Re: [PATCH v6 2/2] arm64: enable context tracking

[Kevin Hilman <khilman@linaro.org>]

Larry Bassel <larry.bassel@linaro.org> writes:

> 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_and_irq).
>
> 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.
> Save/restore optimizations were also done by Kevin.
>
> Signed-off-by: Kevin Hilman <khilman@linaro.org>
> Signed-off-by: Larry Bassel <larry.bassel@linaro.org>
> ---
>  arch/arm64/Kconfig                   |  1 +
>  arch/arm64/include/asm/thread_info.h |  4 ++++
>  arch/arm64/kernel/entry.S            | 39 +++++++++++++++++++++++++++++++++++-
>  3 files changed, 43 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index e759af5..ef18ae5 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -55,6 +55,7 @@ config ARM64
>  	select RTC_LIB
>  	select SPARSE_IRQ
>  	select SYSCTL_EXCEPTION_TRACE
> +	select HAVE_CONTEXT_TRACKING
>  	help
>  	  ARM 64-bit (AArch64) Linux support.
>  
> diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h
> index 720e70b..8363f34 100644
> --- a/arch/arm64/include/asm/thread_info.h
> +++ b/arch/arm64/include/asm/thread_info.h
> @@ -100,6 +100,7 @@ static inline struct thread_info *current_thread_info(void)
>  #define TIF_SIGPENDING		0
>  #define TIF_NEED_RESCHED	1
>  #define TIF_NOTIFY_RESUME	2	/* callback before returning to user */
> +#define TIF_NOHZ                7

FWIW, in earlier versions this was bit 24, but we had to move it into
the first 2 bytes..

>  #define TIF_SYSCALL_TRACE	8
>  #define TIF_POLLING_NRFLAG	16
>  #define TIF_MEMDIE		18	/* is terminating due to OOM killer */
> @@ -113,9 +114,12 @@ static inline struct thread_info *current_thread_info(void)
>  #define _TIF_NEED_RESCHED	(1 << TIF_NEED_RESCHED)
>  #define _TIF_NOTIFY_RESUME	(1 << TIF_NOTIFY_RESUME)
>  #define _TIF_32BIT		(1 << TIF_32BIT)
> +#define _TIF_SYSCALL_TRACE      (1 << TIF_SYSCALL_TRACE)
> +#define _TIF_NOHZ               (1 << TIF_NOHZ)
>  
>  #define _TIF_WORK_MASK		(_TIF_NEED_RESCHED | _TIF_SIGPENDING | \
>  				 _TIF_NOTIFY_RESUME)
> +#define _TIF_SYSCALL_WORK       (_TIF_SYSCALL_TRACE | _TIF_NOHZ)

...so that when this is used...

[...]

> @@ -616,9 +651,11 @@ el0_svc:
>  el0_svc_naked:					// compat entry point
>  	stp	x0, scno, [sp, #S_ORIG_X0]	// save the original x0 and syscall number
>  	enable_dbg_and_irq
> +	ct_user_exit 1
>  
>  	ldr	x16, [tsk, #TI_FLAGS]		// check for syscall tracing
> -	tbnz	x16, #TIF_SYSCALL_TRACE, __sys_trace // are we tracing syscalls?
> +	and	x16, x16, #_TIF_SYSCALL_WORK    // are we tracing syscalls?
> +	cbnz	x16, __sys_trace

...here, it doesn't get something like this:

entry.S:697: Error: immediate out of range at operand 3 -- `and x16,x16,#((1<<8)|(1<<24))'

Kevin