error-injection: Add injectable error types

Add injectable error types for each error-injectable function.

One motivation of error injection test is to find software flaws,
mistakes or mis-handlings of expectable errors. If we find such
flaws by the test, that is a program bug, so we need to fix it.

But if the tester miss input the error (e.g. just return success
code without processing anything), it causes unexpected behavior
even if the caller is correctly programmed to handle any errors.
That is not what we want to test by error injection.

To clarify what type of errors the caller must expect for each
injectable function, this introduces injectable error types:

 - EI_ETYPE_NULL : means the function will return NULL if it
		    fails. No ERR_PTR, just a NULL.
 - EI_ETYPE_ERRNO : means the function will return -ERRNO
		    if it fails.
 - EI_ETYPE_ERRNO_NULL : means the function will return -ERRNO
		       (ERR_PTR) or NULL.

ALLOW_ERROR_INJECTION() macro is expanded to get one of
NULL, ERRNO, ERRNO_NULL to record the error type for
each function. e.g.

 ALLOW_ERROR_INJECTION(open_ctree, ERRNO)

This error types are shown in debugfs as below.

  ====
  / # cat /sys/kernel/debug/error_injection/list
  open_ctree [btrfs]	ERRNO
  io_ctl_init [btrfs]	ERRNO
  ====

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Reviewed-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

2 files changed, 20 insertions, 5 deletions

diff --git a/include/asm-generic/error-injection.h b/include/asm-generic/error-injection.h
index 08352c9d9f97..296c65442f00 100644
--- a/include/asm-generic/error-injection.h
+++ b/include/asm-generic/error-injection.h
@@ -3,17 +3,32 @@
 #define _ASM_GENERIC_ERROR_INJECTION_H
 
 #if defined(__KERNEL__) && !defined(__ASSEMBLY__)
+enum {
+	EI_ETYPE_NONE,		/* Dummy value for undefined case */
+	EI_ETYPE_NULL,		/* Return NULL if failure */
+	EI_ETYPE_ERRNO,		/* Return -ERRNO if failure */
+	EI_ETYPE_ERRNO_NULL,	/* Return -ERRNO or NULL if failure */
+};
+
+struct error_injection_entry {
+	unsigned long	addr;
+	int		etype;
+};
+
 #ifdef CONFIG_FUNCTION_ERROR_INJECTION
 /*
  * Whitelist ganerating macro. Specify functions which can be
  * error-injectable using this macro.
  */
-#define ALLOW_ERROR_INJECTION(fname)					\
-static unsigned long __used						\
+#define ALLOW_ERROR_INJECTION(fname, _etype)				\
+static struct error_injection_entry __used				\
 	__attribute__((__section__("_error_injection_whitelist")))	\
-	_eil_addr_##fname = (unsigned long)fname;
+	_eil_addr_##fname = {						\
+		.addr = (unsigned long)fname,				\
+		.etype = EI_ETYPE_##_etype,				\
+	};
 #else
-#define ALLOW_ERROR_INJECTION(fname)
+#define ALLOW_ERROR_INJECTION(fname, _etype)
 #endif
 #endif
 
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index f2068cca5206..ebe544e048cd 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -137,7 +137,7 @@
 #endif
 
 #ifdef CONFIG_FUNCTION_ERROR_INJECTION
-#define ERROR_INJECT_WHITELIST()	. = ALIGN(8);			      \
+#define ERROR_INJECT_WHITELIST()	STRUCT_ALIGN();			      \
 			VMLINUX_SYMBOL(__start_error_injection_whitelist) = .;\
 			KEEP(*(_error_injection_whitelist))		      \
 			VMLINUX_SYMBOL(__stop_error_injection_whitelist) = .;