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SubjectRe: [PATCH v6 2/2] arm64: enable context tracking
Date
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


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