Chore: cleaned up the exit code to cleanly interface with libc

We use weak linking to ensure we clean up at exit time correctly. If
libc is linked, then we call our cleanup function by registering an
atexit callback with the library. If libc is not linked, we have a weak
symbol that results in a noop. Similarly, if we call rt·exit while
linked with libc, this immediately calls libc's exit (which will call
our cleanup as we registered it). If we are not linked to libc, exit()
is given as a weak link to a noop function.

11 files changed, 175 insertions, 19 deletions

diff --git a/sys/linux/amd64/arch/constants.h b/sys/linux/amd64/arch/constants.h
new file mode 100644
index 0000000..1949bdf
--- /dev/null
+++ b/sys/linux/amd64/arch/constants.h
@@ -0,0 +1,23 @@
+#pragma once
+
+#define  sys·OCreate     0100
+#define  sys·OUnique     0200
+#define  sys·ONoTTY      0400
+#define  sys·OTrunc      01000
+#define  sys·OAppend     02000
+#define  sys·ONoBlock    04000
+#define  sys·ODsync      010000
+#define  sys·OSync       04010000
+#define  sys·ORsync      04010000
+#define  sys·ODirectory  0200000
+#define  sys·ONoFollow   0400000
+#define  sys·OCloseExec  02000000
+
+#define  sys·OAsync      020000
+#define  sys·ODirect     040000
+#define  sys·OLargeFile  0
+#define  sys·ONoATime    01000000
+#define  sys·OPath       010000000
+#define  sys·OTempFile   020200000
+
+#define SYS·HAVE_FCNTL
diff --git a/sys/linux/arm/arch/constants.h b/sys/linux/arm/arch/constants.h
new file mode 100644
index 0000000..149c2eb
--- /dev/null
+++ b/sys/linux/arm/arch/constants.h
@@ -0,0 +1,20 @@
+#pragma once
+
+#define  sys·OCreate     0100
+#define  sys·OUnique     0200
+#define  sys·ONoTTY      0400
+#define  sys·OTrunc      01000
+#define  sys·OAppend     02000
+#define  sys·ONoBlock    04000
+#define  sys·ODsync      010000
+#define  sys·OSync       04010000
+#define  sys·ORsync      04010000
+#define  sys·ODirectory  040000
+#define  sys·ONoFollow   0100000
+#define  sys·OCloseExec  02000000
+#define  sys·OAsync      020000
+#define  sys·ODirect     0200000
+#define  sys·OLargeFile  0400000
+#define  sys·ONoATime    01000000
+#define  sys·OPath       010000000
+#define  sys·OTempFile   020040000
diff --git a/sys/linux/arm64/arch/constants.h b/sys/linux/arm64/arch/constants.h
new file mode 100644
index 0000000..f3f42e5
--- /dev/null
+++ b/sys/linux/arm64/arch/constants.h
@@ -0,0 +1,22 @@
+#pragma once
+
+#define  sys·OCreate     0100
+#define  sys·OUnique     0200
+#define  sys·ONoTTY      0400
+#define  sys·OTrunc      01000
+#define  sys·OAppend     02000
+#define  sys·ONoBlock    04000
+#define  sys·ODsync      010000
+#define  sys·OSync       04010000
+#define  sys·ORsync      04010000
+#define  sys·ODirectory  040000
+#define  sys·ONoFollow   0100000
+#define  sys·OCloseExec  02000000
+#define  sys·OAsync      020000
+#define  sys·ODirect     0200000
+#define  sys·OLargeFile  0400000
+#define  sys·ONoATime    01000000
+#define  sys·OPath       010000000
+#define  sys·OTempFile   020040000
+
+#define SYS·HAVE_FCNTL
diff --git a/sys/linux/i386/arch/constants.h b/sys/linux/i386/arch/constants.h
new file mode 100644
index 0000000..ff6aa0c
--- /dev/null
+++ b/sys/linux/i386/arch/constants.h
@@ -0,0 +1,20 @@
+#pragma once
+
+#define  sys·OCreate     0100
+#define  sys·OUnique     0200
+#define  sys·ONoTTY      0400
+#define  sys·OTrunc      01000
+#define  sys·OAppend     02000
+#define  sys·ONoBlock    04000
+#define  sys·ODsync      010000
+#define  sys·OSync       04010000
+#define  sys·ORsync      04010000
+#define  sys·ODirectory  0200000
+#define  sys·ONoFollow   0400000
+#define  sys·OCloseExec  02000000
+#define  sys·OAsync      020000
+#define  sys·ODirect     040000
+#define  sys·OLargeFile  0100000
+#define  sys·ONoATime    01000000
+#define  sys·OPath       010000000
+#define  sys·OTempfile   020200000
diff --git a/sys/linux/port/os/constants.h b/sys/linux/port/os/constants.h
index 8fb913f..ffe8610 100644
--- a/sys/linux/port/os/constants.h
+++ b/sys/linux/port/os/constants.h
@@ -1,18 +1,5 @@
 #pragma once
 
-/* open */
-#define sys·OCreate     0x40u
-#define sys·ONoTTY      0x100u
-#define sys·OTrunc      0x200u
-#define sys·OAppend     0x400u
-#define sys·ONoBlock    0x800u
-#define sys·OSync       0x1000u
-#define sys·OAsync      0x2000u
-#define sys·OLargeFile  0x8000u
-#define sys·ODirectory  0x10000u
-#define sys·ONoFollow   0x20000u
-#define sys·OTmpFile    0x410000u
-
 /* device modes */
 #define sys·ModeFile   0170000
 #define sys·ModeDir    0040000
diff --git a/sys/linux/riscv64/arch/constants.h b/sys/linux/riscv64/arch/constants.h
new file mode 100644
index 0000000..ff6aa0c
--- /dev/null
+++ b/sys/linux/riscv64/arch/constants.h
@@ -0,0 +1,20 @@
+#pragma once
+
+#define  sys·OCreate     0100
+#define  sys·OUnique     0200
+#define  sys·ONoTTY      0400
+#define  sys·OTrunc      01000
+#define  sys·OAppend     02000
+#define  sys·ONoBlock    04000
+#define  sys·ODsync      010000
+#define  sys·OSync       04010000
+#define  sys·ORsync      04010000
+#define  sys·ODirectory  0200000
+#define  sys·ONoFollow   0400000
+#define  sys·OCloseExec  02000000
+#define  sys·OAsync      020000
+#define  sys·ODirect     040000
+#define  sys·OLargeFile  0100000
+#define  sys·ONoATime    01000000
+#define  sys·OPath       010000000
+#define  sys·OTempfile   020200000
diff --git a/sys/rt/atexit.c b/sys/rt/atexit.c
new file mode 100644
index 0000000..208cc6e
--- /dev/null
+++ b/sys/rt/atexit.c
@@ -0,0 +1,49 @@
+#include <u.h>
+#include <rt.h>
+
+#define COUNT 32
+
+static struct cleaner
+{
+    struct cleaner *next;
+    void (*clean[COUNT])(void *);
+    void *arg[COUNT];
+} arena, *head;
+static int slot;
+
+void weaklink exit(int code){};
+
+void
+rt·clean(void)
+{
+    void (*clean)(void *), *arg;
+    /*LOCK*/
+    for(; head; head=head->next, slot=COUNT) {
+        while(slot-- > 0){
+            arg   = head->arg[slot];
+            clean = head->clean[slot];
+            /* UNLOCK */
+            clean(arg);
+            /* LOCK */
+        }
+    }
+}
+
+int
+rt·atexit(void (*clean)(void *), void *arg)
+{
+    /* LOCK */
+    if(!head)
+        head = &arena;
+
+    /* we need malloc... */
+    if(slot==COUNT)
+        return -1;
+
+    head->arg[slot]   = arg;
+    head->clean[slot] = clean;
+    slot++;
+
+    /* UNLOCK */
+    return 0;
+}
diff --git a/sys/rt/boot.c b/sys/rt/boot.c
index 320a596..8c6616d 100644
--- a/sys/rt/boot.c
+++ b/sys/rt/boot.c
@@ -3,7 +3,10 @@
 #include <elf.h>
 
 /* tell linker to go find */
+int atexit(void (*)(void));
 int __libc_start_main(int (*main)(int,char **,char **), int argc, char **argv);
+
+void rt·clean(void);
 void rt·guardstack(void);
 
 #define NAUX 38
@@ -30,6 +33,7 @@ rt·boot(int (*main)(), int argc, char **argv, void (*init)(), void (*fini)(), v
 	rt·init(env, argv[0]);
 
 	/* ring libc, anyone home? */
+    atexit(rt·clean);
 	__libc_start_main(main, argc, argv);
 
 	/* no? ok we continue on if there is no libc linked */
diff --git a/sys/rt/dummy.c b/sys/rt/dummy.c
index f123d16..0cef224 100644
--- a/sys/rt/dummy.c
+++ b/sys/rt/dummy.c
@@ -4,3 +4,6 @@
 /* provide a dummy implementation if libc is not linked */
 static int noop(int (*main)(), int argc, char **argv) { return 0; }
 weakalias(noop, __libc_start_main);
+
+static int noop2(void (*func)(void)) { return 0; }
+weakalias(noop, atexit);
diff --git a/sys/rt/exit.c b/sys/rt/exit.c
index e6027b7..386a1bf 100644
--- a/sys/rt/exit.c
+++ b/sys/rt/exit.c
@@ -2,10 +2,13 @@
 #include <rt.h>
 #include <syscall.h>
 
-/* XXX:
- * if we are here, we are in charge, call exit syscalls
- * think of better way to encapsulate these syscalls?
- */
+/* tell linker to go find */
+void noreturn exit(int code);
+
+/* if did not call rt·atexit, then don't pull it in */
+static void noop(void){}
+weakalias(noop, rt·clean);
+
 static noreturn void
 rt·shutdown(int code)
 {
@@ -14,14 +17,18 @@ rt·shutdown(int code)
     if(rt·context.exit)
         rt·context.exit();
 
+    /* XXX: better way to encapsulate these calls? */
 	_syscall1(·ExitGroup, code);
     for(;;)
 		_syscall1(·Exit, code);
 }
-weakalias(rt·shutdown, exit);
 
 noreturn void
 rt·exit(int code)
 {
-	rt·shutdown(code);
+    /* ring libc, anyone home? */
+	exit(code);
+    /* if we are here, we are in charge, shut it down */
+    rt·clean();
+    rt·shutdown(code);
 }
diff --git a/sys/rules.mk b/sys/rules.mk
index 4bba9aa..1cbe50e 100644
--- a/sys/rules.mk
+++ b/sys/rules.mk
@@ -20,6 +20,7 @@ RT1_OBJ := $(patsubst $(SYS_DIR)/rt/%, $(OBJ_DIR)/rt/%, $(RT1_OBJ))
 RT3_SRC := \
 	$(SYS_DIR)/rt/stack.c\
 	$(SYS_DIR)/rt/dummy.c\
+	$(SYS_DIR)/rt/atexit.c\
 	$(SYS_DIR)/rt/exit.c
 
 RT3_OBJ := $(filter %.o, $(RT3_SRC:.c=.o))