diff options
| author | Nicolas Pitre <nico@cam.org> | 2006-02-08 21:19:37 +0000 |
|---|---|---|
| committer | Russell King <rmk+kernel@arm.linux.org.uk> | 2006-02-08 21:19:37 +0000 |
| commit | 49bca4c2815feafd5f999bf43baf87e0dd8d1d08 (patch) | |
| tree | 6bc9a59e2fa217d346841418fd45dd704cf61071 /arch/arm | |
| parent | 99595d0237926b5aba1fe4c844a011a1ba1ee1f8 (diff) | |
[ARM] 3309/1: disable the pre-ARMv5 NPTL kernel helper in the non MMU case
Patch from Nicolas Pitre
The cmpxchg emulation on pre-ARMv5 relies on user code executed from a
kernel address. If the operation cannot complete atomically, it is
aborted from the usr_entry macro by clearing the Z flag. This clearing
of the Z flag is done whenever the user pc is above TASK_SIZE.
However this "pc >= TASK_SIZE" test cannot work in the non MMU case.
Worse: the current code will corrupt the Z flag on every entry to the
kernel.
Let's disable it in the non MMU case for now. Using NPTL on non MMU
targets needs to be worked out anyway.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch/arm')
| -rw-r--r-- | arch/arm/kernel/entry-armv.S | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S index d401d908c46..f248bbfe745 100644 --- a/arch/arm/kernel/entry-armv.S +++ b/arch/arm/kernel/entry-armv.S @@ -333,10 +333,14 @@ __pabt_svc: @ from the exception stack #if __LINUX_ARM_ARCH__ < 6 && !defined(CONFIG_NEEDS_SYSCALL_FOR_CMPXCHG) +#ifndef CONFIG_MMU +#warning "NPTL on non MMU needs fixing" +#else @ make sure our user space atomic helper is aborted cmp r2, #TASK_SIZE bichs r3, r3, #PSR_Z_BIT #endif +#endif @ @ We are now ready to fill in the remaining blanks on the stack: @@ -756,12 +760,18 @@ __kuser_cmpxchg: @ 0xffff0fc0 * exception happening just after the str instruction which would * clear the Z flag although the exchange was done. */ +#ifdef CONFIG_MMU teq ip, ip @ set Z flag ldr ip, [r2] @ load current val add r3, r2, #1 @ prepare store ptr teqeq ip, r0 @ compare with oldval if still allowed streq r1, [r3, #-1]! @ store newval if still allowed subs r0, r2, r3 @ if r2 == r3 the str occured +#else +#warning "NPTL on non MMU needs fixing" + mov r0, #-1 + adds r0, r0, #0 +#endif mov pc, lr #else |