| Message ID | 1359554912-26872-2-git-send-email-will.deacon@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
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 <cdall@cs.columbia.edu> > Signed-off-by: Will Deacon <will.deacon@arm.com> > --- > 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. Nicolas
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 <cdall@cs.columbia.edu> > > Signed-off-by: Will Deacon <will.deacon@arm.com> > > --- > > 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
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)) /* * The maximum size of a 26-bit user space task.
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 <cdall@cs.columbia.edu> Signed-off-by: Will Deacon <will.deacon@arm.com> --- arch/arm/include/asm/memory.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)