linux-kernel - [PATCH 2/2] overflow, tracing: Define the is_signed

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Date:   Fri, 26 Aug 2022 09:21:16 -0700
From:   Bart Van Assche <bvanassche@....org>
To:     Kees Cook <keescook@...omium.org>
Cc:     linux-kernel@...r.kernel.org, Bart Van Assche <bvanassche@....org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Arnd Bergmann <arnd@...db.de>,
        Dan Williams <dan.j.williams@...el.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Ingo Molnar <mingo@...hat.com>,
        Isabella Basso <isabbasso@...eup.net>,
        "Jason A. Donenfeld" <Jason@...c4.com>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Luc Van Oostenryck <luc.vanoostenryck@...il.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Sander Vanheule <sander@...nheule.net>,
        Steven Rostedt <rostedt@...dmis.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Yury Norov <yury.norov@...il.com>
Subject: [PATCH 2/2] overflow, tracing: Define the is_signed_type() macro once

There are two definitions of the is_signed_type() macro: one in
<linux/overflow.h> and a second definition in <linux/trace_events.h>.

As suggested by Linus Torvalds, move the definition of the
is_signed_type() macro into the <linux/compiler.h> header file. Change
the definition of the is_signed_type() macro to make sure that it does
not trigger any sparse warnings with future versions of sparse for
bitwise types. See also:
https://lore.kernel.org/all/CAHk-=whjH6p+qzwUdx5SOVVHjS3WvzJQr6mDUwhEyTf6pJWzaQ@mail.gmail.com/
https://lore.kernel.org/all/CAHk-=wjQGnVfb4jehFR0XyZikdQvCZouE96xR_nnf5kqaM5qqQ@mail.gmail.com/

Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Arnd Bergmann <arnd@...db.de>
Cc: Dan Williams <dan.j.williams@...el.com>
Cc: Eric Dumazet <edumazet@...gle.com>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Isabella Basso <isabbasso@...eup.net>
Cc: "Jason A. Donenfeld" <Jason@...c4.com>
Cc: Josh Poimboeuf <jpoimboe@...nel.org>
Cc: Luc Van Oostenryck <luc.vanoostenryck@...il.com>
Cc: Masami Hiramatsu <mhiramat@...nel.org>
Cc: Nathan Chancellor <nathan@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Rasmus Villemoes <linux@...musvillemoes.dk>
Cc: Sander Vanheule <sander@...nheule.net>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Vlastimil Babka <vbabka@...e.cz>
Cc: Yury Norov <yury.norov@...il.com>
Signed-off-by: Bart Van Assche <bvanassche@....org>
---
 include/linux/compiler.h     | 6 ++++++
 include/linux/overflow.h     | 1 -
 include/linux/trace_events.h | 2 --
 3 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 01ce94b58b42..7713d7bcdaea 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -239,6 +239,12 @@ static inline void *offset_to_ptr(const int *off)
 /* &a[0] degrades to a pointer: a different type from an array */
 #define __must_be_array(a)	BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))
 
+/*
+ * Whether 'type' is a signed type or an unsigned type. Supports scalar types,
+ * bool and also pointer types.
+ */
+#define is_signed_type(type) (((type)(-1)) < (__force type)1)
+
 /*
  * This is needed in functions which generate the stack canary, see
  * arch/x86/kernel/smpboot.c::start_secondary() for an example.
diff --git a/include/linux/overflow.h b/include/linux/overflow.h
index f1221d11f8e5..0eb3b192f07a 100644
--- a/include/linux/overflow.h
+++ b/include/linux/overflow.h
@@ -30,7 +30,6 @@
  * https://mail-index.netbsd.org/tech-misc/2007/02/05/0000.html -
  * credit to Christian Biere.
  */
-#define is_signed_type(type)       (((type)(-1)) < (type)1)
 #define __type_half_max(type) ((type)1 << (8*sizeof(type) - 1 - is_signed_type(type)))
 #define type_max(T) ((T)((__type_half_max(T) - 1) + __type_half_max(T)))
 #define type_min(T) ((T)((T)-type_max(T)-(T)1))
diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h
index b18759a673c6..8401dec93c15 100644
--- a/include/linux/trace_events.h
+++ b/include/linux/trace_events.h
@@ -814,8 +814,6 @@ extern int trace_add_event_call(struct trace_event_call *call);
 extern int trace_remove_event_call(struct trace_event_call *call);
 extern int trace_event_get_offsets(struct trace_event_call *call);
 
-#define is_signed_type(type)	(((type)(-1)) < (type)1)
-
 int ftrace_set_clr_event(struct trace_array *tr, char *buf, int set);
 int trace_set_clr_event(const char *system, const char *event, int set);
 int trace_array_set_clr_event(struct trace_array *tr, const char *system,