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Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1sbKUd-00000001pz8-2mVJ; Tue, 06 Aug 2024 13:44:51 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1sbKTw-00000001pnI-43Yj for linux-arm-kernel@lists.infradead.org; Tue, 06 Aug 2024 13:44:10 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 97A33FEC; Tue, 6 Aug 2024 06:44:31 -0700 (PDT) Received: from e124191.cambridge.arm.com (e124191.cambridge.arm.com [10.1.197.45]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id D72173F766; Tue, 6 Aug 2024 06:44:02 -0700 (PDT) Date: Tue, 6 Aug 2024 14:43:57 +0100 From: Joey Gouly To: Dave Martin Cc: linux-arm-kernel@lists.infradead.org, akpm@linux-foundation.org, aneesh.kumar@kernel.org, aneesh.kumar@linux.ibm.com, bp@alien8.de, broonie@kernel.org, catalin.marinas@arm.com, christophe.leroy@csgroup.eu, dave.hansen@linux.intel.com, hpa@zytor.com, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, maz@kernel.org, mingo@redhat.com, mpe@ellerman.id.au, naveen.n.rao@linux.ibm.com, npiggin@gmail.com, oliver.upton@linux.dev, shuah@kernel.org, szabolcs.nagy@arm.com, tglx@linutronix.de, will@kernel.org, x86@kernel.org, kvmarm@lists.linux.dev Subject: Re: [PATCH v4 15/29] arm64: handle PKEY/POE faults Message-ID: <20240806134357.GA2017741@e124191.cambridge.arm.com> References: <20240503130147.1154804-1-joey.gouly@arm.com> <20240503130147.1154804-16-joey.gouly@arm.com> <20240801160110.GC841837@e124191.cambridge.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240806_064409_117476_EDC4EF35 X-CRM114-Status: GOOD ( 37.81 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Aug 06, 2024 at 02:33:37PM +0100, Dave Martin wrote: > Hi, > > On Thu, Aug 01, 2024 at 05:01:10PM +0100, Joey Gouly wrote: > > On Thu, Jul 25, 2024 at 04:57:09PM +0100, Dave Martin wrote: > > > On Fri, May 03, 2024 at 02:01:33PM +0100, Joey Gouly wrote: > > > > If a memory fault occurs that is due to an overlay/pkey fault, report that to > > > > userspace with a SEGV_PKUERR. > > > > > > > > Signed-off-by: Joey Gouly > > > > Cc: Catalin Marinas > > > > Cc: Will Deacon > > > > --- > > > > arch/arm64/include/asm/traps.h | 1 + > > > > arch/arm64/kernel/traps.c | 12 ++++++-- > > > > arch/arm64/mm/fault.c | 56 ++++++++++++++++++++++++++++++++-- > > > > 3 files changed, 64 insertions(+), 5 deletions(-) > > > > > > > > diff --git a/arch/arm64/include/asm/traps.h b/arch/arm64/include/asm/traps.h > > > > index eefe766d6161..f6f6f2cb7f10 100644 > > > > --- a/arch/arm64/include/asm/traps.h > > > > +++ b/arch/arm64/include/asm/traps.h > > > > @@ -25,6 +25,7 @@ try_emulate_armv8_deprecated(struct pt_regs *regs, u32 insn) > > > > void force_signal_inject(int signal, int code, unsigned long address, unsigned long err); > > > > void arm64_notify_segfault(unsigned long addr); > > > > void arm64_force_sig_fault(int signo, int code, unsigned long far, const char *str); > > > > +void arm64_force_sig_fault_pkey(int signo, int code, unsigned long far, const char *str, int pkey); > > > > void arm64_force_sig_mceerr(int code, unsigned long far, short lsb, const char *str); > > > > void arm64_force_sig_ptrace_errno_trap(int errno, unsigned long far, const char *str); > > > > > > > > diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c > > > > index 215e6d7f2df8..1bac6c84d3f5 100644 > > > > --- a/arch/arm64/kernel/traps.c > > > > +++ b/arch/arm64/kernel/traps.c > > > > @@ -263,16 +263,24 @@ static void arm64_show_signal(int signo, const char *str) > > > > __show_regs(regs); > > > > } > > > > > > > > -void arm64_force_sig_fault(int signo, int code, unsigned long far, > > > > - const char *str) > > > > +void arm64_force_sig_fault_pkey(int signo, int code, unsigned long far, > > > > + const char *str, int pkey) > > > > { > > > > arm64_show_signal(signo, str); > > > > if (signo == SIGKILL) > > > > force_sig(SIGKILL); > > > > + else if (code == SEGV_PKUERR) > > > > + force_sig_pkuerr((void __user *)far, pkey); > > > > > > Is signo definitely SIGSEGV here? It looks to me like we can get in > > > here for SIGBUS, SIGTRAP etc. > > > > > > si_codes are not unique between different signo here, so I'm wondering > > > whether this should this be: > > > > > > else if (signo == SIGSEGV && code == SEGV_PKUERR) > > > > > > ...? > > > > > > > > > > else > > > > force_sig_fault(signo, code, (void __user *)far); > > > > } > > > > > > > > +void arm64_force_sig_fault(int signo, int code, unsigned long far, > > > > + const char *str) > > > > +{ > > > > + arm64_force_sig_fault_pkey(signo, code, far, str, 0); > > > > > > Is there a reason not to follow the same convention as elsewhere, where > > > -1 is passed for "no pkey"? > > > > > > If we think this should never be called with signo == SIGSEGV && > > > code == SEGV_PKUERR and no valid pkey but if it's messy to prove, then > > > maybe a WARN_ON_ONCE() would be worth it here? > > > > > > > Anshuman suggested to separate them out, which I did like below, I think that > > addresses your comments too? > > > > diff --git arch/arm64/kernel/traps.c arch/arm64/kernel/traps.c > > index 215e6d7f2df8..49bac9ae04c0 100644 > > --- arch/arm64/kernel/traps.c > > +++ arch/arm64/kernel/traps.c > > @@ -273,6 +273,13 @@ void arm64_force_sig_fault(int signo, int code, unsigned long far, > > force_sig_fault(signo, code, (void __user *)far); > > } > > > > +void arm64_force_sig_fault_pkey(int signo, int code, unsigned long far, > > + const char *str, int pkey) > > +{ > > + arm64_show_signal(signo, str); > > + force_sig_pkuerr((void __user *)far, pkey); > > +} > > + > > void arm64_force_sig_mceerr(int code, unsigned long far, short lsb, > > const char *str) > > { > > > > diff --git arch/arm64/mm/fault.c arch/arm64/mm/fault.c > > index 451ba7cbd5ad..1ddd46b97f88 100644 > > --- arch/arm64/mm/fault.c > > +++ arch/arm64/mm/fault.c > > (Guessing where this is means to apply, since there is no hunk header > or context...) Sorry I had some other changes and just mashed the bits into a diff-looking-thing. > > > > > - arm64_force_sig_fault(SIGSEGV, si_code, far, inf->name); > > + if (si_code == SEGV_PKUERR) > > + arm64_force_sig_fault_pkey(SIGSEGV, si_code, far, inf->name, pkey); > > Maybe drop the the signo and si_code argument? This would mean that > arm64_force_sig_fault_pkey() can't be called with a signo/si_code > combination that makes no sense. > > I think pkey faults are always going to be SIGSEGV/SEGV_PKUERR, right? > Or are there other combinations that can apply for these faults? Ah yes, I can simplify it even more, thanks. diff --git arch/arm64/kernel/traps.c arch/arm64/kernel/traps.c index 49bac9ae04c0..d9abb8b390c0 100644 --- arch/arm64/kernel/traps.c +++ arch/arm64/kernel/traps.c @@ -273,10 +273,9 @@ void arm64_force_sig_fault(int signo, int code, unsigned long far, force_sig_fault(signo, code, (void __user *)far); } -void arm64_force_sig_fault_pkey(int signo, int code, unsigned long far, - const char *str, int pkey) +void arm64_force_sig_fault_pkey(unsigned long far, const char *str, int pkey) { - arm64_show_signal(signo, str); + arm64_show_signal(SIGSEGV, str); force_sig_pkuerr((void __user *)far, pkey); } > > > > + else > > + arm64_force_sig_fault(SIGSEGV, si_code, far, inf->name); > > Otherwise yes, I think splitting things this way makes sense. > > Cheers > ---Dave