efi/libstub: Add efi_warn and *_once logging helpers

Add an efi_warn logging helper for warnings, and implement an analog of
printk_once for once-only logging.
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Link: https://lore.kernel.org/r/20200914213535.933454-1-nivedita@alum.mit.eduSigned-off-by: Ard Biesheuvel <ardb@kernel.org>

drivers/firmware/efi/libstub/efistub.h

@@ -52,11 +52,34 @@ efi_status_t __efiapi efi_pe_entry(efi_handle_t handle,
 
 #define efi_info(fmt, ...) \
 	efi_printk(KERN_INFO fmt, ##__VA_ARGS__)
+#define efi_warn(fmt, ...) \
+	efi_printk(KERN_WARNING "WARNING: " fmt, ##__VA_ARGS__)
 #define efi_err(fmt, ...) \
 	efi_printk(KERN_ERR "ERROR: " fmt, ##__VA_ARGS__)
 #define efi_debug(fmt, ...) \
 	efi_printk(KERN_DEBUG "DEBUG: " fmt, ##__VA_ARGS__)
 
+#define efi_printk_once(fmt, ...) 		\
+({						\
+	static bool __print_once;		\
+	bool __ret_print_once = !__print_once;	\
+						\
+	if (!__print_once) {			\
+		__print_once = true;		\
+		efi_printk(fmt, ##__VA_ARGS__);	\
+	}					\
+	__ret_print_once;			\
+})
+
+#define efi_info_once(fmt, ...) \
+	efi_printk_once(KERN_INFO fmt, ##__VA_ARGS__)
+#define efi_warn_once(fmt, ...) \
+	efi_printk_once(KERN_WARNING "WARNING: " fmt, ##__VA_ARGS__)
+#define efi_err_once(fmt, ...) \
+	efi_printk_once(KERN_ERR "ERROR: " fmt, ##__VA_ARGS__)
+#define efi_debug_once(fmt, ...) \
+	efi_printk_once(KERN_DEBUG "DEBUG: " fmt, ##__VA_ARGS__)
+
 /* Helper macros for the usual case of using simple C variables: */
 #ifndef fdt_setprop_inplace_var
 #define fdt_setprop_inplace_var(fdt, node_offset, name, var) \