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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id g7sm4283587pfq.33.2020.02.26.13.41.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 26 Feb 2020 13:41:19 -0800 (PST) Date: Wed, 26 Feb 2020 13:41:18 -0800 From: Kees Cook To: Mark Brown Cc: Catalin Marinas , Will Deacon , Alexander Viro , Paul Elliott , Peter Zijlstra , Yu-cheng Yu , Amit Kachhap , Vincenzo Frascino , Marc Zyngier , Eugene Syromiatnikov , Szabolcs Nagy , "H . J . Lu " , Andrew Jones , Arnd Bergmann , Jann Horn , Richard Henderson , Kristina =?utf-8?Q?Mart=C5=A1enko?= , Thomas Gleixner , Florian Weimer , Sudakshina Das , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-fsdevel@vger.kernel.org, Dave Martin , Mark Rutland Subject: Re: [PATCH v7 07/11] arm64: unify native/compat instruction skipping Message-ID: <202002261341.17C9BC2222@keescook> References: <20200226155714.43937-1-broonie@kernel.org> <20200226155714.43937-8-broonie@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200226155714.43937-8-broonie@kernel.org> Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Wed, Feb 26, 2020 at 03:57:10PM +0000, Mark Brown wrote: > From: Dave Martin > > Skipping of an instruction on AArch32 works a bit differently from > AArch64, mainly due to the different CPSR/PSTATE semantics. > > Currently arm64_skip_faulting_instruction() is only suitable for > AArch64, and arm64_compat_skip_faulting_instruction() handles the IT > state machine but is local to traps.c. > > Since manual instruction skipping implies a trap, it's a relatively > slow path. > > So, make arm64_skip_faulting_instruction() handle both compat and > native, and get rid of the arm64_compat_skip_faulting_instruction() > special case. > > Signed-off-by: Dave Martin Reviewed-by: Kees Cook -Kees > Reviewed-by: Mark Rutland > Signed-off-by: Mark Brown > --- > arch/arm64/kernel/traps.c | 18 ++++++++---------- > 1 file changed, 8 insertions(+), 10 deletions(-) > > diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c > index b8c714dda851..bc9f4292bfc3 100644 > --- a/arch/arm64/kernel/traps.c > +++ b/arch/arm64/kernel/traps.c > @@ -272,6 +272,8 @@ void arm64_notify_die(const char *str, struct pt_regs *regs, > } > } > > +static void advance_itstate(struct pt_regs *regs); > + > void arm64_skip_faulting_instruction(struct pt_regs *regs, unsigned long size) > { > regs->pc += size; > @@ -282,6 +284,9 @@ void arm64_skip_faulting_instruction(struct pt_regs *regs, unsigned long size) > */ > if (user_mode(regs)) > user_fastforward_single_step(current); > + > + if (regs->pstate & PSR_MODE32_BIT) > + advance_itstate(regs); > } > > static LIST_HEAD(undef_hook); > @@ -644,19 +649,12 @@ static void advance_itstate(struct pt_regs *regs) > compat_set_it_state(regs, it); > } > > -static void arm64_compat_skip_faulting_instruction(struct pt_regs *regs, > - unsigned int sz) > -{ > - advance_itstate(regs); > - arm64_skip_faulting_instruction(regs, sz); > -} > - > static void compat_cntfrq_read_handler(unsigned int esr, struct pt_regs *regs) > { > int reg = (esr & ESR_ELx_CP15_32_ISS_RT_MASK) >> ESR_ELx_CP15_32_ISS_RT_SHIFT; > > pt_regs_write_reg(regs, reg, arch_timer_get_rate()); > - arm64_compat_skip_faulting_instruction(regs, 4); > + arm64_skip_faulting_instruction(regs, 4); > } > > static const struct sys64_hook cp15_32_hooks[] = { > @@ -676,7 +674,7 @@ static void compat_cntvct_read_handler(unsigned int esr, struct pt_regs *regs) > > pt_regs_write_reg(regs, rt, lower_32_bits(val)); > pt_regs_write_reg(regs, rt2, upper_32_bits(val)); > - arm64_compat_skip_faulting_instruction(regs, 4); > + arm64_skip_faulting_instruction(regs, 4); > } > > static const struct sys64_hook cp15_64_hooks[] = { > @@ -697,7 +695,7 @@ void do_cp15instr(unsigned int esr, struct pt_regs *regs) > * There is no T16 variant of a CP access, so we > * always advance PC by 4 bytes. > */ > - arm64_compat_skip_faulting_instruction(regs, 4); > + arm64_skip_faulting_instruction(regs, 4); > return; > } > > -- > 2.20.1 > -- Kees Cook