[PATCH v3 2/2] arm64: enable context tracking
will.deacon at arm.com
Mon May 19 08:32:20 PDT 2014
On Fri, May 09, 2014 at 10:51:50PM +0100, Larry Bassel wrote:
> Make calls to ct_user_enter when the kernel is exited
> and ct_user_exit when the kernel is entered (in el0_da,
> el0_ia, el0_svc, el0_irq and all of the "error" paths).
> These macros expand to function calls which will only work
> properly if el0_sync and related code has been rearranged
> (in a previous patch of this series).
> The calls to ct_user_exit are made after hw debugging has been
> enabled (enable_dbg).
> The call to ct_user_enter is made at the beginning of the
> kernel_exit macro.
> This patch is based on earlier work by Kevin Hilman.
> diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h
> index 720e70b..301ea6a 100644
> --- a/arch/arm64/include/asm/thread_info.h
> +++ b/arch/arm64/include/asm/thread_info.h
> @@ -108,6 +108,7 @@ static inline struct thread_info *current_thread_info(void)
> #define TIF_SINGLESTEP 21
> #define TIF_32BIT 22 /* 32bit process */
> #define TIF_SWITCH_MM 23 /* deferred switch_mm */
> +#define TIF_NOHZ 24
> #define _TIF_SIGPENDING (1 << TIF_SIGPENDING)
> #define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED)
> diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
> index 136bb7d..c839bab 100644
> --- a/arch/arm64/kernel/entry.S
> +++ b/arch/arm64/kernel/entry.S
> @@ -30,6 +30,44 @@
> #include <asm/unistd32.h>
> + * Context tracking subsystem. Used to instrument transitions
> + * between user and kernel mode.
> + */
> + .macro ct_user_exit, save = 0
> +#ifdef CONFIG_CONTEXT_TRACKING
> + bl context_tracking_user_exit
> + .if \save == 1
It would be clearer to refer to the parameter as `restore' for the exit
case, I reckon.
> + /*
> + * save/restore needed during syscalls. Restore syscall arguments from
> + * the values already saved on stack during kernel_entry
> + */
> + ldp x0, x1, [sp]
> + ldp x2, x3, [sp, #S_X2]
> + ldp x4, x5, [sp, #S_X4]
> + ldp x6, x7, [sp, #S_X6]
> + .endif
> + .endm
> .macro kernel_exit, el, ret = 0
> ldp x21, x22, [sp, #S_PC] // load ELR, SPSR
> .if \el == 0
> + ct_user_enter \ret
> ldr x23, [sp, #S_SP] // load return stack pointer
> .if \ret
You should check how this patch applies against my debug exception rework:
2a2830703a23 ("arm64: debug: avoid accessing mdscr_el1 on fault paths where
possible") in today's next.
As well as addressing the conflicts, it's worth nothing that the thread_info
becomes available in tsk much earlier for exceptions from userspace with
that patch applied.
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