From: Mark Rutland <mark.rutland@arm.com>
To: James Morse <james.morse@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
linux-arm-kernel@lists.infradead.org,
Julien Thierry <julien.thierry.kdev@gmail.com>,
Masami Hiramatsu <mhiramat@kernel.org>
Subject: Re: [PATCH 6/8] arm64: entry: convert el0_sync to C
Date: Fri, 4 Oct 2019 17:37:13 +0100 [thread overview]
Message-ID: <20191004163712.GM34756@lakrids.cambridge.arm.com> (raw)
In-Reply-To: <b2a62a69-a82a-90ba-9546-1392ca37a3c2@arm.com>
On Fri, Oct 04, 2019 at 05:09:31PM +0100, James Morse wrote:
> Hi Mark,
>
> On 04/10/2019 13:57, Mark Rutland wrote:
> > On Thu, Oct 03, 2019 at 06:16:40PM +0100, James Morse wrote:
> >> From: Mark Rutland <mark.rutland@arm.com>
> >>
> >> This is largely a 1-1 conversion of asm to C, with a couple of caveats.
> >>
> >> The el0_sync{_compat} switches explicitly handle all the EL0 debug
> >> cases, so el0_dbg doesn't have to try to bail out for unexpected EL1
> >> debug ESR values. This also means that an unexpected vector catch from
> >> AArch32 is routed to el0_inv.
> >>
> >> We *could* merge the native and compat switches, which would make the
> >> diffstat negative, but I've tried to stay as close to the existing
> >> assembly as possible for the moment.
>
> >> +static void notrace el0_dbg(struct pt_regs *regs, unsigned long esr)
> >> +{
> >> + unsigned long addr_if_watchpoint = read_sysreg(far_el1);
> >> +
> >> + if (system_uses_irq_prio_masking())
> >> + gic_write_pmr(GIC_PRIO_IRQON | GIC_PRIO_PSR_I_SET);
> >> +
> >> + user_exit_irqoff();
> >> + do_debug_exception(addr_if_watchpoint, esr, regs);
> >> + local_daif_restore(DAIF_PROCCTX_NOIRQ);
> >> +}
> >> +NOKPROBE_SYMBOL(el0_dbg);
> >
> > I think that it'd be best to stick with 'far' here, and only have the
> > 'addr_if_watchpoint' name within do_debug_exception(), where it used to
> > be 'addr'. That way all of this code consistently uses 'far'.
>
> I'm nervous reading junk into a variable called 'far'... someone might assume its an address.
>
> Of the exceptions that come through here, FAR_EL1 is only written by the CPU for a
> watchpoint, for all the others its UNKNOWN.
My argument is that "far" just means "the contents of FAR_EL1", and
whether the value has any meaning for the current exception is
context-dependent (i.e. within do_debug_exception()).
> > Otherwise this all looks good to me:
> >
> > Reviewed-by: Mark Rutland <mark.rutland@arm.com>
>
> I'll leave this for now, let me know if my paranoia needs re-tuning!
Sure; my R-B holds either way. I just think it'd be nicer to use 'far'
here for consistency.
Thanks,
Mark.
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next prev parent reply other threads:[~2019-10-04 16:37 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-03 17:16 [PATCH 0/8] arm64: Convert entry.S synchronous exception handling to C James Morse
2019-10-03 17:16 ` [PATCH 1/8] arm64: Fix incorrect irqflag restore for priority masking for compat James Morse
2019-10-03 17:16 ` [PATCH 2/8] arm64: remove __exception annotations James Morse
2019-10-04 10:17 ` Mark Rutland
2019-10-04 14:10 ` Masami Hiramatsu
2019-10-04 16:08 ` James Morse
2019-10-04 16:34 ` Mark Rutland
2019-10-04 13:03 ` Marc Gonzalez
2019-10-04 16:08 ` James Morse
2019-10-03 17:16 ` [PATCH 3/8] arm64: Add prototypes for functions called by entry.S James Morse
2019-10-04 10:22 ` Mark Rutland
2019-10-03 17:16 ` [PATCH 4/8] arm64: add local_daif_inherit() James Morse
2019-10-03 17:16 ` [PATCH 5/8] arm64: entry: convert el1_sync to C James Morse
2019-10-04 10:39 ` Mark Rutland
2019-10-03 17:16 ` [PATCH 6/8] arm64: entry: convert el0_sync " James Morse
2019-10-04 12:57 ` Mark Rutland
2019-10-04 16:09 ` James Morse
2019-10-04 16:37 ` Mark Rutland [this message]
2019-10-03 17:16 ` [PATCH 7/8] arm64: Remove asmlinkage from updated functions James Morse
2019-10-04 12:58 ` Mark Rutland
2019-10-03 17:16 ` [PATCH 8/8] arm64: entry-common: don't touch daif before bp-hardening James Morse
2019-10-04 13:31 ` Mark Rutland
2019-10-04 16:09 ` James Morse
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