Re: [PATCH 2/6] freepgt2: sys_mincore ignore FIRST_USER_PGD_NR
On Fri, 8 Apr 2005, Nick Piggin wrote: > David Howells wrote: > > Hugh Dickins <[EMAIL PROTECTED]> wrote: > > > > > Remove use of FIRST_USER_PGD_NR from sys_mincore: it's inconsistent > > > (no > > > other syscall refers to it), unnecessary (sys_mincore loops over vmas > > > further down) and incorrect (misses user addresses in ARM's first > > > pgd). > > > > You should make it use FIRST_USER_ADDRESS instead. This check allows NULL > > pointers and suchlike to be weeded out before having to take the > > semaphore. > > I'm not sure whether it is worth keeping the singular special > case here to slightly speed up what would probably be a bug in > a userspace program. Well put - though you're more diffident about it than I would be! Furthermore, it only allows NULL pointers and suchlike to be weeded out on the ARM (and ARM26) architecture, no other. I'm not averse to optimizing ARM and ARM26, but it's much too insignificant an optimization to warrant reference to such an architectural detail. And it breaks the (peculiar) sys_mincore convention of doing all the work while returning -ENOMEM, if there were any holes in the address range. David's check stops it from doing any work in that case. FIRST_USER_ADDRESS should be used in the very few places it is necessary, and not spread around beyond them. Hugh - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH 2/6] freepgt2: sys_mincore ignore FIRST_USER_PGD_NR
David Howells wrote: Hugh Dickins <[EMAIL PROTECTED]> wrote: Remove use of FIRST_USER_PGD_NR from sys_mincore: it's inconsistent (no other syscall refers to it), unnecessary (sys_mincore loops over vmas further down) and incorrect (misses user addresses in ARM's first pgd). You should make it use FIRST_USER_ADDRESS instead. This check allows NULL pointers and suchlike to be weeded out before having to take the semaphore. I'm not sure whether it is worth keeping the singular special case here to slightly speed up what would probably be a bug in a userspace program. -- SUSE Labs, Novell Inc. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH 2/6] freepgt2: sys_mincore ignore FIRST_USER_PGD_NR
Hugh Dickins <[EMAIL PROTECTED]> wrote: > > Remove use of FIRST_USER_PGD_NR from sys_mincore: it's inconsistent (no > other syscall refers to it), unnecessary (sys_mincore loops over vmas > further down) and incorrect (misses user addresses in ARM's first pgd). You should make it use FIRST_USER_ADDRESS instead. This check allows NULL pointers and suchlike to be weeded out before having to take the semaphore. Also, just because no other syscall refers to such a value doesn't mean that this one shouldn't and that others shouldn't. David - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH 2/6] freepgt2: sys_mincore ignore FIRST_USER_PGD_NR
Hugh Dickins [EMAIL PROTECTED] wrote: Remove use of FIRST_USER_PGD_NR from sys_mincore: it's inconsistent (no other syscall refers to it), unnecessary (sys_mincore loops over vmas further down) and incorrect (misses user addresses in ARM's first pgd). You should make it use FIRST_USER_ADDRESS instead. This check allows NULL pointers and suchlike to be weeded out before having to take the semaphore. Also, just because no other syscall refers to such a value doesn't mean that this one shouldn't and that others shouldn't. David - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH 2/6] freepgt2: sys_mincore ignore FIRST_USER_PGD_NR
David Howells wrote: Hugh Dickins [EMAIL PROTECTED] wrote: Remove use of FIRST_USER_PGD_NR from sys_mincore: it's inconsistent (no other syscall refers to it), unnecessary (sys_mincore loops over vmas further down) and incorrect (misses user addresses in ARM's first pgd). You should make it use FIRST_USER_ADDRESS instead. This check allows NULL pointers and suchlike to be weeded out before having to take the semaphore. I'm not sure whether it is worth keeping the singular special case here to slightly speed up what would probably be a bug in a userspace program. -- SUSE Labs, Novell Inc. - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH 2/6] freepgt2: sys_mincore ignore FIRST_USER_PGD_NR
On Fri, 8 Apr 2005, Nick Piggin wrote: David Howells wrote: Hugh Dickins [EMAIL PROTECTED] wrote: Remove use of FIRST_USER_PGD_NR from sys_mincore: it's inconsistent (no other syscall refers to it), unnecessary (sys_mincore loops over vmas further down) and incorrect (misses user addresses in ARM's first pgd). You should make it use FIRST_USER_ADDRESS instead. This check allows NULL pointers and suchlike to be weeded out before having to take the semaphore. I'm not sure whether it is worth keeping the singular special case here to slightly speed up what would probably be a bug in a userspace program. Well put - though you're more diffident about it than I would be! Furthermore, it only allows NULL pointers and suchlike to be weeded out on the ARM (and ARM26) architecture, no other. I'm not averse to optimizing ARM and ARM26, but it's much too insignificant an optimization to warrant reference to such an architectural detail. And it breaks the (peculiar) sys_mincore convention of doing all the work while returning -ENOMEM, if there were any holes in the address range. David's check stops it from doing any work in that case. FIRST_USER_ADDRESS should be used in the very few places it is necessary, and not spread around beyond them. Hugh - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH 2/6] freepgt2: sys_mincore ignore FIRST_USER_PGD_NR
Remove use of FIRST_USER_PGD_NR from sys_mincore: it's inconsistent (no other syscall refers to it), unnecessary (sys_mincore loops over vmas further down) and incorrect (misses user addresses in ARM's first pgd). Signed-off-by: Hugh Dickins <[EMAIL PROTECTED]> --- mm/mincore.c |3 --- 1 files changed, 3 deletions(-) --- 2.6.12-rc2-mm1/mm/mincore.c 2005-04-05 15:21:02.0 +0100 +++ linux/mm/mincore.c 2005-04-05 18:59:01.0 +0100 @@ -118,9 +118,6 @@ asmlinkage long sys_mincore(unsigned lon if (start & ~PAGE_CACHE_MASK) goto einval; - if (start < FIRST_USER_PGD_NR * PGDIR_SIZE) - goto enomem; - limit = TASK_SIZE; if (start >= limit) goto enomem; - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH 2/6] freepgt2: sys_mincore ignore FIRST_USER_PGD_NR
Remove use of FIRST_USER_PGD_NR from sys_mincore: it's inconsistent (no other syscall refers to it), unnecessary (sys_mincore loops over vmas further down) and incorrect (misses user addresses in ARM's first pgd). Signed-off-by: Hugh Dickins [EMAIL PROTECTED] --- mm/mincore.c |3 --- 1 files changed, 3 deletions(-) --- 2.6.12-rc2-mm1/mm/mincore.c 2005-04-05 15:21:02.0 +0100 +++ linux/mm/mincore.c 2005-04-05 18:59:01.0 +0100 @@ -118,9 +118,6 @@ asmlinkage long sys_mincore(unsigned lon if (start ~PAGE_CACHE_MASK) goto einval; - if (start FIRST_USER_PGD_NR * PGDIR_SIZE) - goto enomem; - limit = TASK_SIZE; if (start = limit) goto enomem; - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
