Report for unitialized variable warning

Clang/Reports/Report_0001.md

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+# Warning Analysis Report
+
+### General
+
+**_Warning Type:_** -Wunused-parameter<br/>
+**_Warning Explanation:_**
+
+> In file included from ./include/linux/compiler.h:246:<br/>
+ ./include/linux/kasan-checks.h:9:58: warning: unused parameter 'p' [-Wunused-parameter]<br/>
+ static inline void kasan_check_read(const volatile void *p, unsigned int size)<br/>
+ ./include/linux/kasan-checks.h:9:74: warning: unused parameter 'size' [-Wunused-parameter]<br/>
+ static inline void kasan_check_read(const volatile void *p, unsigned int size)<br/>
+ ./include/linux/kasan-checks.h:11:59: warning: unused parameter 'p' [-Wunused-parameter]<br/>
+ static inline void kasan_check_write(const volatile void *p, unsigned int size)<br/>
+ ./include/linux/kasan-checks.h:11:75: warning: unused parameter 'size' [-Wunused-parameter]<br/>
+ static inline void kasan_check_write(const volatile void *p, unsigned int size)<br/>
+
+### History
+
+**_Introduced in version:_** v4.7-rc1<br/>
+**_Date:_** 2016-05-20<br/>
+**_Author:_** Andrey Ryabinin<br/>
+**_Patch:_**
+https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=64f8ebaf115bcddc4aaa902f981c57ba6506bc42
+
+#### Recent Changes
+
+**_Date:_** 2017-06-22<br/>
+**_Author:_** Dmitry Vyukov<br/>
+**_Patch:_** https://patchwork.kernel.org/patch/9768477/
+
+### Warning Assessment
+
+**_File Location:_** include/linux/kasan-checks.h
+
+```
+#ifdef CONFIG_KASAN
+void kasan_check_read(const volatile void *p, unsigned int size);
+void kasan_check_write(const volatile void *p, unsigned int size);
+#else
+static inline void kasan_check_read(const volatile void *p, unsigned int size)
+{ }
+static inline void kasan_check_write(const volatile void *p, unsigned int size)
+{ }
+#endif
+```
+
+### Conclusion
+
+Warning is true but the functions kasan_check_{read, write} were
+purposefully made empty. So, ignore this warning.
+
+### Observations
+
+I checked few other warnings of the same type. If the file is located in
+include directory, then most of them needs to be ignored due to one of
+the following reasons:
+
+1. If some macro is not defined then empty function with parameter is used.<br/>
+   The function is made purposefully empty as there are non empty functions<br/>
+   used when the macro is defined.
+
+Example Warnings:
+
+> In file included from ./include/linux/kernel.h:14:<br/>
+ ./include/linux/printk.h:519:53: warning: unused parameter 'prefix_str' [-Wunused-parameter]<br/>
+ static inline void print_hex_dump_debug(const char *prefix_str, int prefix_type,<br/>
+ ./include/linux/printk.h:519:69: warning: unused parameter 'prefix_type' [-Wunused-parameter]<br/>
+ static inline void print_hex_dump_debug(const char *prefix_str, int prefix_type,<br/>
+ ./include/linux/printk.h:520:10: warning: unused parameter 'rowsize' [-Wunused-parameter]<br/>
+                                        int rowsize, int groupsize,<br/>
+ ./include/linux/printk.h:520:23: warning: unused parameter 'groupsize' [-Wunused-parameter]<br/>
+                                        int rowsize, int groupsize,<br/>
+ ./include/linux/printk.h:521:18: warning: unused parameter 'buf' [-Wunused-parameter]<br/>
+                                        const void *buf, size_t len, bool ascii)<br/>
+ ./include/linux/printk.h:521:30: warning: unused parameter 'len' [-Wunused-parameter]<br/>
+                                        const void *buf, size_t len, bool ascii)<br/>
+ ./include/linux/printk.h:521:40: warning: unused parameter 'ascii' [-Wunused-parameter]<br/>
+                                        const void *buf, size_t len, bool ascii)
+
+Patch which introduced the above lines<br/>
+https://github.com/torvalds/linux/commit/cdf17449af1d9b596742c260134edd6c1fac2792
+
+> ./include/linux/kernel.h:230:49: warning: unused parameter 'file' [-Wunused-parameter]<br/>
+  static inline void ___might_sleep(const char *file, int line,<br/>
+ ./include/linux/kernel.h:230:59: warning: unused parameter 'line' [-Wunused-parameter]<br/>
+  static inline void ___might_sleep(const char *file, int line,<br/>
+./include/linux/kernel.h:231:12: warning: unused parameter 'preempt_offset' [-Wunused-parameter]<br/>
+                                   int preempt_offset) { }<br/>
+./include/linux/kernel.h:232:48: warning: unused parameter 'file' [-Wunused-parameter]<br/>
+  static inline void __might_sleep(const char *file, int line,<br/>
+ ./include/linux/kernel.h:232:58: warning: unused parameter 'line' [-Wunused-parameter]<br/>
+  static inline void __might_sleep(const char *file, int line,<br/>
+ ./include/linux/kernel.h:233:12: warning: unused parameter 'preempt_offset' [-Wunused-parameter]<br/>
+                                   int preempt_offset) { }<br/>
+
+> In file included from ./arch/x86/include/asm/string_64.h:6:<br/>
+./include/linux/jump_label.h:233:50: warning: unused parameter 'start' [-Wunused-parameter]<br/>
+static inline int jump_label_text_reserved(void *start, void *end)<br/>
+./include/linux/jump_label.h:233:63: warning: unused parameter 'end' [-Wunused-parameter]<br/>
+static inline int jump_label_text_reserved(void *start, void *end)<br/>
+
+```
+static inline int jump_label_text_reserved(void *start, void *end)
+{
+        return 0;
+}
+```
+
+> In file included from ./arch/x86/include/asm/string_64.h:6:<br/>
+./include/linux/jump_label.h:241:56: warning: unused parameter 'mod' [-Wunused-parameter]<br/>
+static inline int jump_label_apply_nops(struct module *mod)
+
+Patches which introduced the above lines<br/>
+https://github.com/torvalds/linux/commit/d430d3d7e646eb1eac2bb4aa244a644312e67c76<br/>
+https://github.com/torvalds/linux/commit/4c3ef6d79328c0e23ade60cbfc8d496123a6855c
+
+2. Empty functions to annotate something. This too is purposefully added.
+
+Example Warnings:
+
+> In file included from ./include/linux/spinlock_types.h:18:<br/>
+./include/linux/lockdep.h:475:49: warning: unused parameter 'force' [-Wunused-parameter]<br/>
+static inline void lockdep_invariant_state(bool force) {}<br/>
+
+Patch: https://github.com/torvalds/linux/commit/f52be5708076b75a045ac52c6fef3fffb8300525
+
+> In file included from ./include/linux/spinlock_types.h:18:<br/>
+./include/linux/lockdep.h:476:58: warning: unused parameter 'task' [-Wunused-parameter]<br/>
+static inline void lockdep_init_task(struct task_struct *task) {}<br/>
+>
+> In file included from ./include/linux/spinlock_types.h:18:<br/>
+./include/linux/lockdep.h:477:58: warning: unused parameter 'task' [-Wunused-parameter]<br/>
+static inline void lockdep_free_task(struct task_struct *task) {}<br/>
+
+Patch: https://github.com/torvalds/linux/commit/b09be676e0ff25bd6d2e7637e26d349f9109ad75
+
+> In file included from ./include/linux/spinlock_types.h:18:<br/>
+./include/linux/lockdep.h:622:36: warning: unused parameter 'file' [-Wunused-parameter]<br/>
+lockdep_rcu_suspicious(const char *file, const int line, const char *s)<br/>
+./include/linux/lockdep.h:622:52: warning: unused parameter 'line' [-Wunused-parameter]<br/>
+lockdep_rcu_suspicious(const char *file, const int line, const char *s)<br/>
+./include/linux/lockdep.h:622:70: warning: unused parameter 's' [-Wunused-parameter]<br/>
+lockdep_rcu_suspicious(const char *file, const int line, const char *s)<br/>
+
+Patch: https://github.com/torvalds/linux/commit/d24209bb689e2c7f7418faec9b4a948e922d24da
+
+3. Empty function will be updated in future.
+
+Example Warning:
+
+> In file included from ./arch/x86/include/asm/processor.h:19:<br/>
+./arch/x86/include/asm/pgtable_types.h:361:43: warning: unused parameter 'p4d' [-Wunused-parameter]<br/>
+static inline p4dval_t p4d_pfn_mask(p4d_t p4d)
+
+References<br/>
+https://lwn.net/Articles/708526/<br/>
+https://github.com/torvalds/linux/commit/fe1e8c3e9634071ac608172e29bf997596d17c7c<br/>
+
+There can be warnings of which are true and needs to be fixed but I did<br/>
+not find any till now.<br/>
+
+Also, there are warnings which are false positive, the parameters are<br/>
+used but clang did not understand their usage.<br/>
+
+Example Warning:
+
+> In file included from ./include/linux/compiler.h:246:<br/>
+./include/linux/kasan-checks.h:9:58: warning: unused parameter 'p' [-Wunused-parameter]<br/>
+static inline void kasan_check_read(const volatile void *p, unsigned int size)<br/>
+
+There is one more category of **legacy code**, the warning in this code needs to be<br/>
+ignored.<br/>
+
+Example Warning:
+```
+In file included from scripts/kconfig/conf.c:19:
+scripts/kconfig/lkc.h:158:56: warning: unused parameter 'ch' [-Wunused-parameter]
+static inline bool sym_set_choice_value(struct symbol *ch, struct symbol *chval)
+                                                       ^
+1 warning generated.
+  HOSTCC  scripts/kconfig/zconf.tab.o
+In file included from scripts/kconfig/zconf.tab.c:79:
+scripts/kconfig/lkc.h:158:56: warning: unused parameter 'ch' [-Wunused-parameter]
+static inline bool sym_set_choice_value(struct symbol *ch, struct symbol *chval)
+```
+
+Patch: https://github.com/torvalds/linux/commit/1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
+
+```
+In file included from scripts/kconfig/zconf.tab.c:2486:
+scripts/kconfig/expr.c:1282:63: warning: unused parameter 'sym' [-Wunused-parameter]
+static void expr_print_file_helper(void *data, struct symbol *sym, const char *str)
+                                                              ^
+
+scripts/kconfig/expr.c:1282:static void expr_print_file_helper(void *data, struct symbol *sym, const char *str)
+scripts/kconfig/expr.c:1289:    expr_print(e, expr_print_file_helper, out, E_NONE);
+```
+
+Patch: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ab45d190fd4acf0b0e5d307294ce24a90a69cc23
+
+Another category where knowingly the parameter is not used. 
+
+Example Warning:
+
+```
+scripts/mod/file2alias.c:909:40: warning: unused parameter 'filename' [-Wunused-parameter]
+static int do_virtio_entry(const char *filename, void *symval,
+                                       ^
+```
+
+Patch: https://lists.linuxfoundation.org/pipermail/virtualization/2007-September/008955.html

Clang/Reports/Report_0002.md

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+# Warning Analysis Report
+
+### General
+
+**Warning Type:** Wparentheses-equality<br/>
+**Warning Explanation:**
+```
+drivers/crypto/cavium/zip/zip_regs.h:820:15: warning: equality comparison with
+      extraneous parentheses [-Wparentheses-equality]
+        if (((param1 == 0)))
+              ~~~~~~~^~~~
+drivers/crypto/cavium/zip/zip_regs.h:820:15: note: remove extraneous parentheses
+      around the comparison to silence this warning
+        if (((param1 == 0)))
+            ~        ^    ~
+drivers/crypto/cavium/zip/zip_regs.h:820:15: note: use '=' to turn this equality
+      comparison into an assignment
+        if (((param1 == 0)))
+```
+### History
+
+**Date:** 2017-02-15<br/>
+**Version:** v4.12-rc1<br/>
+**Author:** Mahipal Challa<br/>
+Patch: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=640035a2dc5534b49cd64580e41874b71f131a1c
+
+### Warning Assessment
+
+**File Location:** drivers/crypto/cavium/zip/zip_regs.h
+```
+static inline u64 ZIP_MSIX_PBAX(u64 param1)
+{
+ if (((param1 == 0)))
+ return 0x0000838000FF0000ull;
+ pr_err("ZIP_MSIX_PBAX: %llu\n", param1);
+ return 0;
+}
+```
+The warning is true. There are few other places in the same file, where
+extra parentheses is used. One of them is in ZIP_MSIX_VECX_ADDR
+function.
+```
+static inline u64 ZIP_MSIX_VECX_ADDR(u64 param1)
+{
+ if (((param1 <= 17)))
+ return 0x0000838000F00000ull + (param1 & 31) * 0x10ull;
+ pr_err("ZIP_MSIX_VECX_ADDR: %llu\n", param1);
+ return 0;
+}
+```
+### Solution
+
+Use the following Coccinelle script to remove extra parentheses.
+```
+@@
+identifier i;
+constant c;
+expression e;
+@@
+(
+!((e))
+|
+-((
+\(i == c\|i != c\|i <= c\|i < c\|i >= c\|i > c\)
+-))
+)
+```
+### Accepted Patch
+Commit Id: 5b0aa2556<br/>
+Link: https://git.kernel.org/pub/scm/linux/kernel/git/herbert/cryptodev-2.6.git/commit/?id=5b0aa2556ec9ea98f98e2a802818f75827896d25
+

Clang/Reports/Report_0003.md

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+# Warning Analysis Report
+
+### General
+
+**Warning Type:** -Wsometimes-uninitialized
+
+**Warning Explanation:**
+```
+drivers/gpu/drm/i915/intel_pm.c:4670:6: warning: variable 'trans_min' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
+        if (INTEL_GEN(dev_priv) >= 10)
+            ^~~~~~~~~~~~~~~~~~~~~~~~~
+drivers/gpu/drm/i915/i915_drv.h:2535:29: note: expanded from macro 'INTEL_GEN'
+#define INTEL_GEN(dev_priv)     ((dev_priv)->info.gen)
+                                ^
+drivers/gpu/drm/i915/intel_pm.c:4673:19: note: uninitialized use occurs here
+        trans_offset_b = trans_min + trans_amount;
+                         ^~~~~~~~~
+drivers/gpu/drm/i915/intel_pm.c:4670:2: note: remove the 'if' if its condition is always true
+        if (INTEL_GEN(dev_priv) >= 10)
+        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+drivers/gpu/drm/i915/intel_pm.c:4655:20: note: initialize the variable 'trans_min' to silence this warning
+        uint16_t trans_min, trans_y_tile_min;
+                          ^
+                           = 0
+```
+### History
+
+**Introduced in version:** v4.15-rc1<br/>
+**Date:** 2017-08-17<br/>
+**Author:** Kumar, Mahesh<br/>
+**Patch:** https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ca47667f523e588318f89c735e127c256de6cb16
+
+### Warning Assessment
+
+**File Location:** drivers/gpu/drm/i915/intel_pm.c
+
+The variable trans_min is declared in the function<br/>
+skl_compute_transition_wm
+```
+        uint16_t trans_min, trans_y_tile_min;
+```
+This variable is initialized only if the following condition is true.
+```
+        if (INTEL_GEN(dev_priv) >= 10)
+                trans_min = 4;
+```
+The variable is used in two places, one within the if condition and <br/>
+other is outside the condition. The trans_offset_b can have garbage <br/>
+value if the trans_min is not initialized during declaration. <br/>
+```
+        trans_offset_b = trans_min + trans_amount;
+```
+### Conclusion
+
+Clang warning is true in this case.<br/>
+The variable needs to be initialised to zero.<br/>
+
+### Fixed By
+
+**Author:** Chris Wilson<br/>
+**Date:** 2017-11-15<br/>
+**Patch:** https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/gpu/drm/i915/intel_pm.c?id=be3fa66857051e2943960a06f8046e8445cdfe6e