From 39f5404c5394802e107347e6014297c05951202a Mon Sep 17 00:00:00 2001
From: dzwdz
Date: Fri, 16 Aug 2024 19:06:07 +0200
Subject: kernel/pcpy: minor cleanup, implement pcpy_from_str

might potentially be used in a reworked open(), mount() etc interface
---
 src/kernel/pcpy.c | 67 ++++++++++++++++++++++++++++++++++---------------------
 src/kernel/proc.h |  4 ++++
 2 files changed, 45 insertions(+), 26 deletions(-)

(limited to 'src/kernel')

diff --git a/src/kernel/pcpy.c b/src/kernel/pcpy.c
index 9cf7c37..5b9efef 100644
--- a/src/kernel/pcpy.c
+++ b/src/kernel/pcpy.c
@@ -12,7 +12,6 @@
 struct virt_iter {
 	void *frag;
 	size_t frag_len;
-	size_t prior; // sum of all prior frag_lens
 	bool error;
 
 	void __user *_virt;
@@ -22,10 +21,6 @@ struct virt_iter {
 	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,
@@ -35,7 +30,7 @@ static bool virt_iter_next(struct virt_iter *);
 static size_t virt_cpy(
 	Pagedir *dest_pages,       void __user *dest,
 	Pagedir  *src_pages, const void __user *src,
-	size_t length, struct virt_cpy_error *err
+	size_t length
 );
 
 
@@ -46,7 +41,6 @@ virt_iter_new(
 ) {
 	iter->frag       = NULL;
 	iter->frag_len   = 0;
-	iter->prior      = 0;
 	iter->error      = false;
 	iter->_virt      = virt;
 	iter->_remaining = length;
@@ -58,13 +52,7 @@ virt_iter_new(
 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.
-	 * TODO test this */
-
 	size_t partial = iter->_remaining;
-	iter->prior   += iter->frag_len;
 	if (partial <= 0) return false;
 
 	if (iter->_pages) { // if iterating over virtual memory
@@ -95,15 +83,14 @@ static size_t
 virt_cpy(
 		Pagedir *dest_pages,       void __user *dest,
 		Pagedir  *src_pages, const void __user *src,
-		size_t length, struct virt_cpy_error *err
+		size_t length
 ) {
 	struct virt_iter dest_iter, src_iter;
 	size_t total = 0, partial;
 
+	/*                                                            user  write */
 	virt_iter_new(&dest_iter,           dest, length, dest_pages, true, true);
 	virt_iter_new( &src_iter, (userptr_t)src, length,  src_pages, true, false);
-	dest_iter.frag_len = 0;
-	src_iter.frag_len  = 0;
 
 	for (;;) {
 		if (dest_iter.frag_len <= 0 && !virt_iter_next(&dest_iter)) break;
@@ -119,14 +106,11 @@ virt_cpy(
 		src_iter.frag      += partial;
 	}
 
-	if (err) {
-		err->read_fail  = src_iter.error;
-		err->write_fail = dest_iter.error;
-	}
-	if (src_iter.error || dest_iter.error)
-		assert(total != length);
-	else
+	if (src_iter.error || dest_iter.error) {
+		assert(total < length);
+	} else {
 		assert(total == length);
+	}
 	return total;
 }
 
@@ -135,7 +119,7 @@ pcpy_to(Proc *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);
+	return virt_cpy(p->pages, dst, NULL, (__user void*)src, len);
 }
 
 size_t
@@ -143,7 +127,7 @@ pcpy_from(Proc *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);
+	return virt_cpy(NULL, (__user void*)dst, p->pages, src, len);
 }
 
 size_t
@@ -155,5 +139,36 @@ pcpy_bi(
 	assert(dstp && srcp);
 	if (!dstp->pages) return 0;
 	if (!srcp->pages) return 0;
-	return virt_cpy(dstp->pages, dst, srcp->pages, src, len, NULL);
+	return virt_cpy(dstp->pages, dst, srcp->pages, src, len);
+}
+
+// XXX: not used atm
+size_t
+pcpy_from_str(Proc *p, char *dst, const __user char *src, size_t len)
+{
+	struct virt_iter iter;
+	size_t pos = 0;
+
+	assert(p);
+	if (p->pages == NULL) return 0;
+
+	virt_iter_new(&iter, (userptr_t)src, len, p->pages, true, false);
+	for (;;) {
+		assert(iter.frag_len == 0);
+		if (!virt_iter_next(&iter)) {
+			return 0;
+		}
+
+		char *c = iter.frag;
+		for (size_t i = 0; i < iter.frag_len; i++) {
+			dst[pos++] = c[i];
+			if (c[i] == '\0') {
+				assert(pos <= len);
+				return pos;
+			}
+		}
+
+		iter.frag += iter.frag_len;
+		iter.frag_len = 0;
+	}
 }
diff --git a/src/kernel/proc.h b/src/kernel/proc.h
index 0de740f..4ad6580 100644
--- a/src/kernel/proc.h
+++ b/src/kernel/proc.h
@@ -145,3 +145,7 @@ size_t pcpy_bi(
 	Proc *srcp, const __user void *src,
 	size_t len
 );
+/* Copies a NUL-terminated string from the process.
+ * Returns the size of the string including the NUL terminator,
+ * and 0 on error or if the string didn't fit in dst. */
+size_t pcpy_from_str(Proc *p, char *dst, const __user char *src, size_t len);
-- 
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