linux-kernel - [PATCH 4.4 53/58] powerpc/ps3: Fix system hang with GCC 5 builds

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Date:   Fri,  6 Jan 2017 22:44:38 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Geoff Levand <geoff@...radead.org>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: [PATCH 4.4 53/58] powerpc/ps3: Fix system hang with GCC 5 builds

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

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: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/powerpc/boot/ps3-head.S |    5 -----
 arch/powerpc/boot/ps3.c      |    8 +-------
 2 files changed, 1 insertion(+), 12 deletions(-)

--- 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 */
--- 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_ch
 
 	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();