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Subject[PATCH 2/7] Add assertion checking macros
Date
Add a range of ASSERT* macros to linux/assert.h for performing runtime
assertions. These will use assertion_failure() to cause an annotated oops if
the check fails.

The checks are only enabled under two circumstances:

(1) CONFIG_DEBUG_ENABLE_ASSERTIONS=y

(2) ENABLE_ASSERTIONS is defined prior to the #inclusion of <linux/assert.h>

There are five macros provided:

(a) ASSERT(X)

Issue an assertion failure error if X is false. In other words, require
the expression X to be true. For example:

ASSERT(val != 0);

There is no need to display val here in the case the expression fails
since it can only be 0. If this fails, it produces an error like the
following:

------------[ cut here ]------------
ASSERTION FAILED at fs/fscache/main.c:109!
invalid opcode: 0000 [#1] SMP

(b) ASSERTCMP(X, OP, Y)

Issue an assertion failure error if the expression X OP Y is false. For
example:

ASSERTCMP(x, >, 12)


If an oops is produced, then the values of X and Y will be displayed in
hex, along with OP:

------------[ cut here ]------------
ASSERTION FAILED at fs/fscache/main.c:109!
Check 2 > c is false
invalid opcode: 0000 [#1] SMP

(c) ASSERTRANGE(X, OP, Y, OP2, Z)

Issue an assertion failure error if the expression X OP Y or if the
expression Y OP2 Z is false. Typically OP and OP2 would be < or <=,
looking something like:

ASSERTRANGE(11, <, x, <=, 13);

and giving the following error:

------------[ cut here ]------------
ASSERTION FAILED at fs/fscache/main.c:109!
Check b < 2 <= d is false
invalid opcode: 0000 [#1] SMP

and for compactness, where an assertion should only apply under certain
circumstances:

(d) ASSERTIF(C, X)

If condition C is true, issue an assertion failure error if X is false.
For example:

ASSERTIF(test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags),
object->n_exclusive != 0);

(e) ASSERTIFCMP(C, X, OP, Y)

This is a combination of ASSERTIF and ASSERTCMP. For example:

ASSERTIFCMP(test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags),
object->n_exclusive, >, 0);

Signed-off-by: David Howells <dhowells@redhat.com>
---

include/linux/assert.h | 94 ++++++++++++++++++++++++++++++++++++++++++++++++
lib/Kconfig.debug | 8 ++++
2 files changed, 102 insertions(+), 0 deletions(-)

diff --git a/include/linux/assert.h b/include/linux/assert.h
index 739ebf7..a65d1a8 100644
--- a/include/linux/assert.h
+++ b/include/linux/assert.h
@@ -33,4 +33,98 @@ void do_assertion_failed(const char *file, int line, const char *fmt, ...)
do_assertion_failed(__FILE__, __LINE__, FMT, ## __VA_ARGS__); \
} while (0)

+/*
+ * ENABLE_ASSERTIONS can be set by an individual module to override the global
+ * setting and turn assertions on for just that module.
+ */
+#if defined(CONFIG_DEBUG_ENABLE_ASSERTIONS) || defined(ENABLE_ASSERTIONS)
+
+#define cond_assertion_failed(FMT, ...) \
+ do { \
+ do_assertion_failed(__FILE__, __LINE__, FMT, ## __VA_ARGS__); \
+ } while (0)
+
+#else
+
+#define cond_assertion_failed(FMT, ...) \
+ do { \
+ no_printk(FMT, ## __VA_ARGS__); \
+ } while (0)
+
+#endif
+
+/**
+ * ASSERT - Oops if the given expression is not true
+ * X: The expression to check
+ */
+#define ASSERT(X) \
+do { \
+ if (unlikely(!(X))) \
+ cond_assertion_failed(NULL); \
+} while (0)
+
+/**
+ * ASSERTCMP - Oops if the specified check fails
+ * X: The value to check
+ * OP: The operator to use for comparison
+ * Y: The value to compare against
+ *
+ * The two values are displayed in the oops report if the assertion fails.
+ */
+#define ASSERTCMP(X, OP, Y) \
+do { \
+ if (unlikely(!((X) OP (Y)))) \
+ cond_assertion_failed("Check %lx " #OP " %lx is false\n", \
+ (unsigned long)(X), \
+ (unsigned long)(Y)); \
+} while (0)
+
+/**
+ * ASSERTIF - If condition is true, oops if the given expression is not true
+ * C: The condition under which to perform the check
+ * X: The expression to check
+ */
+#define ASSERTIF(C, X) \
+do { \
+ if (unlikely((C) && !(X))) \
+ cond_assertion_failed(NULL); \
+} while (0)
+
+/**
+ * ASSERTIFCMP - If condition is true, oops if the specified check fails
+ * C: The condition under which to perform the check
+ * X: The value to check
+ * OP: The operator to use for comparison
+ * Y: The value to compare against
+ *
+ * The two values are displayed in the oops report if the assertion fails.
+ */
+#define ASSERTIFCMP(C, X, OP, Y) \
+do { \
+ if (unlikely((C) && !((X) OP (Y)))) \
+ cond_assertion_failed("Check %lx " #OP " %lx is false\n", \
+ (unsigned long)(X), \
+ (unsigned long)(Y)); \
+} while (0)
+
+/**
+ * ASSERTCMP - Oops if the value is outside of the specified range
+ * X: The lower bound
+ * OP: The operator to use to check against the lower bound (< or <=)
+ * Y: The value to check
+ * OP2: The operator to use to check against the upper bound (< or <=)
+ * Z: The upper bound
+ *
+ * The three values are displayed in the oops report if the assertion fails.
+ */
+#define ASSERTRANGE(X, OP, Y, OP2, Z) \
+do { \
+ if (unlikely(!((X) OP (Y)) || !((Y) OP2 (Z)))) \
+ cond_assertion_failed("Check %lx " #OP " %lx " #OP2 \
+ " %lx is false\n", \
+ (unsigned long)(X), \
+ (unsigned long)(Y), \
+ (unsigned long)(Z)); \
+} while(0)
+
#endif /* _LINUX_ASSERT_H */
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index c0cb9c4..604eede9 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -149,6 +149,14 @@ config DEBUG_KERNEL
Say Y here if you are developing drivers or trying to debug and
identify kernel problems.

+config DEBUG_ENABLE_ASSERTIONS
+ bool "Enable assertion checks"
+ depends on BUG
+ help
+ Say Y here to globally enable checks made by the ASSERT*() macros.
+ If such a check fails, BUG() processing will be invoked and an
+ annotated oops will be emitted.
+
config DEBUG_SHIRQ
bool "Debug shared IRQ handlers"
depends on DEBUG_KERNEL && GENERIC_HARDIRQS


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