From: will.deacon@arm•com (Will Deacon)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v3 1/4] arm64: kgdb: fix single stepping
Date: Mon, 5 Jun 2017 17:29:25 +0100 [thread overview]
Message-ID: <20170605162925.GO21944@arm.com> (raw)
In-Reply-To: <20170523043058.5463-2-takahiro.akashi@linaro.org>
On Tue, May 23, 2017 at 01:30:55PM +0900, AKASHI Takahiro wrote:
> After entering kgdb mode, the first 'stepi' can succeed, but the following
> 'stepi' never executes the next instruction.
>
> This is because a software step cannot get enabled as the software step
> bit(SS) in SPSR, which is cleared by the first single stepping, will not
> be set again for the following 's' commands.
For userspace, we have user_rewind_single_step to re-arm the state machine
on an unhandled step exception. It sounds like we need the kernel version of
that?
> Please note that this bit, as well as the software step control bit(SS)
> in MDSCR, must be set before resuming the execution.
> kernel_active_single_step() called by kgdb_arch_handle_exception() checks
> only for the bit in MDSCR, and so kgdb_enable_single_step() will never be
> called.
MDSCR.SS shouldn't get cleared by the hardware, so I don't understand your
point here.
Will
next prev parent reply other threads:[~2017-06-05 16:29 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-23 4:30 [PATCH v3 0/4] arm64: kgdb: fix single stepping AKASHI Takahiro
2017-05-23 4:30 ` [PATCH v3 1/4] " AKASHI Takahiro
2017-06-05 16:29 ` Will Deacon [this message]
2017-06-07 4:43 ` AKASHI Takahiro
2017-05-23 4:30 ` [PATCH v3 2/4] arm64: kgdb: disable interrupts while a software step is enabled AKASHI Takahiro
2017-06-05 16:29 ` Will Deacon
2017-06-07 5:34 ` AKASHI Takahiro
2017-06-07 16:50 ` Will Deacon
2017-06-20 2:43 ` AKASHI Takahiro
2017-06-20 17:07 ` Will Deacon
2017-06-21 2:43 ` AKASHI Takahiro
2017-06-21 10:00 ` Will Deacon
2017-05-23 4:30 ` [PATCH v3 3/4] arm64: kgdb: prevent kgdb from being invoked recursively AKASHI Takahiro
2017-05-23 4:30 ` [PATCH v3 4/4] kgdb: select a correct cpu while in a single stepping AKASHI Takahiro
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