From: Florian Bezdeka <florian.bezdeka@siemens.com>
To: Johannes Kirchmair <johannes.kirchmair@sigmatek.at>,
Clara Kowalsky <clara.kowalsky@siemens.com>,
"xenomai@lists.linux.dev" <xenomai@lists.linux.dev>
Cc: "jan.kiszka@siemens.com" <jan.kiszka@siemens.com>
Subject: Re: [RFC PATCH v2 1/2] arm64: dovetail: Fix undefinstr/break trap handling
Date: Mon, 09 Oct 2023 15:17:21 +0200 [thread overview]
Message-ID: <3b9681c7b077b7a0a282f91c12b6a9cf25699e62.camel@siemens.com> (raw)
In-Reply-To: <VE1PR08MB4909ACFB96F3BEBA2D813FD092CEA@VE1PR08MB4909.eurprd08.prod.outlook.com>
On Mon, 2023-10-09 at 12:44 +0000, Johannes Kirchmair wrote:
> Hey Clara,
>
> > -----Original Message-----
> > From: Clara Kowalsky <clara.kowalsky@siemens.com>
> > Sent: Freitag, 6. Oktober 2023 12:43
> > To: xenomai@lists.linux.dev
> > Cc: jan.kiszka@siemens.com; florian.bezdeka@siemens.com; Clara Kowalsky
> > <clara.kowalsky@siemens.com>
> > Subject: [RFC PATCH v2 1/2] arm64: dovetail: Fix undefinstr/break trap handling
> >
> > [Sie erhalten nicht häufig E-Mails von clara.kowalsky@siemens.com. Weitere
> > Informationen, warum dies wichtig ist, finden Sie unter
> > https://aka.ms/LearnAboutSenderIdentification ]
> >
> > CAUTION: External E-Mail !
> >
> > From: Florian Bezdeka <florian.bezdeka@siemens.com>
> >
> > When running an compat RT application on arm64 the break trap is
> > handled via the undefined instruction trap.
> >
> > A possible call stack looks like this:
> >
> > Call trace:
> > handle_inband_event+0x2d0/0x320
> > inband_event_notify+0x28/0x50
> > signal_wake_up_state+0x7c/0xa4
> > complete_signal+0x104/0x2d0
> > __send_signal_locked+0x1d0/0x3e4
> > send_signal_locked+0xf0/0x140
> > force_sig_info_to_task+0xa0/0x164
> > force_sig_fault+0x64/0x94
> > arm64_force_sig_fault+0x48/0x80
> > send_user_sigtrap+0x50/0x8c
> > aarch32_break_handler+0xac/0x1d0
> > do_undefinstr+0x6c/0x360
> > el0_undef+0x4c/0xd0
> > el0t_32_sync_handler+0xd0/0x140
> > el0t_32_sync+0x190/0x194
> >
> > The trap is never reported to the companion core at that stage so
> > running_oob() in do_undefinstr() will always return true. As the
> > following bailout happens before calling the compat breakpoint
> > detection (aarch32_break_handler()) debugging the compat
> > application does not work.
> >
> > In addition aarch32_break_handler() has to report the trap entry to the
> > companion core.
> >
> > Reported-by: Clara Kowalsky <clara.kowalsky@siemens.com>
> > Tested-by: Clara Kowalsky <clara.kowalsky@siemens.com>
> > Signed-off-by: Florian Bezdeka <florian.bezdeka@siemens.com>
> > ---
> > arch/arm64/kernel/debug-monitors.c | 2 ++
> > arch/arm64/kernel/traps.c | 7 -------
> > 2 files changed, 2 insertions(+), 7 deletions(-)
> >
> > diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-
> > monitors.c
> > index 32271ed24ef5..8157496bea62 100644
> > --- a/arch/arm64/kernel/debug-monitors.c
> > +++ b/arch/arm64/kernel/debug-monitors.c
> > @@ -373,7 +373,9 @@ int aarch32_break_handler(struct pt_regs *regs)
> > if (!bp)
> > return -EFAULT;
> >
> > + mark_trap_entry(ARM64_TRAP_UNDI, regs);
> > send_user_sigtrap(TRAP_BRKPT);
> > + mark_trap_entry(ARM64_TRAP_UNDI, regs);
> Should this be a mark_trap_exit?
It should (and it was in v1). That means that you manually modified the
patch... Seems like a broken workflow on your end.
>
>
> > return 0;
> > }
> > NOKPROBE_SYMBOL(aarch32_break_handler);
> > diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
> > index b0db35eda8f5..a8c3642c61dc 100644
> > --- a/arch/arm64/kernel/traps.c
> > +++ b/arch/arm64/kernel/traps.c
> > @@ -456,13 +456,6 @@ void do_el0_undef(struct pt_regs *regs, unsigned long
> > esr)
> > {
> > u32 insn;
> >
> > - /*
> > - * If the companion core did not switched us to in-band
> > - * context, we may assume that it has handled the trap.
> > - */
> > - if (running_oob())
> > - return;
> Shouldn't this be moved below the mark_trap_entry?
> If the companion core decides to handle the undefined instructions, we will be running_oob after mark_trap_entry and we should not emit an signal in that case.
>
> Best regards
> Johannes
> > -
> > /* check for AArch32 breakpoint instructions */
> > if (!aarch32_break_handler(regs))
> > return;
> > --
> > 2.39.2
> >
>
next prev parent reply other threads:[~2023-10-09 13:17 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-06 10:43 [RFC PATCH v2 0/2] Fix trap related handling Clara Kowalsky
2023-10-06 10:43 ` [RFC PATCH v2 1/2] arm64: dovetail: Fix undefinstr/break trap handling Clara Kowalsky
2023-10-09 12:44 ` Johannes Kirchmair
2023-10-09 13:17 ` Florian Bezdeka [this message]
2023-10-06 10:43 ` [RFC PATCH v2 2/2] arm64: dovetail: Fix armv8 SWP{B} instruction handling Clara Kowalsky
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