linux-kernel - [PATCH 3.10 078/268] powerpc/ps3: Fix system hang with GCC 5 builds

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Date:   Mon, 19 Jun 2017 20:29:37 +0200
From:   Willy Tarreau <w@....eu>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        linux@...ck-us.net
Cc:     Geoff Levand <geoff@...radead.org>,
        Michael Ellerman <mpe@...erman.id.au>, Willy Tarreau <w@....eu>
Subject: [PATCH 3.10 078/268] powerpc/ps3: Fix system hang with GCC 5 builds

From: Geoff Levand <geoff@...radead.org>

commit 6dff5b67054e17c91bd630bcdda17cfca5aa4215 upstream.

GCC 5 generates different code for this bootwrapper null check that
causes the PS3 to hang very early in its bootup. This check is of
limited value, so just get rid of it.

Signed-off-by: Geoff Levand <geoff@...radead.org>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Signed-off-by: Willy Tarreau <w@....eu>
---
 arch/powerpc/boot/ps3-head.S | 5 -----
 arch/powerpc/boot/ps3.c      | 8 +-------
 2 files changed, 1 insertion(+), 12 deletions(-)

diff --git a/arch/powerpc/boot/ps3-head.S b/arch/powerpc/boot/ps3-head.S
index b6fcbaf..3dc44b0 100644
--- a/arch/powerpc/boot/ps3-head.S
+++ b/arch/powerpc/boot/ps3-head.S
@@ -57,11 +57,6 @@ __system_reset_overlay:
 	bctr
 
 1:
-	/* Save the value at addr zero for a null pointer write check later. */
-
-	li	r4, 0
-	lwz	r3, 0(r4)
-
 	/* Primary delays then goes to _zimage_start in wrapper. */
 
 	or	31, 31, 31 /* db16cyc */
diff --git a/arch/powerpc/boot/ps3.c b/arch/powerpc/boot/ps3.c
index 9954d98..029ea3c 100644
--- a/arch/powerpc/boot/ps3.c
+++ b/arch/powerpc/boot/ps3.c
@@ -119,13 +119,12 @@ void ps3_copy_vectors(void)
 	flush_cache((void *)0x100, 512);
 }
 
-void platform_init(unsigned long null_check)
+void platform_init(void)
 {
 	const u32 heapsize = 0x1000000 - (u32)_end; /* 16MiB */
 	void *chosen;
 	unsigned long ft_addr;
 	u64 rm_size;
-	unsigned long val;
 
 	console_ops.write = ps3_console_write;
 	platform_ops.exit = ps3_exit;
@@ -153,11 +152,6 @@ void platform_init(unsigned long null_check)
 
 	printf(" flat tree at 0x%lx\n\r", ft_addr);
 
-	val = *(unsigned long *)0;
-
-	if (val != null_check)
-		printf("null check failed: %lx != %lx\n\r", val, null_check);
-
 	((kernel_entry_t)0)(ft_addr, 0, NULL);
 
 	ps3_exit();
-- 
2.8.0.rc2.1.gbe9624a