Re: [XEN PATCH for-4.19] xen/bitmap: amend MISRA C deviation for Rule 20.7

Tue, 09 Jul 2024 03:16:20 -0700 

On 2024-07-09 11:40, Jan Beulich wrote:

On 09.07.2024 11:34, Nicola Vetrini wrote:

As noticed in the gitlab analyses, deviating bitmap_switch
for Rule 20.7 in this way does not work for ECLAIR.

Instead, the deviation should be put in the macro invocation.


Why is this? I ask in particular because ...


--- a/xen/include/xen/bitmap.h
+++ b/xen/include/xen/bitmap.h
@@ -103,18 +103,16 @@ extern int bitmap_allocate_region(unsigned long *bitmap, int pos, int order); 
 #define bitmap_switch(nbits, zero, small, large)                         \
        unsigned int n__ = (nbits);                                       \
        if (__builtin_constant_p(nbits) && !n__) {                        \
-               /* SAF-7-safe Rule 20.7 non-parenthesized macro argument */ \
                zero;                                                     \
        } else if (__builtin_constant_p(nbits) && n__ <= BITS_PER_LONG) { \
-               /* SAF-7-safe Rule 20.7 non-parenthesized macro argument */ \
                small;                                                    \
        } else {                                                          \
-               /* SAF-7-safe Rule 20.7 non-parenthesized macro argument */ \
                large;                                                    \
        }
static inline void bitmap_zero(unsigned long *dst, unsigned int nbits) 
 {
+       /* SAF-7-safe Rule 20.7 non-parenthesized macro argument */
        bitmap_switch(nbits,,
                *dst = 0UL,
                memset(dst, 0, bitmap_bytes(nbits)));
@@ -139,6 +137,7 @@ static inline void bitmap_fill(unsigned long *dst, unsigned int nbits) static inline void bitmap_copy(unsigned long *dst, const unsigned long *src, 
                        unsigned int nbits)
 {
+        /* SAF-7-safe Rule 20.7 non-parenthesized macro argument */
        bitmap_switch(nbits,,
                *dst = *src,
                memcpy(dst, src, bitmap_bytes(nbits)));
@@ -147,6 +146,7 @@ static inline void bitmap_copy(unsigned long *dst, const unsigned long *src, static inline void bitmap_and(unsigned long *dst, const unsigned long *src1, 
                        const unsigned long *src2, unsigned int nbits)
 {
+       /* SAF-7-safe Rule 20.7 non-parenthesized macro argument */
        bitmap_switch(nbits,,
                *dst = *src1 & *src2,
                __bitmap_and(dst, src1, src2, nbits));
@@ -155,6 +155,7 @@ static inline void bitmap_and(unsigned long *dst, const unsigned long *src1, static inline void bitmap_or(unsigned long *dst, const unsigned long *src1, 
                        const unsigned long *src2, unsigned int nbits)
 {
+       /* SAF-7-safe Rule 20.7 non-parenthesized macro argument */
        bitmap_switch(nbits,,
                *dst = *src1 | *src2,
                __bitmap_or(dst, src1, src2, nbits));
@@ -163,6 +164,7 @@ static inline void bitmap_or(unsigned long *dst, const unsigned long *src1, static inline void bitmap_xor(unsigned long *dst, const unsigned long *src1, 
                        const unsigned long *src2, unsigned int nbits)
 {
+       /* SAF-7-safe Rule 20.7 non-parenthesized macro argument */
        bitmap_switch(nbits,,
                *dst = *src1 ^ *src2,
                __bitmap_xor(dst, src1, src2, nbits));
@@ -171,6 +173,7 @@ static inline void bitmap_xor(unsigned long *dst, const unsigned long *src1, static inline void bitmap_andnot(unsigned long *dst, const unsigned long *src1, 
                        const unsigned long *src2, unsigned int nbits)
 {
+       /* SAF-7-safe Rule 20.7 non-parenthesized macro argument */
        bitmap_switch(nbits,,
                *dst = *src1 & ~*src2,
                __bitmap_andnot(dst, src1, src2, nbits));
@@ -179,6 +182,7 @@ static inline void bitmap_andnot(unsigned long *dst, const unsigned long *src1, static inline void bitmap_complement(unsigned long *dst, const unsigned long *src, 
                        unsigned int nbits)
 {
+       /* SAF-7-safe Rule 20.7 non-parenthesized macro argument */
        bitmap_switch(nbits,,
                *dst = ~*src & BITMAP_LAST_WORD_MASK(nbits),
                __bitmap_complement(dst, src, nbits));
@@ -187,6 +191,7 @@ static inline void bitmap_complement(unsigned long *dst, const unsigned long *sr 
 static inline int bitmap_equal(const unsigned long *src1,
                        const unsigned long *src2, unsigned int nbits)
 {
+       /* SAF-7-safe Rule 20.7 non-parenthesized macro argument */
        bitmap_switch(nbits,
                return -1,
                return !((*src1 ^ *src2) & BITMAP_LAST_WORD_MASK(nbits)),
@@ -196,6 +201,7 @@ static inline int bitmap_equal(const unsigned long *src1, 
 static inline int bitmap_intersects(const unsigned long *src1,
                        const unsigned long *src2, unsigned int nbits)
 {
+       /* SAF-7-safe Rule 20.7 non-parenthesized macro argument */
        bitmap_switch(nbits,
                return -1,
                return ((*src1 & *src2) & BITMAP_LAST_WORD_MASK(nbits)) != 0,
@@ -205,6 +211,7 @@ static inline int bitmap_intersects(const unsigned long *src1, 
 static inline int bitmap_subset(const unsigned long *src1,
                        const unsigned long *src2, unsigned int nbits)
 {
+       /* SAF-7-safe Rule 20.7 non-parenthesized macro argument */
        bitmap_switch(nbits,
                return -1,
                return !((*src1 & ~*src2) & BITMAP_LAST_WORD_MASK(nbits)),
@@ -213,6 +220,7 @@ static inline int bitmap_subset(const unsigned long *src1,
static inline int bitmap_empty(const unsigned long *src, unsigned int nbits) 
 {
+       /* SAF-7-safe Rule 20.7 non-parenthesized macro argument */
        bitmap_switch(nbits,
                return -1,
                return !(*src & BITMAP_LAST_WORD_MASK(nbits)),
@@ -221,6 +229,7 @@ static inline int bitmap_empty(const unsigned long *src, unsigned int nbits)
static inline int bitmap_full(const unsigned long *src, unsigned int nbits) 
 {
+       /* SAF-7-safe Rule 20.7 non-parenthesized macro argument */
        bitmap_switch(nbits,
                return -1,
                return !(~*src & BITMAP_LAST_WORD_MASK(nbits)),
... having the same comment on every invocation is naturally quite a bit 
less desirable. So far I was under the impression that macro-specific
deviations can be dealt with by marking the macro definition accordingly. 

Not with a comment-based one, but one based on ECL.
As stated under the cut:
An alternative approach would be to use an ecl configuration, but that
would be tool-specific.
Stefano had a preference for a tool-agnostic SAF comment, so that's what I used. 


I've been assuming this is a general pattern. If it isn't, would you
please first clarify what Eclair's specific requirements are for a SAF
marker to take effect when involving a macro?
it should be put directly above macro invocations. ECLAIR has a tool-specific comment-based deviation that essentially deviates a range of lines, but that is not supported by the SAF framework, so I avoided that.
Is it safe to say that the uses of bitmap_switch will likely not change much over time? 

Thanks,

--
Nicola Vetrini, BSc
Software Engineer, BUGSENG srl (https://bugseng.com)

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