kernel: add _sys_getprocfs in place of HANDLE_PROCFS

This makes the side-effects more explicit, and feels less hacky than
`HANDLE_PROCFS`. I don't think accessing a handle alone should have
side-effects, even if it's a "special" one.

src/bootstrap/main.c

@@ -1,10 +1,11 @@
 #include <_proc.h>
+#include <camellia.h>
 #include <camellia/flags.h>
+#include <camellia/fs/misc.h>
 #include <camellia/syscalls.h>
+#include <elfload.h>
 #include <stdio.h>
 #include <string.h>
-#include <elfload.h>
-#include <camellia/fs/misc.h>
 
 #include "tar.h"
 
@@ -17,7 +18,7 @@ int main(void) {
 	_sys_memflag(_psdata_loc, 1, MEMFLAG_PRESENT);
 	setprogname("bootstrap");
 
-	_sys_mount(HANDLE_PROCFS, "/proc/", strlen("/proc/"));
+	camellia_procfs("/proc/");
 	MOUNT_AT("/") {
 		fs_dirinject2((const char*[]) {
 			"/proc/",

src/cmd/ps/ps.c

@@ -5,14 +5,24 @@
 #include <stdlib.h>
 #include <string.h>
 
-int
-main(void)
+void
+usage(void)
 {
+	fprintf(stderr, "usage: ps [path]\n");
+	exit(1);
+}
+
+int
+main(int argc, const char *argv[])
+{
+	const char *path = argc >= 2 ? argv[1] : "/proc/";
+	if (argc > 2) usage();
+
 	char *readbuf = malloc(4096);
 	char *procbuf = malloc(4096);
-	FILE *f = fopen("/proc/", "r");
+	FILE *f = fopen(path, "r");
 	if (!f) {
-		err(1, "couldn't open /proc/");
+		err(1, "couldn't open %s", path);
 	}
 
 	// TODO library for iterating over directories
@@ -27,7 +37,7 @@ main(void)
 			size_t entryl = end - (readbuf+pos) + 1;
 			if (isdigit(readbuf[pos])) {
 				FILE *g;
-				sprintf(procbuf, "/proc/%smem", readbuf+pos);
+				sprintf(procbuf, "%s%smem", path, readbuf+pos);
 				g = fopen(procbuf, "r");
 				if (!g) {
 					warn("couldn't open \"%s\"", procbuf);

src/cmd/shell/shell.c

@@ -1,5 +1,6 @@
 #include "builtins.h"
 #include "shell.h"
+#include <camellia.h>
 #include <camellia/compat.h>
 #include <camellia/flags.h>
 #include <camellia/syscalls.h>
@@ -61,7 +62,7 @@ void run_args(int argc, char **argv, struct redir *redir) {
 			fprintf(stderr, "procmnt: missing mountpoint\n");
 			return;
 		}
-		_sys_mount(HANDLE_PROCFS, argv[1], strlen(argv[1]));
+		camellia_procfs(argv[1]);
 		/*
 		if (!(3 <= argc && !strcmp(argv[2], "raw"))) {
 			if (!mount_at("/")) {

src/kernel/proc.c

@@ -6,7 +6,6 @@
 #include <kernel/panic.h>
 #include <kernel/proc.h>
 #include <kernel/vfs/mount.h>
-#include <kernel/vfs/procfs.h>
 #include <shared/mem.h>
 #include <stdint.h>
 
@@ -384,7 +383,6 @@ void proc_tryreap(Proc *dead) {
 		return; /* keep the tombstone */
 	}
 
-	handle_close(dead->specialh.procfs);
 	assert(dead->refcount == 0);
 	if (parent) { /* not applicable to init */
 		proc_forget(dead);
@@ -513,18 +511,6 @@ Handle *proc_handle_get(Proc *p, hid_t id) {
 			.refcount = 2, /* never free */
 		};
 		return &h;
-	} else if (id == HANDLE_PROCFS) {
-		if (!p->specialh.procfs) {
-			Handle *h = kmalloc(sizeof *h);
-			proc_ns_create(p);
-			*h = (Handle){
-				.type = HANDLE_FS_FRONT,
-				.backend = procfs_backend(p),
-				.refcount = 1,
-			};
-			p->specialh.procfs = h;
-		}
-		return p->specialh.procfs;
 	} else if (0 <= id && id < HANDLE_MAX) {
 		return p->_handles[id];
 	} else {

src/kernel/proc.h

@@ -69,9 +69,6 @@ struct Proc {
 	VfsMount *mount;
 	Handle **_handles; /* points to Handle *[HANDLE_MAX] */
 	uint64_t *handles_refcount; /* works just like pages_refcount */
-	struct {
-		Handle *procfs;
-	} specialh;
 
 	// TODO pids should be 64bit. also typedef pid_t
 	uint32_t globalid; /* only for internal use, don't expose to userland */

src/kernel/syscalls.c

@@ -8,6 +8,7 @@
 #include <kernel/panic.h>
 #include <kernel/pipe.h>
 #include <kernel/proc.h>
+#include <kernel/vfs/procfs.h>
 #include <shared/mem.h>
 #include <stdint.h>
 
@@ -120,7 +121,6 @@ long _sys_mount(hid_t hid, const char __user *path, long len) {
 	// remove trailing slash
 	// mounting something under `/this` and `/this/` should be equalivent
 	if (path_buf[len - 1] == '/') {
-		if (len == 0) goto fail;
 		len--;
 	}
 
@@ -404,6 +404,21 @@ int _sys_wait2(int pid, int flags, struct sys_wait2 __user *out) {
 	return 0; // dummy
 }
 
+hid_t _sys_getprocfs(int flags) {
+	if (flags != 0) {
+		SYSCALL_RETURN(-ENOSYS);
+	}
+	proc_ns_create(proc_cur);
+
+	Handle *h;
+	hid_t hid = proc_handle_init(proc_cur, HANDLE_FS_FRONT, &h);
+	if (hid < 0) {
+		SYSCALL_RETURN(-EMFILE);
+	}
+	h->backend = procfs_backend(proc_cur);
+	SYSCALL_RETURN(hid);
+}
+
 long _sys_execbuf(void __user *ubuf, size_t len) {
 	if (len == 0) SYSCALL_RETURN(0);
 	if (len > EXECBUF_MAX_LEN)
@@ -458,6 +473,7 @@ long _syscall(long num, long a, long b, long c, long d, long e) {
 		break; case _SYS_GETPID:	_sys_getpid();
 		break; case _SYS_GETPPID:	_sys_getppid();
 		break; case _SYS_WAIT2:	_sys_wait2(a, b, (userptr_t)c);
+		break; case _SYS_GETPROCFS:	_sys_getprocfs(a);
 		break; case _SYS_EXECBUF:	_sys_execbuf((userptr_t)a, b);
 		break; case _SYS_DEBUG_KLOG:	_sys_debug_klog((userptr_t)a, b);
 		break;

src/libc/camellia.c

@@ -28,3 +28,14 @@ hid_t camellia_open(const char *path, int flags) {
 
 	return ret;
 }
+
+int camellia_procfs(const char *path) {
+	hid_t hid = _sys_getprocfs(0);
+	if (hid < 0) {
+		errno = -hid;
+		return -1;
+	}
+	_sys_mount(hid, path, strlen(path));
+	close(hid);
+	return 0;
+}

src/libc/include/camellia.h

@@ -3,3 +3,5 @@
 #include <camellia/types.h>
 
 hid_t camellia_open(const char *path, int flags);
+
+int camellia_procfs(const char *path);

src/libc/syscall.c

@@ -90,6 +90,10 @@ int _sys_wait2(int pid, int flags, struct sys_wait2 __user *out) {
 	return (int)_syscall(_SYS_WAIT2, (long)pid, (long)flags, (long)out, 0, 0);
 }
 
+hid_t _sys_getprocfs(int flags) {
+	return (hid_t)_syscall(_SYS_GETPROCFS, (long)flags, 0, 0, 0, 0);
+}
+
 long _sys_execbuf(void __user *buf, size_t len) {
 	return _syscall(_SYS_EXECBUF, (long)buf, (long)len, 0, 0, 0);
 }

src/libk/include/camellia/flags.h

@@ -32,4 +32,3 @@
 
 /* special handles */
 #define HANDLE_NULLFS -2
-#define HANDLE_PROCFS -3

src/libk/include/camellia/syscalls.h

@@ -21,6 +21,7 @@
 #define _SYS_GETPID 19
 #define _SYS_GETPPID 20
 #define _SYS_WAIT2 21
+#define _SYS_GETPROCFS 22
 
 #define _SYS_EXECBUF 100
 #define _SYS_DEBUG_KLOG 101
@@ -81,6 +82,8 @@ uint32_t _sys_getppid(void);
 
 int _sys_wait2(int pid, int flags, struct sys_wait2 __user *out);
 
+hid_t _sys_getprocfs(int flags);
+
 /* see shared/execbuf.h */
 long _sys_execbuf(void __user *buf, size_t len);