Reduce false positives from Static Analyzers

Both Clang's Static Analyzer and Synopsys' Coverity would ignore
assertions. Following Clang's advice, we annotate our assertions:

https://clang-analyzer.llvm.org/annotations.html#custom_assertions

This makes both Clang's Static Analyzer and Coverity properly identify
assertions. This change reduced Clang's reported defects from 246 to
180. It also reduced the false positives reported by Coverityi by 10,
while enabling Coverity to find 9 more defects that previously were
false negatives.

A couple examples of this would be CID-1524417 and CID-1524423. After
submitting a build to coverity with the modified assertions, CID-1524417
disappeared while the report for CID-1524423 no longer claimed that the
assertion tripped.

Coincidentally, it turns out that it is possible to more accurately
annotate our headers than the Coverity modelling file permits in the
case of format strings. Since we can do that and this patch annotates
headers whenever `__coverity_panic__()` would have been used in the
model file, we drop all models that use `__coverity_panic__()` from the
model file.

Upon seeing the success in eliminating false positives involving
assertions, it occurred to me that we could also modify our headers to
eliminate coverity's false positives involving byte swaps. We now have
coverity specific byteswap macros, that do nothing, to disable
Coverity's false positives when we do byte swaps. This allowed us to
also drop the byteswap definitions from the model file.

Lastly, a model file update has been done beyond the mentioned
deletions:

 * The definitions of `umem_alloc_aligned()`, `umem_alloc()` andi
   `umem_zalloc()` were originally implemented in a way that was
   intended to inform coverity that when KM_SLEEP has been passed these
   functions, they do not return NULL. A small error in how this was
   done was found, so we correct it.

 * Definitions for umem_cache_alloc() and umem_cache_free() have been
   added.

In practice, no false positives were avoided by making these changes,
but in the interest of correctness from future coverity builds, we make
them anyway.

Reviewed-by: Brian Behlendorf <[email protected]>
Reviewed-by: Ryan Moeller <[email protected]>
Signed-off-by: Richard Yao <[email protected]>
Closes #13902 

1 files changed, 29 insertions, 92 deletions

diff --git a/contrib/coverity/model.c b/contrib/coverity/model.c
index d27abd038..8baa3a7e2 100644
--- a/contrib/coverity/model.c
+++ b/contrib/coverity/model.c
@@ -31,66 +31,6 @@
 
 int condition0, condition1;
 
-void
-abort()
-{
-	__coverity_panic__();
-}
-
-void
-exit(int status)
-{
-	(void) status;
-
-	__coverity_panic__();
-}
-
-void
-_exit(int status)
-{
-	(void) status;
-
-	__coverity_panic__();
-}
-
-void
-zed_log_die(const char *fmt, ...)
-{
-	__coverity_format_string_sink__(fmt);
-	__coverity_panic__();
-}
-
-void
-panic(const char *fmt, ...)
-{
-	__coverity_format_string_sink__(fmt);
-	__coverity_panic__();
-}
-
-void
-vpanic(const char *fmt, va_list adx)
-{
-	(void) adx;
-
-	__coverity_format_string_sink__(fmt);
-	__coverity_panic__();
-}
-
-void
-uu_panic(const char *format, ...)
-{
-	__coverity_format_string_sink__(format);
-	__coverity_panic__();
-}
-
-int
-libspl_assertf(const char *file, const char *func, int line,
-    const char *format, ...)
-{
-	__coverity_format_string_sink__(format);
-	__coverity_panic__();
-}
-
 int
 ddi_copyin(const void *from, void *to, size_t len, int flags)
 {
@@ -125,7 +65,7 @@ umem_alloc_aligned(size_t size, size_t align, int kmflags)
 {
 	(void) align;
 
-	if (UMEM_NOFAIL & kmflags == UMEM_NOFAIL)
+	if ((UMEM_NOFAIL & kmflags) == UMEM_NOFAIL)
 		return (__coverity_alloc__(size));
 	else if (condition0)
 		return (__coverity_alloc__(size));
@@ -136,7 +76,7 @@ umem_alloc_aligned(size_t size, size_t align, int kmflags)
 void *
 umem_alloc(size_t size, int kmflags)
 {
-	if (UMEM_NOFAIL & kmflags == UMEM_NOFAIL)
+	if ((UMEM_NOFAIL & kmflags) == UMEM_NOFAIL)
 		return (__coverity_alloc__(size));
 	else if (condition0)
 		return (__coverity_alloc__(size));
@@ -147,7 +87,7 @@ umem_alloc(size_t size, int kmflags)
 void *
 umem_zalloc(size_t size, int kmflags)
 {
-	if (UMEM_NOFAIL & kmflags == UMEM_NOFAIL)
+	if ((UMEM_NOFAIL & kmflags) == UMEM_NOFAIL)
 		return (__coverity_alloc__(size));
 	else if (condition0)
 		return (__coverity_alloc__(size));
@@ -163,6 +103,32 @@ umem_free(void *buf, size_t size)
 	__coverity_free__(buf);
 }
 
+typedef struct {} umem_cache_t;
+
+void *
+umem_cache_alloc(umem_cache_t *skc, int flags)
+{
+	(void) skc;
+
+	if (condition1)
+		__coverity_sleep__();
+
+	if ((UMEM_NOFAIL & flags) == UMEM_NOFAIL)
+		return (__coverity_alloc_nosize__());
+	else if (condition0)
+		return (__coverity_alloc_nosize__());
+	else
+		return (NULL);
+}
+
+void
+umem_cache_free(umem_cache_t *skc, void *obj)
+{
+	(void) skc;
+
+	__coverity_free__(obj);
+}
+
 void *
 spl_kmem_alloc(size_t sz, int fl, const char *func, int line)
 {
@@ -244,13 +210,6 @@ free(void *buf)
 }
 
 int
-spl_panic(const char *file, const char *func, int line, const char *fmt, ...)
-{
-	__coverity_format_string_sink__(fmt);
-	__coverity_panic__();
-}
-
-int
 sched_yield(void)
 {
 	__coverity_sleep__();
@@ -398,25 +357,3 @@ __cond_resched(void)
 		__coverity_sleep__();
 	}
 }
-
-/*
- * An endian-independent filesystem must support doing byte swaps on data. We
- * attempt to suppress taint warnings, which are false positives for us.
- */
-void
-byteswap_uint64_array(void *vbuf, size_t size)
-{
-	__coverity_tainted_data_sanitize__(vbuf);
-}
-
-void
-byteswap_uint32_array(void *vbuf, size_t size)
-{
-	__coverity_tainted_data_sanitize__(vbuf);
-}
-
-void
-byteswap_uint16_array(void *vbuf, size_t size)
-{
-	__coverity_tainted_data_sanitize__(vbuf);
-}