4init: minimal but functional init

8 files changed, 134 insertions, 55 deletions

diff --git a/.gitignore b/.gitignore
index 845cda6..5761abc 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,55 +1 @@
-# Prerequisites
-*.d
-
-# Object files
 *.o
-*.ko
-*.obj
-*.elf
-
-# Linker output
-*.ilk
-*.map
-*.exp
-
-# Precompiled Headers
-*.gch
-*.pch
-
-# Libraries
-*.lib
-*.a
-*.la
-*.lo
-
-# Shared objects (inc. Windows DLLs)
-*.dll
-*.so
-*.so.*
-*.dylib
-
-# Executables
-*.exe
-*.out
-*.app
-*.i*86
-*.x86_64
-*.hex
-
-# Debug files
-*.dSYM/
-*.su
-*.idb
-*.pdb
-
-# Kernel Module Compile Results
-*.mod*
-*.cmd
-.tmp_versions/
-modules.order
-Module.symvers
-Mkfile.old
-dkms.conf
-
-# debug information files
-*.dwo
diff --git a/4init/.gitignore b/4init/.gitignore
new file mode 100644
index 0000000..79cfb58
--- /dev/null
+++ b/4init/.gitignore
@@ -0,0 +1 @@
+4init
\ No newline at end of file
diff --git a/4init/4init.c b/4init/4init.c
new file mode 100644
index 0000000..50807b6
--- /dev/null
+++ b/4init/4init.c
@@ -0,0 +1,82 @@
+#define _POSIX_C_SOURCE 200809L
+
+#include <signal.h>
+#include <stdio.h>
+#include <sys/signalfd.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#include "config.h"
+
+static void reap(void)
+{
+	int status;
+	while (waitpid(-1, &status, WNOHANG) > 0) {}
+}
+
+int main(void)
+{
+	int sigfd = -1;
+	pid_t pid = -1;
+	sigset_t set;
+
+	if (getpid() != 1) {
+		fprintf(stderr, "4init - you need to run this as PID 1...\n");
+		return 1;
+	}
+
+	sigfillset(&set);
+	sigdelset(&set, SIGILL);
+	sigdelset(&set, SIGTRAP);
+	sigdelset(&set, SIGBUS);
+	sigdelset(&set, SIGFPE);
+	sigdelset(&set, SIGSEGV);
+
+	if (sigprocmask(SIG_SETMASK, &set, NULL) < 0) {
+		perror("sigprocmask");
+		return 1;
+	}
+
+	sigfd = signalfd(-1, &set, SFD_CLOEXEC);
+	if (sigfd < 0) {
+		perror("signalfd");
+		return 1;
+	}
+
+	pid = fork();
+	if (pid < 0) {
+		perror("fork");
+		return 1;
+	}
+
+	if (pid == 0) {
+		sigset_t empty_set;
+
+		sigemptyset(&empty_set);
+		sigprocmask(SIG_SETMASK, &empty_set, NULL);
+
+		if (setsid() == -1) {
+			perror("setsid");
+		}
+
+		close(sigfd);
+
+		execve(rc_path, rc_argv, rc_envp);
+		perror("execve");
+		_exit(1);
+	} else {
+		struct signalfd_siginfo fdsi;
+
+		reap();
+
+		for (;;) {
+			if (read(sigfd, &fdsi, sizeof(fdsi)) == sizeof(fdsi)) {
+				switch (fdsi.ssi_signo) {
+				case SIGCHLD:
+					reap();
+					break;
+				}
+			}
+		}
+	}
+}
diff --git a/4init/Makefile b/4init/Makefile
new file mode 100644
index 0000000..e56e105
--- /dev/null
+++ b/4init/Makefile
@@ -0,0 +1,21 @@
+include config.mk
+
+BIN = 4init
+OBJ = 4init.o
+
+all: $(BIN)
+
+$(BIN): $(OBJ)
+	$(CC) $(LDFLAGS) -o $@ $(OBJ)
+
+$(OBJ): config.h
+
+install: all
+	mkdir -pv $(DESTDIR)$(PREFIX)/bin
+	cp -fv $(BIN) $(DESTDIR)$(PREFIX)/bin
+
+uninstall: all
+	rm -f $(DESTDIR)$(PREFIX)/bin/$(BIN)
+
+clean: all
+	rm -f 4init.o 4init
diff --git a/4init/README.md b/4init/README.md
new file mode 100644
index 0000000..44fbde5
--- /dev/null
+++ b/4init/README.md
@@ -0,0 +1,5 @@
+# 4init: minimal but functional init
+
+It's only purpose is to manage processes, it by defaults calls 4rc, but you can change that in `config.h`, it's started as PID 1, and if it crashes, the kernel will panic, read the article in Wikipedia if you want to know more.
+
+Inspired by [rofl0r](https://gist.github.com/rofl0r/6168719)'s minimal init.
\ No newline at end of file
diff --git a/4init/config.h b/4init/config.h
new file mode 100644
index 0000000..6c36ccf
--- /dev/null
+++ b/4init/config.h
@@ -0,0 +1,17 @@
+#ifndef CONFIG_H
+#define CONFIG_H
+
+static const char *rc_path = "/usr/bin/4rc";
+
+static char *const rc_argv[] = {
+    "4rc",
+    NULL
+};
+
+static char *const rc_envp[] = {
+    "PATH=/usr/local/sbin:/usr/local/bin:/usr/bin:/bin:/sbin",
+    "TERM=linux",
+    NULL
+};
+
+#endif // CONFIG_H
diff --git a/4init/config.mk b/4init/config.mk
new file mode 100644
index 0000000..ab7e752
--- /dev/null
+++ b/4init/config.mk
@@ -0,0 +1,5 @@
+PREFIX = /usr/local
+
+CC = musl-gcc
+CFLAGS = -std=c99 -Wextra -Wall -Os -fhardened
+LDFLAGS = -s -static
diff --git a/README.md b/README.md
index 52b57ff..de0e8a0 100644
--- a/README.md
+++ b/README.md
@@ -1,2 +1,4 @@
 # 4suite
-A self-contained C boot stack (init, rc, logger, user) with Plan 9 namespace isolation
+
+A self-contained C boot stack (init, rc, logger, user).
+Each component has it's own README.md, worth checking it out.