uaccess: Add non-pagefault user-space read functions
Add probe_user_read(), strncpy_from_unsafe_user() and
strnlen_unsafe_user() which allows caller to access user-space
in IRQ context.
Current probe_kernel_read() and strncpy_from_unsafe() are
not available for user-space memory, because it sets
KERNEL_DS while accessing data. On some arch, user address
space and kernel address space can be co-exist, but others
can not. In that case, setting KERNEL_DS means given
address is treated as a kernel address space.
Also strnlen_user() is only available from user context since
it can sleep if pagefault is enabled.
To access user-space memory without pagefault, we need
these new functions which sets USER_DS while accessing
the data.
Link: http://lkml.kernel.org/r/155789869802.26965.4940338412595759063.stgit@devnote2
Acked-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
index 5a43ef7..9c435c3 100644
--- a/include/linux/uaccess.h
+++ b/include/linux/uaccess.h
@@ -243,6 +243,17 @@ extern long probe_kernel_read(void *dst, const void *src, size_t size);
extern long __probe_kernel_read(void *dst, const void *src, size_t size);
/*
+ * probe_user_read(): safely attempt to read from a location in user space
+ * @dst: pointer to the buffer that shall take the data
+ * @src: address to read from
+ * @size: size of the data chunk
+ *
+ * Safely read from address @src to the buffer at @dst. If a kernel fault
+ * happens, handle that and return -EFAULT.
+ */
+extern long probe_user_read(void *dst, const void __user *src, size_t size);
+
+/*
* probe_kernel_write(): safely attempt to write to a location
* @dst: address to write to
* @src: pointer to the data that shall be written
@@ -255,6 +266,9 @@ extern long notrace probe_kernel_write(void *dst, const void *src, size_t size);
extern long notrace __probe_kernel_write(void *dst, const void *src, size_t size);
extern long strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count);
+extern long strncpy_from_unsafe_user(char *dst, const void __user *unsafe_addr,
+ long count);
+extern long strnlen_unsafe_user(const void __user *unsafe_addr, long count);
/**
* probe_kernel_address(): safely attempt to read from a location