From f6a869614e5bdf9a3819a845f7a90d8c9ede0fc3 Mon Sep 17 00:00:00 2001
From: Tim Chase <tim@chase2k.com>
Date: Wed, 18 Jun 2014 15:22:50 -0500
Subject: [PATCH] Safer debugging and assertion macros.

Spl's debugging and assertion macros macro used the typical do/while(0)
form for if/else friendliness, however, this limits their use in contexts
where a do loop is not valid; such as within another multi-statement
style macro.

The following macros have been converted to not use do/while(0):
	PANIC, ASSERT, ASSERTF, VERIFY, VERIFY3_IMPL

PANIC has been converted to a wrapper around the new spl_PANIC() function.

The other macros have been converted to use the "&&" operator for the
branch-predicition conditional and also to use spl_PANIC().

The __ASSERT() macro was not touched.  It is only used by the debugging
infrastructure and that code, including this macro, will be retired when
the tracepoint patches are merged.

Signed-off-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #367
---
 include/sys/debug.h  | 56 ++++++++++++++++++++------------------------
 module/spl/spl-err.c | 21 +++++++++++++++++
 2 files changed, 46 insertions(+), 31 deletions(-)

diff --git a/include/sys/debug.h b/include/sys/debug.h
index 9fa2653d4d..3a4b1352fb 100644
--- a/include/sys/debug.h
+++ b/include/sys/debug.h
@@ -54,28 +54,23 @@
 #define SPL_DEBUG_STR	""
 
 #define PANIC(fmt, a...)						\
-do {									\
-	printk(KERN_EMERG fmt, ## a);					\
-	spl_debug_bug(__FILE__, __FUNCTION__, __LINE__, 0);		\
-} while (0)
+	spl_PANIC(__FILE__, __FUNCTION__, __LINE__, fmt, ## a)
 
 #define __ASSERT(x)			((void)0)
 #define ASSERT(x)			((void)0)
 #define ASSERTF(x, y, z...)		((void)0)
 #define ASSERTV(x)
 #define VERIFY(cond)							\
-do {									\
-	if (unlikely(!(cond)))						\
-		PANIC("VERIFY(" #cond ") failed\n");			\
-} while (0)
+	(void)(unlikely(!(cond)) &&					\
+		spl_PANIC(__FILE__, __FUNCTION__, __LINE__,		\
+		"%s", "VERIFY(" #cond ") failed\n"))
 
 #define VERIFY3_IMPL(LEFT, OP, RIGHT, TYPE, FMT, CAST)			\
-do {									\
-	if (!((TYPE)(LEFT) OP (TYPE)(RIGHT)))				\
-		PANIC("VERIFY3(" #LEFT " " #OP " " #RIGHT ") "		\
+	(void)((!((TYPE)(LEFT) OP (TYPE)(RIGHT))) &&			\
+		spl_PANIC(__FILE__, __FUNCTION__, __LINE__,		\
+		"VERIFY3(" #LEFT " " #OP " " #RIGHT ") "		\
 		    "failed (" FMT " " #OP " " FMT ")\n",		\
-		    CAST (LEFT), CAST (RIGHT));				\
-} while (0)
+		    CAST (LEFT), CAST (RIGHT)))
 
 #define VERIFY3S(x,y,z)	VERIFY3_IMPL(x, y, z, int64_t, "%lld", (long long))
 #define VERIFY3U(x,y,z)	VERIFY3_IMPL(x, y, z, uint64_t, "%llu",		\
@@ -94,11 +89,7 @@ do {									\
 #define SPL_DEBUG_STR	" (DEBUG mode)"
 
 #define PANIC(fmt, a...)						\
-do {									\
-	spl_debug_msg(NULL, 0, 0,					\
-	     __FILE__, __FUNCTION__, __LINE__,	fmt, ## a);		\
-	spl_debug_bug(__FILE__, __FUNCTION__, __LINE__, 0);		\
-} while (0)
+	spl_PANIC(__FILE__, __FUNCTION__, __LINE__, fmt, ## a)
 
 /* ASSERTION that is safe to use within the debug system */
 #define __ASSERT(cond)							\
@@ -111,24 +102,21 @@ do {									\
 
 /* ASSERTION that will debug log used outside the debug sysytem */
 #define ASSERT(cond)							\
-do {									\
-	if (unlikely(!(cond)))						\
-		PANIC("ASSERTION(" #cond ") failed\n");			\
-} while (0)
+	(void)(unlikely(!(cond)) &&					\
+		spl_PANIC(__FILE__, __FUNCTION__, __LINE__,		\
+		"%s", "ASSERTION(" #cond ") failed\n"))
 
 #define ASSERTF(cond, fmt, a...)					\
-do {									\
-	if (unlikely(!(cond)))						\
-		PANIC("ASSERTION(" #cond ") failed: " fmt, ## a);	\
-} while (0)
+	(void)(unlikely(!(cond)) &&					\
+		spl_PANIC(__FILE__, __FUNCTION__, __LINE__,		\
+		"ASSERTION(" #cond ") failed: " fmt, ## a))
 
 #define VERIFY3_IMPL(LEFT, OP, RIGHT, TYPE, FMT, CAST)			\
-do {									\
-	if (!((TYPE)(LEFT) OP (TYPE)(RIGHT)))				\
-		PANIC("VERIFY3(" #LEFT " " #OP " " #RIGHT ") "		\
+	(void)((!((TYPE)(LEFT) OP (TYPE)(RIGHT))) &&			\
+		spl_PANIC(__FILE__, __FUNCTION__, __LINE__,		\
+		"VERIFY3(" #LEFT " " #OP " " #RIGHT ") "		\
 		    "failed (" FMT " " #OP " " FMT ")\n",		\
-		    CAST (LEFT), CAST (RIGHT));				\
-} while (0)
+		    CAST (LEFT), CAST (RIGHT)))
 
 #define VERIFY3S(x,y,z)	VERIFY3_IMPL(x, y, z, int64_t, "%lld", (long long))
 #define VERIFY3U(x,y,z)	VERIFY3_IMPL(x, y, z, uint64_t, "%llu",		\
@@ -146,6 +134,12 @@ do {									\
 
 #endif /* NDEBUG */
 
+/*
+ * Helpers for the Solaris debug macros above
+ */
+extern int spl_PANIC(char *filename, const char *functionname,
+	int lineno, const char *fmt, ...);
+
 /*
  * Compile-time assertion. The condition 'x' must be constant.
  */
diff --git a/module/spl/spl-err.c b/module/spl/spl-err.c
index b6d15f0191..2706f9bd13 100644
--- a/module/spl/spl-err.c
+++ b/module/spl/spl-err.c
@@ -39,6 +39,27 @@ static char ce_prefix[CE_IGNORE][10] = { "", "NOTICE: ", "WARNING: ", "" };
 static char ce_suffix[CE_IGNORE][2] = { "", "\n", "\n", "" };
 #endif
 
+int
+spl_PANIC(char *filename, const char *functionname,
+    int lineno, const char *fmt, ...) {
+	char msg[MAXMSGLEN];
+	va_list ap;
+
+	va_start(ap, fmt);
+	if (vsnprintf(msg, sizeof (msg), fmt, ap) == sizeof (msg))
+		msg[sizeof (msg) - 1] = '\0';
+	va_end(ap);
+#ifdef NDEBUG
+	printk(KERN_EMERG "%s", msg);
+#else
+	spl_debug_msg(NULL, 0, 0,
+	     filename, functionname, lineno, "%s", msg);
+#endif
+	spl_debug_bug(filename, functionname, lineno, 0);
+	return 1;
+}
+EXPORT_SYMBOL(spl_PANIC);
+
 void
 vpanic(const char *fmt, va_list ap)
 {