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From:   Nathan Chancellor <natechancellor@gmail.com>
To:     Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc:     Florian Fainelli <f.fainelli@gmail.com>,
        John Crispin <john@phrozen.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        bcm-kernel-feedback-list@broadcom.com, linux-mips@vger.kernel.org,
        linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com,
        Nathan Chancellor <natechancellor@gmail.com>
Subject: [PATCH] MIPS: Use address-of operator on section symbols
Date:   Tue,  5 Jan 2021 13:18:27 -0700
Message-Id: <20210105201827.51766-1-natechancellor@gmail.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

When building xway_defconfig with clang:

arch/mips/lantiq/prom.c:82:23: error: array comparison always evaluates
to true [-Werror,-Wtautological-compare]
        else if (__dtb_start != __dtb_end)
                             ^
1 error generated.

These are not true arrays, they are linker defined symbols, which are
just addresses. Using the address of operator silences the warning
and does not change the resulting assembly with either clang/ld.lld
or gcc/ld (tested with diff + objdump -Dr). Do the same thing across
the entire MIPS subsystem to ensure there are no more warnings around
this type of comparison.

Link: https://github.com/ClangBuiltLinux/linux/issues/1232
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
---
 arch/mips/bmips/setup.c          | 2 +-
 arch/mips/lantiq/prom.c          | 2 +-
 arch/mips/pic32/pic32mzda/init.c | 2 +-
 arch/mips/ralink/of.c            | 2 +-
 4 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/mips/bmips/setup.c b/arch/mips/bmips/setup.c
index 19308df5f577..1b06b25aea87 100644
--- a/arch/mips/bmips/setup.c
+++ b/arch/mips/bmips/setup.c
@@ -167,7 +167,7 @@ void __init plat_mem_setup(void)
 		dtb = phys_to_virt(fw_arg2);
 	else if (fw_passed_dtb) /* UHI interface or appended dtb */
 		dtb = (void *)fw_passed_dtb;
-	else if (__dtb_start != __dtb_end)
+	else if (&__dtb_start != &__dtb_end)
 		dtb = (void *)__dtb_start;
 	else
 		panic("no dtb found");
diff --git a/arch/mips/lantiq/prom.c b/arch/mips/lantiq/prom.c
index 51a218f04fe0..3f568f5aae2d 100644
--- a/arch/mips/lantiq/prom.c
+++ b/arch/mips/lantiq/prom.c
@@ -79,7 +79,7 @@ void __init plat_mem_setup(void)
 
 	if (fw_passed_dtb) /* UHI interface */
 		dtb = (void *)fw_passed_dtb;
-	else if (__dtb_start != __dtb_end)
+	else if (&__dtb_start != &__dtb_end)
 		dtb = (void *)__dtb_start;
 	else
 		panic("no dtb found");
diff --git a/arch/mips/pic32/pic32mzda/init.c b/arch/mips/pic32/pic32mzda/init.c
index 50f376f058f4..f232c77ff526 100644
--- a/arch/mips/pic32/pic32mzda/init.c
+++ b/arch/mips/pic32/pic32mzda/init.c
@@ -28,7 +28,7 @@ static ulong get_fdtaddr(void)
 	if (fw_passed_dtb && !fw_arg2 && !fw_arg3)
 		return (ulong)fw_passed_dtb;
 
-	if (__dtb_start < __dtb_end)
+	if (&__dtb_start < &__dtb_end)
 		ftaddr = (ulong)__dtb_start;
 
 	return ftaddr;
diff --git a/arch/mips/ralink/of.c b/arch/mips/ralink/of.c
index cbae9d23ab7f..2c9af61efc20 100644
--- a/arch/mips/ralink/of.c
+++ b/arch/mips/ralink/of.c
@@ -75,7 +75,7 @@ void __init plat_mem_setup(void)
 	 */
 	if (fw_passed_dtb)
 		dtb = (void *)fw_passed_dtb;
-	else if (__dtb_start != __dtb_end)
+	else if (&__dtb_start != &__dtb_end)
 		dtb = (void *)__dtb_start;
 
 	__dt_setup_arch(dtb);

base-commit: 36bbbd0e234d817938bdc52121a0f5473b3e58f5
-- 
2.30.0