From: Sven Schnelle <svens@linux.ibm.com>
To: "Michal Suchánek" <msuchanek@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@kernel.org>,
"H. Peter Anvin" <hpa@zytor.com>,
Jonathan Corbet <corbet@lwn.net>,
Shuah Khan <skhan@linuxfoundation.org>,
Huacai Chen <chenhuacai@kernel.org>,
WANG Xuerui <kernel@xen0n.name>,
Madhavan Srinivasan <maddy@linux.ibm.com>,
Michael Ellerman <mpe@ellerman.id.au>,
Nicholas Piggin <npiggin@gmail.com>,
"Christophe Leroy (CS GROUP)" <chleroy@kernel.org>,
Paul Walmsley <pjw@kernel.org>,
Palmer Dabbelt <palmer@dabbelt.com>,
Albert Ou <aou@eecs.berkeley.edu>,
Alexandre Ghiti <alex@ghiti.fr>,
Heiko Carstens <hca@linux.ibm.com>,
Vasily Gorbik <gor@linux.ibm.com>,
Alexander Gordeev <agordeev@linux.ibm.com>,
Christian Borntraeger <borntraeger@linux.ibm.com>,
Andy Lutomirski <luto@kernel.org>, Ingo Molnar <mingo@redhat.com>,
Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, Andrew Donnellan <andrew+kernel@donnellan.id.au>,
Mark Rutland <mark.rutland@arm.com>,
Arnd Bergmann <arnd@arndb.de>,
Jiaxun Yang <jiaxun.yang@flygoat.com>,
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Mukesh Kumar Chaurasiya <mkchauras@linux.ibm.com>,
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Deepak Gupta <debug@rivosinc.com>,
Lukas Gerlach <lukas.gerlach@cispa.de>,
Rui Qi <qirui.001@bytedance.com>, Kees Cook <kees@kernel.org>,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
loongarch@lists.linux.dev, linuxppc-dev@lists.ozlabs.org,
linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org
Subject: Re: [RFC] entry: Untangle the return value of syscall_enter_from_user_mode from syscall NR
Date: Fri, 03 Jul 2026 13:39:18 +0200 [thread overview]
Message-ID: <yt9dtsqg480p.fsf@linux.ibm.com> (raw)
In-Reply-To: <akecJWAJP-e5CYP_@kunlun.suse.cz>
Michal Suchánek <msuchanek@suse.de> writes:
> The same could be asked of syscall_enter_from_user_mode. I find it very
> odd. Why does it conflate the syscall number with its return value?
>
> It never uses the syscall number passed in except when returning it
> unchanged. When it pokes the registers it reads the syscall number from
> them.
>
> If the caller of syscall_enter_from_user_mode only read the syscall
> number from the registers when syscall_enter_from_user_mode returns and
> indicates the syscall should be still executed this whole shenigan would
I agree. The fact that if (nr < NR_syscall) just works because -1 gets
casted to 0xffffffff and is therefore out of bounds is very odd.
next prev parent reply other threads:[~2026-07-03 11:40 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-01 17:42 [RFC] entry: Untangle the return value of syscall_enter_from_user_mode from syscall NR Michal Suchánek
2026-07-01 18:29 ` H. Peter Anvin
2026-07-02 9:30 ` Michal Suchánek
2026-07-02 21:49 ` Thomas Gleixner
2026-07-03 6:26 ` Sven Schnelle
2026-07-03 9:25 ` Peter Zijlstra
2026-07-03 9:27 ` Thomas Gleixner
2026-07-03 9:59 ` Sven Schnelle
2026-07-03 10:57 ` Peter Zijlstra
2026-07-03 11:17 ` Sven Schnelle
2026-07-03 11:25 ` Michal Suchánek
2026-07-03 11:39 ` Sven Schnelle [this message]
2026-07-02 8:12 ` Sven Schnelle
2026-07-02 9:12 ` Michal Suchánek
2026-07-02 12:01 ` Sven Schnelle
2026-07-02 12:13 ` Michal Suchánek
2026-07-03 6:16 ` Sven Schnelle
2026-07-02 11:24 ` Thomas Gleixner
2026-07-02 11:45 ` Michal Suchánek
2026-07-02 20:45 ` Thomas Gleixner
2026-07-03 7:53 ` Michal Suchánek
2026-07-03 9:34 ` Thomas Gleixner
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