kernel: pagecache: provided buffers are not always in user memory

Source or destination buffers passed to pagecache functions may belong
to kernel memory (e.g. when the caller is packagefs). Because of that
we should tell vm_memcpy_{from, to}_physical() truth, not assume that all
buffers are in user memory. That's important because user memory page fault
handlers cannot be nested and these functions may be used while handling
a page fault.

With high probability fixes #11246.

Signed-off-by: Paweł Dziepak <pdziepak@quarnos.org>

src/system/kernel/cache/file_cache.cpp

@@ -434,7 +434,7 @@ read_into_cache(file_cache_ref* ref, void* cookie, off_t offset,
 
 			vm_memcpy_from_physical((void*)buffer,
 				pages[i]->physical_page_number * B_PAGE_SIZE + pageOffset,
-				bytes, true);
+				bytes, IS_USER_ADDRESS(buffer));
 
 			buffer += bytes;
 			bufferSize -= bytes;
@@ -588,7 +588,7 @@ write_to_cache(file_cache_ref* ref, void* cookie, off_t offset,
 		if (useBuffer) {
 			// copy data from user buffer
 			vm_memcpy_to_physical(base + pageOffset, (void*)buffer, bytes,
-				true);
+				IS_USER_ADDRESS(buffer));
 		} else {
 			// clear buffer instead
 			vm_memset_physical(base + pageOffset, 0, bytes);
@@ -808,16 +808,17 @@ cache_io(void* _cacheRef, void* cookie, off_t offset, addr_t buffer,
 				phys_addr_t pageAddress
 					= (phys_addr_t)page->physical_page_number * B_PAGE_SIZE
 						+ pageOffset;
+				bool userBuffer = IS_USER_ADDRESS(buffer);
 				if (doWrite) {
 					if (useBuffer) {
 						vm_memcpy_to_physical(pageAddress, (void*)buffer,
-							bytesInPage, true);
+							bytesInPage, userBuffer);
 					} else {
 						vm_memset_physical(pageAddress, 0, bytesInPage);
 					}
 				} else if (useBuffer) {
 					vm_memcpy_from_physical((void*)buffer, pageAddress,
-						bytesInPage, true);
+						bytesInPage, userBuffer);
 				}
 
 				locker.Lock();