From e0c7bad47a54d865ef6194643e2cd20f6094e507 Mon Sep 17 00:00:00 2001
From: dzwdz
Date: Fri, 6 Jan 2023 20:45:30 +0100
Subject: kernel: turn the NULLFS into an always present special handle
preparing for HANDLE_PROCFS
---
src/kernel/proc.c | 14 ++++++++++++--
src/kernel/syscalls.c | 12 +++++-------
src/shared/include/camellia/flags.h | 4 ++++
src/user/app/shell/shell.c | 7 +++++++
4 files changed, 28 insertions(+), 9 deletions(-)
(limited to 'src')
diff --git a/src/kernel/proc.c b/src/kernel/proc.c
index 85992d5..6bc7754 100644
--- a/src/kernel/proc.c
+++ b/src/kernel/proc.c
@@ -287,6 +287,14 @@ handle_t process_find_free_handle(struct process *proc, handle_t start_at) {
}
struct handle *process_handle_get(struct process *p, handle_t id) {
+ if (id == HANDLE_NULLFS) {
+ static struct handle h = (struct handle){
+ .type = HANDLE_FS_FRONT,
+ .backend = NULL,
+ .refcount = 2,
+ };
+ return &h;
+ }
if (id < 0 || id >= HANDLE_MAX) return NULL;
return p->_handles[id];
}
@@ -311,7 +319,7 @@ handle_t process_handle_dup(struct process *p, handle_t from, handle_t to) {
if (to == from) return to;
toh = &p->_handles[to];
- fromh = (from >= 0 && from < HANDLE_MAX) ? p->_handles[from] : NULL;
+ fromh = process_handle_get(p, from);
if (*toh) handle_close(*toh);
*toh = fromh;
@@ -321,7 +329,9 @@ handle_t process_handle_dup(struct process *p, handle_t from, handle_t to) {
}
struct handle *process_handle_take(struct process *p, handle_t hid) {
- if (hid < 0 || hid >= HANDLE_MAX) return NULL;
+ if (hid < 0 || hid >= HANDLE_MAX) {
+ return process_handle_get(p, hid);
+ }
struct handle *h = p->_handles[hid];
p->_handles[hid] = NULL;
return h;
diff --git a/src/kernel/syscalls.c b/src/kernel/syscalls.c
index 88e98c6..2ace0f4 100644
--- a/src/kernel/syscalls.c
+++ b/src/kernel/syscalls.c
@@ -145,13 +145,11 @@ long _syscall_mount(handle_t hid, const char __user *path, long len) {
len--;
}
- if (hid >= 0) { // mounting a real backend?
- struct handle *handle = process_handle_get(process_current, hid);
- if (!handle || handle->type != HANDLE_FS_FRONT)
- goto fail;
- backend = handle->backend;
- backend->refcount++;
- } // otherwise backend == NULL
+ struct handle *handle = process_handle_get(process_current, hid);
+ if (!handle || handle->type != HANDLE_FS_FRONT)
+ goto fail;
+ backend = handle->backend;
+ if (backend) backend->refcount++;
// append to mount list
// TODO move to kernel/vfs/mount.c
diff --git a/src/shared/include/camellia/flags.h b/src/shared/include/camellia/flags.h
index b7cc42d..632ac3e 100644
--- a/src/shared/include/camellia/flags.h
+++ b/src/shared/include/camellia/flags.h
@@ -27,3 +27,7 @@
* The idea is that if all flags which allow modifying the filesystem state require
* OPEN_WRITE to be set, filesystem handlers could just check for the OPEN_WRITE flag. */
#define OPEN_CREATE 4
+
+
+/* special handles */
+#define HANDLE_NULLFS -2
diff --git a/src/user/app/shell/shell.c b/src/user/app/shell/shell.c
index 909d625..8aa640b 100644
--- a/src/user/app/shell/shell.c
+++ b/src/user/app/shell/shell.c
@@ -46,6 +46,13 @@ void run_args(int argc, char **argv, struct redir *redir) {
exit(1);
}
return;
+ } else if (!strcmp(argv[0], "shadow")) {
+ if (argc < 2) {
+ fprintf(stderr, "shadow: missing path\n");
+ } else {
+ _syscall_mount(HANDLE_NULLFS, argv[1], strlen(argv[1]));
+ }
+ return;
} else if (!strcmp(argv[0], "cd")) {
if (chdir(argc > 1 ? argv[1] : "/") < 0)
perror("cd");
--
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