From 7f636b2e933e198512bee412769328d2d57e7f4e Mon Sep 17 00:00:00 2001
From: dzwdz
Date: Sun, 27 Mar 2022 13:22:29 +0200
Subject: kernel/vfs: `/vga` node
---
src/init/main.c | 6 ++++++
src/kernel/vfs/root.c | 48 +++++++++++++++++++++++++++++++++++++++++++++++-
2 files changed, 53 insertions(+), 1 deletion(-)
(limited to 'src')
diff --git a/src/init/main.c b/src/init/main.c
index 2fe17eb..ba5fdcd 100644
--- a/src/init/main.c
+++ b/src/init/main.c
@@ -26,6 +26,12 @@ int main(void) {
if (__tty_fd < 0)
_syscall_exit(1);
+ // change screen color
+ handle_t vga = _syscall_open(argify("/vga"));
+ for (int i = 1; i < 80*25*2; i += 2)
+ _syscall_write(vga, "\x4f", 1, i);
+ _syscall_close(vga);
+
fs_prep();
shell_loop();
diff --git a/src/kernel/vfs/root.c b/src/kernel/vfs/root.c
index f4bdcc2..9833330 100644
--- a/src/kernel/vfs/root.c
+++ b/src/kernel/vfs/root.c
@@ -8,6 +8,7 @@
enum {
HANDLE_ROOT,
HANDLE_TTY,
+ HANDLE_VGA,
};
static bool exacteq(struct vfs_request *req, const char *str) {
@@ -16,17 +17,48 @@ static bool exacteq(struct vfs_request *req, const char *str) {
return req->input.len == len && !memcmp(req->input.buf_kern, str, len);
}
+/* truncates the length */
+static void req_preprocess(struct vfs_request *req, int max_len) {
+ // max_len is signed because req->*.len are signed too
+ // potential place for VULNs to occur - arbitrary kernel reads etc
+ if (req->offset < 0) {
+ // TODO negative offsets
+ req->offset = 0;
+ }
+
+ if (req->offset >= max_len) {
+ req->input.len = 0;
+ req->output.len = 0;
+ req->offset = max_len;
+ return;
+ }
+
+ if (req->input.len < 0) req->input.len = 0;
+ if (req->output.len < 0) req->output.len = 0;
+
+ req->input.len = min(req->input.len, max_len - req->offset);
+ req->output.len = min(req->output.len, max_len - req->offset);
+
+ assert(req->input.len >= 0);
+ assert(req->output.len >= 0);
+
+ assert(req->input.len + req->offset <= max_len);
+ assert(req->input.len + req->offset <= max_len);
+}
+
int vfs_root_handler(struct vfs_request *req) {
switch (req->type) {
case VFSOP_OPEN:
if (exacteq(req, "/")) return HANDLE_ROOT;
if (exacteq(req, "/tty")) return HANDLE_TTY;
+ if (exacteq(req, "/vga")) return HANDLE_VGA;
return -1;
case VFSOP_READ:
switch (req->id) {
case HANDLE_ROOT: {
- const char *src = "tty"; // TODO document directory read format
+ // TODO document directory read format
+ const char *src = "tty\0vga\0";
if (req->output.len < 0) return 0; // is this needed? TODO make that a size_t or something
int len = min((size_t) req->output.len, strlen(src) + 1);
virt_cpy_to(req->caller->pages, req->output.buf, src, len);
@@ -40,6 +72,13 @@ int vfs_root_handler(struct vfs_request *req) {
tty_read(iter.frag, iter.frag_len);
return iter.prior;
}
+ case HANDLE_VGA: {
+ char *vga = (void*)0xB8000;
+ req_preprocess(req, 80*25*2);
+ virt_cpy_to(req->caller->pages, req->output.buf,
+ vga + req->offset, req->output.len);
+ return req->output.len;
+ }
default: panic_invalid_state();
}
@@ -54,6 +93,13 @@ int vfs_root_handler(struct vfs_request *req) {
tty_write(iter.frag, iter.frag_len);
return iter.prior;
}
+ case HANDLE_VGA: {
+ void *vga = (void*)0xB8000;
+ req_preprocess(req, 80*25*2);
+ virt_cpy_from(req->caller->pages, vga + req->offset,
+ req->input.buf, req->input.len);
+ return req->input.len;
+ }
default: panic_invalid_state();
}
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