linux-kernel - [PATCH] powerpc/boot: Use address-of operator on section symbols

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Date:   Tue, 23 Jun 2020 20:59:20 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Michael Ellerman <mpe@...erman.id.au>
Cc:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Geoff Levand <geoff@...radead.org>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        clang-built-linux@...glegroups.com,
        Nathan Chancellor <natechancellor@...il.com>,
        Joel Stanley <joel@....id.au>
Subject: [PATCH] powerpc/boot: Use address-of operator on section symbols

Clang warns:

arch/powerpc/boot/main.c:107:18: warning: array comparison always
evaluates to a constant [-Wtautological-compare]
        if (_initrd_end > _initrd_start) {
                        ^
arch/powerpc/boot/main.c:155:20: warning: array comparison always
evaluates to a constant [-Wtautological-compare]
        if (_esm_blob_end <= _esm_blob_start)
                          ^
2 warnings 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).

Link: https://github.com/ClangBuiltLinux/linux/issues/212
Reported-by: Joel Stanley <joel@....id.au>
Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
---
 arch/powerpc/boot/main.c | 4 ++--
 arch/powerpc/boot/ps3.c  | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/boot/main.c b/arch/powerpc/boot/main.c
index a9d209135975..cae31a6e8f02 100644
--- a/arch/powerpc/boot/main.c
+++ b/arch/powerpc/boot/main.c
@@ -104,7 +104,7 @@ static struct addr_range prep_initrd(struct addr_range vmlinux, void *chosen,
 {
 	/* If we have an image attached to us, it overrides anything
 	 * supplied by the loader. */
-	if (_initrd_end > _initrd_start) {
+	if (&_initrd_end > &_initrd_start) {
 		printf("Attached initrd image at 0x%p-0x%p\n\r",
 		       _initrd_start, _initrd_end);
 		initrd_addr = (unsigned long)_initrd_start;
@@ -152,7 +152,7 @@ static void prep_esm_blob(struct addr_range vmlinux, void *chosen)
 	unsigned long esm_blob_addr, esm_blob_size;
 
 	/* Do we have an ESM (Enter Secure Mode) blob? */
-	if (_esm_blob_end <= _esm_blob_start)
+	if (&_esm_blob_end <= &_esm_blob_start)
 		return;
 
 	printf("Attached ESM blob at 0x%p-0x%p\n\r",
diff --git a/arch/powerpc/boot/ps3.c b/arch/powerpc/boot/ps3.c
index c52552a681c5..6e4efbdb6b7c 100644
--- a/arch/powerpc/boot/ps3.c
+++ b/arch/powerpc/boot/ps3.c
@@ -127,7 +127,7 @@ void platform_init(void)
 	ps3_repository_read_rm_size(&rm_size);
 	dt_fixup_memory(0, rm_size);
 
-	if (_initrd_end > _initrd_start) {
+	if (&_initrd_end > &_initrd_start) {
 		setprop_val(chosen, "linux,initrd-start", (u32)(_initrd_start));
 		setprop_val(chosen, "linux,initrd-end", (u32)(_initrd_end));
 	}

base-commit: 3e08a95294a4fb3702bb3d35ed08028433c37fe6
-- 
2.27.0