2014-11-02 02:07:07

by Chen Gang

Subject: [PATCH v2] arch: tile: kernel: signal.c: Use __copy_from/to_user() instead of __get/put_user()

setup/restore_sigcontext() want to copy all related registers between
user and kernel. So use block copy instead of each registers copy. Then
can let code simple and clearer (which can avoid compiler's warning):

The related warning (with allmodconfig under tile):

CC arch/tile/kernel/signal.o
In file included from include/linux/poll.h:11:0,
from include/linux/ring_buffer.h:7,
from include/linux/ftrace_event.h:5,
from include/trace/syscall.h:6,
from include/linux/syscalls.h:81,
from arch/tile/kernel/signal.c:30:
arch/tile/kernel/signal.c: In function 'setup_sigcontext':
arch/tile/kernel/signal.c:116:31: warning: iteration 53u invokes undefined behavior [-Waggressive-loop-optimizations]
err |= __put_user(regs->regs[i], &sc->gregs[i]);
^
./arch/tile/include/asm/uaccess.h:236:26: note: in definition of macro '__put_user_asm'
: "r" (ptr), "r" (x), "i" (-EFAULT))
^
./arch/tile/include/asm/uaccess.h:297:10: note: in expansion of macro '__put_user_8'
case 8: __put_user_8(x, ptr, __ret); break; \
^
arch/tile/kernel/signal.c:116:10: note: in expansion of macro '__put_user'
err |= __put_user(regs->regs[i], &sc->gregs[i]);
^
arch/tile/kernel/signal.c:115:2: note: containing loop
for (i = 0; i < sizeof(struct pt_regs)/sizeof(long); ++i)
^

Signed-off-by: Chen Gang <[email protected]>
---
arch/tile/kernel/signal.c | 12 ++----------
1 file changed, 2 insertions(+), 10 deletions(-)

diff --git a/arch/tile/kernel/signal.c b/arch/tile/kernel/signal.c
index 7c2fecc..f867783 100644
--- a/arch/tile/kernel/signal.c
+++ b/arch/tile/kernel/signal.c
@@ -46,7 +46,6 @@ int restore_sigcontext(struct pt_regs *regs,
struct sigcontext __user *sc)
{
int err = 0;
- int i;

/* Always make any pending restarted system calls return -EINTR */
current_thread_info()->restart_block.fn = do_no_restart_syscall;
@@ -57,9 +56,7 @@ int restore_sigcontext(struct pt_regs *regs,
*/
BUILD_BUG_ON(sizeof(struct sigcontext) != sizeof(struct pt_regs));
BUILD_BUG_ON(sizeof(struct sigcontext) % 8 != 0);
-
- for (i = 0; i < sizeof(struct pt_regs)/sizeof(long); ++i)
- err |= __get_user(regs->regs[i], &sc->gregs[i]);
+ err = __copy_from_user(regs, sc, sizeof(*regs));

/* Ensure that the PL is always set to USER_PL. */
regs->ex1 = PL_ICS_EX1(USER_PL, EX1_ICS(regs->ex1));
@@ -110,12 +107,7 @@ badframe:

int setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs)
{
- int i, err = 0;
-
- for (i = 0; i < sizeof(struct pt_regs)/sizeof(long); ++i)
- err |= __put_user(regs->regs[i], &sc->gregs[i]);
-
- return err;
+ return __copy_to_user(sc, regs, sizeof(*regs));
}

/*
--
1.9.3

2014-11-04 15:42:52

by Chris Metcalf

Subject: Re: [PATCH v2] arch: tile: kernel: signal.c: Use __copy_from/to_user() instead of __get/put_user()

On 11/1/2014 10:13 PM, Chen Gang wrote:
> setup/restore_sigcontext() want to copy all related registers between
> user and kernel. So use block copy instead of each registers copy. Then
> can let code simple and clearer (which can avoid compiler's warning):
>
> [...]
>
> Signed-off-by: Chen Gang <[email protected]>
> ---
> arch/tile/kernel/signal.c | 12 ++----------
> 1 file changed, 2 insertions(+), 10 deletions(-)
>
> diff --git a/arch/tile/kernel/signal.c b/arch/tile/kernel/signal.c
> index 7c2fecc..f867783 100644
> --- a/arch/tile/kernel/signal.c
> +++ b/arch/tile/kernel/signal.c
> @@ -46,7 +46,6 @@ int restore_sigcontext(struct pt_regs *regs,
> struct sigcontext __user *sc)
> {
> int err = 0;
> - int i;

Taken into the tile tree, but I removed the now-redundant initialization
of err (shown above).

Thanks!

--
Chris Metcalf, Tilera Corp.
http://www.tilera.com