[U-Boot] [PATCH] ARM: Fix overflow in MMU setup

[U-Boot] [PATCH] ARM: Fix overflow in MMU setup

[Marek Vasut]

The patch fixes a corner case where adding size to DRAM start resulted
in a value (1 << 32), which in turn overflew the u32 computation, which
resulted in 0 and it therefore prevented correct setup of the MMU tables.

The addition of DRAM bank start and it's size can end up right at the end
of the address space in the special case of a machine with enough memory.
To prevent this overflow, shift the start and size separately and add them
only after they were shifted.

Hopefully, we only have systems in tree which have DRAM size aligned to
1MiB boundary. If not, this patch would break such systems. On the other
hand, such system would be broken by design anyway.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Albert ARIBAUD <albert.u.boot@aribaud.net>
---
 arch/arm/lib/cache-cp15.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/lib/cache-cp15.c b/arch/arm/lib/cache-cp15.c
index 5fdfdbf..3e62d58 100644
--- a/arch/arm/lib/cache-cp15.c
+++ b/arch/arm/lib/cache-cp15.c
@@ -69,7 +69,7 @@ __weak void dram_bank_mmu_setup(int bank)
 
 	debug("%s: bank: %d\n", __func__, bank);
 	for (i = bd->bi_dram[bank].start >> 20;
-	     i < (bd->bi_dram[bank].start + bd->bi_dram[bank].size) >> 20;
+	     i < (bd->bi_dram[bank].start >> 20) + (bd->bi_dram[bank].size >> 20);
 	     i++) {
 #if defined(CONFIG_SYS_ARM_CACHE_WRITETHROUGH)
 		set_section_dcache(i, DCACHE_WRITETHROUGH);
-- 
2.0.1

[U-Boot] ARM: Fix overflow in MMU setup

[Tom Rini]

On Mon, Aug 04, 2014 at 01:45:46AM +0200, Marek Vasut wrote:

> The patch fixes a corner case where adding size to DRAM start resulted
> in a value (1 << 32), which in turn overflew the u32 computation, which
> resulted in 0 and it therefore prevented correct setup of the MMU tables.
> 
> The addition of DRAM bank start and it's size can end up right at the end
> of the address space in the special case of a machine with enough memory.
> To prevent this overflow, shift the start and size separately and add them
> only after they were shifted.
> 
> Hopefully, we only have systems in tree which have DRAM size aligned to
> 1MiB boundary. If not, this patch would break such systems. On the other
> hand, such system would be broken by design anyway.
> 
> Signed-off-by: Marek Vasut <marex@denx.de>
> Cc: Albert ARIBAUD <albert.u.boot@aribaud.net>

Applied to u-boot/master, thanks!

-- 
Tom
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