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On Tue, Oct 31, Hugh Dickins wrote:
> +++ linux/include/asm-powerpc/current.h 2006-10-30 19:27:05.000000000 +0000
> +static inline struct task_struct *get_current(void)
> +{
> + struct task_struct *task;
> +
> + __asm__ __volatile__("ld %0,%1(13)"
> + : "=r" (task)
> + : "i" (offsetof(struct paca_struct, __current)));
This breaks compile of 2.6.18.8:
CC [M] drivers/media/video/pwc/pwc-uncompress.o
In file included from /home/olaf/kernel/linux-2.6.18.8/drivers/media/video/pwc/pwc-uncompress.c:29:
include2/asm/current.h: In function 'get_current':
include2/asm/current.h:23: warning: implicit declaration of function 'offsetof'
include2/asm/current.h:23: error: expected expression before 'struct'
make[5]: *** [drivers/media/video/pwc/pwc-uncompress.o] Error 1
Signed-off-by: Olaf Hering <olaf@aepfle.de>
Signed-off-by: Paul Mackerras <paulus@samba.org>
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Repeated -j20 kernel builds on a G5 Quad running an SMP PREEMPT kernel
would often collapse within a day, some exec failing with "Bad address".
In each case examined, load_elf_binary was doing a kernel_read, but
generic_file_aio_read's access_ok saw current->thread.fs.seg as USER_DS
instead of KERNEL_DS.
objdump of filemap.o shows gcc 4.1.0 emitting "mr r5,r13 ... ld r9,416(r5)"
here for get_paca()->__current, instead of the expected and much more usual
"ld r9,416(r13)"; I've seen other gcc4s do the same, but perhaps not gcc3s.
So, if the task is preempted and rescheduled on a different cpu in between
the mr and the ld, r5 will be looking at a different paca_struct from the
one it's now on, pick up the wrong __current, and perhaps the wrong seg.
Presumably much worse could happen elsewhere, though that split is rare.
Other architectures appear to be safe (x86_64's read_pda is more limiting
than get_paca), but ppc64 needs to force "current" into one instruction.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
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include/asm-ppc/ had #ifdef __KERNEL__ in all header files that
are not meant for use by user space, include/asm-powerpc does
not have this yet.
This patch gets us a lot closer there. There are a few cases
where I was not sure, so I left them out. I have verified
that no CONFIG_* symbols are used outside of __KERNEL__
any more and that there are no obvious compile errors when
including any of the headers in user space libraries.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Paul Mackerras <paulus@samba.org>
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This patch merges current.h. This is a one-big-ifdef merge, but both
versions are so tiny, I think we can live with it. While we're at it,
we get rid of the fairly pointless redirection through get_current()
in the ppc64 version.
Built and booted on POWER5 LPAR (ARCH=powerpc & ARCH=ppc64). Built
for 32-bit pmac (ARCH=powerpc & ARCH=ppc).
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>
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