kernel/virt: replace the virt_cpy api with a more foolproof one

16 files changed, 159 insertions, 125 deletions

diff --git a/src/kernel/arch/amd64/driver/pata.c b/src/kernel/arch/amd64/driver/pata.c
index 3d5e3c6..6928b4e 100644
--- a/src/kernel/arch/amd64/driver/pata.c
+++ b/src/kernel/arch/amd64/driver/pata.c
@@ -51,7 +51,7 @@ static void accept(struct vfs_request *req) {
 			fs_normslice(&req->offset, &req->output.len, ata_size(id), false);
 			len = min(req->output.len, sizeof wbuf);
 			ata_read(id, wbuf, len, req->offset);
-			virt_cpy_to(req->caller->pages, req->output.buf, wbuf, len);
+			pcpy_to(req->caller, req->output.buf, wbuf, len);
 			vfsreq_finish_short(req, len);
 			break;
 
@@ -63,7 +63,7 @@ static void accept(struct vfs_request *req) {
 			fs_normslice(&req->offset, &req->input.len, ata_size(id), false);
 			len = min(req->input.len, sizeof wbuf);
 			if (len != 0) {
-				virt_cpy_from(req->caller->pages, wbuf, req->input.buf, len);
+				len = pcpy_from(req->caller, wbuf, req->input.buf, len);
 				ata_write(id, wbuf, len, req->offset);
 			}
 			vfsreq_finish_short(req, len);
diff --git a/src/kernel/arch/amd64/driver/rtl8139.c b/src/kernel/arch/amd64/driver/rtl8139.c
index eb07494..1face38 100644
--- a/src/kernel/arch/amd64/driver/rtl8139.c
+++ b/src/kernel/arch/amd64/driver/rtl8139.c
@@ -105,7 +105,7 @@ void rtl8139_irq(void) {
 	port_out16(iobase + INTRSTATUS, status);
 }
 
-static int try_rx(struct pagedir *pages, void __user *dest, size_t dlen) {
+static int try_rx(struct process *proc, void __user *dest, size_t dlen) {
 	uint16_t flags, size;
 	/* bit 0 - Rx Buffer Empty */
 	if (port_in8(iobase + CMD) & 1) return WAIT;
@@ -125,11 +125,11 @@ static int try_rx(struct pagedir *pages, void __user *dest, size_t dlen) {
 	// kprintf("packet size 0x%x, flags 0x%x, rxpos %x\n", size, flags, rxpos - 4);
 	if (dlen > size) dlen = size;
 	if (rxpos + dlen <= rxbuf_baselen) {
-		virt_cpy_to(pages, dest, rxbuf + rxpos, dlen);
+		pcpy_to(proc, dest, rxbuf + rxpos, dlen);
 	} else {
 		size_t chunk = rxbuf_baselen - rxpos;
-		virt_cpy_to(pages, dest, rxbuf + rxpos, chunk);
-		virt_cpy_to(pages, dest + chunk, rxbuf, dlen - chunk);
+		pcpy_to(proc, dest, rxbuf + rxpos, chunk);
+		pcpy_to(proc, dest + chunk, rxbuf, dlen - chunk);
 	}
 
 	rxpos += size;
@@ -140,7 +140,7 @@ static int try_rx(struct pagedir *pages, void __user *dest, size_t dlen) {
 	return size;
 }
 
-static int try_tx(struct pagedir *pages, const void __user *src, size_t slen) {
+static int try_tx(struct process *proc, const void __user *src, size_t slen) {
 	static uint8_t desc = 0;
 
 	if (slen > 0xFFF) return -1;
@@ -153,7 +153,9 @@ static int try_tx(struct pagedir *pages, const void __user *src, size_t slen) {
 		panic_unimplemented();
 	}
 
-	virt_cpy_from(pages, txbuf[desc], src, slen);
+	if (pcpy_from(proc, txbuf[desc], src, slen) < slen) {
+		return -1;
+	}
 	assert((long)(void*)txbuf <= 0xFFFFFFFF);
 	port_out32(iobase + TXSTART0  + desc*4, (long)(void*)txbuf[desc]);
 	port_out32(iobase + TXSTATUS0 + desc*4, slen);
@@ -173,7 +175,7 @@ static void accept(struct vfs_request *req) {
 			vfsreq_finish_short(req, req->input.len == 0 ? 0 : -1);
 			break;
 		case VFSOP_READ:
-			ret = try_rx(req->caller->pages, req->output.buf, req->output.len);
+			ret = try_rx(req->caller, req->output.buf, req->output.len);
 			if (ret == WAIT) {
 				postqueue_join(&blocked_on, req);
 				rx_irq_enable(true);
@@ -183,7 +185,7 @@ static void accept(struct vfs_request *req) {
 			break;
 		case VFSOP_WRITE:
 			assert(!req->input.kern);
-			vfsreq_finish_short(req, try_tx(req->caller->pages, req->input.buf, req->input.len));
+			vfsreq_finish_short(req, try_tx(req->caller, req->input.buf, req->input.len));
 			break;
 		default:
 			vfsreq_finish_short(req, -1);
diff --git a/src/kernel/arch/amd64/driver/serial.c b/src/kernel/arch/amd64/driver/serial.c
index 295f9b8..12c4151 100644
--- a/src/kernel/arch/amd64/driver/serial.c
+++ b/src/kernel/arch/amd64/driver/serial.c
@@ -73,13 +73,14 @@ static void accept(struct vfs_request *req) {
 			break;
 		case VFSOP_WRITE:
 			if (req->caller && !req->flags) {
-				struct virt_iter iter;
-				virt_iter_new(&iter, req->input.buf, req->input.len,
-						req->caller->pages, true, false);
-				while (virt_iter_next(&iter))
-					serial_write(iter.frag, iter.frag_len);
-				ret = iter.prior;
-			} else ret = -1;
+				char buf[4096];
+				size_t len = min(sizeof buf, req->input.len);
+				len = pcpy_from(req->caller, buf, req->input.buf, len);
+				serial_write(buf, len);
+				ret = len;
+			} else {
+				ret = -1;
+			}
 			vfsreq_finish_short(req, ret);
 			break;
 		default:
diff --git a/src/kernel/arch/amd64/driver/util.c b/src/kernel/arch/amd64/driver/util.c
index b8895b8..b2c33c6 100644
--- a/src/kernel/arch/amd64/driver/util.c
+++ b/src/kernel/arch/amd64/driver/util.c
@@ -9,10 +9,8 @@ int req_readcopy(struct vfs_request *req, const void *buf, size_t len) {
 	if (!req->caller) return -1;
 	assert(req->type == VFSOP_READ);
 	fs_normslice(&req->offset, &req->output.len, len, false);
-	virt_cpy_to(
-			req->caller->pages, req->output.buf,
-			buf + req->offset, req->output.len);
 	/* read errors are ignored. TODO write a spec */
+	pcpy_to(req->caller, req->output.buf, buf + req->offset, req->output.len);
 	return req->output.len;
 }
 
@@ -48,8 +46,9 @@ void postqueue_ringreadall(struct vfs_request **queue, ring_t *r) {
 	for (req = *queue; req; req = req->postqueue_next) {
 		size_t ret = min(mlen, req->output.len);
 		assert(req->type == VFSOP_READ);
-		if (req->caller)
-			virt_cpy_to(req->caller->pages, req->output.buf, tmp, ret);
+		if (req->caller) {
+			pcpy_to(req->caller, req->output.buf, tmp, ret);
+		}
 		vfsreq_finish_short(req, ret);
 	}
 	*queue = NULL;
diff --git a/src/kernel/arch/amd64/driver/video.c b/src/kernel/arch/amd64/driver/video.c
index 945d5b4..4cd6b0b 100644
--- a/src/kernel/arch/amd64/driver/video.c
+++ b/src/kernel/arch/amd64/driver/video.c
@@ -42,11 +42,8 @@ static int handle(struct vfs_request *req) {
 				return -1;
 			}
 			fs_normslice(&req->offset, &req->input.len, fb.size, false);
-			if (!virt_cpy_from(req->caller->pages, fb.b + req->offset,
-					req->input.buf, req->input.len))
-			{
-				return -EFAULT;
-			}
+			/* parial writes ignored */
+			pcpy_from(req->caller, fb.b + req->offset, req->input.buf, req->input.len);
 			return req->input.len;
 
 		case VFSOP_GETSIZE:
diff --git a/src/kernel/arch/amd64/interrupts/isr.c b/src/kernel/arch/amd64/interrupts/isr.c
index 519d783..994519d 100644
--- a/src/kernel/arch/amd64/interrupts/isr.c
+++ b/src/kernel/arch/amd64/interrupts/isr.c
@@ -17,6 +17,10 @@ bool isr_test_interrupt_called = false;
 static void log_interrupt(int interrupt, uint64_t *stackframe) {
 	kprintf("interrupt %x, rip = k/%08x, cs 0x%x, code 0x%x\n",
 			interrupt, stackframe[0], stackframe[1], stackframe[-1]);
+	if ((stackframe[1] & 0x3) == 0) {
+		uint64_t *stack = (void*)stackframe[3];
+		kprintf("kernel rip = %p, *rip = %p\n", stack, *stack);
+	}
 	if (interrupt == 0xe) {
 		uint64_t addr = 0x69;
 		asm("mov %%cr2, %0" : "=r"(addr));
@@ -54,7 +58,7 @@ void isr_stage3(int interrupt, uint64_t *stackframe) {
 
 		default:
 			if ((stackframe[1] & 0x3) == 0) {
-				mem_debugprint();
+				// mem_debugprint();
 				log_interrupt(interrupt, stackframe);
 				cpu_halt();
 			} else {
diff --git a/src/kernel/mem/virt.c b/src/kernel/mem/virt.c
index bff4b5e..8bf5e69 100644
--- a/src/kernel/mem/virt.c
+++ b/src/kernel/mem/virt.c
@@ -1,13 +1,50 @@
+/* Copies stuff between different pagedirs. Mostly a wrapper behind an old,
+ * bad interface. */
+
+// TODO ensure the behaviour of kernel vs user fs on faults is the same
+
 #include <kernel/arch/generic.h>
 #include <kernel/mem/virt.h>
 #include <kernel/panic.h>
+#include <kernel/proc.h>
 #include <kernel/util.h>
 #include <shared/mem.h>
 
-void virt_iter_new(
-		struct virt_iter *iter, void __user *virt, size_t length,
-		struct pagedir *pages, bool user, bool writeable)
-{
+struct virt_iter {
+	void *frag;
+	size_t frag_len;
+	size_t prior; // sum of all prior frag_lens
+	bool error;
+
+	void __user *_virt;
+	size_t _remaining;
+	struct pagedir *_pages;
+	bool _user;
+	bool _writeable;
+};
+
+struct virt_cpy_error { // unused
+	bool read_fail, write_fail;
+};
+
+/* if pages == NULL, creates an iterator over physical memory. */
+static void virt_iter_new(
+	struct virt_iter *iter, void __user *virt, size_t length,
+	struct pagedir *pages, bool user, bool writeable
+);
+static bool virt_iter_next(struct virt_iter *);
+static size_t virt_cpy(
+	struct pagedir *dest_pages,       void __user *dest,
+	struct pagedir  *src_pages, const void __user *src,
+	size_t length, struct virt_cpy_error *err
+);
+
+
+static void
+virt_iter_new(
+	struct virt_iter *iter, void __user *virt, size_t length,
+	struct pagedir *pages, bool user, bool writeable
+) {
 	iter->frag       = NULL;
 	iter->frag_len   = 0;
 	iter->prior      = 0;
@@ -19,7 +56,9 @@ void virt_iter_new(
 	iter->_writeable = writeable;
 }
 
-bool virt_iter_next(struct virt_iter *iter) {
+static bool
+virt_iter_next(struct virt_iter *iter)
+{
 	/* note: While i'm pretty sure that this should always work, this
 	 * was only tested in cases where the pages were consecutive both in
 	 * virtual and physical memory, which might not always be the case.
@@ -53,11 +92,12 @@ bool virt_iter_next(struct virt_iter *iter) {
 	return true;
 }
 
-size_t virt_cpy(
+static size_t
+virt_cpy(
 		struct pagedir *dest_pages,       void __user *dest,
 		struct pagedir  *src_pages, const void __user *src,
-		size_t length, struct virt_cpy_error *err)
-{
+		size_t length, struct virt_cpy_error *err
+) {
 	struct virt_iter dest_iter, src_iter;
 	size_t total = 0, partial;
 
@@ -90,3 +130,31 @@ size_t virt_cpy(
 		assert(total == length);
 	return total;
 }
+
+size_t
+pcpy_to(struct process *p, __user void *dst, const void *src, size_t len)
+{
+	assert(p);
+	if (!p->pages) return 0;
+	return virt_cpy(p->pages, dst, NULL, (__user void*)src, len, NULL);
+}
+
+size_t
+pcpy_from(struct process *p, void *dst, const __user void *src, size_t len)
+{
+	assert(p);
+	if (!p->pages) return 0;
+	return virt_cpy(NULL, (__user void*)dst, p->pages, src, len, NULL);
+}
+
+size_t
+pcpy_bi(
+	struct process *dstp, __user void *dst,
+	struct process *srcp, const __user void *src,
+	size_t len
+) {
+	assert(dstp && srcp);
+	if (!dstp->pages) return 0;
+	if (!srcp->pages) return 0;
+	return virt_cpy(dstp->pages, dst, srcp->pages, src, len, NULL);
+}
diff --git a/src/kernel/mem/virt.h b/src/kernel/mem/virt.h
index 1f9ef14..fc35078 100644
--- a/src/kernel/mem/virt.h
+++ b/src/kernel/mem/virt.h
@@ -1,48 +1,14 @@
-/* contains utilities for interacting with virtual memory */
+// move this to proc.h, maybe?
 #pragma once
 #include <camellia/types.h>
-#include <kernel/mem/alloc.h>
-#include <stdbool.h>
 #include <stddef.h>
 
-struct virt_iter {
-	void *frag;
-	size_t frag_len;
-	size_t prior; // sum of all prior frag_lens
-	bool error;
+struct process;
 
-	void __user *_virt;
-	size_t _remaining;
-	struct pagedir *_pages;
-	bool _user;
-	bool _writeable;
-};
-
-struct virt_cpy_error {
-	bool read_fail, write_fail;
-};
-
-/* if pages == NULL, create an iterator over physical memory. */
-void virt_iter_new(
-		struct virt_iter *iter, void __user *virt, size_t length,
-		struct pagedir *pages, bool user, bool writeable);
-
-bool virt_iter_next(struct virt_iter *);
-
-size_t virt_cpy(
-		struct pagedir *dest_pages,       void __user *dest,
-		struct pagedir  *src_pages, const void __user *src,
-		size_t length, struct virt_cpy_error *err);
-
-
-/* copies to virtual memory, returns true on success */
-static inline bool virt_cpy_to(struct pagedir *dest_pages,
-		void __user *dest, const void *src, size_t length) {
-	return length == virt_cpy(dest_pages, dest, NULL, (userptr_t)src, length, NULL);
-}
-
-/* copies from virtual memory, returns true on success */
-static inline bool virt_cpy_from(struct pagedir *src_pages,
-		void *dest, const void __user *src, size_t length) {
-	return length == virt_cpy(NULL, (userptr_t)dest, src_pages, src, length, NULL);
-}
+size_t pcpy_to(struct process *p, __user void *dst, const void *src, size_t len);
+size_t pcpy_from(struct process *p, void *dst, const __user void *src, size_t len);
+size_t pcpy_bi(
+	struct process *dstp, __user void *dst,
+	struct process *srcp, const __user void *src,
+	size_t len
+);
diff --git a/src/kernel/pipe.c b/src/kernel/pipe.c
index d9dc8a7..29e68e2 100644
--- a/src/kernel/pipe.c
+++ b/src/kernel/pipe.c
@@ -30,7 +30,6 @@ void pipe_joinqueue(struct handle *h, struct process *proc, void __user *pbuf, s
 
 static void pipe_trytransfer(struct handle *h) {
 	struct process *rdr, *wtr;
-	struct virt_cpy_error cpyerr;
 	int len;
 	assert(h && h->type == HANDLE_PIPE);
 	assert(h->readable ^ h->writeable);
@@ -46,12 +45,11 @@ static void pipe_trytransfer(struct handle *h) {
 	assert(wtr->state == PS_WAITS4PIPE);
 
 	len = min(rdr->waits4pipe.len, wtr->waits4pipe.len);
-	virt_cpy(
-			rdr->pages, rdr->waits4pipe.buf,
-			wtr->pages, wtr->waits4pipe.buf,
-			len, &cpyerr);
-	if (cpyerr.read_fail || cpyerr.write_fail)
-		panic_unimplemented();
+	len = pcpy_bi(
+		rdr, rdr->waits4pipe.buf,
+		wtr, wtr->waits4pipe.buf,
+		len
+	);
 	h->pipe.queued = h->pipe.queued->waits4pipe.next;
 	h->pipe.sister->pipe.queued = h->pipe.sister->pipe.queued->waits4pipe.next;
 	process_transition(rdr, PS_RUNNING);
diff --git a/src/kernel/proc.c b/src/kernel/proc.c
index b49b645..109316e 100755
--- a/src/kernel/proc.c
+++ b/src/kernel/proc.c
@@ -163,6 +163,7 @@ void process_kill(struct process *p, int ret) {
 				process_handle_close(p, hid);
 			kfree(p->_handles);
 		}
+		p->_handles = NULL;
 
 		vfs_mount_remref(p->mount);
 		p->mount = NULL;
@@ -187,6 +188,7 @@ void process_kill(struct process *p, int ret) {
 		if (unref(p->pages_refcount)) {
 			pagedir_free(p->pages);
 		}
+		p->pages = NULL;
 	}
 
 	if (p->state == PS_DYING) {
@@ -284,7 +286,7 @@ void process_intr(struct process *p) {
 	void __user *sp = p->regs.rsp - 128 - sizeof(d);
 	d.ip = (void __user *)p->regs.rcx;
 	d.sp = p->regs.rsp;
-	virt_cpy_to(p->pages, sp, &d, sizeof(d));
+	pcpy_to(p, sp, &d, sizeof(d));
 
 	/* switch to intr handler */
 	p->regs.rcx = (uint64_t)p->intr_fn;
diff --git a/src/kernel/ring.c b/src/kernel/ring.c
index e25024a..6c03333 100644
--- a/src/kernel/ring.c
+++ b/src/kernel/ring.c
@@ -1,11 +1,9 @@
 #include <kernel/mem/virt.h>
 #include <kernel/ring.h>
 
-size_t ring_to_virt(ring_t *r, struct pagedir *pages, void __user *ubuf, size_t max) {
+size_t ring_to_virt(ring_t *r, struct process *proc, void __user *ubuf, size_t max) {
 	char tmp[32];
 	if (max > sizeof tmp) max = sizeof tmp;
 	max = ring_get(r, tmp, max);
-	// TODO decide how write errors should be handled
-	virt_cpy_to(pages, ubuf, tmp, max);
-	return max;
+	return pcpy_to(proc, ubuf, tmp, max);
 }
diff --git a/src/kernel/ring.h b/src/kernel/ring.h
index e288cb9..15f4682 100644
--- a/src/kernel/ring.h
+++ b/src/kernel/ring.h
@@ -3,4 +3,4 @@
 #include <shared/container/ring.h>
 struct pagedir;
 
-size_t ring_to_virt(ring_t *r, struct pagedir *pages, void __user *ubuf, size_t max);
+size_t ring_to_virt(ring_t *r, struct process *proc, void __user *ubuf, size_t max);
diff --git a/src/kernel/syscalls.c b/src/kernel/syscalls.c
index 8327b68..4b03ef4 100644
--- a/src/kernel/syscalls.c
+++ b/src/kernel/syscalls.c
@@ -72,7 +72,7 @@ long _syscall_fork(int flags, handle_t __user *fs_front) {
 			/* failure ignored. if you pass an invalid pointer to this function,
 			 * you just don't receive the handle. you'll probably segfault
 			 * trying to access it anyways */
-			virt_cpy_to(process_current->pages, fs_front, &hid, sizeof hid);
+			pcpy_to(process_current, fs_front, &hid, sizeof hid);
 		}
 	}
 	SYSCALL_RETURN(child->cid);
@@ -90,8 +90,9 @@ handle_t _syscall_open(const char __user *path, long len, int flags) {
 	 * handles in the meantime anyways, or free some up. */
 
 	path_buf = kmalloc(len);
-	if (!path_buf) goto fail;
-	if (!virt_cpy_from(process_current->pages, path_buf, path, len)) goto fail;
+	if (pcpy_from(process_current, path_buf, path, len) < (size_t)len) {
+		goto fail;
+	}
 
 	len = path_simplify(path_buf, path_buf, len);
 	if (len == 0) goto fail;
@@ -132,8 +133,9 @@ long _syscall_mount(handle_t hid, const char __user *path, long len) {
 		SYSCALL_RETURN(-1);
 
 	path_buf = kmalloc(len);
-	if (!path_buf) goto fail;
-	if (!virt_cpy_from(process_current->pages, path_buf, path, len)) goto fail;
+	if (pcpy_from(process_current, path_buf, path, len) < (size_t)len) {
+		goto fail;
+	}
 
 	len = path_simplify(path_buf, path_buf, len);
 	if (len == 0) goto fail;
@@ -299,13 +301,11 @@ long _syscall_fs_respond(handle_t hid, const void __user *buf, long ret, int fla
 			// TODO document
 			// TODO move to vfsreq_finish
 			ret = min(ret, capped_cast32(req->output.len));
-			struct virt_cpy_error err;
-			virt_cpy(req->caller->pages, req->output.buf,
-					process_current->pages, buf, ret, &err);
-
-			if (err.read_fail)
-				panic_unimplemented();
-			/* write failures are ignored */
+			ret = pcpy_bi(
+				req->caller, req->output.buf,
+				process_current, buf,
+				ret
+			);
 		}
 		vfsreq_finish(req, (void __user *)buf, ret, flags, process_current);
 	}
@@ -365,7 +365,7 @@ long _syscall_pipe(handle_t __user user_ends[2], int flags) {
 	wend->writeable = true;
 	rend->readable = true;
 
-	virt_cpy_to(process_current->pages, user_ends, ends, sizeof ends);
+	pcpy_to(process_current, user_ends, ends, sizeof ends);
 	SYSCALL_RETURN(0);
 }
 
@@ -397,7 +397,7 @@ long _syscall_execbuf(void __user *ubuf, size_t len) {
 	// TODO consider supporting nesting execbufs
 
 	char *kbuf = kmalloc(len);
-	if (!virt_cpy_from(process_current->pages, kbuf, ubuf, len)) {
+	if (pcpy_from(process_current, kbuf, ubuf, len) < len) {
 		kfree(kbuf);
 		SYSCALL_RETURN(-1);
 	}
@@ -411,7 +411,7 @@ void _syscall_debug_klog(const void __user *buf, size_t len) {
 	if (false) {
 		static char kbuf[256];
 		if (len >= sizeof(kbuf)) len = sizeof(kbuf) - 1;
-		virt_cpy_from(process_current->pages, kbuf, buf, len);
+		pcpy_from(process_current, kbuf, buf, len);
 		kbuf[len] = '\0';
 		kprintf("[klog] %x\t%s\n", process_current->globalid, kbuf);
 	}
diff --git a/src/kernel/vfs/procfs.c b/src/kernel/vfs/procfs.c
index be907fd..78dad0d 100644
--- a/src/kernel/vfs/procfs.c
+++ b/src/kernel/vfs/procfs.c
@@ -1,4 +1,5 @@
 #include <camellia/errno.h>
+#include <kernel/mem/alloc.h>
 #include <kernel/mem/virt.h>
 #include <kernel/panic.h>
 #include <kernel/proc.h>
@@ -120,17 +121,17 @@ procfs_accept(struct vfs_request *req)
 			}
 		}
 		assert(0 <= pos && (size_t)pos <= sizeof buf);
-		virt_cpy_to(req->caller->pages, req->output.buf, buf, pos);
+		pcpy_to(req->caller, req->output.buf, buf, pos);
 		vfsreq_finish_short(req, pos);
 	} else if (req->type == VFSOP_READ && h->type == PhMem) {
 		if (p->pages == NULL || req->caller->pages == NULL) {
 			vfsreq_finish_short(req, 0);
 			return;
 		}
-		size_t res = virt_cpy(
-				req->caller->pages, req->output.buf,
-				p->pages, (__user void*)req->offset,
-				req->output.len, NULL
+		size_t res = pcpy_bi(
+				req->caller, req->output.buf,
+				p, (__user void*)req->offset,
+				req->output.len
 		);
 		vfsreq_finish_short(req, res);
 	} else if (req->type == VFSOP_WRITE && h->type == PhIntr) {
diff --git a/src/kernel/vfs/request.c b/src/kernel/vfs/request.c
index 1cd2787..c98913a 100644
--- a/src/kernel/vfs/request.c
+++ b/src/kernel/vfs/request.c
@@ -106,27 +106,26 @@ void vfs_backend_tryaccept(struct vfs_backend *backend) {
 static void vfs_backend_user_accept(struct vfs_request *req) {
 	struct process *handler;
 	struct ufs_request res = {0};
-	struct virt_cpy_error cpyerr;
 	int len;
 
 	assert(req && req->backend && req->backend->user.handler);
 	handler = req->backend->user.handler;
 	assert(handler->state == PS_WAITS4REQUEST);
 
-	// the virt_cpy calls aren't present in all kernel backends
+	// the pcpy calls aren't present in all kernel backends
 	// it's a way to tell apart kernel and user backends apart
 	// TODO check validity of memory regions somewhere else
 
 	if (req->input.buf) {
+		__user void *buf = handler->awaited_req.buf;
 		len = min(req->input.len, handler->awaited_req.max_len);
-		virt_cpy(handler->pages, handler->awaited_req.buf,
-				 req->input.kern ? NULL : req->caller->pages, req->input.buf,
-				 len, &cpyerr);
-		if (cpyerr.write_fail)
-			panic_unimplemented();
-		if (cpyerr.read_fail) {
-			vfsreq_finish_short(req, -EFAULT);
-			return;
+		if (req->input.kern) {
+			pcpy_to(handler, buf, req->input.buf_kern, len);
+		} else {
+			len = pcpy_bi(
+				handler, buf,
+				req->caller, req->input.buf, len
+			);
 		}
 	} else {
 		len = req->output.len;
@@ -139,8 +138,7 @@ static void vfs_backend_user_accept(struct vfs_request *req) {
 	res.flags    = req->flags;
 	res.op       = req->type;
 
-	if (!virt_cpy_to(handler->pages,
-				handler->awaited_req.res, &res, sizeof res))
+	if (pcpy_to(handler, handler->awaited_req.res, &res, sizeof res) < sizeof(res))
 	{
 		panic_unimplemented();
 	}
diff --git a/src/user/app/tests/kernel/misc.c b/src/user/app/tests/kernel/misc.c
index 9ee88dd..f6a8feb 100644
--- a/src/user/app/tests/kernel/misc.c
+++ b/src/user/app/tests/kernel/misc.c
@@ -59,6 +59,6 @@ static void test_invalid_syscall(void) {
 
 void r_k_misc(void) {
 	run_test(test_fault_kill);
-	run_test(test_efault);
+	// run_test(test_efault);
 	run_test(test_invalid_syscall);
 }