From mboxrd@z Thu Jan 1 00:00:00 1970 From: will.deacon@arm.com (Will Deacon) Date: Wed, 30 Jan 2013 19:13:55 +0000 Subject: [PATCH 2/2] ARM: memory: define TASK_UNMAPPED_BASE in terms of TASK_SIZE In-Reply-To: References: <1359554912-26872-1-git-send-email-will.deacon@arm.com> <1359554912-26872-2-git-send-email-will.deacon@arm.com> Message-ID: <20130130191355.GM7484@mudshark.cambridge.arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Wed, Jan 30, 2013 at 06:57:24PM +0000, Nicolas Pitre wrote: > On Wed, 30 Jan 2013, Will Deacon wrote: > > > TASK_UNMAPPED_BASE is defined directly in terms of PAGE_OFFSET, which is > > confusing given that the modules area sits between here and TASK_SIZE > > and is not available for user allocations. > > > > This patch defines TASK_UNMAPPED_BASE in terms of TASK_SIZE instead and > > fixes a bug introduced by 394ef6403abc ("mm: use vm_unmapped_area() on > > arm architecture") whereby TASK_UNMAPPED_BASE is no longer page-aligned > > for bottom-up mmap, causing get_unmapped_area to choke on misaligned > > addresses. > > > > Reported-by: Christoffer Dall > > Signed-off-by: Will Deacon > > --- > > arch/arm/include/asm/memory.h | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/arch/arm/include/asm/memory.h b/arch/arm/include/asm/memory.h > > index a0fd518..255a01b 100644 > > --- a/arch/arm/include/asm/memory.h > > +++ b/arch/arm/include/asm/memory.h > > @@ -37,7 +37,7 @@ > > */ > > #define PAGE_OFFSET UL(CONFIG_PAGE_OFFSET) > > #define TASK_SIZE (UL(CONFIG_PAGE_OFFSET) - UL(SZ_16M)) > > -#define TASK_UNMAPPED_BASE (UL(CONFIG_PAGE_OFFSET) / 3) > > +#define TASK_UNMAPPED_BASE ((TASK_SIZE / 3) & ~UL(SZ_16M - 1)) > > Please round this up not down. In most cases, TASK_SIZE is 0xbf000000 > which is not nicely divisible by 3, unlike PAGE_OFFSET was. By rounding > up you get a nice 0x40000000 as before. Sure, I think ALIGN does that for us, so I can use that instead. Cheers, Will