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Thu, 23 Apr 2026 08:04:40 +0000 Date: Thu, 23 Apr 2026 09:04:39 +0100 Message-ID: <868qae14rs.wl-maz@kernel.org> From: Marc Zyngier To: Anshuman Khandual Cc: Jinjie Ruan , catalin.marinas@arm.com, will@kernel.org, mark.rutland@arm.com, kees@kernel.org, ada.coupriediaz@arm.com, smostafa@google.com, leitao@debian.org, mrigendra.chaubey@gmail.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] arm64: traps: Add a macro to simplify the condition codes check In-Reply-To: References: <20260320082846.1235016-1-ruanjinjie@huawei.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/30.1 (aarch64-unknown-linux-gnu) MULE/6.0 (HANACHIRUSATO) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: anshuman.khandual@arm.com, ruanjinjie@huawei.com, catalin.marinas@arm.com, will@kernel.org, mark.rutland@arm.com, kees@kernel.org, ada.coupriediaz@arm.com, smostafa@google.com, leitao@debian.org, mrigendra.chaubey@gmail.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false On Thu, 23 Apr 2026 06:29:09 +0100, Anshuman Khandual wrote: > > > > On 20/03/26 1:58 PM, Jinjie Ruan wrote: > > Add DEFINE_COND_CHECK macro to define the simple __check_* functions > > to simplify the condition codes check. > > > > No functional changes. > > > > Signed-off-by: Jinjie Ruan > > --- > > arch/arm64/kernel/traps.c | 59 ++++++++++----------------------------- > > 1 file changed, 15 insertions(+), 44 deletions(-) > > > > diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c > > index 914282016069..6216fe9e8e42 100644 > > --- a/arch/arm64/kernel/traps.c > > +++ b/arch/arm64/kernel/traps.c > > @@ -49,45 +49,21 @@ > > #include > > #include > > > > -static bool __kprobes __check_eq(unsigned long pstate) > > -{ > > - return (pstate & PSR_Z_BIT) != 0; > > -} > > - > > -static bool __kprobes __check_ne(unsigned long pstate) > > -{ > > - return (pstate & PSR_Z_BIT) == 0; > > -} > > - > > -static bool __kprobes __check_cs(unsigned long pstate) > > -{ > > - return (pstate & PSR_C_BIT) != 0; > > -} > > - > > -static bool __kprobes __check_cc(unsigned long pstate) > > -{ > > - return (pstate & PSR_C_BIT) == 0; > > -} > > - > > -static bool __kprobes __check_mi(unsigned long pstate) > > -{ > > - return (pstate & PSR_N_BIT) != 0; > > -} > > - > > -static bool __kprobes __check_pl(unsigned long pstate) > > -{ > > - return (pstate & PSR_N_BIT) == 0; > > -} > > - > > -static bool __kprobes __check_vs(unsigned long pstate) > > -{ > > - return (pstate & PSR_V_BIT) != 0; > > -} > > - > > -static bool __kprobes __check_vc(unsigned long pstate) > > -{ > > - return (pstate & PSR_V_BIT) == 0; > > -} > > +#define DEFINE_COND_CHECK(name, flag, expected) \ > > +static bool __kprobes __check_##name(unsigned long pstate) \ > > +{ \ > > + return ((pstate & (flag)) != 0) == (expected); \ > > +} > > + > > +DEFINE_COND_CHECK(eq, PSR_Z_BIT, true) > > +DEFINE_COND_CHECK(ne, PSR_Z_BIT, false) > > +DEFINE_COND_CHECK(cs, PSR_C_BIT, true) > > +DEFINE_COND_CHECK(cc, PSR_C_BIT, false) > > +DEFINE_COND_CHECK(mi, PSR_N_BIT, true) > > +DEFINE_COND_CHECK(pl, PSR_N_BIT, false) > > +DEFINE_COND_CHECK(vs, PSR_V_BIT, true) > > +DEFINE_COND_CHECK(vc, PSR_V_BIT, false) > > +DEFINE_COND_CHECK(al, 0, false) /* Always true */ > > (((pstate & 0 == 0) != 0) == false) ---> return true > > Although this looks OK but wondering if __check_al() should > be left unchanged for simplicity. OR could all its call sites > be changed assuming an unconditional 'true' return thus later > __check_al() can be dropped. Which call site? We emulate an instruction, and we're not in control of the condition code associated with it. The condition code directly indexes into aarch32_opcode_cond_checks[]. Anyway, this is a moot point, as we have consensus to not touch that code at all. M. -- Without deviation from the norm, progress is not possible.