linux-kernel - [PATCH] kcov: add prototypes for helper functions

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Date:   Wed, 17 May 2023 14:49:25 +0200
From:   Arnd Bergmann <arnd@...nel.org>
To:     kasan-dev@...glegroups.com
Cc:     Arnd Bergmann <arnd@...db.de>, Dmitry Vyukov <dvyukov@...gle.com>,
        Andrey Konovalov <andreyknvl@...il.com>,
        Rong Tao <rongtao@...tc.cn>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] kcov: add prototypes for helper functions

From: Arnd Bergmann <arnd@...db.de>

A number of internal functions in kcov are only called from
generated code and don't technically need a declaration, but
'make W=1' warns about global symbols without a prototype:

kernel/kcov.c:199:14: error: no previous prototype for '__sanitizer_cov_trace_pc' [-Werror=missing-prototypes]
kernel/kcov.c:264:14: error: no previous prototype for '__sanitizer_cov_trace_cmp1' [-Werror=missing-prototypes]
kernel/kcov.c:270:14: error: no previous prototype for '__sanitizer_cov_trace_cmp2' [-Werror=missing-prototypes]
kernel/kcov.c:276:14: error: no previous prototype for '__sanitizer_cov_trace_cmp4' [-Werror=missing-prototypes]
kernel/kcov.c:282:14: error: no previous prototype for '__sanitizer_cov_trace_cmp8' [-Werror=missing-prototypes]
kernel/kcov.c:288:14: error: no previous prototype for '__sanitizer_cov_trace_const_cmp1' [-Werror=missing-prototypes]
kernel/kcov.c:295:14: error: no previous prototype for '__sanitizer_cov_trace_const_cmp2' [-Werror=missing-prototypes]
kernel/kcov.c:302:14: error: no previous prototype for '__sanitizer_cov_trace_const_cmp4' [-Werror=missing-prototypes]
kernel/kcov.c:309:14: error: no previous prototype for '__sanitizer_cov_trace_const_cmp8' [-Werror=missing-prototypes]
kernel/kcov.c:316:14: error: no previous prototype for '__sanitizer_cov_trace_switch' [-Werror=missing-prototypes]

Adding prototypes for these in a header solves that problem, but now
there is a mismatch between the built-in type and the prototype on
64-bit architectures because they expect some functions to take
a 64-bit 'unsigned long' argument rather than an 'unsigned long long'
u64 type:

include/linux/kcov.h:84:6: error: conflicting types for built-in function '__sanitizer_cov_trace_switch'; expected 'void(long long unsigned int,  void *)' [-Werror=builtin-declaration-mismatch]
   84 | void __sanitizer_cov_trace_switch(u64 val, u64 *cases);
      |      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~

Avoid this as well with a custom type definition.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 include/linux/kcov.h | 17 +++++++++++++++++
 kernel/kcov.c        |  7 ++++---
 2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/include/linux/kcov.h b/include/linux/kcov.h
index ee04256f28af..b851ba415e03 100644
--- a/include/linux/kcov.h
+++ b/include/linux/kcov.h
@@ -72,6 +72,23 @@ static inline void kcov_remote_stop_softirq(void)
 		kcov_remote_stop();
 }
 
+#ifdef CONFIG_64BIT
+typedef unsigned long kcov_u64;
+#else
+typedef unsigned long long kcov_u64;
+#endif
+
+void __sanitizer_cov_trace_pc(void);
+void __sanitizer_cov_trace_cmp1(u8 arg1, u8 arg2);
+void __sanitizer_cov_trace_cmp2(u16 arg1, u16 arg2);
+void __sanitizer_cov_trace_cmp4(u32 arg1, u32 arg2);
+void __sanitizer_cov_trace_cmp8(kcov_u64 arg1, kcov_u64 arg2);
+void __sanitizer_cov_trace_const_cmp1(u8 arg1, u8 arg2);
+void __sanitizer_cov_trace_const_cmp2(u16 arg1, u16 arg2);
+void __sanitizer_cov_trace_const_cmp4(u32 arg1, u32 arg2);
+void __sanitizer_cov_trace_const_cmp8(kcov_u64 arg1, kcov_u64 arg2);
+void __sanitizer_cov_trace_switch(kcov_u64 val, void *cases);
+
 #else
 
 static inline void kcov_task_init(struct task_struct *t) {}
diff --git a/kernel/kcov.c b/kernel/kcov.c
index ddcf4f3ca9c9..c3124f6d5536 100644
--- a/kernel/kcov.c
+++ b/kernel/kcov.c
@@ -279,7 +279,7 @@ void notrace __sanitizer_cov_trace_cmp4(u32 arg1, u32 arg2)
 }
 EXPORT_SYMBOL(__sanitizer_cov_trace_cmp4);
 
-void notrace __sanitizer_cov_trace_cmp8(u64 arg1, u64 arg2)
+void notrace __sanitizer_cov_trace_cmp8(kcov_u64 arg1, kcov_u64 arg2)
 {
 	write_comp_data(KCOV_CMP_SIZE(3), arg1, arg2, _RET_IP_);
 }
@@ -306,16 +306,17 @@ void notrace __sanitizer_cov_trace_const_cmp4(u32 arg1, u32 arg2)
 }
 EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp4);
 
-void notrace __sanitizer_cov_trace_const_cmp8(u64 arg1, u64 arg2)
+void notrace __sanitizer_cov_trace_const_cmp8(kcov_u64 arg1, kcov_u64 arg2)
 {
 	write_comp_data(KCOV_CMP_SIZE(3) | KCOV_CMP_CONST, arg1, arg2,
 			_RET_IP_);
 }
 EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp8);
 
-void notrace __sanitizer_cov_trace_switch(u64 val, u64 *cases)
+void notrace __sanitizer_cov_trace_switch(kcov_u64 val, void *arg)
 {
 	u64 i;
+	u64 *cases = arg;
 	u64 count = cases[0];
 	u64 size = cases[1];
 	u64 type = KCOV_CMP_CONST;
-- 
2.39.2