr);
+		if (!file) {
+			perror("failed to seek to address to read");
+			kill_child(pid);
+			return false;
+		}
+
+		int buf = 0x12345678;
+		{
+			file.read(&buf, sizeof(buf));
+			if (!file) {
+				*read_broken  = true;
+				*write_broken = true;
+				kill_child(pid);
+				return false;
+			}
+		}
+
+		file.seekp(addr);
+		if (!file) {
+			perror("failed to seek to address to write");
+			kill_child(pid);
+			return false;
+		}
+
+		{
+			file.write(&buf, sizeof(buf));
+			if (!file) {
+				*read_broken  = false;
+				*write_broken = true;
+			} else {
+				*read_broken  = false;
+				*write_broken = false;
+			}
+		}
+		kill_child(pid);
+		return true;
+	}
+	}
+
+}
+
+}
+}