From: will.deacon@arm•com (Will Deacon)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH 3/6] arm64: Add support for hooks to handle undefined instructions
Date: Tue, 26 Aug 2014 15:30:11 +0100 [thread overview]
Message-ID: <20140826143011.GV23445@arm.com> (raw)
In-Reply-To: <CAKv+Gu8Nji0Jspk2cMCwVGKeODsiOb0NFUFWucm3rAbNdb_bTQ@mail.gmail.com>
On Tue, Aug 26, 2014 at 03:21:09PM +0100, Ard Biesheuvel wrote:
> On 26 August 2014 15:13, Will Deacon <will.deacon@arm•com> wrote:
> > On Tue, Aug 26, 2014 at 11:28:47AM +0100, Punit Agrawal wrote:
> >> Add support to register hooks for undefined instructions. The handlers
> >> will be called when the undefined instruction and the processor state
> >> (as contained in pstate) match criteria used at registration.
> >>
> >> Note: The patch only deals with ARM instruction encodings and needs
> >> fixing to handle thumb instructions as well.
> >
> > [...]
> >
> >> +static int call_undef_hook(struct pt_regs *regs)
> >> +{
> >> + struct undef_hook *hook;
> >> + unsigned long flags;
> >> + u32 instr;
> >> + int (*fn)(struct pt_regs *regs, u32 instr) = NULL;
> >> + void __user *pc = (void __user *)instruction_pointer(regs);
> >> +
> >> + /*
> >> + * Currently, undefined instruction patching is only supported
> >> + * for user mode. Also, as we're not emulating any thumb
> >> + * instructions lets not add thumb instruction decoding until
> >> + * it is needed.
> >> + */
> >> + if (!compat_user_mode(regs) || compat_thumb_mode(regs))
> >> + return 1;
> >
> > What do you mean by `undefined instruction patching'? I don't see anything
> > in the mechanism that means this can't be reused for kernel code, then we
> > just register the SWP emulation hook for userspace only using the mode (like
> > we do for kgdb).
> >
>
> You need this patch in order to be able to return from an undef
> exception taken in EL1:
>
> --- a/arch/arm64/kernel/entry.S
> +++ b/arch/arm64/kernel/entry.S
> @@ -287,7 +287,9 @@ el1_undef:
> */
> enable_dbg
> mov x0, sp
> - b do_undefinstr
> + bl do_undefinstr
> +
> + kernel_exit 1
> el1_dbg:
> /*
> * Debug exception handling
Hmm, I'm surprised we don't already need something like this for KGDB...
Will
next prev parent reply other threads:[~2014-08-26 14:30 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-08-26 10:28 [PATCH 0/6] Legacy instruction emulation for arm64 Punit Agrawal
2014-08-26 10:28 ` [PATCH 1/6] arm: Fix in-correct barrier usage in SWP{B} emulation Punit Agrawal
2014-08-26 13:04 ` Will Deacon
2014-08-27 16:40 ` Catalin Marinas
2014-08-27 17:05 ` Punit Agrawal
2014-08-26 10:28 ` [PATCH 2/6] arm64: Create arch debugfs directory Punit Agrawal
2014-08-26 10:28 ` [PATCH 3/6] arm64: Add support for hooks to handle undefined instructions Punit Agrawal
2014-08-26 13:13 ` Will Deacon
2014-08-26 14:21 ` Ard Biesheuvel
2014-08-26 14:30 ` Will Deacon [this message]
2014-08-27 16:47 ` Catalin Marinas
2014-08-27 16:51 ` Will Deacon
2014-08-26 14:56 ` Punit Agrawal
2014-08-26 18:14 ` Will Deacon
2014-08-27 16:58 ` Catalin Marinas
2014-08-26 10:28 ` [PATCH 4/6] arm64: Add AArch32 instruction set condition code checks Punit Agrawal
2014-08-26 10:28 ` [PATCH 5/6] arm64: Port SWP/SWPB emulation support from arm Punit Agrawal
2014-08-26 11:32 ` Arnd Bergmann
2014-08-26 12:25 ` Will Deacon
2014-08-26 13:26 ` Arnd Bergmann
2014-08-26 13:56 ` Will Deacon
2014-08-27 17:35 ` Punit Agrawal
2014-08-27 18:30 ` Arnd Bergmann
2014-08-28 10:21 ` Punit Agrawal
2014-08-27 17:29 ` Catalin Marinas
2014-08-26 10:28 ` [PATCH 6/6] arm64: Emulate CP15 Barrier instructions Punit Agrawal
2014-08-26 13:16 ` Will Deacon
2014-08-27 17:40 ` Catalin Marinas
2014-08-28 9:34 ` Punit Agrawal
2014-08-28 9:42 ` Catalin Marinas
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